Traction

[BobDrye]

I thought these figures were Illuminating.


Coefficient of Traction for Rubber Tires on Various Surfaces


Concrete (dry .70
Asphalt (dry) .50
Asphalt (wet) .45
Gravel (packed oiled, dry) .50
Gravel (packed, oiled, wet .40
Dirt (packed, dry) .50
Mud .15-.40
Snow (dry, on loose gravel .25
Ice (free of snow) .07



:7head: :7head: :7head:

[slngsht]

asphalt and dirt are the same? :confused:

[xflow7]

"packed" is pretty vague. I'd almost believe that a truly hard-pack dirt road could have similar friction to asphalt. Having said that, I also believe there's an enormous variation among different asphalts.

[Dave W]

I find that hard to believe that concrete is better then asphalt. If you have ever raced on a track with concrete patches, it's like nite and day between the two surfaces.

Dave W :7drive:

[Kitcat]

Any auto-x er can tell you that concrete is way grippier than asphalt. Really demands a different car set up. Most concrete auto-x courses around here are on old airport runways. Not many concrete parking lots out there. Concrete is much harder on the race rubber too.

Mid-Ohio's concrete patches are tricky but my memory is that is only in the rain, in the dry they have better grip than the mostly asphalt track.

[southwind25]

We think it must also depend on what the surface texture is of the material.

you can have concrete to almost a polished level. or it can be finished like velcro.

the grippiest surface we ever auto-x'd on was a freshly dried concrete at an airport..you could literally see the dust chaff off the tires. I dont think anyone spun the whole day but we had allot of 3 wheeled corners that day. The worst surface we ever ran on was also concrete that had been pounded and polished by a couple years worth of racing tires..it was like glass.

new asphalt with the surface weeping it's oil..YIKES!...

i would guess these surfaces tested are labratory?..not real world.

[Dave W]

Mid-Ohio was the track, I had to drive around the out side, or inside of the patches.

Worst was the patches going on to the front home straight and the tight U just leading on to the long back straight.

My guess is that the actual surface texture probably plays more into it.
Dave W

[BobDrye]

I found the information on the following site.

http://www.saltflats.com/traction.html

Have any of you guys been to speed week?

:)