I have a Boxster Spyder which came with Bridgestone Protenzas but they need to be replaced after my most recent track day. I'm looking to get something more aggressive like Yoko AD08, Nitto NT05 and Hankook Ventus v12. (If you have any tire recommendations, I would love to hear them!) My problem is that I can't find any of these tires that match my stock tire dimensions at 235/25-19 and 265/35-19.

How large of a tire can my wheels accomodate? There seem to be more options with wider tires. Stock Spyder wheels are 8.5" x 19" and 10" x 19".

 

Don't laugh. Running same size 19" Rufs on wife's 987S. Had tire issue on one rear and put a pair I had sitting around. I wanted to rethink tires before I spent the big bucks and didn't expect to use them more than a couple of weeks... so why not try?

They fit/work much better than I expected and I have no plans to swap them until we wear them out. Wife is happy...especially that I didn't spend $$$ on tires.

Oh, we have 305/30 PS2s. [!] Only slight bulge out and no clearance issues. It also helps with trying to get late corner power down. I am used to 911/930/etc and didn't realize how much I enjoy sling shotting out of corners until I tried it in the 987S. [Too much wheel spin for my taste.] I never would have thought these would work, but they do. Balance isn't bad either. Some push, but I have no problem pushing the tail out. I will probably go to 285 or so when I replace the set.

GL

JR

 

That's one reason I got 18" wheels for mine - NT01's will fit. And 18" rubber costs less than 19" rubber.

The main concern is the overall tire diameter. You don't want to vary too much from the stock diameter ratios or you may have ABS issues.

 

245/295 would be the widest I would be comfortable with recommending. Or, a wider-than-average 235/275 combo like AD08's.

305 is not recommended by Michelin for a 10" factory wheel.

 

I will be getting my first Cayman S very soon. The car I'm getting has 18" wheels so what would the widest tire combination be for 18" wheels? Same as the 19"?

 

The Cayman S has 18x8F and 18x9R. You are limited to a 235F and 265R at max width. Anything above will budget and sidewall will have too much flex.

RE: Spyder wheels

19x8.5F and 19x10R is the usual aftermarket fitment on which we run 245F and 275R - you have a lot of options in these sizes.