×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

CoF in similar tyres with different loads

CoF in similar tyres with different loads

CoF in similar tyres with different loads

(OP)
Morning,

I read recently that the coeff. of friction of a tyre to road interface will decrease with increasing mass of the vehicle. If it didn't then any vehicle of any mass running similar tyres would, with all else equal, be able to hold an equal corner speed. Common sense says not to me, my question is why? What assumedly microscopic action takes place at the interface to reduce the value of mu? Or is it macroscopic and am I missing something obvious? Bear in mind i'm not talking about straight line accel or braking distance, just steady state cornering. Disregard any aerodynamic effects too.

thanks,

Kurtis.

RE: CoF in similar tyres with different loads

No answers - OK - I'll give this a go with the caveat that I'm not an elastomers engineer and whole books are dedicated to understanding just parts of this.
For constant slip and camber angles, the coefficient of friction does decrease with increasing load.  You are right that there are two general principles at work - macro and micro.
In the macro view, the tire distorts under greater load and alters the tire contact patch shape, pressure and slip distributions.
In the micro view, the coefficient is comprised of two components - adhesion & hysteresis.  The adhesion portion is inversely proportional to the pressure (temperature).  This is also the result of molecular bonding and the strain cycle (bonding, elongating, rupture).  The higher the pressure and temperatures, the easier they are to rupture.
The hysteresis portion is associated with localized tread deformation. A differential area deforms and absorbs a certain amount of energy. This generally absorbs less energy than adhesion.
Kevin

RE: CoF in similar tyres with different loads

(OP)
Kevin,

good answer. The adhesion portion is I think what I was looking for. I wondered if the contact patch would make a difference and couldn't find a definite answer, so thanks for that too.

At least I know the article was factual.

thanks,

Kurtis.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources