Tire Options
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Tire Options So As all of us with the GXP know we have a somewhat f uped tire sizing on our cars. I have looked at tires and i have notice that u can find 225-235 45 18 alot easier than 225-235 50. What do u think of going this way to open up more choices
Her is a link to discount dires with the Stock 255-45-18 and 235-50-18
Alot of choices
http://discounttires.com/list.php?si...earch=tiresize
Her is a link to discount dires with the Stock 255-45-18 and 235-50-18
Alot of choices
http://discounttires.com/list.php?si...earch=tiresize
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Do u have pics of that. NO rubbing or anything like that ? How do u look on the front wheels
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I was also looking around and was wondering how a 265/40 18 and a 235/45 18 would work. General tires Exclaim UHP tire is avalible in this size are really cheap. front $165 rears $129.. Now if we could do a 255/45 18 and a 225/45 18 instead ofthe 50 serious the prices would be.. Fronts $140 and Rears $109
http://www.tirerack.com/tires/tires....el=Exclaim+UHP
http://www.tirerack.com/tires/tires....el=Exclaim+UHP
https://ls1tech.com/forums/ls4-front...p-s-tires.html
You could run 265/40-18s & 235/45-18s. Your speedo would be off. It would read 65 when you are only doing about 63.3mph. It potentially can also hurt your gas mileage slightly and cause your odometer to accumulate miles faster than you are actually putting them on. Going to the wider tires really only opens you up to running the General Exlclaim tires you are looking at. Nobody else offers a tire that matches those sizes for front and rear.
I myself am going with the Goodyear Eagle F1 A/S in the stock sizes.
You could run 265/40-18s & 235/45-18s. Your speedo would be off. It would read 65 when you are only doing about 63.3mph. It potentially can also hurt your gas mileage slightly and cause your odometer to accumulate miles faster than you are actually putting them on. Going to the wider tires really only opens you up to running the General Exlclaim tires you are looking at. Nobody else offers a tire that matches those sizes for front and rear.
I myself am going with the Goodyear Eagle F1 A/S in the stock sizes.
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If you were driving 65mph and you ran a 255/45-18 in front and a 225/45-18 in the rear, your rear tires would only be spinning 62.4 mph. Might be enough to throw ABS codes.
Play around with this:
http://www.discounttiredirect.com/di...foTireMath.jsp
Play around with this:
http://www.discounttiredirect.com/di...foTireMath.jsp
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With 255/45 R18's all around, my car handles very well. I was somewhat apprehensive about putting the front rims on the rear and the rears on the front but it worked better than I expected. There was a slight rubbing with the rears on the front, but it was only when I turned the steering wheel completely to the left or right. The rubbing was on the rear portion of the inside of the wheel well but it was minor. Only a 1 inch area. I actually only noticed it when I rotated the rears from the front to the rear. The care did handle slightly worse but I emphasize that it was slight. And it did not look bad at all. No one noticed the difference and I could barely notice the difference. And the best part, the tires are lasting much better. I would say if you choose to go this route, you shouldn't have any problems. I certainly did not.
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I actually like the staggared tire sizes. i have pushed my car hard enough to actually feel the rear end come around they way it was designed to. Its pretty cool i think. But atleast we know that we can do it. That opens up alot of options.
There is a good reason for GM staggering the tire/wheel sizes. It costs them more money to run goofy sized tires and rims. If they couldn't justify the benefit, they wouldn't have done it. The GXP was designed to outhandle the Monte Carlo SS and the Impala SS. The MC and the Imp however have a numerically higher final drive for faster acceleration than the GXP.
This is what Car & Driver had to say about the tire sizes:
This is what Car & Driver had to say about the tire sizes:
Pontiac Grand Prix GXP - Road Test
Pontiac rewrites the front-drive-performance rulebook.
BY TONY SWAN, PHOTOGRAPHY BY AARON KILEY
October 2005
The obvious part of the formula is obviously far from new: Cram a big ol' V-8 in there, make the car go faster. Detroit has been doing this since the '60s. But what may not be so obvious is that there's a big asterisk to the formula when you start applying it to a front-wheel-drive car. The footnote reads something like this: "Put enough power through a front-drive system, and the driver will find himself turning right or left when he was planning on straight ahead."
It's called torque steer, and it's the major limiting factor in front-drive performance cars. Despite various engineering advances, the problem persists in cars such as Acura's otherwise superb TL, which sends 270 horsepower through a six-speed manual transmission to the front wheels via a helical limited-slip differential. But in the Grand Prix GXP, with more horsepower (303 at 5600 rpm) and a lot more torque (323 pound-feet at 4400 rpm), torque steer is not a serious issue. There are hints—a little tugging when the driver cracks the throttle at low speed—but no real wrestling.
How'd they do that? By adopting a measure no one else has ever put into production. More in a minute. But first, another front-engine, front-drive problem, one that's even more chronic than torque steer. With a design that puts all the heavy powertrain hardware up front, front-drive cars invariably have a pronounced forward weight bias, 64/36 percent in this case. As a consequence, the front wheels carry more than their fair share of the car's mass, diluting the ability of the tires to transmit steering inputs. Worse, the front tires are also required to transmit power to the pavement, and all things being equal, the poor things just can't handle their multiple assignments as well as the front tires of rear-drive cars. The result is understeer. The faster the driver herds the car into a turn, the more it wants to go straight.
Pontiac's solution to these two inherent front-drive directional control problems—understeer and torque steer—is unique. Instead of four tires of equal size, the GXP has a lot more rubber up front than at the rear: Bridgestone Potenza RE050As, 255/45-18 front, 225/50-18 rear.
"We wanted a car to run with BMWs," says program engineering manager Phil Minch. "But we were limited by the W-car architecture, in other words, by front-wheel drive.
"The rear end never lets go when you have the same size tires all around. So we put our computer guys on it, and they came back with a recommendation for a smaller rear tire, to give the car better balance."
This is a radical departure from conventional wisdom, and the idea proved out in initial testing. But there was a nasty side effect: Increasing the contact patch at the front amplified torque steer. However, after experimenting with a number of different tires from a variety of manufacturers, Minch and company decided the problem lay in the tire's construction-the way the plies were wrapped-and not the footprint. With sufficient application of power, the tire sidewalls distort, thus affecting directional stability.
Bridgestone, the supplier of choice, was initially reluctant to accept this theory, but when the GXP team achieved improved results using an off-the-shelf tire from another maker, the Bridgestone people got to work and developed a tire that delivered the desired performance.
Pontiac rewrites the front-drive-performance rulebook.
BY TONY SWAN, PHOTOGRAPHY BY AARON KILEY
October 2005
The obvious part of the formula is obviously far from new: Cram a big ol' V-8 in there, make the car go faster. Detroit has been doing this since the '60s. But what may not be so obvious is that there's a big asterisk to the formula when you start applying it to a front-wheel-drive car. The footnote reads something like this: "Put enough power through a front-drive system, and the driver will find himself turning right or left when he was planning on straight ahead."
It's called torque steer, and it's the major limiting factor in front-drive performance cars. Despite various engineering advances, the problem persists in cars such as Acura's otherwise superb TL, which sends 270 horsepower through a six-speed manual transmission to the front wheels via a helical limited-slip differential. But in the Grand Prix GXP, with more horsepower (303 at 5600 rpm) and a lot more torque (323 pound-feet at 4400 rpm), torque steer is not a serious issue. There are hints—a little tugging when the driver cracks the throttle at low speed—but no real wrestling.
How'd they do that? By adopting a measure no one else has ever put into production. More in a minute. But first, another front-engine, front-drive problem, one that's even more chronic than torque steer. With a design that puts all the heavy powertrain hardware up front, front-drive cars invariably have a pronounced forward weight bias, 64/36 percent in this case. As a consequence, the front wheels carry more than their fair share of the car's mass, diluting the ability of the tires to transmit steering inputs. Worse, the front tires are also required to transmit power to the pavement, and all things being equal, the poor things just can't handle their multiple assignments as well as the front tires of rear-drive cars. The result is understeer. The faster the driver herds the car into a turn, the more it wants to go straight.
Pontiac's solution to these two inherent front-drive directional control problems—understeer and torque steer—is unique. Instead of four tires of equal size, the GXP has a lot more rubber up front than at the rear: Bridgestone Potenza RE050As, 255/45-18 front, 225/50-18 rear.
"We wanted a car to run with BMWs," says program engineering manager Phil Minch. "But we were limited by the W-car architecture, in other words, by front-wheel drive.
"The rear end never lets go when you have the same size tires all around. So we put our computer guys on it, and they came back with a recommendation for a smaller rear tire, to give the car better balance."
This is a radical departure from conventional wisdom, and the idea proved out in initial testing. But there was a nasty side effect: Increasing the contact patch at the front amplified torque steer. However, after experimenting with a number of different tires from a variety of manufacturers, Minch and company decided the problem lay in the tire's construction-the way the plies were wrapped-and not the footprint. With sufficient application of power, the tire sidewalls distort, thus affecting directional stability.
Bridgestone, the supplier of choice, was initially reluctant to accept this theory, but when the GXP team achieved improved results using an off-the-shelf tire from another maker, the Bridgestone people got to work and developed a tire that delivered the desired performance.
