# Latex v's Butyl tubes



## kiwimike (Feb 10, 2007)

I was wondering about Latex v's Butyl inner tubes.
Like most bike parts peoples views on Latex tubes seem to be very polorised. The reviews I have read on them give very conflicting points of view, it seems you either like them or hate them, have no punctures or are fixing punctures all the time, etc.
I just bought a set of custom wheels that I intend to use solely as a road race set.
As I won't be riding them every day so don't mind having to pump them up before each race I thought maybe Latex would be the way to go.
Peoples opinions on the pro's and con's would be appreciated. Thanks.


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## filtersweep (Feb 4, 2004)

For a race only wheel, you should be fine. I personally don't think they are worth the fuss, but if you insist, you shouldn't waste them on anything less than an "open" style tire like a Veloflex or Open Corsa. I doubt you would feel the difference on a Michelin or similar tire.



kiwimike said:


> I was wondering about Latex v's Butyl inner tubes.
> Like most bike parts peoples views on Latex tubes seem to be very polorised. The reviews I have read on them give very conflicting points of view, it seems you either like them or hate them, have no punctures or are fixing punctures all the time, etc.
> I just bought a set of custom wheels that I intend to use solely as a road race set.
> As I won't be riding them every day so don't mind having to pump them up before each race I thought maybe Latex would be the way to go.
> Peoples opinions on the pro's and con's would be appreciated. Thanks.


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## enki42ea (Apr 11, 2005)

Doesn't latex leak more air through the tube then butyl? (the slow multiday leak, so doesn't effect a normal ride but does mean you should check your tires each day of the week when you plan to go riding)

edit to add- sorry, just realized that probably doesn't apply to you.


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## DIRT BOY (Aug 22, 2002)

filtersweep said:


> but if you insist, you shouldn't waste them on anything less than an "open" style tire like a Veloflex or Open Corsa. I doubt you would feel the difference on a Michelin or similar tire.


+1 on that one.


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## spookyload (Jan 30, 2004)

I ride the vredestein and michelin latex tubes. They lose about 20 psi overnight. I always pump up my tires before every ride so it doesn't bother me. With the veloflex pave tires, you get a great feeling combo. I can run the latex tubes at 120 and get the same road feel of a butyl tube at 100.


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## Mr. Versatile (Nov 24, 2005)

I honestly can't tell the difference between the two when riding. I get more flats with latex, and IMO it's a pita to have to pump them up prior to every ride. I pump my butyl tubes maybe once per week.


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## ewitz (Sep 11, 2002)

Some carbon clincher makes recommend butyl tubes only with the use of their wheels


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## DIRT BOY (Aug 22, 2002)

ewitz said:


> Some carbon clincher makes recommend butyl tubes only with the use of their wheels


I wonder why?


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## rruff (Feb 28, 2006)

kiwimike said:


> I was wondering about Latex v's Butyl inner tubes.


Latex tubes have lower rolling resistance, and the puncture resistance is better for the same weight, so they are superior for racing... whether you can "feel" the difference or not.

One thing you have to be careful with is making sure that the tube isn't pinched in the tire bead. Take your time when mounting them; pump a little, check all around, repeat, etc.


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## filtersweep (Feb 4, 2004)

Can you back any of that up with science? 

BTW- to suggest they are "superior" for racing--- compared to what? Superior implies being significantly better.



rruff said:


> Latex tubes have lower rolling resistance, and the puncture resistance is better for the same weight, so they are superior for racing... whether you can "feel" the difference or not.
> 
> One thing you have to be careful with is making sure that the tube isn't pinched in the tire bead. Take your time when mounting them; pump a little, check all around, repeat, etc.


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## rruff (Feb 28, 2006)

filtersweep said:


> Can you back any of that up with science?
> 
> BTW- to suggest they are "superior" for racing--- compared to what? Superior implies being significantly better.


Of course it is science. On the biketechreview site there is a large compilation of Crr test data. The difference between a latex and a butyl tube is ~.0005 in Crr, with a typical Crr being around .0030... or in other words 17% of the rolling resistance

A .0005 reduction in Crr is worth about 0.7% in top speed on the flat, or a climb... almost as much as a $1500 carbon wheelset will give you on the flat... or losing 2lbs of weight on a climb!

Seems like a significant improvement to me for a cost of only ~$20...


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## Kerry Irons (Feb 25, 2002)

*Mixed data*



rruff said:


> Of course it is science. On the biketechreview site there is a large compilation of Crr test data. The difference between a latex and a butyl tube is ~.0005 in Crr, with a typical Crr being around .0030... or in other words 17% of the rolling resistance
> 
> A .0005 reduction in Crr is worth about 0.7% in top speed on the flat, or a climb... almost as much as a $1500 carbon wheelset will give you on the flat... or losing 2lbs of weight on a climb!
> 
> Seems like a significant improvement to me for a cost of only ~$20...


Lest you get all wound up in this, for every test you can find that shows an improvement with latex tubes, I can find one that does not. Also, many of these tests are done on small diameter steel rollers, or very smooth rollers, neither of which reflect the real world of riding on pavement. Extremely smooth surfaces significantly over-emphasize the differences between tires/tubes.


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## rruff (Feb 28, 2006)

Kerry Irons said:


> Extremely smooth surfaces significantly over-emphasize the differences between tires/tubes.


That is true Kerry. Road roughness can end up being as big of a power loss as as the Crr, but the difference between butyl and latex will still be there. I'm not aware of any tests that show no difference in Crr between them. If you have some data or links I'd be interested. 

Butyl is a very "dead" material... it's forte is being able to hold air well. Latex has a very high coefficient of restitution (ie it will return most of it's energy when it flexes) so it I would certainly expect a difference between the two.


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## Kerry Irons (Feb 25, 2002)

*A reference*



rruff said:


> That is true Kerry. Road roughness can end up being as big of a power loss as as the Crr, but the difference between butyl and latex will still be there. I'm not aware of any tests that show no difference in Crr between them. If you have some data or links I'd be interested.


I don't have a link handy, though I remember some Google searches I did came up with 1) very scant data, 2) some data showing latex faster, 3) some showing no difference, and 4) some showing latex slower.

Volume 5, No. 1 of Bicycle Quarterly included a very extensive set of "coast down" road tests (150 trials) of tires. Among other conclusions: "tires were slightly slower with Michelin latex tubes than with butyl tubes. Michelin lates tubes are relatively thick. Thinner latex tubes . . . may offer better performance. However, when used in clincher tires, we have found them to be prone to punctures . . ."

IME of over 30 years in industrial research, when there is this kind of mix of results, it is pretty hard to claim a solid advantage of one over the other. This is especially the case when a test is used because it is easy to control rather than because it mimics reality (i.e. roller or drum tests instead of pavement tests).


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## peabody (Oct 17, 2005)

*go with michelin*

latex tubes and veloflex paves or vitts open corsa, you won't regret it.


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## burkeqc (Sep 25, 2006)

A well done roll out test done by Cyclopedia in 1993 on asphalt parking lot (assumed not rough asphalt like Bicycle Qtyr) shows a difference of .0075 to .018 in favor of latex tubes. Difference was done on belted & non belted Specialized tires, 125 PSI,23x700c Difference was not explained. Tube brands were not identified. Test was done on tricycle. Percentage differences I calculated based on differences between rollout distances.


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## rruff (Feb 28, 2006)

From another Tour test... I think Nov '06.

Tests were made with a 23 mm Continental Supersonic at 
7.5 bar and 30 km/h.

- latex (80 g) 23.9 W 
- polyurethane (60 g) 25.1 W 
- butyl (50 g) 25.9 W, (75 g) 28.8 W, (104 g) 32.1 W


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## burkeqc (Sep 25, 2006)

Thank you for Tour data. I assume it was done on a steel drum, so road wattages will be closer, problem is how much? For the comparison between the Deda Giro D;Italia & the Conti Ultra Gator Skin the RR for tour mag was .0038, .0058, (52% difference) Bicycle Qty, 25.3, 27.1 seconds (7% difference) Admittedly this is a very crude comparision. Too bad someone cannot afford to do a test on smooth asphalt road at normal ride speeds.


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## rruff (Feb 28, 2006)

burkeqc said:


> Too bad someone cannot afford to do a test on smooth asphalt road at normal ride speeds.


It is very tough to isolate the tire and vibration losses from flucuating air resistance at normal riding speeds... in other words, all the problems that the BQ people faced in getting good results just get magnified the faster you go.

Still, I think somebody with an SRM could get useful data if they wanted to spend the time doing a long controlled test. After all the best and worst tires from Tour are about 1mph apart at normal speeds.


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## Kerry Irons (Feb 25, 2002)

*Data problems*




burkeqc said:


> Thank you for Tour data. I assume it was done on a steel drum, so road wattages will be closer, problem is how much? For the comparison between the Deda Giro D;Italia & the Conti Ultra Gator Skin the RR for tour mag was .0038, .0058, (52% difference) Bicycle Qty, 25.3, 27.1 seconds (7% difference) Admittedly this is a very crude comparision. Too bad someone cannot afford to do a test on smooth asphalt road at normal ride speeds.


The analysis below notes that drum tests don't relate well to real road data, and that the Michelin latex tube was slower than a standard Michelin butyl.

Notes on Bicycle Quarterly Volume 5, No. 1 article on Performance of Tires by Jan Heine and Mark Vande Kamp. Focus is on real roads vs. roller and drum tests. From the rec.bicycles.tech web site authors' comments: "The tests showed excellent reproducibility - the same tires tested at different times during the test to check this gave identical results. Each combination of tire/pressure/tube was tested at least 3 times to weed out erroneous results. . . We had doubts at first whether the rider could keep the same position (on the hoods, arms locked), but the reproducibility of the results indicates that he could." Regarding the effect of wind, which was assumed to be zero but not measured: "In the end, the fact that our results are reproducible gives us confidence that these factors do not play a great enough role to affect our results significantly. Of our 155 measurements (timed runs that were not aborted due to wind), we have only 5 or 6 outliers, where there is more than a spread of 0.8 seconds between the slowest and fastest run for the same configuration." Showing the high reproducibility of the results: "Once, the rider forgot to put on their gloves after a break, and we noticed immediately in the results of our "reference" wheels. He put on his gloves, and the results were back to normal." Regarding drum tests vs. road tests: "Do the rankings of drum tests hold up on the road? The answer is no. For example, we tested two tires, the Continental Ultra Gator Skin and the Michelin Pro2 Race, both 700C x 23 mm. TOUR magazine had tested them on the Continental drum, and they found the Michelin to have a much lower coefficient of rolling resistance (0.0042) than the Conti (0.0058). We found both were identical on the road."

Notes from the article. 
•	They found 20% speed difference (55% power difference) at 16 mph from the fastest to the slowest tire. However, among normal width tires, the difference was less than 8% (20% power difference). Still a pretty big difference.
•	One of the 5 fastest tires was a 650x37 at 55 psi.
•	The only "current" tire tested was the Michelin Pro2 Race (no Conti GP4K or 3K, no Vittoria, Vredestein, Schwalbe, etc.).
•	Test rider was asked how fast the tires felt, and his impressions did not correlate with the results.
•	Worn tires are faster, probably due to thinner tread.
•	Harder rubber tires test faster on the rollers, but not on the road - Pro2 Race is much faster than Conti Ultra Gator Skin on the drum, but not on the road.
•	Tire pressure has a much smaller effect on the road than on the drum tester. Dropping from 105 to 85 psi resulted in a 2% speed decrease (5% power increase) whereas drum tests suggest a 15% increase in resistance. Wider tires (28 mm) showed no speed increase above 85 psi, and are only slightly slower at 55 psi. Tubulars are worse at 130 psi vs. 105 psi.
•	The speed disadvantage of tubulars on the road is smaller than that shown with drum tests.
•	Both a 24 mm and 37 mm tire were slower with Michelin latex tubes (relatively thick tube). The standard tube was a Michelin 1A and a Kenda thick butyl.
•	New tires are slower, possibly due to thicker tread and a stiffer casing.
•	Lab tests ignore suspension losses (from the tire not being able to conform to surface irregularities).
•	The authors claim that warm tires are faster, but they apparently didn't correct for air density.


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## burkeqc (Sep 25, 2006)

I agree with most of what was in the Bicycle Qty article. Unfortunately the roll out was done on moderately rough pavement at 10.6-16.9 MPH. This is why I would like to see a test on smooth asphalt at speeds ranging from 15-25 MPH. I would expect extremely small differences due to rolling resistance, especially as the speed increases.


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## rruff (Feb 28, 2006)

Kerry Irons said:


> For example, we tested two tires, the Continental Ultra Gator Skin and the Michelin Pro2 Race, both 700C x 23 mm. TOUR magazine had tested them on the Continental drum, and they found the Michelin to have a much lower coefficient of rolling resistance (0.0042) than the Conti (0.0058). We found both were identical on the road."
> 
> •	Harder rubber tires test faster on the rollers, but not on the road - Pro2 Race is much faster than Conti Ultra Gator Skin on the drum, but not on the road.


I'm surprised that the Pro2 (racing tire) has harder rubber than the Gatorskin (durable tire), but assuming that this is true, then what is the mechanism that would make the on-road performance so much different than the rollers? The assumption must be that the Pro2 fails to conform to the road because of its "hard" tread, but if that was true then it would have a rough ride. Elsewhere, they state that the ride of the Gatorskin was poor compared to the Pro2. 

I know this doesn't have anything to do with latex tubes, but I'm concerned that their test method included too many random, uncontolled, and unmeasured variables. I'll be getting a copy of the article soon...


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## burkeqc (Sep 25, 2006)

The article will explain reason for the large difference between drum & on road testing. 
Other road tests have shown the similar results. The best controlled rolling resisstance test I have seen was in Bicycling in May 1985, author, Chester Kyle. Tire brands were not identified, but similiar were relatively close together. The test was done on a special trike on smooth pavement at very low speed.


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## tanhalt (Nov 9, 2005)

Kerry Irons said:


> The analysis below notes that drum tests don't relate well to real road data, and that the Michelin latex tube was slower than a standard Michelin butyl...


Kerry, have you even read the article in BQ? Or, are you going by the word of the author's writings on RBR about the "conclusions"? 

If you haven't, it's pretty careless of you to use this "test" without knowing the details of how it was performed.

If you HAVE, I'm disappointed that someone who has in the past demanded "scientific rigor" would use this as backup for his preconceived opinion.

Perhaps you should discuss this with your friend Al...he seems to have some good insight on the subject and has done some real "hands-on" testing.:thumbsup:


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## tanhalt (Nov 9, 2005)

burkeqc said:


> The article will explain reason for the large difference between drum & on road testing.


It does not. It merely provides misinformed speculation which shows a fundamental misunderstanding of pneumatic tire behavior.

Ron, when you get the article, your suspicions will be largely confirmed. A simple look at possible sources of error and their effects on the results will be enlightening.

The authors "hang their hat" on their supposed "reproducibility". Consistency doesn't necessarily mean accurate.


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## Kerry Irons (Feb 25, 2002)

*Wow!*



tanhalt said:


> Kerry, have you even read the article in BQ? Or, are you going by the word of the author's writings on RBR about the "conclusions"?
> 
> If you haven't, it's pretty careless of you to use this "test" without knowing the details of how it was performed.
> 
> ...


Geez Tom, in the attack mode are we? Yes I read the article, several times, along with the comments and discussion on rec.bicycles.tech. The bulleted items in my post are my observations. 

In my world, when someone does detailed testing, applies statistical analysis to demonstrate the validity and reproducibility of the results, controls for variables, thoroughly explains their methodology, and subjects their work to two levels of external review (pre-publishing and post-publishing), then that qualifies as scientific rigor. I know that you don't agree with my opinion, but you haven't shown the data from on-road tests that supports yours.

Maybe instead of attacking me, you could explain why you think the methodolgy and conclusions of the authors of this article are wrong, and provide some alternate source of quality data which proves them wrong. Otherwise, we're just hearing YOUR biases, but no reasoned argument to support them. The authors state that suspension losses are important along with hysteresis losses and that drum/roller tests only measure the latter. If you have data to the contrary, let's hear it.


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## tanhalt (Nov 9, 2005)

Kerry Irons said:


> Geez Tom, in the attack mode are we? Yes I read the article, several times, along with the comments and discussion on rec.bicycles.tech. The bulleted items in my post are my observations.


Nope. Just "cutting to the chase".



Kerry Irons said:


> In my world, when someone does detailed testing, applies statistical analysis to demonstrate the validity and reproducibility of the results,...


What proof of this "statistical analysis" do you see? All I see are averages and references to "tires with times within a half second of each other should be considered equal in performance." They talk of doing a regression analysis to determine what factors are statistically significant to the performance and refer to a seperate article, but that article is basically just term definitions, with an erroneous understanding of internal losses and how they relate to "suspension" losses. BTW, I'm sure you realize that reproducibility doesn't necessarily correspond to validity. It's pretty easy to consistantly do something wrong.

I see them making "determinations" about which tires are faster than each other based on averages that are less than 0.5 seconds apart, yet they have spreads of data on individual tires that range up to 2 seconds. On top of that, there's no actual data reported, just a chart with "x"s on it representing the data that's pretty crude...and some of the data (like in the latex vs. butyl testing) isn't shown, just the averages. 



Kerry Irons said:


> ...controls for variables,...


Hmmm...do you mean like how they controlled for wind? Or barometric pressure? Or, how they controlled for the entrance speed (and thus the initial kinetic energy) into their "speed trap"? Or weight? They state a specific weight but don't say how they controlled for it. I know that my own weight can vary by up to 1 kg (or more) on a daily basis, depending on what time the weight is taken. Or how they controlled for temperature effects? Admittedly, they DID apparently correct one set of data for temperature, but only AFTER their testing showed something was WAY out of whack. They should've researched the temp effects on rolling resistance and applied corrections to the data initially (not to mention the temp effects on air density). 



Kerry Irons said:


> ...thoroughly explains their methodology, and subjects their work to two levels of external review (pre-publishing and post-publishing),....


Yes...they talk of it as being reviewed. But what was the result of that review? What were the "reservations" of the reviewers? Did they take into account any suggestions of the reviewers? IMO, the reviewers have been noticeably silent. I know that Jim P. occasionally pops up on RBtech...



Kerry Irons said:


> Maybe instead of attacking me, you could explain why you think the methodolgy and conclusions of the authors of this article are wrong, and provide some alternate source of quality data which proves them wrong. Otherwise, we're just hearing YOUR biases, but no reasoned argument to support them.


Now, to set the record straight, I initially had high hopes for this testing, but as I studied the actual article and took a critical look, my reservations rose. Besides what I've detailed above, here is the main problem I had with the testing: Even at these admittedly low speeds (compared to racing bicycles) the aerodynamic drag component of the testing accounts for ~75% of the power requirement for motion. So, we're left with ~25% of the power requirement and we're looking for relatively small changes in that ~25% between test articles. Doesn't sound like a very "robust" way of "teasing out" the differences. A simple "uncertainty analysis" using the published (and validated) equation of forward motion for a cyclist will go a long way towards pointing out the difficulties in getting "valid" results from this methodology. 



Kerry Irons said:


> The authors state that suspension losses are important along with hysteresis losses and that drum/roller tests only measure the latter. If you have data to the contrary, let's hear it.


And that statement demonstrates a fundamental misunderstanding of the behavior of pnuematic tires. In short, suspension losses are internal losses, and vice versa. You can't seperate the two. They occur from the same mechanisms. THAT is why basically every tire manufacturer in the world uses drum testing to evaluate tires. In fact, in the previous thread on this, "California L33" pointed out this industry test which appears to confirm the validity of drum testing to "on the road" performance:
http://scitation.aip.org/getabs/ser...00023000004000256000001&idtype=cvips&gifs=yes

I've in the past offered to work with you to come up with a testing protocol that would satisfy your requirements AND mine as well. I've got a PowerTap wheel waiting to be used. I propose a simple "hillclimb" test in a sheltered area on a straight, extremely low traffic road. Let's actually MEASURE the power and speed in a condition that minimizes the aerodynamic effects. I'm not concerned about the speed being even lower than the BQ testing, since large amounts of data have previously shown that Crr is basically linear with velocity. What do you say? Are you game?


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## Kerry Irons (Feb 25, 2002)

*The test*



tanhalt said:


> I've in the past offered to work with you to come up with a testing protocol that would satisfy your requirements AND mine as well. I've got a PowerTap wheel waiting to be used. I propose a simple "hillclimb" test in a sheltered area on a straight, extremely low traffic road. Let's actually MEASURE the power and speed in a condition that minimizes the aerodynamic effects. I'm not concerned about the speed being even lower than the BQ testing, since large amounts of data have previously shown that Crr is basically linear with velocity. What do you say? Are you game?


I'm travelling right now, and can't respond to the details of your comments because I don't have the article in front of me. In general, it sounds as if you simply don't believe that they did a good statistical analysis, even though they say they did. You don't believe that they had a positive review of their article, even though they say they did. IMO, the reproducibility of their results speak strongly to the quality of their testing. You obviously disagree on principle. 

IMO, you are not correct on suspension losses. As defined by these authors, suspension losses are what you experience when your tire bounces, shoving the bike and rider and thereby dissipating energy by "shaking" the rider. This is NOT the same as the energy dissipated by flexing the tire casing, tread and tube. At the limit, an infinitely stiff casing would have no energy losses due to hysteresis, and such a tire would test as having a very good CRR, but it WOULD cause energy losses in the entire bike/rider system. They note the "steel wheels" analogy for your understanding.

Regards your proposed test, I'm not sure what you're asking from me. You can conduct the tests you propose and report the results. I would suggest that you review your protocol with some knowlegeable people, including the authors of the BQ article. I don't live anywhere near a road that offers the conditions you propose.


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## tanhalt (Nov 9, 2005)

Kerry Irons said:


> I'm travelling right now, and can't respond to the details of your comments because I don't have the article in front of me. In general, it sounds as if you simply don't believe that they did a good statistical analysis, even though they say they did.


I didn't write that...I merely pointed out that a claim was made about a statistical analysis, yet no details were provided about the results of that analysis. Heck, at least Al gives a mean and std. dev. for his roller results.




Kerry Irons said:


> You don't believe that they had a positive review of their article, even though they say they did.


Again, there's been no information provided about the results (positive OR negative) of their review. My problem with both this and the lack of statistical analysis info is that people are quick to latch on to the "results" and "conclusions" based on the fact that the authors said they did these things...yet there's no way of independently evaluating how well they did the testing. People appear to claim "They did statistics and they had reviewers...this is SCIENCE!"...when it may not necessarily be the case. The problem is that with the information revealed so far, we just don't know one way or the other...



 Kerry Irons said:


> IMO, the reproducibility of their results speak strongly to the quality of their testing. You obviously disagree on principle.


I would call that "repeatability", not necessarily "reproducibility." Reproducibility would be if independent testers could repeat the results using the same or similar testing methods. Right now, there are parts of their testing that don't follow the results of many other tests...that throws up a big "red flag" right there. Repeatability of results doesn't necessarily mean that the results are correct...just that the same thing was done over and over again.



Kerry Irons said:


> IMO, you are not correct on suspension losses. As defined by these authors, suspension losses are what you experience when your tire bounces, shoving the bike and rider and thereby dissipating energy by "shaking" the rider. This is NOT the same as the energy dissipated by flexing the tire casing, tread and tube. At the limit, an infinitely stiff casing would have no energy losses due to hysteresis, and such a tire would test as having a very good CRR, but it WOULD cause energy losses in the entire bike/rider system. They note the "steel wheels" analogy for your understanding.


The "steel wheels" analogy is a "red herring". We aren't talking about solid wheels here, we're talking about pnuematic tires. There's a HUGE difference.

Obviously, one can make a pnuematic tire stiffer just by increasing the pressure and this tire would demonstrate low rolling resistance on both smooth AND rough surfaces. However, as you state, this stiffer tire WOULD also tend to increase the "resistance to forward motion" due to energy transfer (and dissipation) in the rest of the bike+rider system. That's NOT what the authors were describing. They are specifically stating that there's a difference between the losses due to deflection of the casing from straight rolling and losses due to surface roughness causing the maximum deflection to vary over time. It's unclear how this is possible with tire casing materials.

Remember, they're not claiming that the tires were low rolling resistance at HIGH pressures on the rollers, but then rolled relatively poorly on the road. They're claiming that the tires had low RR at LOW and MODERATE pressures on the rollers and then rolled relatively poorly on the road. Obviously, if a tire is flexible and elastic enough to have low losses under those conditions, how does it magically become "too hard" on a road surface that is still relatively smooth? I hardly think that a soap box derby hill is paved with very rough pavement. I also think their claim of the Michelin tires having a "harder" rubber compound that somehow causes this effect is specious. IME, the rubber on these tires is not appreciably different in hardness than the rubber compounds on other good performing tires, such as Vittoria Open Corsas. Besides, there's no logical explanation of how a harder durometer rubber compound could perform well on a drum but not on a road. What's the physical mechanism?..it just doesn't follow.



Kerry Irons said:


> Regards your proposed test, I'm not sure what you're asking from me. You can conduct the tests you propose and report the results. I would suggest that you review your protocol with some knowlegeable people, including the authors of the BQ article. I don't live anywhere near a road that offers the conditions you propose.


I have just the perfect road near me (AND I have the PT). In fact, I've done "on the road" tire evaluations in the past on that road and was easily able to discern the rolling resistance difference between Tufo tubulars and Michelin ProRace tires...and guess what? The magnitude of the difference was the same as reported from the Tour drum testing...go figure. With our springtime weather soon to start with typical morning overcast conditions, I should be able to go there and do testing in relatively constant temperature conditions. The nice thing about the hillclimb test (the average grade on this hill is over 9%) is that the speeds are low enough that the aerodynamic force contribution to the power requirement is MUCH less than in a rolldown type of test. Since much research has shown that Crr is basically linear with velocity, the fact that this is a low speed test should not prevent the results from being extrapolated to slightly higher speeds.

What I'm asking from you is to participate in the design and conducting of an "on the road" test that will either support or disprove, to YOUR satisfaction and MINE, whether or not drum testing correlates to "on the road" performance, and whether or not latex tubes have a measurable affect on the rolling resistance of bicycle tires. The intent is to design and conduct a test where the measurement uncertainties are evaluated and known, the confounding factors are minimized or compensated for, and the data is evaluated in a logical fashion with the appropriate statistics. How could you resist taking part?


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## rruff (Feb 28, 2006)

Kerry Irons said:


> IMO, you are not correct on suspension losses. As defined by these authors, suspension losses are what you experience when your tire bounces, shoving the bike and rider and thereby dissipating energy by "shaking" the rider. This is NOT the same as the energy dissipated by flexing the tire casing, tread and tube. At the limit, an infinitely stiff casing would have no energy losses due to hysteresis, and such a tire would test as having a very good CRR, but it WOULD cause energy losses in the entire bike/rider system. They note the "steel wheels" analogy for your understanding.


I agree with that, and I think Tom does too. But in regards to normal bicycle tires, the casing is not stiff enough to significantly effect the size of the contact patch... ie the amount of flex is governed by the pressure and the width of the tire. And a tire with a stiff casing will almost surely have greater hysteresis (Tom's point I think) as well as transmitting more vibration (suspension losses). 

If the latex tubes are better on rollers, but have a greater loss in the "real world"... what could possibly account for this? Compared to butyl, latex has a much higher coefficient of restituion, and is very flexible... if there is any measurable difference it would have to be better... and on rollers it clearly is. BQs tests say they are worse on the road though, which means that latex would need to cause added *vibration* losses that exceed it's benefit (vs butyl) on the rollers. But then they say that latex provides a better ride! How can vibration losses be higher when the ride is smoother?

Same for the Pro2 vs Gatorskin comparison. How can the Gatorskins have lower vibration losses in the real world, when their ride is clearly worse?


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## Kerry Irons (Feb 25, 2002)

*Resistance*



tanhalt said:


> I didn't write that...I merely pointed out that a claim was made about a statistical analysis, yet no details were provided about the results of that analysis.
> 
> Again, there's been no information provided about the results (positive OR negative) of their review. My problem with both this and the lack of statistical analysis info is that people are quick to latch on to the "results" and "conclusions" based on the fact that the authors said they did these things...yet there's no way of independently evaluating how well they did the testing.
> 
> ...


It is not common to provide the first level data details in research reports. You are essentially asking that the raw data and all of the manipulations of it be provided before you will accept the quality of the work. That is not normal practice, nor is it something that (most) people want to read in an article in BQ.

Reproducibility in the context of these results is out there for anyone to test. The way research works is that someone publishes their results, and then it is indeed up to others to try to reproduce them, or alternatively to show that they are not reproducible. It is through generating data that you challenge the results of others, not by asking them (after the fact) to prove a negative (that what they did was not invalid). 

The authors have been very forthcoming in discussing their study, their methodology, and data analysis, so how about you talk to them about all the issues you have? Why argue with me about it? I didn't do the tests, didn't do the analysis, and know no more about this work than you do. Likewise, these authors, and perhaps others that they consulted, are the ones to talk to about designing and conducting your test. 

When I read all of the stuff I can find on tire and tube testing, I find a lot of conflicting results. This could be because there are a lot of poorly conducted tests, because people don't do good statistical analysis of their results, because no one has yet developed a truly valid test, or other factors of which I am not aware. All I am attempting to do in these discussions is to challenge the many flat-out claims that are made when in fact there is conflicting data to these claims. I am not an expert in tire testing and don't claim to be. I did spend 30 years in R&D, and have seen a lot of bad work, improper use of statistics, etc. and when I have seen the kind of data scatter that I find in the tire/tube rolling resistance I am immediately suspicious. When there is not consensus on a topic like this, then I'm going to call it when someone makes a claim where the data is not consistent.


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## pkgdave9144 (Nov 21, 2006)

rruff said:


> I
> 
> If the latex tubes are better on rollers, but have a greater loss in the "real world"... what could possibly account for this?
> 
> . How can the Gatorskins have lower vibration losses in the real world, when their ride is clearly worse?


I cant believe y'all are arguing with these guys.....

Just let them ride their 36 hole, 3x open pros with heavy tires and butyl tubes. They think its the best...OK fine, whatever (smile and wink) 

When they ask us how we like our low-count deep section wheels with Pro Race tires and Latex tubes, just say "oh, they are OK I guess....they arent as fast as your 1972 technolgy wheels and tires, but they are good enough for me"

Seriously.... look at all the old folks buying 1960's technology Pushrod V-8 Ford Crown Vic's. You cant even begin to explain to them how much better "the new technology" is. They wont listen. Just let them drive it and be happy.


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## tanhalt (Nov 9, 2005)

Kerry Irons said:


> It is not common to provide the first level data details in research reports. You are essentially asking that the raw data and all of the manipulations of it be provided before you will accept the quality of the work. That is not normal practice, nor is it something that (most) people want to read in an article in BQ.


No...I'm not asking for all the gory details...BUT, it would be nice to at least see some averages and std. deviations, and for things they say are not "statistically significantly different", how about a confidence (p) level.

AND...like I said, before they even started, there should have been a sensitivity analysis done to even see if it's possible to measure to the "accuracy" they claim to be able to measure (i.e. within 0.5s).



Kerry Irons said:


> Reproducibility in the context of these results is out there for anyone to test. The way research works is that someone publishes their results, and then it is indeed up to others to try to reproduce them, or alternatively to show that they are not reproducible. It is through generating data that you challenge the results of others, not by asking them (after the fact) to prove a negative (that what they did was not invalid).


SEE! That's what I'm talking about...you're falling into the mode of treating this as some sort of peer reviewed research in the traditional sense. It's NOT. You're also changing your definition of "reproducibility". Before, you were equating that to repeatability in their measurements. I'm glad to see that you now agree with me that there's a difference in those 2 terms.

I'm not saying that they need to prove that "what they did was not invalid", I'm asking for it to be shown that what they did had a reasonable probability of being valid. There's a difference, which I'm sure you're aware. 



Kerry Irons said:


> The authors have been very forthcoming in discussing their study, their methodology, and data analysis, so how about you talk to them about all the issues you have? Why argue with me about it? I didn't do the tests, didn't do the analysis, and know no more about this work than you do. Likewise, these authors, and perhaps others that they consulted, are the ones to talk to about designing and conducting your test.


All of the issues I've brought up have been mentioned already in the discussions on RBT. I'm talking to YOU about it now because you're holding up this test as evidence that latex tubes do not provide any rolling resistance advantages. I'm just pointing out to you the flaws in the methodology so that you can appropriately consider the testing results.

For the test proposal, I'm just attempting to come up with a way that we can come to some sort of resolution between our differing viewpoints on the latex vs. butyl subject. I'm offering my time and resources to make it happen. All you have to do is contribute your desires in the test protocol to ensure your satisfaction with the results, no matter which way they turn out. What's so hard about that?




Kerry Irons said:


> When I read all of the stuff I can find on tire and tube testing, I find a lot of conflicting results. This could be because there are a lot of poorly conducted tests, because people don't do good statistical analysis of their results, because no one has yet developed a truly valid test, or other factors of which I am not aware. All I am attempting to do in these discussions is to challenge the many flat-out claims that are made when in fact there is conflicting data to these claims. I am not an expert in tire testing and don't claim to be. I did spend 30 years in R&D, and have seen a lot of bad work, improper use of statistics, etc. and when I have seen the kind of data scatter that I find in the tire/tube rolling resistance I am immediately suspicious. When there is not consensus on a topic like this, then I'm going to call it when someone makes a claim where the data is not consistent.


Another way to resolve conflicting data is to go back and look at "first principles". If you can't find a physical mechanism or reason for why a test is giving data that appears to be in conflict with what is expected, or is in conflict with previous testing...that should call those test results into question. As Ron pointed out above, we KNOW that latex has a higher elasticity and coefficient of restitution than butyl. Does it make sense that replacing a butyl tube with a latex tube would actually make a tire slower? If so, what's the physical mechanism by which this could happen??

BTW, I'd be VERY interested to know if the butyl vs. latex testing was done on the same day. If it wasn't, I'd also be VERY interested to know what the air density was on those 2 days, especially since at the test speeds, the air resistance accounts for ~75% of the total resistance to movement.

Oh yeah...they didn't take air density into account. Oops.


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## burkeqc (Sep 25, 2006)

See http://www.users.globalnet.co.uk/~hadland/lafford.htm. Note small difference on road with Conti Gran Prix 28-406 with latex tubes. Yes there may be data differences & tire condition differences, but its very small.


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## tanhalt (Nov 9, 2005)

burkeqc said:


> See http://www.users.globalnet.co.uk/~hadland/lafford.htm. Note small difference on road with Conti Gran Prix 28-406 with latex tubes. Yes there may be data differences & tire condition differences, but its very small.


Here's my previous comments about the Lafford testing and data:

http://forums.roadbikereview.com/showthread.php?p=816419#poststop

One thing to remember is that the benefits of latex tubes can be overwhelmed by the large hysteresis losses in a relatively poorly rolling tire like a Cont Gran Prix. In fact, here's John Lafford's own words on the subject from the article in "Human Power" that discusses his testing and data:

"4. The list includes some examples of the effect of using latex inner tubes instead of butyl inner tubes. Generally, the latex tube will give an improvement. However, if the tyre has a thick tread, this will dominate the energy absorption, and latex will show no benefit. Latex gives a good improvement where the tyre tread is thin and flexible so that the reduction in energy caused by substituting the butyl tube can be seen."


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## steel515 (Sep 6, 2004)

filtersweep said:


> Can you back any of that up with science?
> 
> I can't backup witih science but
> Most of top tubulars used, available locally and used in tour de france use latex tubes.
> I think there is a reason for this.


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## tanhalt (Nov 9, 2005)

steel515 said:


> filtersweep said:
> 
> 
> > Can you back any of that up with science?
> ...


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## Kerry Irons (Feb 25, 2002)

*Closure*

Just to wrap this up, I would make the following points:

1. While you say that you are not claiming the BQ results are no good, everything you say implies just that. You have listed everything that could possibly have been done wrong by the testers and given them no benefit of the doubt that they may have actually done things right. In my view, the fact that they have gotten the same results with their "reference tires" on multiple days and multiple runs on each day is a very strong argument that they have done things right. Their methodology does not develop absolute numbers (CRRs); it just shows where a given tire/tube combination is in reference to their bench mark.

2. Since you feel so strongly that their methodology and analysis may be flawed, you should be discussing it with them. Here is Jan Heine's e-mail address: heine94 (at) earthlink (dot) net. This approach where you whittle away at their results without having them involved in the discussion is not that productive. These authors have been very forthcoming in discussing their results, so you should talk to them directly. Feel free to share the results of that dialog.

3. As I stated before, I am neither a tire expert nor a tire testing expert. I am simply reading various reported results, seeing a lot of inconsistencies, and calling out people who claim definitive positions when there are conflicting results from what appear to be quality studies. I am not in a position to define a good test for tires/tubes. If you have a proposed test protocol, I'm sure that the authors of the BQ work (Heine or Vande Kamp) and/or those who reviewed the study (Berto, Oehler, Papdopoulos, Wetmore, Peterson, Tsuchyia, or Petit) would be far better qualified than me to comment on your proposed methodology. If you are serious about this, and not just trying to bluff and intimidate me, then I suggest you seek their input.

4. You state categorically that suspension losses are not at issue for determining which tire/tube combinations are fastest. The authors of the BQ article would state that suspension losses are the reason that a tire would show ever-decreasing CRR on a drum/roller test as pressure is increased, would not have the same result on the road. On the road, with constant power input, speed increases as a function of increasing pressure, then flattens out, and has often been reported to decrease on rougher road surfaces. If these are not suspension losses, what is your explanation of this phenomenon?


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## rruff (Feb 28, 2006)

*BQ error analysis*

I got a copy of the BQ article a few days ago and put a spreadsheet together to do an analysis of their testing. I had to use an initial run slope of 7% to get something similar to their speed numbers (they claimed it was ~4.5%). At first I thought I'd made a mistake, but Tom Compton agrees with me, so I'm going to assume that they were off in their slope estimation... or else they have a super low CdA for riding straight-armed on the hoods. I assumed .35 there which is probably lower than it should be... but then I'd just need an even greater slope. 

The biggest source of error is probably the wind uncertainty. They claimed it was always "zero"... but if so, that is a climate condition that essentially never occurs anywhere that I've lived. Even a 0.5mph wind is enough to give an error of 1.10 sec in the elapsed time, which is equivalent to an increase in Crr from .0050 to .0068! The other big potential source of error is the CdA... or body position. A change from .35 to .36 is equivalent to a Crr change from .0050 to .00535... not a huge amount, but I'd be surprised if they could be that consistent. 

I also don't see the rationale for their findings. The idea that there are losses associated with transmitted vibration ("suspension losses") that are in addition to frictional losses due to deflection of the tire casing, seems sound. I've been saying that this is an important "loss" in the bike/rider system for awhile. But suspension losses, since they are transmitted to and disappated by the rider's body are losses that can be felt... ie a rough riding tire must have inherently high suspension losses, regardless of the hysteresis losses... and a smooth riding tire must have low suspension losses. But their findings contradict this. They claim that latex tubes have a higher total loss, even though their hysteresis loss is clearly less... *and* they say they have a smoother ride! So where does this extra loss come from? The some goes for their comparison of the Pro2 and Gatorskin. The Pro2 has a lower Crr on rollers, *and* a smoother ride on the road... yet somehow the total loss is the same in their testing. Why?

I think there are serious challenges when trying to get good Crr data with this sort of test, and the authors of this article didn't go to great enough lengths to confidently make the claims they did.


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## linus (Mar 24, 2005)

You guys have way too much time on your hands. Why don't we just go out for a ride.

tanhalt, you are trying too hard.


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## burkeqc (Sep 25, 2006)

You obviously have an engineering type background which makes your analysis better than my laymans. I took what I could from their article: the wind definately disturbed me & the course road surface. I ride mainly on smooth asphalt. I now see why rolling resistance tests (like Chester Kyle) are done at very low speeds. Other wise a test would have to be done indoors, with rider position & line strictly controlled. Power meters would have to be very accurate at road speeds, since I assume the differences would be small.


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## rruff (Feb 28, 2006)

It's a catch22... to really evaluate the tires we need to test them on real roads at real speeds... but then all these random variables swamp out the thing we are looking to measure. The only thing to do in that case, is to account for the random variables as best as we can, and take a *lot* of data... like dozen's of measurements for each tire.


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## Kerry Irons (Feb 25, 2002)

*Talk to the authors*

I sent the authors a question regarding the "heat effect" and got a reply back in two days. I'm sure they would respond to your analysis.

Regards the often raised wind concerns, it seems to me that if they were able to get the same results in multiple trials on multiple days with their "reference" tire setup, then their claim about wind is reasonable. Since very small amounts of wind would significantly change the speeds, the fact that the speeds DIDN'T change, suggests that wind was not an issue. Also, the fact that dust tossed in the air didn't move also suggests very quiet air.


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## tanhalt (Nov 9, 2005)

Kerry Irons said:


> Just to wrap this up, I would make the following points:
> 
> 1. While you say that you are not claiming the BQ results are no good, everything you say implies just that. You have listed everything that could possibly have been done wrong by the testers and given them no benefit of the doubt that they may have actually done things right. In my view, the fact that they have gotten the same results with their "reference tires" on multiple days and multiple runs on each day is a very strong argument that they have done things right. Their methodology does not develop absolute numbers (CRRs); it just shows where a given tire/tube combination is in reference to their bench mark.


So...they got the "same" results with their "reference tires." OK...how "same" were the results? Within what range of times? Is that described anywhere, or are you just taking their word for it. BTW, I noticed in the article that they actually had 2 reference wheelsets, with one of the 2 used at the start of each day....hmm, but I thought they only did 4 days of testing. Doesn't sound like a lot of data points on the reference sets. IMHO, there's a LOT of information lacking from this claim of "sameness".



Kerry Irons said:


> 2. Since you feel so strongly that their methodology and analysis may be flawed, you should be discussing it with them. Here is Jan Heine's e-mail address: heine94 (at) earthlink (dot) net. This approach where you whittle away at their results without having them involved in the discussion is not that productive. These authors have been very forthcoming in discussing their results, so you should talk to them directly. Feel free to share the results of that dialog.


Thanks...I'll let you know what I discover.



Kerry Irons said:


> 3. As I stated before, I am neither a tire expert nor a tire testing expert.


No argument from me on that point.




Kerry Irons said:


> I am simply reading various reported results, seeing a lot of inconsistencies, and calling out people who claim definitive positions when there are conflicting results from what appear to be quality studies. I am not in a position to define a good test for tires/tubes. If you have a proposed test protocol, I'm sure that the authors of the BQ work (Heine or Vande Kamp) and/or those who reviewed the study (Berto, Oehler, Papdopoulos, Wetmore, Peterson, Tsuchyia, or Petit) would be far better qualified than me to comment on your proposed methodology. If you are serious about this, and not just trying to bluff and intimidate me, then I suggest you seek their input.


I have no interest at the present to undergo any of this testing for my own satisfaction. I'm confident in the testing that shows what works. I've got a lot better things to do with my time. My intent of the offer was to allow you to participate in a process whereby your opinion on this matter could be influenced by a test that you've participated in...but, I can see you don't want to take the chance that your preconceived notions may be revealed as faulty.



Kerry Irons said:


> 4. You state categorically that suspension losses are not at issue for determining which tire/tube combinations are fastest. The authors of the BQ article would state that suspension losses are the reason that a tire would show ever-decreasing CRR on a drum/roller test as pressure is increased, would not have the same result on the road. On the road, with constant power input, speed increases as a function of increasing pressure, then flattens out, and has often been reported to decrease on rougher road surfaces. If these are not suspension losses, what is your explanation of this phenomenon?


You are once again, like the authors in parts of the article, confusing tire suspension losses with bike+rider system suspension losses. Let me quote from the "definitions" portion of the BQ article.

"Suspension decreases resistance on bumps - If one avoids lifting the vehicle over each irregularity, energy is saved. Pneumatic tires absorb small irregularities. They greatly reduce the amount the vehicle is lifted. On real roads, they have much less rolling resistance than a steel wheel. However, the added deflection of the suspension also increases the internal losses of the wheel: With each rotation, the tire deforms more than a steel wheel, and absorbs more energy doing so."

This shows a good understanding of how pneumatic tires work. But, they then follow it up with this gem:

"For a given surface, the fastest wheel is the one with the best compromise between internal and suspension losses."

As you can see, they are talking about what's going on inside the tire. What they aren't "getting" though, is that they're talking about the same thing. Tire suspension losses ARE internal losses. The physical properties that allow low losses for a PNEUMATIC TIRE on a smooth surface are the same properties that reduce "suspension losses". For a pneumatic tire, the 2 cases of smooth surface performance vs. rough surface performance is really just a case of constant maximum amplitude deflection vs. varying maximum amplitude deflection of the tire casing. For a given tire, at any given tire pressure, the rough surface values will be higher than the smooth surface values...but only because the max amplitudes will be greater for a given speed, and thus more energy is being dissipated in the tire.

Despite what the authors claim, there is no logical explanation for why a tire would perform excellent on a smooth surface relative to other tires (at moderate pressures), yet perform poorly relative to those same tires on a rougher surface (at the same pressures). The only difference in the 2 cases is the maximum amplitude of the casing deflections.

Now...if you start reducing the casing deflections by running too high of pressures, or using a tire with a stiff casing, you start getting into vibrational losses in the rest of the bike+rider system. But, the only tires they tested at "excessively" high pressures (where you'd expect to start seeing these losses) were the tubulars...and, in fact, they did run slower at the higher pressures. BUT, the clinchers were only tested to a max of 105psi, which is still well within their "optimum" for surfaces of normal roughness. In other words, any "suspension losses" they were observing were completely in the tire casing.

A steel wheel is NOT a pneumatic tire.


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## DrRoebuck (May 10, 2004)

I first tried Michelin latex tubes on an aluminum bike and immediately felt like the ride was smoother, and with no noticeable change in rolling resistance. I was not expecting this result and not looking for this result. It's just something I noticed.

After getting a carbon bike, I stuck with the latex, until I got different tires that were extremely difficult to mount. The latex tubes made the mounting just about impossible. So, figuring I was on carbon now and the smoothness wouldn't be as important, I switched to Butyl. I ended up not liking the tires, so switched back to Vreds Fortezza Tri-Comp. Then after a while, had some trouble with flats, so I decided to try switching back to latex. Again, the smoothness on the road was absolutely discernible, and the bike felt faster overall. I don't have stats to back any of this up, just personal experience. Now I'm a latex tuber for life.

As far as flats, I've had a couple due to glass/thorns, etc., but never a pinch, and definitely fewer than many of the people with whom I ride. They are trickier to mount; the most common problem I have re: flats is due to mounting, etc. But it's been a looong time since even that's happened.

And yes, the tires leak overnight.

Hope this helps.


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## burkeqc (Sep 25, 2006)

I have decided to use the latex tubes in my hard riding Conti tires. There was some ride improvement with heavier training wheel tires. Using a rolling resistance test from Bike Tech Review, which I consider fairly close to road conditions, I estimate a speed increase at 18.7MPH of approx 1%. It will be a lessor % at higher speeds, higher % at lower.


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