i've seen some fellas running offset sized rims on their road racing vehicles(15" in the front, 14" in the rear, etc.). i suppose this is for better cornering? anyhoo, how many of you guys are running this kind of setup? anyone? really, i'm just curious how beneficial it would be.


thanks for any feedback.

-Chris

 

technically you don't need too much rubber on the rear of a Fwd car. (i.e 275/35/15 front, 205/50/15 rear . see Chris Travis' autocross car).
and just this weekend our friend won DC region autocross in SM class, first time on 275/35/15 front, 225/45/15 rear.


lot of guys run 225 up front, 205 out back .
I really see two reasons.

Temperature:
The rear tires don't heat up nearly enough as the fronts on a FWD. a smaller rear is going to heat up quicker and reach it's optimal temperature sooner. a 225mm tire in the rear may never heat up to the appropriate temperature (especially a road race compound) so that may make the car slightly unpredictable and loose as it may never reach it's ideal temperature.

Weight:
Going to a 14" (205/50/14) out back, you can definitely save a little bit of weight. a forged 14x7" wheel should be lighter then a forged 15x7" wheel. (availability of off the shelf 14" wheels is nowhere near what is available for 15's) , so unless you have money for some custom 14" wheels, i don't see weight being the primary reason.


those are just two thoughts.

 

Bringing this thread back. I'm starting to see a lot more people running offset tire sizes (ex.225F/205R). Does anyone have actual lap time data to show that an offset tire combo is improving their times?

 

j's racing uses a smaller rim and tire size in the rear.
they seem to be fast..

 

Here is a reply I received from a Tein representative:

"Our Engineer replied to some of your questions. He said that in Japan some Gymkhana (Auto-X) competitors use narrower rear tires. This staggered setup is used to decrease understeer. However, the Gymkhana drivers usually use this on tight courses only. The engineer mentioned that the staggered tire will help decrease understeer but basically it is not the correct way to do it for a car driven on medium to large sized tracks. "