Here's a snippet from the SCCA Forums site (regarding STF)
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Re: STF for 2012 - Whatcha got?


Andy Hollis wrote:
[MNbiker wrote:
[[jasyatz wrote:
...... add the 225's on a 16" wheel and perform all the ST weight reductons adn you'd easily be in low 2300's.]]

I'm thinking 195 Toyo's on 15x7.5 wheels. The MINI should be light enough for the standard ST/STS package to be quite effective.]

If I was doing a MINI, I'd run 225/45-15 Kooks on the front and 195 Toyos on the rear. Given the weight differential, the relative f/r grip level will be consistent as they heat up. Too much weight on the nose for optimal use of a 195 on the front, unless maybe in the cold and/or damp.

Other sizes might work well if you have a 6-spd.

--Andy

I'm seriously considering an asymmetrical setup for 2012 for just the reason you state, but I am very cautious of mixing tire brands. My concern is that variation in sidewall construction could make slaloms, transitions and entries a little hairy...

Have you tried this recipe?

Kind regards,

Charlie
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I wonder if any folks here have experience with this type of approach...

All the best,

Charlie

 

No personal experience, but I read that the MC that won HS at 2011 Solo Nationals was shod with 225/45/15 Hoosiers in front and 205s in the rear. I think they had 225s at both ends when they ran at Danville earlier in the season, but they apparently tested various configurations before Nationals and decided on 205s for the rear. Seemed to work well for them.

Some rear drivers that come stock with wider rear wheels and tires are sometimes run with a "square" setup (same size tires front and rear). If one goes wider in front, a size narrower in the rear might help reduce understeer. Don't think I'd want that on the track though.

As for different brands of tires front and rear, careful testing of a variety of brand combos might lead to a good one. Or one could just trust Andy's advice for the MINI. He has plenty of experience testing various tire configurations; at least on his Honda Civic.

 

Thanks Jim - I am thinking in the same direction...

 

in a FP mini a couple of seasons ago I tried:
275/15 a6's in front (newish) on spinwerks 17lb wheels
225/15 as304's in rear (old rubber) on forged 8lb wheels

theory was to take some unsprung weight off the rear and the front should need more grip anyway. I have an '04 with the steel rear trailing arms and the rear unsprung weight is very high. the car did rotate better.

I'm now running 10.5"wide avons all around, on fairly light wheels.

staggered tires will limit your tire management. Since you cannot rotate.

I would try to tune the back of the car with the spring rates.

I've had the best performance going to high rear rates and deleting the rear bar. this way the rate is linear and works consistently especially in transitions. On a gutted mini with 8" spoiler on the rear, I run between 375 and 500lb/in in the rear.

 

Thanks for sharing your experience. That sounds like quite a beast you are running!

Kind regards,

Charlie

 

We run an 03 S in SMF, with the 275/225 A6 combo. The rears last forever, I flip them on the rims at 80 runs, then sell them when they hit 120-140 runs. The front are another story, they get flipped at 20 runs, flipped again at 40 runs, and if were lucky they'll make it to 50 runs before cording.