staggered tire size FWD

[ryanallan]

hi guys,
just need some outside input for a decision. I recently purchased a set of 17x8 wheels and 225/45/17 tires. the reason for my purchase was to help my efforts in autoX/road-racing. I'm beginning to second guess my self for not going bigger in the front(245/40/17). my theory is to prevent understeer by increasing traction where tractions needs to be added and in my case, the front(FWD).
just wondering how this combo would work as a DD and on the track?
245/40/17-front 225/47/17-rear

Ryan

 

[MIdsm]

I don't think that you should have a problem. Use a tire temperature probe to verify that front and rear tires have similar temperatures. As long as you are not over/under heating tires you should be fine as tires work best within a limited range of temperatures, especially track tires. The tire manufacturer or Tire Rack could probably let you know the best operating temperature range for your tires.

Just my 2 cents.

Good luck.

 

[jtmcinder]

Front vs rear tire temp is not that big a deal and is best dealt with by changing your style of driving. Tire pyrometers are mostly used to check camber (and also pressure).

You should have no problem running 245/40/17 fronts and 225/45/17 rears. Other ways to loosen the car up include some rear toe out, lower or higher rear pressures (which way you go would be an essay unto itself, but both tricks are used), or moving some weight transfer to the rear via springs or bars.

Another thing you can do to reduce understeer will cost your nothing: slow down more for corner entry. If you can't be back on it by apex, then you came in too fast.

- Jtoby

 

[ryanallan]

thanks for the tips guys.

 

[MIdsm]

I believe that the front to rear tire temperature differential may have some interesting info. If the front tires are at their optimum temperature and the rears are 30 or more degrees cooler I would tend to believe that the rears are underworked - the vehicle is over-tired in the back. We could play games with pressures, toe, etc., but that can be very tricky too.

I would prefer to have both sets of tires working near or at the optimum temperature range and then tweak by changing pressures, toe, etc. One could run different compounds front to back - harder up front and softer in the rear OR run wider tires up front and narrower tires in the back (FWD). I would rather use a narrower tire in the back as there would be less mass to accelerate and stop.