# Higher pressure than what's recommended on Zipp Firecrest



## stevepeter833 (Dec 22, 2012)

Hi everyone,

I'm running Zipp 303 front and 404 rear on my bike. On Zipp's website it says that max tire pressure is 125psi. However, I just purchased tire-set from Wiggle prior to checking Zipp's website: Vredestein Fortezza Senso Xtreme Weather which minimum pressure is 115psi and max is 175psi. 

I have pumped my tires at 120psi because I'm nervous of going beyond 120psi and left the 5psi buffer just in case. By pumping the tire at 120psi it feels as if it's flat since the tire can take up to higher psi ie. 175.

So far it has been riding OK but I wonder what effect it could have on the Zipp wheel if I pump the tire to more than 125psi since the tire can take up to 175psi or should I change the tires instead?

PS: my weight is 72.5kg.


Thanks for the help,
Steve


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## NealH (May 2, 2004)

I think that the rim integrity can't be guaranteed if you pump past 125 psi. Also, ride quality suffers with higher pressure. Zipp probably provides guidance on tire size so you can check with them, or the website. Myself, I like 25mm tires (Conti 4000) as I run them at 80# and the ride is very smooth.....and never a flat. 

I am at a loss to understand the 115# minimum pressure on the Vredesteins, especially being an extreme weather type tire. I believe I would send them back and get a pair of Conti's, Michelin or other reputable bike tire. Again, Zipp has good customer service so maybe ask them for advice. Zipp wheels are very good.


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## QuattroCreep (Nov 30, 2009)

At your weight 100psi will be plenty for the 23c and a little less on the 25c. You don't mention what width you have. 

Tires don't feel flat because they can be pumped up to 175psi and only have 100psi. 100psi feels like 100psi. Unless you ride on only super smooth roads or the track 175psi is way to much.


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## stevepeter833 (Dec 22, 2012)

Thanks everyone for the reply. Just received a response from Zipp (dang, they replied literally in 5 minutes after query submission) saying that I shouldn't be running more than 125psi or the tire may roll and cause personal injuries.

So I should probably return the tire and get some other brand.


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## Blue CheeseHead (Jul 14, 2008)

120 psi is too much for someone of your weight. I am with Quattro, 100 psi is plenty for the rear and 95 or so for the front.

To put your mind at ease, you would not notice much difference at 120 vs 175psi as the ride would be stiff at either pressure.


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## Jay Strongbow (May 8, 2010)

stevepeter833 said:


> Thanks everyone for the reply. Just received a response from Zipp (dang, they replied literally in 5 minutes after query submission) saying that I shouldn't be running more than 125psi or the tire may roll and cause personal injuries.
> 
> *So I should probably return the tire and get some other brand*.


No, you should ignore what's printed on the side wall. Vredestein makes great tires and like Vittoria and several other brands what they print for min/max on the side wall is a complete mystery.
Literally millions of people just ignore that and use less than the min. printed on the sidewall with no problems.


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## cxwrench (Nov 9, 2004)

I have never been able to understand why Vredestein seems to think their tires will work well w/ insane pressure. PSI is PSI...it doesn't matter which tire or how it's made. ANY tire at over 120psi is basically wayyyyyyyyy to hard to function as a pneumatic tire. It becomes a rubber covered rock. Keep the tires, run 100psi MAX in the rear and 10% or more lower in the front. You'll love them. The will NOT feel slow, that's all in your head.


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## November Dave (Dec 7, 2011)

+1 to everyone saying ignore the label. 

The lawyers want as low a number as possible so people don't go blowing tires off the rims. The marketing department wants as high a number as possible so people will think it's a super great tire. Neither considers what might actually work best. 

Start at 95 front 105 rear or something around there, and tune it from there to how it works best for you.


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## Marc (Jan 23, 2005)

cxwrench said:


> I have never been able to understand why Vredestein seems to think their tires will work well w/ insane pressure. PSI is PSI...it doesn't matter which tire or how it's made. ANY tire at over 120psi is basically wayyyyyyyyy to hard to function as a pneumatic tire. It becomes a rubber covered rock. Keep the tires, run 100psi MAX in the rear and 10% or more lower in the front. You'll love them. The will NOT feel slow, that's all in your head.



Also you detension the spokes as you go higher in pressure.


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## stevepeter833 (Dec 22, 2012)

OK thanks for all the replies. Will try that soon. Yeah I normally run both 100psi max on rear and front anyway. The only reason I run 120psi is simply because the tires say min 115psi on the wall. Cheers.


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## cxwrench (Nov 9, 2004)

stevepeter833 said:


> OK thanks for all the replies. Will try that soon. Yeah I normally run both 100psi max on rear and front anyway. The only reason I run 120psi is simply because the tires say min 115psi on the wall. Cheers.


Why would you run the same pressure frt/rr when clearly there is more weight on the rear?


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## SauronHimself (Nov 21, 2012)

stevepeter833 said:


> PS: my weight is 72.5kg.
> 
> 
> Thanks for the help,
> Steve


Technically, you don't _weigh_ 72.5 kg. That's your mass. You weigh 711 newtons, or about 160 lbs in English units. There is no reason you should be running above 100 PSI for your weight.


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## Guod (Jun 9, 2011)

SauronHimself said:


> Technically, you don't _weigh_ 72.5 kg. That's your mass. You weigh 711 newtons, or about 160 lbs in English units. There is no reason you should be running above 100 PSI for your weight.


Hooray for technicalities! ;D

FWIW I have the same MASS and run 85psi front 90psi rear with a set of 25c tires. No real issue with pinch flats and we have some crappy roads around here. With 23c, it's more like 90psi front, 95psi rear.


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## berserk87 (Jul 24, 2014)

Marc said:


> Also you detension the spokes as you go higher in pressure.


That's an added element that had not occurred to me. I wonder how significantly pressure can affect spoke tension? I'm sure the higher the pressure, the more of a factor it is.


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## Marc (Jan 23, 2005)

berserk87 said:


> That's an added element that had not occurred to me. I wonder how significantly pressure can affect spoke tension? I'm sure the higher the pressure, the more of a factor it is.


The effect is easily measurable with a Park TM-1 at standard road pressure (i.e. 100PSI). The effect is also grater for tubeless tires than clinchers at a given pressure. [email protected] has noted it, Boyd's seen it, Lennard Zinn has noted it on his TechFAQ column on occasion.

How bad it is at ludicrous pressures like 130PSI plus on a clincher isn't something I can say I've ever wated to find out.


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## November Dave (Dec 7, 2011)

It definitely happens. It's also definitely more profound with tubeless. At 100 psi, a front wheel with 100 KGF on the spokes will typically drop eight or nine KGF with a tubed tire. We haven't measured enough tubeless to give a broad average statement like that. Oddly, rim choice seems to have little effect on this. That is to say, they all do it, to about the same degree.

It's more of a threat on a rear wheel, where you are sort of fighting to hold onto all of the non-drive side spoke tension that you can get.


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## stevesbike (Jun 3, 2002)

this is very useful advice for when you do time trials on the moon. Thanks


SauronHimself said:


> Technically, you don't _weigh_ 72.5 kg. That's your mass. You weigh 711 newtons, or about 160 lbs in English units. There is no reason you should be running above 100 PSI for your weight.


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## AM999 (Jan 22, 2007)

Blue CheeseHead said:


> 120 psi is too much for someone of your weight. I am with Quattro, 100 psi is plenty for the rear and 95 or so for the front.
> 
> To put your mind at ease, you would not notice much difference at 120 vs 175psi as the ride would be stiff at either pressure.


Yes, no need to go any higher than ~ 120 psig. In fact on a real road with surface roughness the rolling resistance will actually increase with increasing pressure above ~ 120 psig (depending on roughness and weight). And the slope is much steeper with over pressure than under pressure so it's best to be a bit under pressure than over. When I was racing (time trials) me and bike were ~ 205 lbs. I'd pump up to ~ 130 psig on very smooth roads - lower for rougher surfaces. If it feels like you are hopping around a bit your tire pressure is too high.

Here is an article by Tom Anhalt with more info on optimum pressure:

What's in a tube? - Slowtwitch.com


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## CactoesGel (Aug 16, 2014)

I say sell the Zipp...

to me! 

I'm 143 lbs and running 100 psi F/R on a 23mm. I'm going to take your advice and do 90 psi front and see if I go faster.


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## AM999 (Jan 22, 2007)

CactoesGel said:


> I say sell the Zipp...
> 
> to me!
> 
> I'm 143 lbs and running 100 psi F/R on a 23mm. I'm going to take your advice and do 90 psi front and see if I go faster.


Reducing that low will actually reduce your speed slightly. On a good road surface I'd run ~ 110 at your weight.


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## cxwrench (Nov 9, 2004)

AM999 said:


> Reducing that low will actually reduce your speed slightly. On a good road surface I'd run ~ 110 at your weight.


At 143lb? He could run 80/90 and be just as fast. As I've posted time and time again the rolling resistance part of this equation is minimal. Where @CactoesGel would see an improvement is cornering traction and comfort.

There is no need for a 143lb rider to run 100psi, much less more, no matter how good the pavement is.


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## AM999 (Jan 22, 2007)

cxwrench said:


> At 143lb? He could run 80/90 and be just as fast. As I've posted time and time again the rolling resistance part of this equation is minimal. Where @CactoesGel would see an improvement is cornering traction and comfort.
> 
> There is no need for a 143lb rider to run 100psi, much less more, no matter how good the pavement is.


To achieve maximum speed per watt the pressure at that weight would be ~ 110 psig on good pavement. On a very smooth surface, track racers always run ~ 200 psig because there is no worry about surface roughness. On a real road however the roughness will actually reduce speed as tire pressure increases. Reducing pressure will reduce speed. That's what the data indicates. But if you want comfort and cornering (lower pressure means larger contact patch) then reduce pressure but watch out for pinch flats.


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## cxwrench (Nov 9, 2004)

AM999 said:


> To achieve maximum speed per watt the pressure at that weight would be ~ 110 psig on good pavement. On a very smooth surface, track racers always run ~ 200 psig because there is no worry about surface roughness. On a real road however the roughness will actually reduce speed as tire pressure increases. Reducing pressure will reduce speed. That's what the data indicates. But if you want comfort and cornering (lower pressure means larger contact patch) then reduce pressure but watch out for pinch flats.


Tell me more about these track racers and their 200psi. I've worked at a few UCI world cups and a bunch of national championships...there is one group in particular that run really high pressure. The majority do not. 

Also tell me where you're getting your numbers on pressure/efficiency. 

And where you're finding this perfect pavement...


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## AM999 (Jan 22, 2007)

cxwrench said:


> Tell me more about these track racers and their 200psi. I've worked at a few UCI world cups and a bunch of national championships...there is one group in particular that run really high pressure. The majority do not.
> 
> Also tell me where you're getting your numbers on pressure/efficiency.
> 
> And where you're finding this perfect pavement...


The track racers that I know - state, national, and world masters participants and winners - all run 200 psig on the smooth wooden tracks. On concrete outdoor tracks they will still run high pressure but use more durable tires. The tires of choice are the Vittoria Pista tubular track tires - the VF Record tubular has a very low Crr but is only rated to 145 psig. On the really smooth wooden indoor tracks some will use the FMB silk casing track tires with latex rubber treads. Never tested on but held one in my hand - it was like a wet noodle hanging off my finger - had to be very fast.

It's not about efficiency but about the hysteresis in the compression of the tire sidewall as the wheel rotates. The weight of the rider compresses the tire flexing the sidewall. As the tire rotates the load is removed and aome (but not all) of the stored energy is returned (the difference manifests as heat in the tire). What this results in is a moment around the center of the center of the contact patch which act as a false flat even though you are riding on a dead flat road - hence resistance to forward motion aka rolling resistance. I posted the link above in which Tom Anhalt did some Chung testing and showed that the optimum pressure for his & bike weight (~ 185 lbs) is ~ 120 psig on a very good asphalt outdoor surface. I rode his course in a car. The testing that I have done on Crr can be found on Bike Tech Review. I haven't done any in the last few years but Tom has taken up the torch so to speak.

A track surface is the closest to "perfect pavement" as you will get. Rollers are very smooth and show that Crr goes down as pressure goes up (100 - 200 psig) with all else held constant.


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## Marc (Jan 23, 2005)

AM999 said:


> A track surface is the closest to "perfect pavement" as you will get. Rollers are very smooth and show that Crr goes down as pressure goes up (100 - 200 psig) with all else held constant.


It is a good thing we all ride plastic rollers all day long. Otherwise that conclusion might be utterly useless in the real world.


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## AM999 (Jan 22, 2007)

Marc said:


> It is a good thing we all ride plastic rollers all day long. Otherwise that conclusion might be utterly useless in the real world.


That conclusion is perfectly valid for a smooth track surface.


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## ericm979 (Jun 26, 2005)

Where does the 110psi for road use come from?


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## cxwrench (Nov 9, 2004)

AM999 said:


> The track racers that I know - state, national, and world masters participants and winners - all run 200 psig on the smooth wooden tracks. On concrete outdoor tracks they will still run high pressure but use more durable tires. The tires of choice are the Vittoria Pista tubular track tires - the VF Record tubular has a very low Crr but is only rated to 145 psig. On the really smooth wooden indoor tracks some will use the FMB silk casing track tires with latex rubber treads. Never tested on but held one in my hand - it was like a wet noodle hanging off my finger - had to be very fast.
> 
> It's not about efficiency but about the hysteresis in the compression of the tire sidewall as the wheel rotates. The weight of the rider compresses the tire flexing the sidewall. As the tire rotates the load is removed and aome (but not all) of the stored energy is returned (the difference manifests as heat in the tire). What this results in is a moment around the center of the center of the contact patch which act as a false flat even though you are riding on a dead flat road - hence resistance to forward motion aka rolling resistance. I posted the link above in which Tom Anhalt did some Chung testing and showed that the optimum pressure for his & bike weight (~ 185 lbs) is ~ 120 psig on a very good asphalt outdoor surface. I rode his course in a car. The testing that I have done on Crr can be found on Bike Tech Review. I haven't done any in the last few years but Tom has taken up the torch so to speak.
> 
> A track surface is the closest to "perfect pavement" as you will get. Rollers are very smooth and show that Crr goes down as pressure goes up (100 - 200 psig) with all else held constant.


Did you miss the part where I said I've actually worked at the world cup level? I know from first hand experience what pressure is used. Pursuit, TT, and Team Sprint racers are about the only ones maxing out pressures. Sprinters and mass start racers are not using anywhere near that pressure and they're the vast majority of participants at any given event.


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## AM999 (Jan 22, 2007)

cxwrench said:


> Did you miss the part where I said I've actually worked at the world cup level? I know from first hand experience what pressure is used. Pursuit, TT, and Team Sprint racers are about the only ones maxing out pressures. Sprinters and mass start racers are not using anywhere near that pressure and they're the vast majority of participants at any given event.


Why are those competitors using the highest pressure possible?

The other types of racers are giving up some speed by running lower pressures. Why is that? Have you asked them why they run lower pressures in different events or possibly why the same racer might change pressures when racing different events? Possibly it is about the relative importance of absolute speed vs. handling in different events.


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## AM999 (Jan 22, 2007)

ericm979 said:


> Where does the 110psi for road use come from?


I don't know - most likely some kind of rule of thumb. I use 120 psig which is based on the clincher tire manufacturer's recommendations. Clincher's are limited by wheel construction in many cases. Tubulars are limited by tire construction but road roughness actually limits the optimum pressure to run a bicycle tire with regard to minimizing rolling resistance. The smoother the surface the higher the pressure to achieve the maximum speed. Speed is not the only consideration however.


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## cxwrench (Nov 9, 2004)

AM999 said:


> Why are those competitors using the highest pressure possible?
> 
> The other types of racers are giving up some speed by running lower pressures. Why is that? Have you asked them why they run lower pressures in different events or possibly why the same racer might change pressures when racing different events? Possibly it is about the relative importance of absolute speed vs. handling in different events.


The racers I listed run the highest pressures possible because on a wood track as you stated it's the fastest tire. They don't have to maneuver, just ride as fast as they can at the bottom of the track. TT and Team Sprint for the same reason. 

Mass start racers on the other hand do have to maneuver and their speeds are variable. Last time I as at the track in Carson the mass start girls were running between 130-140psi. 

On the concrete track in San Jose I run 110 at most as that track is pretty rough. As far as I'm concerned NO rider needs over 100 on the road, whether they're racing or not. If they do to avoid damaging wheels, they need bigger tires. Rolling resistance changes are tiny compared to gains in traction. Traction is a must...if your tire is hard as a rock you're endangering yourself and the other riders around you if you crash.


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## AM999 (Jan 22, 2007)

cxwrench said:


> The racers I listed run the highest pressures possible because on a wood track as you stated it's the fastest tire. They don't have to maneuver, just ride as fast as they can at the bottom of the track. TT and Team Sprint for the same reason.
> 
> Mass start racers on the other hand do have to maneuver and their speeds are variable. Last time I as at the track in Carson the mass start girls were running between 130-140psi.
> 
> On the concrete track in San Jose I run 110 at most as that track is pretty rough. As far as I'm concerned NO rider needs over 100 on the road, whether they're racing or not. If they do to avoid damaging wheels, they need bigger tires. Rolling resistance changes are tiny compared to gains in traction. Traction is a must...if your tire is hard as a rock you're endangering yourself and the other riders around you if you crash.


What tires and pressures do Mark R. and Larry N. run and in what events? A few weekends ago I gave a couple of Vittoria Cronos (a 20 and a 22) to Ray G. who asked my advice - Mark R. was also interested. Also ask Mark R. about my roller tests and their validity.

On the road it's better run pressure that's below the optimum than above. For handling a bigger contact patch resulting from lower pressures. In mass start races you may want to give up some speed for handling. Since mass start races are more tactical absolute speed is less important.


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## cxwrench (Nov 9, 2004)

AM999 said:


> What tires and pressures do Mark R. and Larry N. run and in what events? A few weekends ago I gave a couple of Vittoria Cronos (a 20 and a 22) to Ray G. who asked my advice - Mark R. was also interested. Also ask Mark R. about my roller tests and their validity.
> 
> On the road it's better run pressure that's below the optimum than above. For handling a bigger contact patch resulting from lower pressures. In mass start races you may want to give up some speed for handling. Since mass start races are more tactical absolute speed is less important.


I haven't been down at all this year, but I miss racing w/ all those guys for sure. Larry is a freak of nature and a great guy. Mark just still keeps going fast, and Ray is great. Hellyer has a great crew of masters racers. 

I definitely agree w/ what you're saying about mass start races, that's exactly my thinking.


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## AM999 (Jan 22, 2007)

cxwrench said:


> I haven't been down at all this year, but I miss racing w/ all those guys for sure. Larry is a freak of nature and a great guy. Mark just still keeps going fast, and Ray is great. Hellyer has a great crew of masters racers.
> 
> I definitely agree w/ what you're saying about mass start races, that's exactly my thinking.


Mark and Ray are my sources for track info. Mark is the one who indicated that he was not interested in the VF Record tubular because it is only rated to 145 psig. I sagged Larry in on the Mt. Hamilton RR after he "disintegrated" a CF front wheel descending down the backside.

Hellyer is a much different beast than an indoor wood track.


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## SPlKE (Sep 10, 2007)

Great thread.

Thanks!


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## ValbyDK (Aug 27, 2014)

cxwrench said:


> I have never been able to understand why Vredestein seems to think their tires will work well w/ insane pressure. PSI is PSI...it doesn't matter which tire or how it's made. ANY tire at over 120psi is basically wayyyyyyyyy to hard to function as a pneumatic tire. It becomes a rubber covered rock. Keep the tires, run 100psi MAX in the rear and 10% or more lower in the front. You'll love them. The will NOT feel slow, that's all in your head.


Hi cxwrench - you seem to be a common-sense-guy - : rubber covered rock is my experience as well with psi > 100
Carsten


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## stevepeter833 (Dec 22, 2012)

All, it has been a week or so since I owned the tire and I have now pumped them to 100psi max for both rear and front. And yes, I can confirm that they don't feel as if they're punctured and I have no problems whatsoever so far.

Strangely, when I pumped to 120psi I felt that "puncture" feeling but not with 100psi. So I guess I have learnt something new now that I shouldn't worry about the sidewall printing. Thanks so much for all these great info.

@CactoesGel: Yep I'm thinking of selling them because with 15-35kmh crosswind daily in Perth that rear 404 especially gives me headache. PM me if you're still interested. I'm looking for 38-40mm depth max.


Steve


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## velodog (Sep 26, 2007)

Guod said:


> Hooray for technicalities! ;D
> 
> FWIW I have the same MASS and run 85psi front 90psi rear with a set of 25c tires. No real issue with pinch flats and we have some crappy roads around here. With 23c, it's more like 90psi front, 95psi rear.


I run the same PSI in 25's as you and I'm 185 lbs. The same in 23's.


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