Is there anything that I lose by getting fatter rims/tires all around?

Does having fatter rims/tires up front hurt performance in any way? Handling? Accelleration?

I'm planning on going from the stock 17x8 rims to 18x9 on all four wheels. Is there any reason I should consider 18x9.5 or 18x10 on all four? I would like to be able to rotate my tires.

Is there a benefit to handling or accelleration by having say, 18x9 on the front and 18x10 on the back?

Thanks!

 

Benefits - more grip (obviously)
Drawbacks - tires are more expensive, increases understeer.

 

I think th emain reason people go with the bigger rims and fatter tires is for grip. It also looks **** cool to have some big rims and fat tires on the rear wheels.

 

The biggest drawback is the extra weight from the heavy steel wheels. I did notice a little difference in acceleration when I made the switch, but the looks of the aftermarket wheels and tires ruled out ever going back to stock.

If rotating is important to you go with the 18x9 rims and 275/40/18's all the way around. Personally I would rather have the look I want than to worry about draining every last mile out of the tires.

 

18x9.5 Steedas w/275x40. Looks great & grabs great. If your going to go bigger, I suggest you check the weight of your desired wheels against stock and keep the weight as close as possible to say, stock 18" fanblades.

Another concern is speedo accuracy. You want keep the overall height as close as possible to factory. If not, you'll need a tuner to set your new tire height (this can effect your TC as well).

 

Do wider front rims result in increased understeer, or do wider rear rims result in increased understeer? Or both?

Thanks.

 

If I'm not mistaken, I believe the OEM fanblades are pretty heavy, over 26 pounds each which seems like a lot for a 18" x 8.5". But you're correct about the weight being important as it will hurt braking noticably and acceleration, too.
I'm by no means an expert but I would think wider fronts would cause increased oversteer (decreased understeer) but wider rears will cause increased understeer. So maybe they'll cancel each other out.

 

Bigger wheels can also affect your transmission over time. Those guys with 40" rims are doing mega damage...

 

Wider tires = increased hydroplaning possiblity.

That being said, I am running 18x9 DD Bullitts with 275/40/18 all around (so I can rotate).

Did I mention how cool they look?

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I run a staggered 18x10(295/45/18-rr) and 18x9(255/45/18-frt) and have put over 3000 miles of mountain twisties,hiway and city driving.The car is lowered and havn't experinenced and understeer,bump steer or bad handling.
I did however experience a bad rear end bounce for a couple of hundred miles until I installed some Steeda Pro-Action struts and rear shocks.It did firm up the ride and improved the handling.And I'm still getting 26-28MPG hiway at 75mph.

 

you put bigger tires on the front?

Walt, how does it effect the tc?

 

I'm no expert, but from what I've read, any change in tire height that is more than +/- 3% requires recalibration. The TC relies on tire measurement to do it's job. If the numbers are off, the TC's reaction will be less or more, depending upon the height change. My overall height change is -1.9%. I used this calculator.

http://www.bigcustomwheels.com/rt_specs.jsp

I went with bigger tires on the front because I want to rotate and have more of a "road race" inspired look and feel. I did the research and found that Steeda, Roush and Saleen offer the same, or similar combinations. If they can do it, then I thought it's got to work.

So far I have had no issues. The fenders clear and there is no suspension rub (and I'm lowered 1.5"). I have driven in the rain and haven't experienced any hydroplaining; but I think the fact that I'm using an all season performance radial helps. I don't really see any significant understeer, but then I haven't pushed the car hard enough to induce it either.

 

There is no question that heavier wheels produce a performance loss. They are harder for the engine to turn, for the suspension to control, and for the brakes to stop. Heavier wheels slow acceleration and produce longer stopping distances.

Tirerack.com measured the performance of a BMW 3-series sedan with its stock 16x7 wheel/tire combo and then with a 17x8 wheel/tire combo that weighed 7 lbs more per wheel. The addition of 7 lbs of wheel weight resulted in a deterioration in the car's handling, a measurable increase in its lap times and a 1.7 mpg drop in its average miles per gallon. Conversely, when they installed lightweight rims that reduced the car's road wheel weight, the car's performance (gas mileage, etc.) improved.

 

But it looks goooooood.......!!!!

 

My point is to do your homework when choosing plus size wheel/tire combos.

I've seen the 17" machined stock wheels for the GT listed at 21.6 lbs. The two wheels I'm considering replacing with are 17.5 lbs. for the 17 inch and 20 lbs. for the 18".

 

Thanks for all the help everyone. I've decided I'm going to go with 18x9 all around for now and then look into fatter rear wheels years down the road when I go F.I.

Does anyone know how much the American Muscle GT4 rims weigh? Their website doesn't say: http://www.americanmuscle.com/18x9-g...ated-2005.html

Thanks again.

 

Look at CTRs; they publish weight. http://www.ctrwheels.com

For those of you that have wheel weight questions, here's a cool link...
http://victorylibrary.com/mopar/sprung-c.htm

 

Check out CTRwheels.com. They have very similar wheels for cheaper and the weight is listed.

 

I'm thinking about doing that -- just slighlty bigger tires to fill the wheel wells a little better. Same pros and cons, I suppose?

 

That was a big fat typo The 295's are on the rear.