I just purchased some new rims for my Audi TT - size 18x8.

The concern I have is the tires I would like are 255/35/18 - only problem is tire companies recommend the rims to be 8.5" to 9" is this going to be an issue as my rims are only 8"?

 

It won't be a huge issue, but imagine it like a 10' trampoline with an 11' mat on it, you can probably jump on it, but you're adding alot of slack so the springs won't bounce you as much.

With your extra width squeezed onto a narrower rim, you'll bunch yoursidewallup on the lip of the rim, and youmay get a little side to side flex in the tire that makes it feel sluggish in hard cornering, it may not be a big deal, and you may not even notice though, as its still a close match.

 

35mm height will give you a really rough ride.

 

Its not a 35mm height, its a 35 profile. so probably around 90mm if i do my math right, but math is not my strong point.

 

it's measured in millimeters. 35mm from end of wheel to pavement. 255mm wide by 35mm high by 18 inches wheel diameter. Never understood why they blend american and metric systems on tire measurements.

 

It totally is NOT.

255/35-18 Thats a 255mm section width/35% section height-18"rim diameter.

section width- the width in mm of the tire from sidewall to sidewall when you're looking at it head on

section height- the ratio of the height of the tire sidewall, expressed as a percentage of the width. It is known as the aspect ratio. In this case, 35% of 255mm is 89.25mm - the section height.

 

I stand corrected, the tire bible agrees with you :-)

 

thats because I got lazy, and more or less copy and pasted from there instead of typing the whole thing myself. ; )