Street tire static and kinetic friction coefficients?

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Discussion Overview

The discussion revolves around the coefficients of static and kinetic friction for street tires on dry asphalt, with inquiries about specific values and comparisons to racing slicks. Participants seek data and ranges for these coefficients, as well as methods for estimating them.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant requests data on normal street-tire friction coefficients on dry asphalt, specifically looking for both static and kinetic values.
  • Another participant suggests calculating the static coefficient from braking distances of cars, providing a range of 0.8-0.9 based on typical family cars and a higher value of 1.1 for a Porsche 911 Carrera Turbo on rally tires.
  • A reference is made to police forensics using a kinetic coefficient of 0.7 for dry asphalt and 0.55 for wet asphalt in collision investigations.
  • A participant shares a link to a website that may contain relevant data on tire friction coefficients.

Areas of Agreement / Disagreement

Participants present varying estimates and methods for determining friction coefficients, indicating that no consensus exists on specific values or the best approach to obtain them.

Contextual Notes

Participants express uncertainty regarding the applicability of values found in different contexts, such as the type of tire and surface conditions, which may affect the coefficients.

ektrules
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Anybody know where I can find data on normal street-tire friction coefficients on dry asphalt? I'd like both the static, and the kinetic coefficients. If not, can somebody give me a range of reasonable values?

While I'm at it... What about racing slicks on asphalt?

I found one source that said the static friction coefficient of a tire on concrete is about 1. But, it didn't say what kind of tire, didn't give me the kinetic coefficient, it's on concrete, and it seems too high.
 
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You may calculate static coeff from breaking distance of cars using ABS. For most family cars breaking distance on dry asphalt from 100 km/h is 45-50 meters, thus (static) friction coefficient is 0.8-0.9.
Porsche 911 Carrera Turbo on rally tyres on standard German asfalt pavement claims breaking distance of 34.5m => f.coeff=1.1

Regarding kinetic coeff: police forensics use coeff=0.7 for dry and 0.55 for wet asphalt to compute speed from skid marks during collision investigation.
 
Last edited:
http://hpwizard.com/tire-friction-coefficient.html"

https://www.youtube.com/watch?v=_rVprtWPsiw
 
Last edited by a moderator:
Oh, cool. Before I started this thread, I got search results from that site, but the site was down at the time. I didn't know what was on that site. Thanks.
 

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