Acropora

Just wondering now that the 235/40's are already on the way...

adsc4s

It will be fine. The difference in diameter is minimal.

ScottMellor

It takes more than THAT to toast a VC. Ask me how I know.......
As I understand it the front tire diameter should be slightly smaller than the rear to "pre-load" the VC so it is putting 5% of the power to the fronts in normal driving.

EThec

i think it's the other way around. you want the rears slightly smaller so they are spinning just a little faster. 225X.40=94 ..... 285x.30=85.5 with aspect ratio(sidewall height) being a percent function of section width.

but with respect to this thread, i was curious about running 235's and 285's and the consensus is it is not a problem. The difference between 225 vs. 235 is negligible and others have done it without any issues. don't take my word for it though. i have not done it............

ScottMellor

Oops right. Rears smaller. My bad.

adsc4s

I've run 295/30 with 225/40 on my C4S with no problems. I've run the same combo on my TT as well. I currently run 235/40 with 315/30 in 18's (which I believe Viperbob and CJ do as well) and 245/35 with 285/30 in 19's. Of course, my VC is toast. Unlike Scott, I have yet to fix mine.

DJF1

While I cannot say for sure about the 4 wheel system effects, at the club race in Sebring this winter, I met the Michelin engineer on track. Told him about my understeer issues and he said to me that I actually had 2 problems. One the track temp as it was very cool and the MPSC's love 200 degrees and the 2nd issue was my 225's fronts. He said that I should combine my rears ( 285's) with 235's in the front and I should get great results. I asked him about the diameter difference and he told me its not an issue and that many of his customers who have tried this combo have had great resluts.

Jean

I used 245 front and 275 rear on my previous C4 and it run perfectly well. Understeer was completely cured, no sway bars or any other changes. Steering was a bit heavier, but it ran great and tramlined like a pig Some say is too much but this is my experience.

I am now running 265 upfront, no understeer, and no issues with my VC. Oh! I don't have one

Vince 97' 993 TT

So does everyone experience tramlining in their rides? It sux, expecially under hard braking... Is there anything that can be done to correct this?

pstoppani

Other than staying out of the ruts? Not really, if you want the car to handle well in other circumstances...

Jean

Vince you can change the Toe settings and it will help, advise given by Viken some time back. I am not sure how much or which way sorry. If you run a search for tramlining you should be able to find something.