Handling changes at low temperatures?

[NHAero]

I went out today at 19F for a 20 miler and I think I noticed a difference in how the bike handled in turns. The tires are 650Bx38 Gravelking slicks run at about 40-42 psi tubeless (at least, in the basement). I wonder if they cool down enough to have the pressure drop and that affects the handling. Nothing major, it just felt a bit different.

[R3awak3n]

It would make sense as cold makes rubber harder so less grip.

Same with car tires and why they develop winter tires with a different compount that does not harden up as quick as summer or all seasons.

[dolface]

Originally Posted by R3awak3n

It would make sense as cold makes rubber harder so less grip.

Same with car tires and why they develop winter tires with a different compount that does not harden up as quick as summer or all seasons.

Agree, same for rock-climbing shoes, for especially thin/technical routes we'd time our climbs based on temps.

[merlinmurph]

I bet you lost a few pounds - well, the tires did. When my 40mm tires are softer for trails (<40), they handle noticably different than when pumped up to 50+.

[nmrt]

might be the man and not the machine, methinks.
my old bones take a while to warm up in teen weather.

[AngryScientist]

P2 = (P1*T2)/T1 for a constant volume right?

So if your basement is 65F (mine is...) than T2 @ 19F is 36.5psi (if i did my back of envelope math right...) - so yes, that's a pretty big change IMO

[spoonrobot]

I noticed the same thing when I started riding Hetres years ago. Three big temp swings; from inside to outside to night: 70°->55°->32° dropped the pressure enough to cause self-steer during cornering and also had the tires grabbing the raised paint lines.

Rode for years with 700cx25 in same and colder weather and never noticed a difference. Lower pneumatic/ground trail I suppose, funny that.

[NHAero]

Yes, in theory, if the air in the tires is at the basement temp to begin and equilibrates to the air temp, that's about 3-1/2 psi aroud 40-41 psi to begin with. but I don't know how much the temp of the air in the tires drops in a ride that takes 85 minutes (extra slow so I don't sweat.) And I don't know how the colder temp affects the tire (vs. how it affects the grip on the road). I imagine that with tubeless, the air cools faster.

Originally Posted by AngryScientist

P2 = (P1*T2)/T1 for a constant volume right?

So if your basement is 65F (mine is...) than T2 @ 19F is 36.5psi (if i did my back of envelope math right...) - so yes, that's a pretty big change IMO

[AngryScientist]

Originally Posted by NHAero

Yes, in theory, if the air in the tires is at the basement temp to begin and equilibrates to the air temp, that's about 3-1/2 psi aroud 40-41 psi to begin with. but I don't know how much the temp of the air in the tires drops in a ride that takes 85 minutes (extra slow so I don't sweat.) And I don't know how the colder temp affects the tire (vs. how it affects the grip on the road). I imagine that with tubeless, the air cools faster.

And probably add a few degrees to T1 also given going through your pump probably heats it up a bit.

for 42mm tires there is definitely a pressure where they feel too low and sloppy, it's noticeable and i dont like it.

just pump them up a little higher next time initially when you know it's that cold out. i bet you'll notice a difference.

[nmrt]

If using the gas laws, the temperature has to be in Kelvin. And when you do the conversion, the pressure ought to drop to about 40 psi at 19 F from 42 psi at 65 F.

Originally Posted by AngryScientist

P2 = (P1*T2)/T1 for a constant volume right?

So if your basement is 65F (mine is...) than T2 @ 19F is 36.5psi (if i did my back of envelope math right...) - so yes, that's a pretty big change IMO

[AngryScientist]

Originally Posted by nmrt

If using the gas laws, the temperature has to be in Kelvin. And when you do the conversion, the pressure ought to drop to about 40 psi at 19 F from 42 psi at 65 F.

i did the math. kelvin and pascals yes.

[NHAero]

It is the percentage reduction whether Rankine or Kelvin, about 9%, which is 3.6 psi starting at about 40 psi.

Originally Posted by nmrt

If using the gas laws, the temperature has to be in Kelvin. And when you do the conversion, the pressure ought to drop to about 40 psi at 19 F from 42 psi at 65 F.

[Mark McM]

Originally Posted by NHAero

It is the percentage reduction whether Rankine or Kelvin, about 9%, which is 3.6 psi starting at about 40 psi.

A 9% change in pressure will obviously affect handling. But I'll bet the durometer of the rubber changed more than that, which is going to affect hysteresis, compliance, grip, and rolling resistance. As noted above, there is a reason that they make winter tires - and it's just for snow and ice grip. At low temperatures many winter tires outperform summer tires even on dry pavement.

[Mike Bryant]

Just wondering if grease in the headset (especially), bottom bracket, wheel axles, etc. might affect handling in cold weather. Most Shimano users are aware of slower shifting in cable actuated “brifters” in the cold.


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[tuscanyswe]

Originally Posted by Mark McM

A 9% change in pressure will obviously affect handling. But I'll bet the durometer of the rubber changed more than that, which is going to affect hysteresis, compliance, grip, and rolling resistance. As noted above, there is a reason that they make winter tires - and it's just for snow and ice grip. At low temperatures many winter tires outperform summer tires even on dry pavement.

Is that change in temp and preassure in this example not calculated vs basement temp? Wouldent a more realistic comparison be towards previous riding temps and corresponding preassure difference as this is what the baseline perception of handling took place unless op rides a lot in his basement ofc. Unless the outside temps has taken a nose dive recently i would expect the difference to be much smaller and other causes for handling issues more likely.