My wife and I auto-x our 06 JCW MCS with 215/40-16 Kumho V710's tires all the way around. I'm always in the top 10 overall and more often than not am 1st in SP but I really want to get at least one FTD. The trouble we have is putting the power down and a solution may have come by accident. We bought a new set of (what we thought were) 215/40-16 V710's off e-bay. When they arrived, they were 225/50-16's, not 215/40-16's. Our race rims are 7.5" wide so we decided to mount the 225's on the front and see if they fit-and they do!!! Ok, they are no taller than the 18's we use on the street everyday but are significantly wider than the 215's(which we still run on the back). A quick scoot around the parking lot didn't reveal any rubbing or wierd handling, but our next event is Tuesday and we won't know for sure until then. We have always overinflated the rear tires to reduce traction and understeer, but now it looks like we can maximize rear tire pressures/alignment to balance out the extra front grip. Has anybody else tried this? I'll update with pics and results when I have them.

 

Be very careful with excellent front grip and worse rear grip - MINI owners have lost control and killed their car with that setup

 

I wouldn't try it when I'm road racing, but it may be perfect for auto-x where there's nothing to hit but a pylon. Besides, I have raced a Porsche 911 for years and know a little bit about controlling oversteer.

 

Update: I had my first event on the staggered sizes and am very pleased with the results. I was able to drop front pressures from 45 down to 32 and rear pressures from 65 to 28 and the car responded extremely well. It has even less understeer with those pressures and oversteer is available by increasing rear pressures. There was no rubbing issues and I can get on the gas earlier and brake later. I came in 1st in class and 9th overall. the only fwd car to beat me was a turbocharged Integra Type-R, by 1/100th sec.

 

Whoops, I was signed in as my wife. The previous post was me, not her. She actually doesn't like how the back end comes around easier, she just got used to the way it handled before.

 

The different diameters front/rear should effect your ABS. Did it??? I'd like to try some wide front tires (but of the same diameter) myself. Note, only for the autoX though.

 

The braking thing was my only concern but while braking into corners and a straight line, there was nothing to indicate I had different size tires. The ABS somehow compensated for it and braking was normal, actually I think I was stopping quicker than before.

 

The G-Stock Mini drivers run much smaller race tires and I never hear about them having problems with ABS. You sure your not thinking of the tire pressure monitoring system?