High tire pressure and temperature

[prState]

My Marathon Plus are rated at 85psi. (or 6 bar)

If I fill them inside at 26C degrees, to 80 psi, and start riding outside at 40C, do I risk disaster after awhile after they heat up?

What maximum can I run them at safely?


(now that I know their secret, the thick puncture resistent pad, I know, they will tend to have fairly moderate rolling resisitence no matter what -- that pads are not going to harden up)

Thanks

 

[rog_london]

My Marathon Plus are rated at 85psi. (or 6 bar)

If I fill them inside at 26C degrees, to 80 psi, and start riding outside at 40C, do I risk disaster after awhile after they heat up?

What maximum can I run them at safely?


(now that I know their secret, the thick puncture resistent pad, I know, they will tend to have fairly moderate rolling resisitence no matter what -- that pads are not going to harden up)

Thanks

It makes very little difference. Most people realize that an increase in temperature equates to an increase in pressure if the volume remains the same, but what is not quite so obvious is that the pressure is proportional to the absolute temperature. So, you're talking about absolute temperatures of 299 degrees (26 Celsius) versus 313 degrees (40 Celsius) which is around 4.5% increase. Applying this to your 80psi at 26 Celsius you'll end at around 83.5psi at 40 Celsius.

If you're really curious, you could always take a tyre pressure gauge along with you and do a check while the tyres are at 40 Celsius. You might well find you don't get as high as the theoretical 83.5psi as the tyres will swell a bit due to the higher temperature and any possible extra pressure.

Obviously, don't inflate to above 80psi if your circumstances are as you describe. You need to allow for inaccuracies in the pressure gauge, although of course the tyre manufacturers will have been conservative in their specifications.

Rog.

 

[prState]

Thanks for the info rog_london! I think I will do a "hot" measurement after riding.