ZQQM

In the 1/2005 issue of C&D, page 37 they review the new Pontiac GXP which will have a V8 with 290hpw/325lb-feet through the front wheels. To combat the power, they ( Pontiac ) are mounting 255/45/18's on 8" wide wheels on the front and 225/50/18 on 7" wide in the back. They state that this will decrease understeer and balance the chassis.

I know it won't look great, but will this decrease understeer and create a more balanced feeling in our chassis?

Say it did work, maybe just adding a slightly wider tire up front, say 245/45/17 on the front stock rim might add a benefit without upsetting the looks of the car.

Thoughts...................

dsc888

It sounds like a decent idea but wouldn't a thicker rear sway bar achieve a similar effect WITHOUT adding unnecessary unsprung weight to the front wheels? The extra seveal pounds of rubber will rob performance to some extent. At least that is my take on the situation.

dsc888

avs007

The GXP wheels are forged, so they are probably considerably lighter than the stock cast wheels. Considering that thing is a V8 with gobs of torque, it can't hurt to have beefier tires up front. As long as it's not a staggered look, where the tire actually looks bigger, I think it'll look fine. (That is, as long as the rolling diameter is the same, and the sidewalls are the same height, etc)

SouthernBoy

To ZQQM;

Don't go to 245/45-17's. You'll lose acceleration because the tires are taller. This had the same affect as going to a higher final drive.

Instead, use 245/40-17's.. or even 35-17's.

automata

Here's a question.
If going with wider tires up front does help, witch it makes sense that it would, does using the same width tire in the rear affect or negate the performance increase of the front tires? What I'm saying is why not just increase the width of all the tires? I understand why having wider tires on the driven wheels helps, but does having the same width tires on the non-driven wheels hurt?

avs007

Having wider tires give you more grip, not just for acceleration, but more lateral grip as well. A front heavy car is at a disadvantage, because the front wheels have to bear more weight in the twisties, which is why they tend to understeer more. Having wider tires up front compared to the back, compensates for this somewhat. That's what the meant when they said balance the chassis. I think it's easier/cheaper than modifying the rear suspension. Especially since they prob want wider tires up front anyways, just to handle all that power.

Putting wider tires on all 4 corners won't address the issue mentioned above.

ZQQM

I do a little auto-crossing, and I want to shift the balance of our nose heavy car slightly. I plan on getting a spare pair of stock wheels with the wider rubber ( maybe 255/40/17's ) and swap on run days. I'm not worried about a very slight loss of acceleration do to the slightly taller tire.

geminis2

why not put a stickier compond tires???