Celica Forums General Discussion Exterior 18"s mess up spedometer or odometer?

just wondering if 18" wheels mess up the spedo or odo. anybody know?

It depends on the size your tires. http://www.miata.net/garage/tirecalc.html lets you figure out what the change is. But I did the work for you. The stock 195/60/R15 makes 833 revs/mi, and the 215/35/R18 makes 843 revs/mi. So your new wheels are smaller in overall circumference. The difference is 1.2% and that means when your speedo reads 60 you'll be going 59.3mph.

good question never thinked of that

if you recalibrate the spedo does it fix that? I've always wondered

it will mess up both... just go to toyota and see if one of the techs is nice and will A) let your reprog you ecu for bigger wheels/tires, B) do it for you, with out causing much trouble. or you can take it to say walmart or pep boys, and see if they can do it, its not hard and it should cost alot, so they might be nice and if you buy some shit at the store do it for you for free

thanks for the help.

Isn't the calibration for tire size listed at this site? No need to recalibrate anything. Your going 18" don't worry about a MPH or 2 off below 100. If you need to worry about that on 18's don't race or be wary of the long arm of the law and follow the speed limit. They allow for at least a margin of 5MPH give or take or more depending on the cop. Don't waste your time with calibrations on your speedometer. Don't mess with your ECU!!!! Especially at Toyota. You'll be fine. Just slower for obvious reason, but fine. Don't worry.

Toyota or any body won't recalibrate you ECU, PERIOD. Toyota won't change your speedo for tire size either or can, PERIOD. You'll be fine on the 18" unless you got a tire size in an aspect of 60 on 18's. Read OneShotUno reply again or try it out yourself. Don't waste your time or money going to Toyota or somewhere else to fix a MPH difference. They will take your money and won't fix anything.

Just use the tire calculator to match your stock size..
With 18's you can go with 215/35/18 tire.. it's pretty close to stock size...(little under stock)
Also you have go with 225/35/18 that's little over stock..

You do not want to go size too small nor big... cause it'll unbalance the power transfer compare to engine and rotation mass and gear ratio.. etc... what ever it's designed for... sorry.. can't think of right names...