hot tires + cold roads=

[IG.]

I ride year around, and will go for at least 20 - 30 min ride if it's above 15 deg. I do have www.smartire.com/motorcycles installed and know for a fact that tires do get warm even at freezing temperatures, and can tell you that at those temperatures (and dry conditions) traction is better than in the wet (and warm conditions). The temperature readings I see on display are consistent with the feeel when I touch the tire.

I rode a few days ago in 35 deg in dry conditions. Cold tire pressures were 33 front, 35 rear. After 5 min or riding at... well, you know what speeds... the front was at 37 psi/60 deg, the rear was at 39 psi/75 deg. During the ride I reached the lean angle of no more than 35 deg (zero being vertical).

I've also ridden (in the past) at 20 deg with a reasonable lean angle. No sliding.

My estimate is that there is a marginal loss of traction, but not as much as one may think, and definitely better traction than in the wet but warm conditions. Even tar snakes don't give me any trouble in the cold.

interesting post ..I didnt even realize there was a devise to  tell you all that info .. ,temps and all.
 I hope I didn't  give anyone the impression that its unsafe to ride at cold temps ..   Maybe should have said  unsafe to ride hard at very low temps ..  

I save that kind of riding for weather that lets me get a  tire so hot I can barely touch em .
What kind of tire temps do you see on a hot day?

On a warm summer day with ambient temp let's say 85 and some sun out, and cold pressures 34F/36R, after 10 min of aggressive riding the pressures will go to something like 38F/40R and the temps to 115F/125R.

In another example, let's say you do a mostly straight highway riding with an average of 80 - 90 mph at the same 85 deg and some sun out, and your cold tire pressures are 37F/40R. After 10 min, the pressures go to something like 41F/44R and the temps go to something like 110F/120R.

Note that those temps are inside the tire, so I can imagine the outside to be somewhat cooler. But I will tell you that when I stop and touch the tire which is 125 deg inside, it's pretty warm to the touch - not just a little warm.

Also note that the temp inside the tire is the resultant effect of the two opposite forces - the flexing of the tire (heats it up) and the cooling of the air (cools it down).

I think the effect of the road temp on cooling the tire is negligible - after all the road touches the tire only at the contact patch, while the outside air is in contact with the most of the tire's surface. So, the air temp is what's cooling the tire, not the road surface temp.

I would also put a number on how much traction is lost. I would say at 40 deg vs. 80 deg (air and surface), only about 20% of traction is lost. And I would say that wet vs. dry (same temp), at least 30% of traction is lost.

 

[WWJD]

so road surface temp makes no difference - just the tire heat for adhesion? I could see that colder temps [IE morning] have to do with morning dew lingering CAUSING less traction, but doesn't cooked blacktop, like on a track or good road, >>give<< just enough to "stick" a little better to a tire than a solid unmoving pavement? I dunno, I'm just making stuff up and throwing it out there.

 

[dangerous dave]

As long as we are just throwing stuff out there ....
If I leave the house on a 65 degree day  (meaning tires are about 65- 70 degrees) and wack the throttle good  as Im getting on the big road out, I'll smoke up the rear tire . Now if I tried that after riding a few miles ,  Id be looking at the sky . Complete traction available... So point Im making is, even at 70 degrees   sport bike tires are no where near their optimal  temp.
Im guessing you get all the tire has to offer at 120 degrees and no less.
This is something racers have always known but I run into street riders that dont seem to know about getting some heat to the tires on cool days.

 

[vman1300]

so road surface temp makes no difference

It makes BIG time difference. This past weekend, with my warmers set on high 180 degrees, after a session on the track...tires were actually cooler than when I removed the warmers.

I do not have a temp guage, but after a session I cannot even lay my hand on my tires. Saturday I was able to do that and could tell they were cooler.

The temp were in the 35-40 degree range and I know the track was pulling heat out of the tires.

Who knows that could have been part of my lowside....

 

[BigBSBusa]

Very interesting discussion. You guys need to keep writing so I can learn more.

 

[WWJD]

vman, was not the 35-40 degree plus speed wind temps bleeding off tire heat? maybe more than the pavement? how to tell which pulls of more heat: the air rushing by or pavement? kinda both with no way to tell the difference, since they will both be cool or warm together

I guess one thing I have to say about this is, *I* can't control the temp of the pavement anyway so why should I even care? hahhahhaa when it's cold out, I run my pressure real low 30's [road course track racing for those viewing] so there is a larger contact and faster/more heatup for stick. I can't change the surface temp, but I can affect my tires temp

 

[Revolution]

yup i thought of checkin my tire pressure but looked good and thought "hey if i'm down a pound or two of psi in this cold weather it's ok, more contact patch". i usually run 38 on the street.

 

[cosmo]

so road surface temp makes no difference

It makes BIG time difference. This past weekend, with my warmers set on high 180 degrees, after a session on the track...tires were actually cooler than when I removed the warmers.

I do not have a temp guage, but after a session I cannot even lay my hand on my tires. Saturday I was able to do that and could tell they were cooler.

The temp were in the 35-40 degree range and I know the track was pulling heat out of the tires.

Who knows that could have been part of my lowside....

My Powerstand warmers instruction sheet suggests letting the units run for over an hour in "cool" weather to "bank" some heat in the wheel.

 

[kennym4]

Don't they have trouble with TOO MUCH HEAT on the drag strip ? I've heard people saying "it was just too hot, the track was GREASY" ?

 

[busa_bill]

Don't they have trouble with TOO MUCH HEAT on the drag strip ? I've heard people saying "it was just too hot, the track was GREASY" ?

Yep, I was thinking that while I read through this thread. I believe the "big boys" run different tire compounds depending on track temps. It stands to reason though that you have a layer of rubber laying on the track and rubber gets softer with heat. Personally I've stayed away from the track on scorching hot days. On the flip side, if the track prep is good, you can hook really well by lowering pressure even on 45° evenings. The track usually starts to go away when it gets colder than that depending on the setup and power of the car.