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So, what I want to do is avoid the high cost of buying 4 new winter tires that match the orig. equipment on my daughter's GXP. She's running 18 x 8's (245 & 225's) and I want to drop down to a smaller wheel size, like 245 x 17 or even a 16.I can get all 4 at Costco for a heckuva lot less and still buy 4 steel wheels to fit. Any Grand Prix owners out there with a better idea? It's only city driving in S. Ontario by the way!
 

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Are you referring to a G6 GXP or a G8 GXP?
 

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This is a 325 c.i. Grand Prix GXP, circa 2005-2008, similar to Impala SS and Lacrosse Super.

GP only ran staggered wheels, 18x8 front and 18x7 rear with similarly staggered tire sizes. Look it up, I forget.

IF, IF...17s will clear the brakes, I'd salvage yard some Pontiac wheels.

You can also go narrow profile/taller tire, e.g. 215.60.17 if seventeens will clear the brakes.

Big fat tires are sooo coool and factories put giant stuff on. Quite a few on the Soul forums are swapping out their 18-inchers stock on the ! model for 17s or 16s because they ride hard and cost harder.

Is bigger better? To paraphrase Dirty Harry, a tire's got to know its limitatins.
 

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I haven't personally dealt with this but
since I'm a smaller (ie rational) wheel/tire size advocate,
I've see others mention one more aspect to not forget:

to get a setup that equals the original's LOAD rating
 

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I agree, check the website for Tire Rack, Discount Tire, or even a local tire store chain. They will list your original wheel and tire sizes, plus offer you "plus-size" and "minus-size" combinations that will fit your car. And a taller tire on a smaller wheel (same outside diameter) will give you more sidewall, more cushion to soak up those nasty winter potholes. Narrower tread can also help traction in the snow.

I did this for my G8 (not a GXP) and went down from the factory 18s to 17s. Although you may find it very difficult to find steel wheels that fit in sizes above 16. But the money I saved on tires (over buying the larger 18 dia winter tires) paid for the set of new aluminum wheels to fit them.

I ordered a set of Bridgestone Blizzaks on new wheels (17s) from Tire Rack, and they were delivered in two days, right to my driveway, all mounted and balanced. If you can't mount them on the car yourself, you can even have them delivered to your local service center.
 

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When changing tire size, Always make sure that the replacement tire is rated for at least as much weight as the original. Not usually a problem when changing to larger tires, but pay very close attention when using smaller tires.

Hope this helps.
 
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