Tire Performance

[hashanw007]

Hi
i got a question.
A graph of slip ratio Vs Longitudinal Force (considering zero camber & neglecting SH & Sv functions)is a graph passing through the origin. after it reaches its peak value of longitudinal force, what happens next? i mean how does it perform with increasing slip ratio, after this peak force is reached?

Also, increase in vertical load shows an increase of longitudinal force. What does this mean? is it good or bad for the tire/vehicle?

 

[GregLocock]

On dry asphalt Fx falls away after the peak, typically down to about 80% of the peak (very variable) by the time the slip reaches 100%.

On other surfaces anything can happen.

Don't really know what you mean by the other question.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[bvanhiel]

I think I understand the second question.

More weight = more traction. In an aero car there can be much more downforce than the vehicles own mass and dynamics would provide. That force will then translate into increased traction and better acceleration/braking.

-b

 

[hashanw007]

ya. But, increased in vertical load increases the inertia. then wouldnt the vehicle find it harder to stop?

 

[hashanw007]

look at the attachment & then you will understand my question. i need to know what happens after it reaches its peak point..........(while slip ratio increases more)

 

[Bribyk]

After you pass over the peak slip ratio the tire is spinning/slipping more than is ideal. You just end up with more tire wear/heat and less acceleration (or braking). This extra slip will put heat into the tire which increases the temp and will likely change your slip ratio curve/peak. Take this to the extreme, say, a slip ratio of 5 or 10, and you have a burnout or a braking skid.

 

[SomptingGuy]

Increased vertical load need not come from increased mass.

- Steve

 

[NormPeterson]

Longitudinal force increases as vertical force increases, but less than proportionately. That figure that you attached may demonstrate this, if there is an associated legend that allows you to relate each curve with a vertical force.


Norm

 

[GregLocock]

Your inertia is not increasing, unless you have a very unusual system.

Your graph shows perfectly normal behaviour for a tire, and, astonishingly even agrees with my first post.






Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Bribyk]

As you approach the speed of light your inertia will increase . You need one fast car though...