Coach Borne

I have a 2011 GS. Current rear tire is 325/30R19. If I would increase the size to a 345 what problems may arise.

clearwaterms

Assuming the tire will fit, if the tire is taller it will mess with the active handling system that assumes the height as a proportion of the front tire height.

Unreal

Not only that, it could be a huge downgrade in performance. A wider tire does not mean a better tire. Tire compound, height, tread design, all play a huge roll in the tires performance. I've ran a 345, 325, and 275 on my car, and the 275s are by far the best sticking best performing tire because they are the correct size/height/compound for what I need.

gr86ss

I have a 12 GS, and I have an extra set of factory GS wheels with 345 drag radials. They totally out perform the 325 street tires when I need extra traction. I don't throw any codes running the 345s. The 345s fill the wheel well really nice when using a factory wheel/offset.

CHEV AGAIN

3/4 of an inch each affect handling?

Unreal

It isn't about size, but the overall tire. A 285 R888 will out handle a 345 invo all day long.

AK Drop Top

I would think since your only changing the width of the tire you will be fine in the rear, and if your rear wheels are 19-12, you could use the same wheels.
Just a thought.

Jk

CHEV AGAIN

Could be...But that's not what he asked.

Mark

choppychop

You should be fine...

Seadawg

:agree: Many have done it with no issues, on the GS and Z06 rims

jbc1995fb

Swapped mine and don't have any issues.

BIGMAC

I have Nitto NT05R 345/30/19 DR's on my '12 GS with no codes thrown but no traction at the strip! The NT05R tires spec at 27.4" diameter vs 26.7" for the stockers. I want to go to 28" tall DR's but fear the dreaded AH/TC/ABS codes thrown. I have been frustrated by conflicting information about the tolerance of the nannies for rear/front tire diameter difference. The information is about a 50/50 spit if the 28" rears will work. It appears I will just have to bite the bullet and hope they work.

BIGMAC

LMB-Z

No problems will arise. You will have a wider rear tire, but contact patch with the pavement will only increase minimally. The car will look better too.

eshuber

I think what earlier posts are suggesting: when you fit a wider tire and don't increase the wheel width accordingly , overall handling will suffer. If you just want the "look", then that's another story.

Unreal

My point was what are you wanting out of a wider tire? More traction? Better handling? Looks?

Some brands 345s are narrower than other brands 325s. So if it is looks that could be going backwards.

There is no issue with a 345/355/365/375 as long as the wheel and height is correct and matched to the fronts.

Coach Borne

For Looks. I don't race. My biggest concern is what will it do to MPH and will it decrease miles or increase miles

Unreal

That is all the height of the tire. Make sure you research the actual tire. Like I said, some 345s are actually narrower than other brand 325s. So if it is just for looks keep that in mind.

LMB-Z

It won't do anything for mph. 325/345 is width. Won't make it go any faster or slower, and fuel mileage won't change. Just cost more for tires.

icntdrv55

I went up a bit in size when I replaced the OEM GY Eagle F1 Supercar Gen:2 RFs with Michelin PSS non-RFs. Ordered the fronts in 285/35 and the rears in 345/30 on stock rims. No rubbing or other issues encountered. [NOTE: My car is NOT lowered! Lowered vehicles may have a different outcome.]

Here's a comparison of the specs for the different tires (from Tire Rack website):

GY 275/35 = tread width 9.5", diameter 25.6", revs/mi 818
GY 325/30 = tread width 10.7", diameter 26.7", revs/mi 782
F:R ratio = 1.046

Mich PSS 285/35 = tread width 10.2", diameter 25.9", 804 revs/mi
Mich PSS 345/30 = tread width 13.0", diameter 27.2", 765 revs/mi
F:R ratio = 1.051 (approx 0.5% change from OEM)

In summary, you stay close to the factory F:R tire diameter ratio so as not to confuse the active handling function (based on relative wheel speeds) and you get about a 2.2% overdrive effect at the drive wheels (slightly lower RPM/MPH). I have heard--without any personal experience--that other forum members have installed 345/30 at the rear while keeping the stock 275/35 fronts and not experienced any active handling problems.

AIR_RAM

Im about to order my Super Sport 345/30 19's for my GS... There is not much to chose from in that tire width. From the research I have done, It looks like a good majority of Z06 guys are running them without issue and there is no downside other than cost.

The ones I have seen in pictures look more noticeably beefier than I had initially thought they would. I'm going for performance and look... I doubt there is any noteworthy performance loss.

Should have them in the next few days. Ill be sure to take pics before and after.

SPEED SAFE, AIR RAM