# Tire blow-offs. What is your experience?



## dcgriz (Feb 13, 2011)

There's been a significant amount of discussions lately on several forums about tires blowing off rims.

When it happens during or immediately after a tubed tire change, potential reasons are usually linked to a pinched or faulty inner tube. No surprises here as it has been, is and will be happening for as long as tubes are used. 

What is surprising and problematic however are the blow-offs reported to mysteriously happen after the tire/tube have seen lengthy use, the bike is parked and found with the tire blown off. Operator error still is a possibility, specially when latex tubes are used, but considering that some of the people reporting are either seasoned cyclists or in the bicycle business, it makes me wonder what really is going on. 

When these type of blow-offs happen the typical reaction is to blame the tire. Blame poor QC, poor bead construction or whatever else and move on to another tire. When tire manufacturers are confronted, the finger tends to point to the direction of the rim manufacturer not manufacturing rims in accordance to standards.

Going over several threads reporting the "inexplicable" blow-offs I notice a pattern developing. A lot of them, if not most, are with the super wide tubeless/tubeless ready rims (inner rim width of 19mm+) when fitted with tires of width that is outside the ETRTO standards.

Meeting ETRTO has caused a lot of controversy in the past as these standards have been regarded as unnecessarily too conservative even from authorities in the bicycle world as renowned as the late Mr. Brown. This is true and countless trouble free miles have been put on 17mm rims with 23mm tires.

What is happening now with the newer developments in rim design, however, I think has really stretched the envelope and pushed us into a new territory. It seems to me that the super wide tubeless/tubeless ready inner rims have exhausted the compliance safety margins between tire and rim and when narrower tires (specially ones with supple walls like the Challenge or Veloflex) are used the potential for the tire blowing off the rim is exaggerated. Maybe its time to start looking at the ETRTO stds more seriously than before when using these setups.

Incidentally, I never had any issue with non-tubeless ready rims up to 17mm inner width and any size tire I used; even below the ETRTO standrds. Anything from 23mm Contis on HED C2 to 32mm Strada Bianca on 23mm Archetype. However I do not feel as comfortable with the newer stuff.

What say you?


----------



## ziscwg (Apr 19, 2010)

I've never had a tire blow off using 15mm and 19mm (tubeless) rims (internal width)

I only use 25 or 27 mm tires. The 23 mm tires are just too harsh for me. I'm a knuckle draggin' mtb biker who is used to 140mm of squish.

Running 23 mm tires on 24-25 mm rims (external width) is supposed to be the most aero. However, it's not all that aero if you flat. 

I can see going too wide for a certain tire could be an issue if the bead does not seat correctly. 

I actually feel more comfortable with the new stuff. Maybe because I run 25 mm tires all the time. Or, I like to hear that bead snap when I inflate the tires on the tubeless compatible.


----------



## dcgriz (Feb 13, 2011)

The other thing that is happening to further confuse us all is tire sizing inconsistencies. A 25mm tire may actually measure 28mm on the rim while a 27mm may measure 25mm. 

The mishaps I hear, seem to concentrate more on the "plus" rims. Rims like the Ardennes + at an inner width of 20.6mm outfitted with tires way below the ETRTO listed widths.


----------



## jfaas (Jan 31, 2014)

This is a little concerning as I have outfitted my wife's bike with SL23 V1 rims and Conti GP4000s II 23 mm tires. Have you heard any blow off with this combination? I'm relatively new to the wide rims and have not experienced any blow off events.


----------



## tednugent (Apr 26, 2010)

I had a blowoff of conti gp 4-season on Stan's alpha 400 after install

Reinstall. No issues


----------



## Marc (Jan 23, 2005)

dcgriz said:


> The other thing that is happening to further confuse us all is tire sizing inconsistencies. A 25mm tire may actually measure 28mm on the rim while a 27mm may measure 25mm.
> 
> The mishaps I hear, seem to concentrate more on the "plus" rims. Rims like the Ardennes + at an inner width of 20.6mm outfitted with tires way below the ETRTO listed widths.


23s-28s (sidewall rating) on Belgium+ rims. No blowouts here, either tubed or tubeless.


----------



## November Dave (Dec 7, 2011)

Funny, I was just thinking about this very issue last night. The ERTRO chart is basically useless. What "is" a 23mm or 25mm tire? One that measures that width on some standard rim? Is there some "flatten the tire out and x distance between the beads makes it a y-sized tire" thing? 

Is there any evident reported correlation between tire pressure and this happening?


----------



## Marc (Jan 23, 2005)

November Dave said:


> Funny, I was just thinking about this very issue last night. The ERTRO chart is basically useless. What "is" a 23mm or 25mm tire? One that measures that width on some standard rim? Is there some "flatten the tire out and x distance between the beads makes it a y-sized tire" thing?
> 
> *Is there any evident reported correlation between tire pressure and this happening?*


I'd figure if there was there'd be a CPSC or some such advisory out on it, given the risks to life/limb from a blowout at speed.


----------



## dcgriz (Feb 13, 2011)

November Dave said:


> Funny, I was just thinking about this very issue last night. The ERTRO chart is basically useless. What "is" a 23mm or 25mm tire? One that measures that width on some standard rim? Is there some "flatten the tire out and x distance between the beads makes it a y-sized tire" thing?
> 
> Is there any evident reported correlation between tire pressure and this happening?


I dont think we should be in a hurry to dismiss the value of ETRTO, if for nothing else just for the need of having some traces of a common base to limit experimentation from the public. The inconsistencies in declared tire sizing vs. actual size dont help either. 

In a recent interview of Mavic's Brunand with BikeRadar he said:

"We have not gone crazy wide for a reason, because there are compatibility and safety issues," Brunand said. A 19mm rim, for instance, should not be used with a tyre any narrower than 28mm, and a 17mm rim should not be used with anything smaller than 25mm, according to ETRTO (European Tyre and Rim Technical Organisation), which sets the international ISO standards. As its name implies, ETRTO is comprised of European tyre and rim manufacturers. As the wide-rim trend began, Michelin hosted other ETRTO companies at its facility, Brunand said, "to demonstrate that when you get outside these specifications there is a danger of the tyre blowing off the rim".


----------



## dgaddis1 (Sep 27, 2008)

tednugent said:


> I had a blowoff of conti gp 4-season on Stan's alpha 400 after install
> 
> Reinstall. No issues


Re-using a tire after it blows off is risky, the tire bead is often damaged during the blow off. Stan's Alpha rims have had some reports of blowoffs, I think it's the short sidewall to blame, not rim or tire width.

The one tire I've had blow off was a Challenge Strada Bianca (30mm) on a Pacenti SL23 v1 rim (18mm inner width), which is all good as far as the ETRTO chart is concerned. Wide rim, wide tire, all is bueno. I was using a Challenge latex tube, which apparently have a reputation for sucking.

The tire was STUPID hard to mount. The 2nd tire I mounted I actually pre-stretched by hand, and the bead is stretchy enough that it went on pretty easily. 1,000 times easier than the first tire. I did a ride or two on the tires without problems. Then one I rode to work one day (my morning commute has a 40mph downhill in traffic!!) and when it was time to go home I went out to the bike rack and found this:



Rode home gingerly, and pulled the tires off. A friend is turning one of them into a belt for me.


----------



## dcgriz (Feb 13, 2011)

Your tire/rim combo meets Challenge's recommendations. Challenge tubes have been problematic though. What happened to you may be more on the tube side rather than the rim/tire side. What pressures were you using?

From the Challenge website: http://www.challengetech.it/public/...lenge_Clincher_and_Foldable_Tires_low_res.pdf

_Matching tire sizes and rims

When choosing tires you are restricted to certain tire sizes by
the size of your rims. You will find the tire size marked on the
tire's sidewall. There are two designations for the tire size, with
the more precise one being the standardized millimeter sizing
system. The combination 50 – 559 corresponds, for example,
to a tire width of 50 mm in its inflated state and an (inside) diameter
of 559 mm. The other one is an inch-based designation
for the same tire which, in our example, would be 26 x 1.90.
For new tire fitments, observe rim width matches to DIN 7800:
N_

The DIN 7800 table looks similar to the ETRTO table.


----------



## dgaddis1 (Sep 27, 2008)

I don't remember the pressure, but it was low. The whole idea of using those tires was the make the bike more gravel capable than the tubeless 28's. The Challenge tires measured around 32mm on those rims, and juuuuust fit the bike. I want to say the pressure was somewhere around 50-60psi.

It was WAY less than the 90-130psi recommendation printed right there on the tire sidewall! Which really makes you think "WTF?!" doesn't it?


----------



## dcgriz (Feb 13, 2011)

I am not sure what this 90-130 psi stamp really means. The Challenge instructions say "Never exceed the recommended pressure range during use.". The max pressure limitation is obvious, the low end is not. 

I have been using the Strada Bianca on Archetype for my Rando rig for thousands of miles . I run mine at 85/70. So I have a horse in the race, lets say. No problems so far but I do have to say that the more the miles on the tire the much easier becomes to take the tire off the rim as the beads seem to stretch a lot.


----------



## dgaddis1 (Sep 27, 2008)

They were fun and rode well. But, I lost faith. Maybe it was the tubes. I can't wait to see the belt my buddy is making me though!


----------



## dcgriz (Feb 13, 2011)

I love these tires and with the Vittoria tubes I find them to be the closest thing to a tubular. 

I'm in the process putting a new rig together and was thinking of using 21mm rims and change tire sizes to suit the task at hand- but then got cold feet with all of these things happening. Non-tubeless rims are getting scarce to find and I'm sure the trend will continue and worsen as the road tubeless technology further develops. 

Trying to derive to a common denominator from people's bad experiences I find that to be:
super wide rims tubeless ready (eg 21mm), supple wall tires way off the ETRTO chart and low pressures. 

The accuracy of this determination is debatable because of the difficulty to decipher true cause from people's experiences as described but enough to cause me concern.

For the time being I decided to stay with what I have found to work for me so far


----------



## November Dave (Dec 7, 2011)

The value of the concept of a range of tire widths being appropriate for a range of rim widths is absolute. The current execution of that chart, where there is no definition of what any particular tire size actually is (I feel like Bill Clinton - it depends on what your definition of "is" is...), makes application of ERTRO standards nearly impossible. 

Let's say tire "a" measures 23mm on a 14mm inside Mavic. That's not within ERTRO guidelines. If you put it on a 17mm Kinlin and it measures 25mm, it's all of a sudden within ERTRO guidelines? Makes no sense at all.


----------



## dcgriz (Feb 13, 2011)

I have not. I have used and still use the Conti on Belgium C2, Archetype, Deep V, factory Mavic, factory Fulcrum, Enve, DT Swiss 585, CXP33, CXP22 and a few others without any issues.

I dont think your combo presents concern.


----------



## Marc (Jan 23, 2005)

dcgriz said:


> I dont think we should be in a hurry to dismiss the value of ETRTO, if for nothing else just for the need of having some traces of a common base to limit experimentation from the public. The inconsistencies in declared tire sizing vs. actual size dont help either.
> 
> In a recent interview of Mavic's Brunand with BikeRadar he said:
> 
> "We have not gone crazy wide for a reason, because there are compatibility and safety issues," Brunand said. A 19mm rim, for instance, should not be used with a tyre any narrower than 28mm, and a 17mm rim should not be used with anything smaller than 25mm, according to ETRTO (European Tyre and Rim Technical Organisation), which sets the international ISO standards. As its name implies, ETRTO is comprised of European tyre and rim manufacturers. As the wide-rim trend began, Michelin hosted other ETRTO companies at its facility, Brunand said, "to demonstrate that when you get outside these specifications there is a danger of the tyre blowing off the rim".


Personally...it sounds to me like Mavic is just making BS excuses to keep making 1980s narrow width rims in spite of what everyone other than them are doing. Mavic, the latest in 1980s rim design.

He really does nothing to back his stances. Especially given that most of the newer 23-25mm width rims are designed with tubeless in mind and therefore have stronger/better clincher beads than Mavic.


----------



## tvad (Aug 31, 2003)

In 30 years, I have never had a tire blow off a clincher road rim; over a dozen different rims and tires ranging from 19mm to 25mm.


----------



## Mike T. (Feb 3, 2004)

tvad said:


> In 30 years, I have never had a tire blow off a clincher road rim; over a dozen different rims and tires ranging from 19mm to 25mm.


Me neither in 30 yrs too (it was tubulars before that) even with old tires on Open Pro rims where fingers alone (no thumb or heel of hand struggle) can roll the whole tire and tube assembly off the rim in one motion.


----------



## dcgriz (Feb 13, 2011)

Greg Kopecky (now of HED) wrote a nice article on the matter during his tenure with his past employer Implications of Rim Width - Slowtwitch.com
with a noteworthy take home message:

"_The real take-home is that we should all educate ourselves on the topic, and understand that if we choose to go outside of the standards, it is at-your-own risk. As well, we should continue to push manufacturers for full-disclosure of their rim ETRTO sizes. Perhaps they will tell you if you call them up, but none currently publish this information of their new wide clincher rims."
_
Maybe Mavic is making excuses or simply exaggerating a situation to their benefit. I dont know and I dont think outsiders will ever know. What I know is that where there is smoke there is fire and appears there is enough smoke here to cause concern.


----------



## tvad (Aug 31, 2003)

dcgriz said:


> Maybe Mavic is making excuses or simply exaggerating a situation to their benefit.


Perhaps the take-away is to avoid Mavic wheels (although I've ridden Mavic Open Pro and R-SYS rims without any issues).


----------



## dcgriz (Feb 13, 2011)

Not surprised. This is the product of today's developments.

In the past, a clincher blow-off typically meant operator error (pinched tube) or faulty inner tube. Nowadays is developing to be more than that.


----------



## Marc (Jan 23, 2005)

dcgriz said:


> Greg Kopecky (now of HED) wrote a nice article on the matter during his tenure with his past employer Implications of Rim Width - Slowtwitch.com
> with a noteworthy take home message:
> 
> "_The real take-home is that we should all educate ourselves on the topic, and understand that if we choose to go outside of the standards, it is at-your-own risk. As well, we should continue to push manufacturers for full-disclosure of their rim ETRTO sizes. Perhaps they will tell you if you call them up, but none currently publish this information of their new wide clincher rims."
> ...


With all these statements from people on the topic...the complete lack of any kind of apparent technical analysis is rather deafening. No addresses why we should care about the ETRTO and why apparently no one does, given the unstandard standard IRL tire sizing variations on the same rim....and moreover how did anyone come up with that ETRTO sizing chart to begin with...and further if it still applies because wide-format rims have different (re: stronger) bead geometry than Open Pros of the 1980s, and that chart probably assumes that a 25mm rim is simply a sized up 15mm rim with the same sized beading.

I suspect the issue is tire manufacturers having QC issues with outsourcing. This summer I got a Schwalbe One 28mm tubed tire that was molded wrong. It had a lateral hop in the tread that turned out was molded into it at the factory. Increasingly manufacturers look to cut corners wherever they can get away with it. Could also be because people run wide-profile rims at lower pressures they damage the rim beads from bottoming out more easily without noticing it.


----------



## rm -rf (Feb 27, 2006)

My 23c GP4000S tires lock into my HED Ardennes Plus (25.6mm OD) rims, since the rim is designed to be tubeless compatible. I hear the bead make a noise as I'm pumping up the tire when the bead pops into the seat. When inflated, the tires measure 26.8 to 27.2 mm wide. Yes, the tires only extend about 1mm out on each side.

I've had a flat where both beads are still in the bead lock channel and I need a little thumb pressure to pop them loose. So it seems very stable to me.

~~~~~~~~~
I was on a group ride with a steep downhill. One of the riders rode the brakes all the way down, then had a front blowout (at low speeds, no crash) on the flat runout. It was LOUD. I assume the wheel heated up and the increased pressure pulled the bead over the rim.

When we helped replace the tube, I could see that the tire bead was extremely loose on the rim. No finger pressure was needed to pull the whole bead over the rim. That can't be good. Was it a badly designed/sized tire? I don't know the tire or rim info now.


----------



## rm -rf (Feb 27, 2006)

Older "non-hooked" rims with straight sided walls are limited on how much pressure and therefor how small a tire size they can safely use.

The rule used to be that a 27 inch rim couldn't go much over 80 psi, and a 1 1/4 inch tire was recommended over a 1 1/8. It's probably related to the angle that the tire and bead take at the rim. And that there's nothing to stop the bead from creeping upward if the bead is slightly oversized.

So the newer wide rims probably depend on the rim hook shape and the accurate tire bead to keep the effectively narrower tires on the wide rim.


----------



## Jay Strongbow (May 8, 2010)

I had one come off about 1000 miles after install. I specfically say 'come off' and not 'blow off' because it didn't make a sound. For a second I thought it was an ordinary flat then the part that come off started ticking on the brakes or whatever it rubbed on. 24 mm tire (Vit Pave) on a 19 mm rim (Kinlin 270). Nothing strange there. Total mystery. I put it back on and it was fine for another thousand or so until it wore out naturally. I'd have to think a user error would have been exposed much sooner and a damaged rim or tire would have made itself known subsequently.


----------



## Marc (Jan 23, 2005)

rm -rf said:


> Older "non-hooked" rims with straight sided walls are limited on how much pressure and therefor how small a tire size they can safely use.
> 
> The rule used to be that a 27 inch rim couldn't go much over 80 psi, and a 1 1/4 inch tire was recommended over a 1 1/8. It's probably related to the angle that the tire and bead take at the rim. And that there's nothing to stop the bead from creeping upward if the bead is slightly oversized.
> 
> So the newer wide rims probably depend on the rim hook shape and the accurate tire bead to keep the effectively narrower tires on the wide rim.


A trend I've noticed is a return of the recommended maximum tire pressure on rims. Ardennes and Belgiums are now listed as a 100PSI maximum on the HED site

https://www.hedcycling.com/ardennes/ardennes-plus/ardennes-plus-cl

Whether that is due to tubeless tires inducing more spoke-tension drop than standard clinchers at a given pressure...or blowout fears, who knows.


----------



## Roland44 (Mar 21, 2013)

tednugent said:


> I had a blowoff of conti gp 4-season on Stan's alpha 400 after install
> 
> Reinstall. No issues


That's strange. I never had a blowoff on my conti gp 4-season set.


----------



## dcgriz (Feb 13, 2011)

Good points.
ETRTO being a membership organization makes access of their documents difficult for the nonmember public to obtain.
I understand the following from reading about the ETRTO stds from different sources:
- rim width: distance between beads; determines how wide the casing could spread after inflation
- tire width: I believe the allowable range shown on the chart is based on the premise that the width of the inflated tire remains approximately equal to its height. When looked from this prospective there is room for these "tolerances" to somewhat expand and still maintain relatively reliable performance. Thus the assertion of being "too conservative".


----------



## tednugent (Apr 26, 2010)

Roland44 said:


> That's strange. I never had a blowoff on my conti gp 4-season set.


On what rim?

I have no issues with my Mavic Kysrium ELite. 

But the shorter bead hook height on the Stan's Alpha wheel means you need to be more careful getting the bead seated properly.

After it blew off a few minutes after install, I reinstalled it, then did 60 miles towing a trailer with no issues


----------



## rruff (Feb 28, 2006)

dcgriz said:


> Your tire/rim combo meets Challenge's recommendations. Challenge tubes have been problematic though. What happened to you may be more on the tube side rather than the rim/tire side.


I appreciate you starting this thread, but let's get something clear. 

*TUBES DO NOT AND CANNOT CAUSE BLOWOFFS!!!*

They aren't experiencing any stress if properly installed and even if a hole did develop, it would not blow the bead off the rim. It would just be a fairly fast leak down. 

My guess is that *tubeless ready rims with tiny insufficient bead hooks are the culprit.* 

When you pump the tire up, the tube has to pop the tire bead onto the shelf. This gives it an opportunity to sneak under the bead a bit. And you can't check it because the pressure is too high when that happens. 

Stan designed their own bead retention called BST, which is basically just a small ridge at the edge of the rim. This saves weight and makes the tire larger. But it sucks at keeping tires on. Instead of a standard hook bead which *doesn't even need to have the bead intact to work*, this design requires the bead to fit very tight on the rim. That's usually OK with tubeless tires, which have a stiff carbon bead, but iffy with regular tires that use a kevlar bead. 

Anyway, this wimpy bead hook seems to be a trend. The new SL23 has a much smaller hook than the old one.


----------



## tednugent (Apr 26, 2010)

rruff said:


> I appreciate you starting this thread, but let's get something clear.
> 
> *TUBES DO NOT AND CANNOT CAUSE BLOWOFFS!!!*
> 
> ...


Stan's BST works fine with Kevlar beads 

For low pressure MTB and cyclocross


----------



## dcgriz (Feb 13, 2011)

rruff said:


> I appreciate you starting this thread, but let's get something clear.
> 
> *TUBES DO NOT AND CANNOT CAUSE BLOWOFFS!!!*
> 
> ...


I have had two instances where a tube caused a tire blowing off the rim. One was a pinched tube which was clearly my error in hastily fixing a flat roadside in the middle of the night the other was not explained as easily. The cut was right at the foot of the valve in a place that could not have been possibly pinched by the tire bead. 

Is the later incident anecdotal? Is it representing a result that would not have happened if the tire-rim interphase had closer tolerances? I am not 100% sure because I don't have enough evidence either way. However, polling over older threads I fiound several people complaining about Challenge latex tubes busting at the valve causing blow-offs. 

I am glad you brought up the trend for wimpy bead hooks on the tubeless rims. I eluded to that in my OP but stayed clear of a direct discussion trying to see what people's impressions were without being prompted.
Out of the three interfaces of tube-rim, UST is the one defined by ETRTO. The "Stan's" and the TCS are not. Rims and tires are manufactured with tolerances all over the spectrum; in my opinion rims are more to blame. Some combinations work better than others, some don't work at all. It is left up to us to find which is which. In Europe wheels sold as OEM with the bikes must meet ETRTO standards; wheel sets or rims sold individually do not have to. In US there are no restrictions what so ever. Unless people keep on complaining this will continue to be happening because is profit driven.


----------



## rruff (Feb 28, 2006)

dcgriz said:


> The cut was right at the foot of the valve in a place that could not have been possibly pinched by the tire bead.


The cut would be caused by the tire coming off the rim at that spot. It doesn't have to be a pinched tube. Maybe there is something about the Challenge valve that results in poor seating of the bead? I never had an issue with them but stopped using them a few years ago. 

At any rate I just don't see a mechanism for a properly installed tube to cause a blowout. It's in very intimate contact with the tire and rim bed, and is contained. It is also under very little stress. If an opening develops in the tube but not the container, then the air is going to leak out slowly. A blowout can only be caused by a sudden and large opening in the container.


----------



## dcgriz (Feb 13, 2011)

rruff said:


> The cut would be caused by the tire coming off the rim at that spot. It doesn't have to be a pinched tube. Maybe there is something about the Challenge valve that results in poor seating of the bead? I never had an issue with them but stopped using them a few years ago.
> 
> At any rate I just don't see a mechanism for a properly installed tube to cause a blowout. It's in very intimate contact with the tire and rim bed, and is contained. It is also under very little stress. If an opening develops in the tube but not the container, then the air is going to leak out slowly. A blowout can only be caused by a sudden and large opening in the container.


The tear was at the base of the valve and 3" or 4" long. I only had one incident so definite conclusions are difficult to be drawn; enough suspicions though to make me change products. No tears at the valve incidents since I switched to Vittoria latex and I do use latex tubes with almost all of my clinchers. Lots of talcum powder too, to avoid any part of the tube from fusing onto the tire.


----------



## rruff (Feb 28, 2006)

dcgriz said:


> The tear was at the base of the valve and 3" or 4" long.


A long tear in the tube is the typical symptom of a tire coming off the rim. Not the cause.


----------



## ziscwg (Apr 19, 2010)

tednugent said:


> Stan's BST works fine with Kevlar beads
> 
> For low pressure MTB and cyclocross


Friends don't let friends use Stans rim without a tube


----------



## dcgriz (Feb 13, 2011)

rruff said:


> A long tear in the tube is the typical symptom of a tire coming off the rim. Not the cause.


So basically the product of improper tube installation.

Consider this hypothetical scenario and tell me what you think. Let's start with the assumption the tube has been properly installed and confirmed as such by lifting both tire beads around the tire to make sure the tube is not pinched. Let's also say the tire has undergone several inflation-deflation sequences to make sure the tube is not folded.

Let's now say that we ride this wheel in a fashion liable of generating heat. Is it possible that this could cause a bead lift-up able to pinch the latex tube under it? Now to make things worst (and to go along with subject of this thread) consider an improper tire-rim interface, either due to tire being way too small for the rim (ie significantly off ETRTO stds) or skimpy rim hooks or combination of both. Do you think that under this scenario, an otherwise properly installed tube could blow the tire off the rim?


----------



## dgaddis1 (Sep 27, 2008)

dcgriz said:


> Let's now say that we ride this wheel in a fashion liable of generating heat. Is it possible that this could cause a bead lift-up able to pinch the latex tube under it?


No. Why would it lift because it got warm?


----------



## dcgriz (Feb 13, 2011)

dgaddis1 said:


> No. Why would it lift because it got warm?


Increased volume and pressure from air expansion. Extended braking coming down switchbacks can easily heat up the tire/tube if one rides the brakes. Too much and for too long could significantly heat up the rims.


----------



## velodog (Sep 26, 2007)

Something from "Off the Beaten Path" about rim design.

https://janheine.wordpress.com/2012/05/24/mounting-tires-on-rims-with-deep-wells/


----------



## dcgriz (Feb 13, 2011)

velodog said:


> Something from "Off the Beaten Path" about rim design.
> 
> https://janheine.wordpress.com/2012/05/24/mounting-tires-on-rims-with-deep-wells/


Yeah, Jan is pretty vocal of not riding on poorly seated tires. Each Compass tire he sells comes with instructions on how to visually make sure the tires are properly fitted.


----------



## dgaddis1 (Sep 27, 2008)

dcgriz said:


> Increased volume and pressure from air expansion. Extended braking coming down switchbacks can easily heat up the tire/tube if one rides the brakes. Too much and for too long could significantly heat up the rims.


I don't see the heat (and higher air pressure) causing the tire to lift any more than it would already be lifted (and stopped by the hook of the rim sidewall). You could increase the pressure enough to push it off the rim though. But I don't think it's from the tube getting under it.

I also can't figure out how a tube bursting would cause a tire to blow off the rim. It's not like the tire is seeing an increase in pressure from the tube bursting, it's still the same amount of air inside the same amount of space at the same temperature.

I think the tire gets pushed off the rim, and the tube follows and gets torn up.

I don't ride with tubes anymore tho


----------



## dcgriz (Feb 13, 2011)

dgaddis1 said:


> I don't see the heat (and higher air pressure) causing the tire to lift any more than it would already be lifted (and stopped by the hook of the rim sidewall). You could increase the pressure enough to push it off the rim though. But I don't think it's from the tube getting under it.


I think its the same concept as increasing the pressure enough to push it off the rim. Poor tire-rim interface, inappropriate rim hooks, etc. appear to make it easier to happen.





dgaddis1 said:


> I also can't figure out how a tube bursting would cause a tire to blow off the rim. It's not like the tire is seeing an increase in pressure from the tube bursting, it's still the same amount of air inside the same amount of space at the same temperature.
> 
> I think the tire gets pushed off the rim, and the tube follows and gets torn up.


The bead is already lifted off the rim when the tube is pinched under it so when the tube bursts the location of the pinched tube is where the highest pressure differential exists and that's where the air rushes to get out from the tire completely dislodging it from the rim.


----------



## AllanMuir (Sep 9, 2015)

This is interesting - I recently had a nasty accident that lost me two teeth and gave me concussion. I'm almost recovered but I do not yet understand what actually happened to cause the accident - I have no memory of any of it, but tyre blow-off may be the cause.

I have returned to the scene, examined GPS records and my bike and taken note of comments from the rider behind me. These provide the following facts:



I was cycling at around 35 to 40kmph through a village street that was reasonably wide and the tarmac road was in pretty good condition
7 cyclists were riding in single file, I was number 6.
I passed over a small pothole - a 9"x9" water-board plate that was recessed into the tarmac by about 1 inch or so.
My rear wheel then "fish-tailed" according to the rider behind me.
I then fell to my left and sustained left elbow, shoulder and facial injuries - legs were fine.
The bike (racing bike with drop handlebars) was not too bad - £100 to repair. Both 105 shifters were scruffed and 1 needed replacing
The front tyre (25mm) bead had blown out from the clincher wheel over about 3 inches - presumably from the pothole impact. It remained inflated (100psi originally). Later the blow-out did not "seem" to affect the wheel stability or rub against the brake block under examination (slow speed).
The rear tyre had evidence of skidding, but was not seriously worn.

So my question is: Does anyone have experience of travelling at speed with the front tyre protruding from the wheel slightly? I can only imagine that it caused some instability and that I over-reacted or braked hard in an effort to control it.


----------



## dgaddis1 (Sep 27, 2008)

So, the front tire was partially off the rim, but didn't actually blow and go flat?

What tire, and what rim?


----------



## AllanMuir (Sep 9, 2015)

The Wheels are Campagnolo Khamsim (700c) and the tyres are Schwalbe Durano - either 25 or 23 mm (Can't check until home from work).


----------



## Blue CheeseHead (Jul 14, 2008)

I run Hed Ardennes Plus and have had no issues running 23's. BTW, 23's installed on the Plus rims yield a 25.7mm width, thus I actually downsized from running 25's on standard 19mm rims to 23's on the 25mm Plus.


----------

