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Good idea to swap 18X7 for 18X8?

VDV18

VDV18

New member
Hello

Long time lurker, first time poster. I've got a 2006 GXP and would like to swap out the 18X7 rims that have 225/50/18 tires for another set of 18X8 rims that have 255/45/18's.

This way I could rotate my tires all the way around the car instead of just left to right.

However, I've been told that this may not be such a good idea. I've heard that it can interfere with the ABS, traction control, etc. I've also heard that it could potentially cause transmission issues.

I don't have the knowledge to say one way or another. I do like the stock rims and only wanted the wider width rim/tire in the rear to match the front. But I certainly do not want to cause mechanical issues down the road from doing this.

It's too difficult to tell what would happen 3-5 years down the road or with more miles on the vehicle (I've got 31,000). I've read posts about people wanting to do this, but has anyone ever seeked advice from a tech or someone actually involved with the factory set-up on this specific vehicle?

In reading, there seem to be a lot of members on here that know there way around a car mechanically. Are there any techs that have knowledge on this issue for the GXP?

Any help is appreciated
 


I have heard of two think simliar to what your asking. The first was when the bought his car from the dealership they had rotated the wheels/tires. Put the 18*8 rims on the back. While he didnt know there were different wheel widths at first. He didnt experance any issues for a bit. Others have put 245/45/18 all the way around. If i remeber correctly though. If the car is unloaded only say carring 2 front passengers it was ok. But once you have alot of grocery's/luggage and or a car full of people the suspension settles and will rub the tire on the strut.
 
Good to know Panther, thanks. I guess I don't understand how just 1 inch of width would cause such an issue. Are there no GXP owners out there that have say 20x8.5 rims (common size)?

A 20X8.5 rim would be worse than what I'm trying to do. And the GXP is only 9mm lower than a normal Grand Prix so it just doesn't seem like it would have much impact.

This just seems like it should be a whole lot more simple than it is :confused:
 
There really isnt alot of room. Some time get down low and take a peak of how close suspension components are to the tire/wheel. I know a 235/50/18 will fit for sure. But i do know that the 255 is just too wide. Maybe with a wheel spacer for safety reason a 255/45/18 mounted on a factory 18*8 would fit.
Personally i plan on keeping summer rubber on factory wheels, and get some 17 inch wheels for winter.
 
I believe the 18X8's with the 255-45's will hit the struts also. I run the stock size in spring/summer/fall and then switch to 235-55-17's on 17x7's with ice/snow tires for the winter. Even when I mount these 235's, there VERY little clearance between the tire and the strut.
 
Thats exactally what i plan to do with my car. Got a pic of your winter wheels? i found some 17" enkies for 200 bones. Should make for some nice winter wheels.
 


seriously? what is the offset on those things? why would they rub the strut?

usually an 18x8 is pretty easy to pull off so long as the offset is like +35mm or more.
 
Panther427 said:
Thats exactally what i plan to do with my car. Got a pic of your winter wheels? i found some 17" enkies for 200 bones. Should make for some nice winter wheels.
Click to expand...

Sounds like a good price. Honestly, I don't even remember the brand of wheels I've got. I bought these from the Tire Rack with Goodyear Eagle Ultra Grip tires mounted. I think it was around $1000 for everything (mounted, shipping, TPMS).

I don't have pictures handy since I'm at work and no access to my home files for a couple of days.
 
Bio248 said:
seriously? what is the offset on those things? why would they rub the strut?

usually an 18x8 is pretty easy to pull off so long as the offset is like +35mm or more.
Click to expand...

Great question. Don't know off hand. Like I said, I bought from Tire Rack and I would think they have the same offset. I didn't take any measurements, but just by my hand check when I mounted the wheels I know the 17's are close to the strut.
 
Owfgxp1 said:
Sounds like a good price. Honestly, I don't even remember the brand of wheels I've got. I bought these from the Tire Rack with Goodyear Eagle Ultra Grip tires mounted. I think it was around $1000 for everything (mounted, shipping, TPMS).

I don't have pictures handy since I'm at work and no access to my home files for a couple of days.
Click to expand...

These are the wheels - 'Sport Edition F2', they're actually a 40mm offset, and they're 17x7.5.

Sport Edition F2 Silver Painted
 
I have read many people runing 18x8's on the GXP with no issues. This is true for aftermarket wheels. The issue is that the stock front and stock rear wheels on a GXP have a different offset. Nobody has posted what the offset of the wheels are. So there will be rubbing if the 18x8's are placed in the back. I have also seen many guys switch over to the bonneville GXP wheels since they are all 18x8 and can be used with no issues.
 


The Guz said:
I have read many people runing 18x8's on the GXP with no issues. This is true for aftermarket wheels. The issue is that the stock front and stock rear wheels on a GXP have a different offset. Nobody has posted what the offset of the wheels are. So there will be rubbing if the 18x8's are placed in the back. I have also seen many guys switch over to the bonneville GXP wheels since they are all 18x8 and can be used with no issues.
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I seem to recall reading that the fronts are a 40mm offset and the rears are 55mm offset
 
that should work just fine if the 18x8s are 40mm...im lost. someone do it and report back. just swap the fronts and rears for a couple days.
 


I too have read that the front rims are a 40 off set and the rears are 55. But even if they do physically fit, I've read and heard from many people who work for GM that it just may not be a good idea. I don't know if it's true or not?
 
is this discussion similar to people that say that 5x114.3 bolt patterns dont fit? they are dumb as well.
 
i recently purchased set of four factory rims off another GXP owner who is running aftermarkets i put the 18x8's with factory rubber on the back and have been rolling for two weeks without issue no rubbing on the suspension no issues whatsoever this also includes moving a trunk load of tools for a friend!!!! hope this helps
 
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