Thread: GXP 18x8 Wheels on a GXP All The Way Around - The Good, The Bad, and The Ugly?

If there is a definitive thread on this topic, I have yet to find it...SO!!

Weigh in, here it is!!!

I'm thinking about making a move on this, largely because it is time for skins.

Any down side to running 18x8's all the way around on a GXP (other than $12 per lug nut)? I'm more concerned with handling problems and mechanical problems, appearance wise, you would have to be blind or dead to think the 18x7 look good on the back compared to an 18x8 rim.

I know Pontiac did this so the car would handle more like a BMW, that statement in itself is confusing. Never known a front wheel drive vehicle to handle like a rear wheel drive but then again I'm not a professional driver.

Good after market options need pics, lets see what you did.

Hope I'm doing this right, don't want to go down in flames on my first real post.

Thanks in advance to all who lend advise.

A bit more grip in the back, but you should not experience any huge change. More overall symmetrical look on the exterior. Comparing it to a BMW is a bit stretched tho.

I say do et.

Hey I never said I think it handles like a rear drive BMW, Car and Drive said Pontiac said it.

Link to past post: Question GXP RIMs

Originally Posted by Lenny

this is a little bit of car and drivers review of the GXP: Pontiac Grand Prix GXP - Road Test - Auto Reviews - Car and Driver

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."

Thanks for your input.

I tried to post this yesterday, but the server took a dump before i could finish:

IIRC, the 18x8 wheels will interfere with the strut when mounted on the back of a GXP. I may be wrong, so check to make sure. edit: corrected by bio, see below.

As for handling, on the street you will probably not notice a difference unless its nasty outside. If you take your GXP to road-courses or auto-x, you will likely find that it will understeer worse than before, because you have increased the size of your rear "traction circle" with respect to the front.

my $.02

people have already put the 18x8s on the back without problems.

I run 18X8 alcoas with 255/45/18 all the way around. They do not rub on the strut, in fact, there is very little difference in clearance between the 8" rim/tire and the 7" rim tire.

It gives the car a more agressive stance IMO. I can't comment on handling, etc because I drive very few miles and it's a normal DD for me.

Here's a few pics to show how it sits. I'm not lowering and tinting tails is not happening now, thought I'd get that out of the way. All windows truly are tinted at about 18%, but doesn't look like it b/c of the angle and sun.

Does look better. I think they look a little thin from behind with the 18x7's. More junk under the trunk with the 255/45's in back.

How did you solve the lug nut equations. Did you do $12 X 10 at the stealer or did you find an after market solution?

She's a beauty and looks to be super clean. I'm guessing you don't get much snow or you park it in the winter. Where I live the winters (really the salt they put down for ice control) kills cars. My GTP is my winter ride but she has been mine since zero miles. She's a runner but still looks decent for 12 years and +150K miles. I get the whole chassis oiled up before wither, really helps to keep the rust down, but is a real mess when you have to work on it. On the upside stuff still unbolts after all these years.

Tint looks great, I plan on doing my back window next summer. Ran tint in my last two DD's, but got pulled over in the GTP (black) a couple of years ago. The nice trooper explained that the local town had just bought them 10 meters and they planned on paying them off in one month. All profit after that. At the time I was driving the same route every day so I peeled the side windows (weeping like a girl while I was doing it) and paid the fine. No kidding, every day I drove down that road it seemed like they had a tinted car pulled over. You can't beat a black car with tint IMO. Looks awesome to be sure, but also makes the dark tint stand out.

Funny I see you (VDV18) and our Drunken Moderator both supporting the 18x8x4 initiative with great commitment. Thanks for the input.

wide wheels are a way of life, homie.

I live in Iowa and unfortunately do drive it in the winter. If I had a 3rd stall on my garage I'd have a winter car and park the GXP. But like I said, I drive very few miles, have a car wash 3 blocks from my house, and wash it at least once per week during the winter. I usually wash it on Friday after work and then it sits in our garage until Monday morning, so for a few days it's clean. Pretty tough in the winters though. I am going to run 18X7 alcoas during the winter so I don't ruin my 8" rims.

Being able to rotate tires is so nice. I purchased the longer lugs for the 8" rims from a member of another forum who was selling. If you can get lugs from your dealer for $12 it's not too bad, the local dealer here charges $24....yes you read that right.

I debadged the 'GRAND PRIX' on the trunk, I absolutely hated it. Then I put the GXP badge on and have the yellow inlays on the sides and trunk that match my Hawkeyes license plate. Also have a black inlay for the Pontiac arrow on the front of the car.

Good luck, let me know if you have any other questions.

Wider is better!! Amen brother!!!

Sorry about the winters thing, nothing worse than watching a nice car get torn up by salt. I live in Buffalo NY so it is kind of a way of life when it gets here. That being said, I've got all winter to work it out as long as the GTP holds together (Hear me, baby? Hold together!!).

Here are some link backs:
http://www.grandprixforums.net/gxp-rims-35611.html
http://www.grandprixforums.net/good-...8x8-19592.html
http://www.grandprixforums.net/lower...set-13976.html
http://www.grandprixforums.net/gxp-l...els-35874.html

I'll add others if I find more info.

Any time. There have been others who have said they've "heard" the car will rub on the fenders with a lot of weight and hitting large bumps, etc. Others have said they won't.

I can't confirm this or not because I never have any weight in my car. Personally, I'm not so sure it would.....there would have to be a ton of weight for it to rub.

Cedar Rapids

that does look a lot better.. Nice man

the winter sucks in iowa. its the concentrate salt. my 02 silverado is rusted so bad has 64k on it and i didnt even drive it but a couple times last 2 winters.

The only time i ever had an issue with the 18X8's on the back of my GXP was the camber. I went throught the trouble of installing cam bolts top and bottom to correct the common trouble and wound up skinning the sidewalls on both tires. I was taking some friends to the airport with all their luggage and encountered a rubbing noise in the rear, got to the airport to find what looked like spaghetti hanging off my sidewalls. The lip on the inside of the rear quarter was the culprit.
Lesson focus: Leave a little neg camber to insure the tires clear the lip of the rear quarter.

you could have rolled your fenders and that problem would have been completely eliminated.

Thanks For Your Advice on GXP Rims
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Had it down to 4 options:
1) Stay with OEM sizes and refinish the Alcoa Rims = $650
2) Try to find OEM Alcoa 18x8's and refinish my 2 18x8’s = $1525 + lugnuts
3) Buy aftermarket – Sort of liked the American Racing Mavericks = $900
4) Buy 07-08 18x8’s w/center caps = $790 + lugnuts + keep my old rims

The O7-08 GXP rims seem to be cheap for some reason right now, maybe the OEM for GM got stuck with a boat load of them when GM cancelled the Pontiac line.

So, just received four brand new 07-08 18x8’s from BlackBurn in Cleveland, $790 and they arrived in one day. Best thing is I get to keep my Alcoa’s. Seemed like a no brainer even though I like the look of the Alcoa rims a little better. Lugnuts are on their way from Morad @ $53 for a full set, fronts and rears.

MVP also had the 07-08 rims for ~$900 shipped (no center caps)

Thanks again for your help, the pictures really sold me (VDV18).

Got my lugnuts today from Morad and all is well, and unless I counted wrong , they threw in an extra nut of each size. Nice touch.

Found some possible alternatives on E-Bay which can probably be had at a local parts store as well, but they are probably about 1/2 an inch shorter than the stock GXP front lugs.

Long Bulge Acorn Style 12x1.5 Threads Lug Nuts
This set includes 20 pieces brand new long bulge acorn style 12x1.5 threads nice chromed lug nuts. Total length 1.9".
These sold for $25 (including shipping)
Seller = ezaccessory (99.9% rating)

20 LUG NUTS ACORN BULGE LONG 12 X 1.5 5 LUG BLAZER S-10
THIS AUCTION CONSIST OF 24 ACORN BULGE CHROME LONG LUG NUTS.
THESE LUG NUTS HAVE :
all right hand thread
12 X 1.5 THREAD PITCH
3/4 WRENCH SOCKET
60 DEGREE TAPER
TOTAL LENGTH IS 1.8" OR ABOUT 1 7/8"
THESE LUG NUTS ARE MADE OF STEEL AND NICELY CHROME PLATED.
THESE LUG NUTS HAVE A ACORN BULGE SEAT. THIS BULGE SEAT WILL PREVENT THE LUG NUT FROM GETTING INTO THE BEVELED HOLE.
THESE LUG NUTS ARE SOLID ONE PIECE AND THEY DO NOT HAVE A STAINLEES STEEL COVER.
Buy It Now = $27 (including shipping)
Seller = lugking2005 (100% rating)

I measure the GXP front lugs at ~2.5 inches overall length.

Hope this helps.