I'm going to be switching to a 19" wheel on the back. I don't want the real short tire look. I'd like to run a 1" taller tire then stock. Will the computer correct the speedo, etc. I don't want it to make the shifts any worse then they already are. The stock tire height is 26.7 and the new tire would be 27.6. Can any of you tuners give me some input. I'm going to run a staggered setup with a 19x9.5 on the rear and an 18x8.5 on the front. Then plan to drop it an 1.5. One ince taller tire on my 300 thru the speedo off about 4 mph at 70. The computer would not correct the speedo on that setup.
thanks
locrzn

Need a tune to fix that.

Any time you change tire diameter, you need to have the computer adjusted to fix your odo and speedo. And going with different diameters front/back will screw with the ABS, TC, and stability control.

Recipe for disaster...

Recipe for disaster...

I don't know, guys across the ocean are putting 22's on these cars! But as always, check with your dealer:gears:

I had 22's on my 300, it did mess with the computer a little, mainly the speedo was off about 4, slower that is. The dealer did care and serviced as usual. I'm good friends with my dealer and there are a bunch of drag racers and circle track guys. I'll see if they can recalibrate for the taller tire. The chrysler dealer tried, but, in their program it only went to 28 inches tall. Mine were 29 inches. Looked good on the car with the eibach prokit.
locrzn

The dealer can re-calibrate the speedo.

As long as you keep the outside diameter of your new wheels/tires the same as the stock setup, you are cool. This means that if you get bigger wheels, you will need to get shorter tires. If you change the outside diameter of the tires more than 5%, you will need to update the vehicle's computer to account for the new tire diameter.

This is not a 1970's vehicle where the only casualty of putting on taller tires is a speedo that's off. If you don't update the computer, you risk losing your ABS, and potentially getting into an accident. Worse than that, if your insurance company finds out, **poof** you have no insurance. :eek:

Sandog, thanks for the input. I'm very aware of the deminsions as far as diameters, my question was specific to this car. If you go to my cardomain website, you will see that all my rides have wheel changes, most with up to 1 inch taller tires. I've normally gotten away with up to 1 inch, as with my 300. Yes it did affect the performance, that was mainly due to the weight of the 22's compared to the 18's. When you have 30 pounds difference on each corner of the car, its gonna make a huge difference in stopping, taking off and up and down shifts with the tranny. I faced all those issues with the 300. I was hoping to get some oz reponse, I've seen a lot of the pics with wheel changes that they have made. It appears that many are changing the tire diameter. I'm going to talk to my service manager at the pontiac dealership to see if they can reflash for the taller tire. If not I'll probably stay with the correct diameter which is about 26.8 tall.
locrzn

DIfference between standar 18's and standard 19's is no more than ,2", about 3/4 of 1 percent. Wouldn't surprise me is GM doesn't change anything between the tire sizes. Your choice is 2.6% off from the GM 19's making it ove3r 3 % off from standard 18"s. Must be one heck of a skinny tire compared to what Pntiac sells. Reason for wantning LESS rubber on the ground? Burnouts, smoke? Whatever you do, as was suggested, even if you put bigass 31" truck tuires on it, go all 4 the same diameter, if not width.

Hey, probably will stay with simular diameter, just waiting on rt tire in ohio to try some bmw staggered wheels on his buddies g8 today. I may end up just staying with an 18's all around. I'll first see what he says on fitment for th 9.5 on the rear. I have to have the tires tucked under the car. I plan on doing an eibach drop when they release their pro kit for this car.
http://www.cardomain.com/ride/3049754
see my site for my g8

I don't know, guys across the ocean are putting 22's on these cars! But as always, check with your dealer:gears:

Actually, I meant going with substantially different tire diameter front to rear. The ABS/Stabilitrak will probably flip out.

If I did a 19 in the rear and an 18 up front, there would be only 1 inch difference between the front and rear. Rear 27.7 and front 26.8. I want the rear tires to look the same as the front as far as the tire appears on the wheel. I'm not into the rubber bands around the wheels. I live in Missouri where the roads have pot hole issues. So, a 19 with a 27.7 tire and an 18 with a 26.8 tire will look the same from the ground to the wheel. I've done this on almost every rear drive car I owned except my 300. The tire were the same front to rear. I like the drag look, not the road race look. It will all work out which ever way I decide to go.
locrzn

Actually, I meant going with substantially different tire diameter front to rear. The ABS/Stabilitrak will probably flip out.

Yep,
The rear end on the car either uses the VSS (vehicle speed sensor) on the output shaft, a calibration ring around the ring gear or hub based sensors inthe rear. The front will use a sensor in each hub. The data will be mixed and *should* make the ABS flip out. I wouldn't do it with my money, but it would be nice to know if we are right. Try and let us know.

Worst case senario, the retailer swaps out the tires for those with appropriate dimensions or you drive around without traction control, stabilitrak, ABS and a bright flashing light on the dash board.

I haven't heard back from RT tire, I'll call tomorrow and see how the fitment went on his buddies g8.
locrzn