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Good idea to swap 18X7 for 18X8?

jimgimli - This is exactly what we need to hear, someone who has acutally done it. Thanks. Can you keep us updated? This is definitely something I'm considering when I need new rear rubber.
 


The quad is a 2006 Raptor 700. Only mod was an aftermarket pipe (LRD PRO R-4 racing pipe). Other than that it's just cosmetic things to look cool :D. This thing reaches 70 + or - a few mph as it is and I don't need to be going any faster than that :o. I love riding the dunes, unfortunately I live in Iowa so the nearest is Michigan. But we don't go there very often, we try to get to Wynoka Oklahoma to Little Sahara twice a year.
 
I had a Banshee that was built up and I GPS'd it one time to see what it would do...clocked in 93MPH. Needless to say I was actually scared **itless as I could see the front fenders bending back due to the air moving around them. Loved the Banshee in the dunes, but I do have to say, all around I would rather have a Raptor.
 
I don't know about the fitment issues, but I do have a couple thoughts on what changing the rear tires will do. It add a lot of understeer into the car. This will make it feel like you are going faster at the same speed, and make the car more likely to plow. If you keep the fronts stock, it won't mess with traction control. It will mess with ABS cause they have different revs/mile, but it shouldn't hurt your stopping distance much cause you are adding tire and the front tires do most of the stopping anyway. Where you really suffer is when turning, and it will hurt ESC. You'll loose some g's going around corners, and when ESC kicks on you'll plow a lot more. If you are a straightline only guy, no biggie.

I do know that I'm going back to the stock tires next time I change them. I put Goodyear Eagle F1's on they really screwed up the traction control and ABS. I lit up the tires the other day, and they just roasted and I just sat there waiting for traction control to make them bite. Maybe the Potenza 960's will work better as an all season, I think Panther427 said he put those on. Anyway, my point is changing tires will screw up all the computer stuff way more than putting bigger tires on the rear will.

Understeer is when you hit the wall with the front of your car, oversteer is when you hit the wall with the back of your car. Power is how fast you hit the wall, and torque is how far you move the wall.
 
Unfortunately, I drive my GXP like an 80 year old man would (I'm 33). Several days a week I drive less than 7 miles per day and the hardest corners I turn are to pick up my daughter from school. It's a pretty simple ride for me. The last 2 full tanks I had an average speed of 22.4 and 22.8 mph, this tank won't be much different :o. I don't see how putting 18X8 stock rims on the rear of my car will make much of a difference.
 


Having 18X8 all around will make it drive like a normal GM FWD. On the GXP the smaller tires in the rear was used to help the car turn in better and allow you to not understeer as bad as nmp pointed out. However We are still talking about a nose heavy car and these changes can only do so much in eleminating the under steer. But GM has proved with lap times that with the smaller tires in back the car was faster than a FWD with same size tires all 4 corners.
 
Right, that's if you run lap times drag or drive it like a true performance car. This is just my daily driver that never takes a corner faster than about 2 mph. Don't get me wrong, I get on it when I can, but it's always in a straight line and for a very short period of time. My cars get very few miles put on them. If we go anywhere as a family we take my wife's vehicle and mine sits in the garage.
 
I was just trying to throw some info out there, not trying to discourage you from doing the mod. For your driving habits, changing the rears should basically have no effect. You'll never see a downside, and some of the stuff, like being more stable, feeling faster, and being able to rotate the tires, will be a noticeable upside.
 
Not a problem, I wish I was able to drive it a little harder but it usually just doesn't happen with what I drive for. I drive to/from work and pick up 1 kid from school. I had another car that was leased before this one that I had for 38 months and put about 22,000 miles on it. Needless to say, I bought my GXP. I don't think I even corner hard enough to spill a glass of water most of the time. :( At least I know the miles will stay real low on my GXP.
 
Just for ****s and giggles I swapped the 18x8's with the 18x7's for about a week and I had no trouble with rubbing in the back and the car handled and steered fine, granted I wasn't at the track at all, just daily driving. It did mess up the tire pressure sensors for a day but after a little while everything reset itself.

If you're just looking to get the same width rim all around for rotation purposes 18x8's would be better because you'd still have the wider tires up front for traction. It won't hurt you to go 18x7's either though. I have Monte Carlo SS rims with 235/50/18's for winter tires on the car now and have had no problems. Just depends on what your driving habits are and which rims you can find (18x7's) or (18x8's).
 


I will be putting 18x8 (40mm offset) Boss Wheels 328's on the car this weekend, with the stock size front rubber (255/45/18). I did the figures on the rolling length of the stock sizes and found that there is only a .2 in difference in the tire size, which is minimal at best. The traction control should be fine with that and shouldn't over react to that small of a difference. It is literally less than just putting new front tires on without replacing the rears. I'll let you know if there are any problems with the fitment of the wheels/tires once they are thrown on the car. I will be doing a 500 mile trip right after they are installed so I should know for sure if something is wrong. I'll keep you all up to date on the situation and I will also be putting my stock Alcoa forged rim up for sale.
 
Just put on the Boss 328's 18x8 with a 40mm offset and 255/45 rubber on it. Drove 500 miles with a very heavily packed car with no problems at all. Worked out great!!
 
This is more good news. I've got 2 more 18X8 alcoas sitting in my basement and 2 more 255/45/18's on the way in the mail as I type. They'll be going on in the spring, can't wait.
 
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