: Custom wheel diameter/TPMS height quesitons



550HP STSV
07-05-10, 07:32 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.

EChas3
07-05-10, 08:49 PM
For the TPMS, just swap your stems to the new wheels. If the pressures are above about 26 psi, I wouldn't expect any trouble. You could buy new stem/sensors & match them to your car, if you prefer.

I'd be more concerned about the fronts being more than an inch too big. Some members report stabilty control displays on the DIC when tires are too far out of whack. You might be fine.

Anybody done it?

madmanmogan
07-05-10, 10:23 PM
I had 24535R20 and 277530R20 no problems with rubbing or anything. However, I did at one point rotate my stock 17s and had the 255 45R17 on the front and I thought it rubbed when turning the wheel all the way. If you lower it I wonder if the 45 series would work on the front? I think they would be to tall. Let me know what you do 550, I also swapped out my TPMSs into the new wheels with no problems.

madmanmogan
07-05-10, 10:27 PM
Oops 550 my bad you said the 45 series would be on the rear. 35 series on front would be fine I would watch the width though. My car would sit perfect lowered but im disabled so when getting in or out every inch helps.

550HP STSV
07-06-10, 10:12 AM
any pictures of your car madman?

madmanmogan
07-06-10, 10:38 AM
Yeah 550, check the last page in the 'show us your sts' link. Let me know what you think. I personally love the deep rear wheel lip with a 20X10.

madmanmogan
07-06-10, 10:40 AM
My bad page 19 or heres the link

http://www.cadillacforums.com/forums/cadillac-sts-forum-2005-through-2010/104756-show-us-your-sts-27.html