Cold tire pressure

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Roundybout
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Cold tire pressure

Post by Roundybout » Thu Sep 21, 2017 10:56 am

So the mornings have been getting a lot cooler, 45f-50f and I set my cold tire pressure accordingly to 35psi. Well it still gets warm, upper 70f to lower 80s still. At that point they feel like hockey pucks. The pressure gain goes from 35psi cold to 44-45psi after a highway ride. Sometimes higher if it's over 80f.

So I air them done to 40psi. Much better. No additional pressure build up after doing that riding around. So it appears I'm underinflated cold and the heat build up is increasing psi along with the rising air temps during the day. Ive also noticed that my max tire loading is at 44psi. I assume if I'm not at max load I can air them down a bit and be ok?

bobalattie
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Re: Cold tire pressure

Post by bobalattie » Thu Oct 05, 2017 10:37 pm

That seems like a big rise in pressure with the small temp changes. Is the air very humid where you are at? Have you considered switching to nitrogen to fill the tires? The pressure increase with nitrogen is much less..

Just a thought.

Circlotron
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Re: Cold tire pressure

Post by Circlotron » Sat Nov 18, 2017 5:36 am

bobalattie wrote:
Thu Oct 05, 2017 10:37 pm
The pressure increase with nitrogen is much less..
No, sorry, all gases obey the same pressure vs temperature relationship.
https://en.wikipedia.org/wiki/Boyle%27s_law
The only thing useful about nitrogen in tyres is for aircraft so that it is impossible for inside of a tyre to catch fire when landing.

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Re: Cold tire pressure

Post by nitro2 » Sun Nov 19, 2017 10:57 pm

Circlotron wrote:
Sat Nov 18, 2017 5:36 am
bobalattie wrote:
Thu Oct 05, 2017 10:37 pm
The pressure increase with nitrogen is much less..
No, sorry, all gases obey the same pressure vs temperature relationship.
https://en.wikipedia.org/wiki/Boyle%27s_law
The only thing useful about nitrogen in tyres is for aircraft so that it is impossible for inside of a tyre to catch fire when landing.
That's true, except for one thing, the nitrogen that goes into the tires is dry, but compressor air that goes into the tires is not. Moisture inside the tire (when using compressor air) causes a greater change in pressure in the tire with temperature change than nitrogen (dry) does. If dry air was added to the tire, instead of compressor air, the tire would have pressure fluctuation akin to nitrogen.
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