I ride around 90 and am heavier then you with 24mm wide rims. Never had a pinch flat.

Well, I opened this thread to see why you were running 205 PSI in your tires, but my anticipation has disappointed me.

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Proud Representative of Slowtwitch Anti-Atheists Society.

While high pressure is recommended for larger bodies as the tires heat air expands. It has been estimated that a 10 degrees increase in heat will cause an increase of 2 lbs of pressure. If you are already at 120 you are very likely to over inflate a tube and have it pop an hour or two later.
I weigh about 225 so I ride 25mm tires and inflate them to 110. I have yet to have a problem.

It's likely closer to 15lbs per 10degrees F by merit of temp/pressure proportionality

But regardless, it's unlikely to see tire failure, even with a pre-ride pressure of 120. Unless it's some pretty extreme fluctuation. That's not to say 120 is the correct psi, though

*If 120s have worked for the 23mms (and it does seem a bit high), you'll want to lower it a bit for the larger tires*

Rule of thumb is 2% pressure change per 10 degrees F. 15lb/10deg F would mean you are starting with 750psi in the tires. Would take a long time to get the pressure that high using a bike pump. Imagine how sore your triceps would be.



http://flocycling.blogspot.co.nz/...re-pressure-and.html

Ahh unit conversion. For me in HS, coming back to me now

Except you need to take into account the temperature rise compared to the Rankine temperature rather than Fahrenheit . So if we're talking an ambient temperature of 70*F, that's ~ 530*R so a 10* rise would result in 10/530 or as another poster said ~ 2% increase.

Hugh

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Genetics load the gun, lifestyle pulls the trigger.

So... what pressure should I be running for 25mm rims @ 205 lbs?? LOL

Lower than what you'd run 23s. Try 95-105 depending on road conditions (lower if shittier/wet).

Similar ballpark for the 24, given they're on front and seeing less weight

Thanks! Lowered to 110 this AM.

Will drop a bit more.

It would not pop. Urban myth. As said 2%.......You know how they used to get max pressure years ago? The would pump until failure then divide by 50%. Now I am sure that is not done now but you get the picture.

I am 200 lbs, and ride 23mm conti 4000s at 85 front, 90 rear all day long. But also, they are on hed Ardennes plus wheels, 25 mm at the brake track, and measure 27.25 mm when inflated.

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I typically run about 95psi on my 25mm. 210 pounds.

The other variable that I have a hard time figuring out is that you slowly lose pressure particularly with latex tubes. Unlike a cycling TT our bikes sit in transition from 5:30 am, or so, until we get on it at 8:15, or so. And, then we ride for 5.30 - 6 hrs, or so (not 30 - 60 min). So, how do you calculate the correct amount to pump pre-race so that you hit the optimal for the largest target period . . . which is while you are actually riding!

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David
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