: Correct Tire Fitment

01-20-12, 03:18 PM
Car: 1993 Cadillac Seville

Hi, I've been fixing up my 93' Seville for the past few months and it has come time to work on the visual aspects of the car. I will be putting Lexani LSS-11 20" x 8.5" rims on it, and need to know if the tires I wish to put on it will affix to the rim without major future complications.

From what I've been hearing/reading 245/35R20 is the recommended size for this size of rim. But I was wanting to put the Vogue CBR-VIII White & Gold tires on, but the closest size they make is 245/40R20. Will these tires(245/40R20) fit properly onto the 20" x 8.5" rim?

One other thing, if these rims & vogues will work with each other properly, the overall diameter once they're on the car will be roughly 1" more than the stock wheels and the car will be moving around 4% faster than the car's computer will think it is due to the larger wheels. Would this be something to worry about? The closest place to where I live that can calibrate speedometers is over 100 miles away and I do not have very much free time. So is there a device that will work with my car to calibrate my new wheels that I can order online? I've looked at stuff like "Superchips" that claim to be able to do just what I need, but will not work with my 93' Seville.

Thank you for your time and help! =)

johnny kannapo
01-27-12, 09:40 AM
www.tirerack.com has tire specs calculate this.

The revolutons per mile & width would be important to get as close as possible.

Caddie Shak
02-06-12, 06:51 PM
Wouldn't worry about 4% speedometer error, you can adjust for that in your head while driving. Off-road guys in lifted trucks get into the neighborhood of 25% over stock and usually don't mess with speedo calibration until they go beyond 10%. (Regearing the differentials also helps get the engine's operating RPMs back to where they should be, and helps correct speedo error.)

245/40R20 tires won't fit the rim any different than 245/35R20; the only difference is the amount of tire sidewall. So the rims won't care which tire you use, but your fenders might - so you'll need to research clearance issues with the taller 40-series tires.

02-08-12, 02:35 PM
Thank you very much for you help!

03-23-12, 11:18 AM
The offset and back spacing are also important. Is the rim shifted inwards or out can have a big impact on rubbing issues. The back wheel does not turn left/right like the front steering wheels. Lots of wheel dealers say they guarantee the rim dimension but not whether it will work on your car. Small but important detail.