View Full Version : Custom wheel diameter/TPMS height quesitons.

07-05-10, 07:25 PM
A few weeks ago, I thought I noticed a member that had upgraded to custom wheels saying his computer was limiting his car due to the difference in wheel sizes when he upgraded to larger diameter wheels. It this the case?

Right now, I have:
255/45/18 = 10.1" wide, 27.1" tall - 29.1 lbs
275/40/19 = 10.8" wide, 27.7" tall, - 30 lbs

On my STS-V.

Im thinking of upgrading to 20" wheels, which I have the following options:

255/45/20 = 10.1" wide, 29.1" tall, 32 lbs
255/35/20 = 10.2" wide, 27" tall, 27.1 lbs

Obviously the 255/35/20 would almost be a perfect match all the way around, only .7" smaller in the rear, and .1" smaller.

However, I like the staggered look of our cars. How bad would I be screwing things up if I went with the 255/45/20 in the rear (which would be 1.4" larger than the factory wheel diameter,) and then 255/35/20 in the front, which would be .1" smaller than factory diameter? I'm also planning on lowering the car, so I dont know if increasing the tire size by 1.4" would work with the D3 1.5" drop springs.

Also, what do I do about my tire pressure monitor sensors with the new wheels?

Much thanks to ANYONE that can help with these questions.

07-05-10, 08:55 PM
Don't you have a programmer? If so it can be programmed for the new tire size.

I have heard of some guys having issues with Stabilitrac kicking in at weird times with different size tires.

07-05-10, 09:27 PM
I dont have a programmer yet, but I wasnt sure if that could fix it or not.

07-06-10, 11:41 AM
Yes you can change them and if you get a programmer that has the stored tunes (SCT from Jessie) be sure to let the him know about the change in tires. He can adjust it for you. If you get software like HPTunners or EFILive there is a perameter for you to change the sizes.