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PostPosted: Fri Mar 02, 2012 1:52 pm 
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Joined: Fri Mar 02, 2012 1:08 pm
Posts: 5
hello

This is my first post. I'm a Engeneering student and cyclist here in Brazil. You don't have to think too much to realize that I like reading about equipaments and new technologies even if I don't have money to buy them.

I'm reading about carbon clinchers and almost all the reviews I read have talked about the tire pressure limit. Is there one deep section wheel without pressure limit, besides the Lew racing ?

thanks


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Posted: Fri Mar 02, 2012 1:52 pm 


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PostPosted: Fri Mar 02, 2012 2:47 pm 
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What kind of psi are you wanting to run?
Are you a large rider or riding on a track?
Maybe just looking at a manufacturing or design standpoint.

Most carbon wheels offer a harsher ride due to deeper section of rim, why would you want to run a max high air pressure?

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PostPosted: Fri Mar 02, 2012 5:48 pm 
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I'm just trying to understand if there is one brand that made some advances in mold carbon to resist to compression that clincher tires make. Lightweights Standart c has 115 Psi of max pressure. But bontranger and reynolds doesnt show their max pressure on the site. For these brands, Is there one max tire pressure?

my weigh 61 Kg
my max pressure 115 Psi

thanks


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PostPosted: Fri Mar 02, 2012 8:47 pm 
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Joined: Thu Dec 01, 2011 4:59 pm
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I think the average max tyre pressure for a clincher tends to be about 145psi, i don't think there are many companies that dont have a max tyre pressure. They just simply dont show you them cause they dont expect u to go above them. pressuming most people ride about 115/120 ??


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PostPosted: Sat Mar 03, 2012 11:06 pm 
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I weigh 59 kg and there's no way I would ride 700x23 tires on the road at 115 psi. I usually run them about 90 psi and lower. Higher pressure is not necessarily better for most conditions.

If you are riding a track bike on a smooth track in a velodrome, then I haven't the experience or knowledge to speak about that.

my inane ramblings via tapatalk


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PostPosted: Mon Mar 05, 2012 7:20 pm 
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Location: Near Horgen, Switzerland
Most carbon rims state a pressure limit. Most Aluminium rim manufacturers also state a limit nowadays. More to limit legal liability than to indicate that the rim will explode if you over-inflate it by 5psi. My view as a former Engineer is therefore that higher or lower inflation limits are more indicative of the strength of the legal department than the strength of the rim.

Each firm will have its own rules of thumb on what constitutes the most adverse load case (rider weight, largest-section tyre, worn rim, temperature)... So if you're a light rider and want to try 120psi on on a new rim I wouldn't worry too much. I personally run 125 psi on my tandem wheels and used to run 150psi on 18mm time trial clinchers.

Also, as an Engineer you could make some back of the envelope calculations to estimate the radial and hoop stress in the system (e.g. assume the tyre is a toroid and section it). Then calculate the % change in stress if you change the system design (tyre cross sectional area, rim size, rider weight, inflation pressure...). Then you could work out when the bead will fail (assume the rim bead is an 10mm long encastre beam with all loading at its end), either driven by pressure or rim wear. That would generate some pretty graphs and maybe some insights. Then you could have fun blowing up some rims / tyres to verify your calculations...


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PostPosted: Tue Mar 06, 2012 3:53 am 
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Joined: Tue Jun 21, 2011 8:34 am
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the psi stated on the tires sidewall , is it the maximum preasure the tire can hold or the preasure that we should pumped to ?


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PostPosted: Tue Mar 06, 2012 4:40 am 
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The maximum the tyre is rated to.

I'm 72kg and would never run more than 100F 110R in a 23mm tyre.


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PostPosted: Tue May 08, 2012 7:50 am 
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Joined: Fri Dec 23, 2011 10:09 pm
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Location: Vancouver, Canada
My new Spinergy Stealth FCC wheels had a decal on them stating their max was 120psi.


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PostPosted: Tue May 08, 2012 2:26 pm 
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Posts: 680
Location: Detroit, MI
I know that the rated limit on Reynolds Carbon Clinchers is 160psi but I'd never run them that high.

Generally speaking you won't find me running any tire above 120 and I usually run 110psi for a 190lb rider.


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PostPosted: Tue Jun 25, 2013 4:32 pm 
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Posts: 255
Location: Pittsburgh, PA
New owner of a set of Enve 3.4's with Alchemy Hubs and this is my first set of carbon wheels, My question does anyone change what they run the tire pressure at due to being carbon?

I weigh 165lbs.
alloy setup is:
KINLIN XR19W
CHRIS KING R45
CONTINENTAL GP4000S (110 PSI.)

carbon setup is:
ENVE 3.4
ALCHEMY ORC UL/ELF
CONTINENTAL GP4000S

I have not rode my new wheels yet first ride should be tomorrow. Just asking the question should I view tire pressure a little different based on rim material and width of the 3.4's. Will they ride a little more stiff/harsh or more compliant just looking for some experience for the best ride quality.


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PostPosted: Tue Jun 25, 2013 5:41 pm 
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Joined: Tue Nov 11, 2003 9:47 pm
Posts: 1736
Location: Santa Cruz, California, USA
I find that my carbon clincher wheels ride slightly rougher than aluminium wheels.
You would do better by running 25mm tires (assuming they fit in your frame) and lower pressures.
I use 95f/100r on 23mm tires. Lower for really rough roads. I'm 20 lbs lighter than you are.
Use the Michelin tire pressure guide as a start.

I do not change inflation pressure for carbon wheels.


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PostPosted: Tue Jun 25, 2013 7:08 pm 
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Joined: Sun Jul 29, 2012 12:49 am
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I'm also 165lbs and using the same tires on Lightweight Standard Cs. Lightweight has a specified pressure limit of 115 -- I inflate to 110 using Conti Supersonic tubes. Although I don't find them harsh, I wouldn't consider them overly compliant either. Have a pair of 25mm Conti GP4000s but haven't had a chance to install yet.


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PostPosted: Tue Jun 25, 2013 8:23 pm 
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Location: 604
Let me preface the following by saying I don't mean to sound snobby but it seems strange to me that you are riding lightweights/enves and concerned with ride quality and 5 psi here or there why are you running continental tires? Give veloflex/vittoria/etc and latex tubes a try!


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Posted: Tue Jun 25, 2013 8:23 pm 


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PostPosted: Wed Jun 26, 2013 12:04 am 
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Some stuff on the actual failure point of reynolds wheels in this article, rather interesting stuff http://www.bikeradar.com/gear/article/r ... our-37662/" onclick="window.open(this.href);return false;

Suggesting that the 160psi limit is for a safety factor of more than 2!

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