Road surface temperature and grip

[slofox]

I have just spent some time trying to dig out information on the relationship between road surface temperature (as opposed to tyre temperature) and tyre grip. (Yep. It's another slow day in the wine shop...)
Most of what I found with the aid of the "giggle" searching device deals with stuff like ice making the road slippery...(what? slippery? ice? bullshit! ).
I have found little (nothing actually) that deals with the difference between say a road surface at 2C (dry, no ice) and a road surface at 20C. Which is what I am interested in given that the roads are bloody cold at present, especially at the time of day I mostly ride (early morning).
So, wise gurus, what do y'all think? Is there any significant difference in that temperature range? Like up until the tar melts anyway.
My own experiences so far do not suggest a huge difference but then what the hell would I know..?

[Blackshear]

Being totally uneducated, it is my theory that tyre core temperature will have a far greater effect on grip than road temperature. Rubber = softer/stickier, more grip.

Colder blacktop would just slow the heating process, is my thought.

[YellowDog]

Another glass of wine Mr Fox ?

It is a good question. The tyre temperature is critical however it is also relative to that of what it is attempting to grip.

I remember reading somewhere that 5 degrees is the optimal road surface temperature and after 12 degrees the grip reduces depending upon the expansion properties of the surface.

I will try and see of I can find a reference to it.

[Finn]

I have just spent some time trying to dig out information on the relationship between road surface temperature (as opposed to tyre temperature) and tyre grip.

Given that while riding, you don't know the temperature of either so don't lose too much sleep over it.

Shared a bottle of 00 Grange on the weekend. Of course I ruined it with a cigar. Pity cause is was a great year.

[Jantar]

I believe a lot will have to do with the tyre design, and how much heat transfer occurs between the rubber and the road. Naturally, a colder road will slow the heat buildup in the tyre, and may even prevent the tyre from reaching its optimum temperature. It all depends on what the tyre manufacture has calculated as optimum road temperature for a particular tyre.

I can state quite confidently that Trail Attacks do not reach their optimum temperature with road temperatures below freezing, and is without any ice on the road.

[CookMySock]

I can't get my tires to talk to me at all. The old bridgestones always had something to say, especialy in the wet (sqriggle, wriggle, twitch) but the Michelins just STFU and never say anything. I'm actually a bit baffled by it.. Like, just how fast do I have to GO to make these things SAY something? Unprovokable.

Steve

[Blackbird]

Jantar is right. What keeps you on the road of course is friction (adhesion, deformation and wear). Heat does affect the friction in that you effectively soften your compound which increases friction so yes, heat up to a point does improve grip; hence tyre warmers on circuit bikes and cars. The design of the tyre, the compound itself plus any friction modifiers (silica etc) also have a huge bearing so heat is only part of the equation. You can find a nice "primer" on the principles of tyre grip here: http://insideracingtechnology.com/tirebkexerpt1.htm. It doesn't cover tyre design, but the principles of grip are excellent.

[slofox]

Thoreau said "simplify, simplify."

So to complicate the simplification: all I want to know is how the coefficient of friction of a road surface varies with temperature in the range already stated. Nothing more. Not looking at any practical applications here. Just what the road itself does.
I told you it was a slow day...

[AllanB]

Those V8 supercar chaps are always warbling on about track temperatures - possibly more worried as to how this will affect tyre wear, opposed to grip.

As for friction (gawd love that friction) do two cold surfaces offer less friction than two warm ones?

[slofox]

Those V8 supercar chaps are always warbling on about track temperatures - possibly more worried as to how this will affect tyre wear, opposed to grip.

As for friction (gawd love that friction) do two cold surfaces offer less friction than two warm ones?

So do the Indycar dudes according to what I did find on giggle...

[DEATH_INC.]

It definatly has an effect, try riding taupo racetrack in the winter, the first two and last session are always a bit dodgy, due to very cold track temps.

[steve_t]

I'm gonna go with basically zero change to the coefficient of friction of the road between 2 degrees and 20 degrees celcius. As has been suggested, the major factor influencing grip is getting the tyre up to operating temperature, which takes a lot longer, if at all, when it's 2 degree on the road. If the road temperature is really high and takes the tyre temp above optimal, grip is also reduced. You must have had a really boring day... I'm off to the pub

[slofox]

I'm gonna go with basically zero change to the coefficient of friction of the road between 2 degrees and 20 degrees celcius. As has been suggested, the major factor influencing grip is getting the tyre up to operating temperature, which takes a lot longer, if at all, when it's 2 degree on the road. If the road temperature is really high and takes the tyre temp above optimal, grip is also reduced. You must have had a really boring day... I'm off to the pub

I'm still at bloody work....have a beer for me willya?

[Starky307]

It definatly has an effect, try riding taupo racetrack in the winter, the first two and last session are always a bit dodgy, due to very cold track temps.

I'd second that. The last time I was at Taupo the first two sessions were sketchy as, it was a cold crisp friday and the tires never really "came on". By the 3rd and 4th sessions it took nothing to warm up the tires and they had amazing grip the whole session through out.

So there must be a relationship there some where.

[jono035]

Colder roads could also be a little damp, even on a clear day.

I think surface temperature would be more useful than core temperature... I think core temperature is measured simply because it takes longer to heat and longer to cool, thereby giving you a better idea of what the average temperature of your tires while actually riding is....

Also if the road is cold then it'll be soaking any heat you build up in the tires straight back out again every time the rubber comes down.