I am wondering what effect staggeri

[earlingy]

I am wondering what effect staggering tire size has on brake bias. I'd like to understand effects from both tire diameter and width, independently if possible. Wider rear tires is commonly done for high powered RWD cars, and larger diameter can be a side effect.
Thanks!
Alex

 

[NormPeterson]

The diameter effect - rolling radius effect might be better here - should be apparent.

I think some years ago something ate almost all of Greg's notes on how tire width might affect things like this . . . foggy memory wants to say some small fractional-power relationship was involved, maybe something in the 0.15-ish neighborhood.


Norm

 

[cibachrome]

Larger sized rear tires on production vehicles are the result of wanting an understeering in the limit tendency at full rated load when the RWD vehicle is close to 50% weight distribution at light load. Although the rear tires may look larger (fatter), the rolling radius is usually pretty close to that of the front tires in consideration of spare tire usage on each axle. This is traditionally for compact spares, but the run-flat situation can be different. In that case, yaw stability controls, low coefficient anti-lock braking algorithms and traction controls know the characteristics and capacity of each tire for these circumstances. If you change the tire split, your vehicle may become un-managable and un-defendable in court if you have a crash because of after-market manipulations of tire capacities.

 

[earlingy]

Thanks for the responses. OK, so the width affects the rolling radius, which comes back to diameter. What effect does staggered tire diameter, assuming similar width, have on brake bias?
I agree that most production vehicles have similar diameters on staggered setups because they will use a smaller ratio, i.e. 255/40R19 fronts and 275/35R19 rears. My question is meant to focus on vehicles that do not follow this trend, do not have spare tires, and how/if one would correct for it in the master cylinder brake bias, before tuning traction controls, ABS, etc. Will adding larger diameter rears need more braking force, causing a front-biased condition? Or vice versa?