Has anyone used a 305 35 18 on a 996tt wheel? The tire is 26.8 tall and the car is lowered a bit. I have no rubbing issues with 315 30 NT01
It will be close for sure

 

The 295/30-18s are just at ~25" diameter, so that's a substantial amount. I am at ~103.5mm in rear, and 295/30's are the best I can get in there. Had to buy used 295/35's to get home from track once. They rubbed on bad roads.

 

the 315 30 i run are 25.35 dia and the 305 35 are 26.8. So about 3/4" radially. Not sure how to test the fitment without mounting the tires. I might scrap the idea and go with a different brand so I can get the smaller Diameter.

 

My 305/30/19 are 26.3" and they seem to be ok. Only 0.5" taller so 0.25" on one side radially like you say, I think they will probably work?

 

Just a thought, can you put a piece of foam or something else the appropriate thickness on your current tire to check clearance? might help/give an idea even if you can't drive on them.

 

I messed up, the tire is 26.6 not 26.8. So that helps. I'll try the foam and jack the tire up until I start lifting the chassis. This should give me a good idea.

 

You can install and put the car up on an alignment rack, drive on lift, or put the car on blocks and get under and check clearances. You have to figure some extra room for suspension travel.