Does anyone know if this will work for a 2007 Cayman S? The fronts would be 18x8 with 235-40 tires. Thanks.

 

you might need some spacers to keep the inside of the wheel from hitting anything. you should do a test fit to figure out what size spacers you need. but with or without spacers, the outside edge of the wheel will stick out past the edge of the wheel well (more so with spacers).

 

you are definitely going to need to roll the fenders, but the look is well worth it....

 

You will be dialing in a lot of push. That's a big delta on tread width.

 

+ 1 on what Alan C Said ,I have 19"s but I would not go any wider then 295's on the rear and 35's on the front IMO. I have tried this and even if you get spacers it will handle like crap .
Go with 295's with 17 mm spacers (Or less)on the rear and with the 40 on the front no spacers are needed (I have 35's) and my car handles great.
You can do what you want but IMO the car will be out of control if you go with anything wider and taller .I had to learn the hard way on this. Looks cool but feels out of control ..dont do it it wont feel like a porsche any more

 

hello understeer

 

+1000 % on that . I tried it and my car was out of control

 

I picked up a pair of works that came with 315 in the rear. Several shops and people on the forums all told me that the widest I could get away with in the rear was a 295. I tried keeping the 315 since they were free. They went on no problem and seemed to clear everything without any rubbing, it was close on the inside, but it still cleared. Drove around with them for some time. Ended blowing out one of the rears in a turn. Once I had the tire off, I could see that the car was slashing big gashes into the tires evertime I would make a sharp turn with body roll.

 

If you aren't going to lower your car, and pay attention to brake lines, then you should be fine, I'm sure you can get them fit without any issue.
I've 325/30 20 rear, the ride is terrible, handling is terrible. I'm going back to 305 soon. Wouldn't recommend this size for cayman. but 911 is fine though.

 

Would a LSD or TBD eliminate the understeer? I was thinking on trying 315 Nittos for the track after I got my differential upgraded.

 

depending what rims and the offset you will be using. i already think 295's in the rear is pushing the limits. you'll either need huge spacers (which may put stress on your bearings) or roll your rear quarters so you won't rub. if your car is lowered, you'll definately need to size down or go with a negative camber

again feel free to correct me if i am wrong

 

I have 295's on my cayman now and its lowered with H&Rs , a few months back I started hearing a horrible noise and took it to the dealer .It ended up the tires were rubbing against the brake lines in the rear and they were down to the metal so we zipped tyed them off for clearance and i installed 7mm rear spacers and all is well . You are right though you will need to do that same as I did but with a lot bigger spacer

 

I put Porsche Turbo Twists 11 inch rim with 295 tire on my 07 boxster, I used 23mm spacers. It looked great, no issues with tire rubbing. It did however slightly increase understeer in low speed tight cornering, but handled much better in wide high speed corners..