2009 stock wheel max tire size

Dennis Thomas

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Hello

I have an 2009 GT 45th anniversary mustang with the stock 18 x 8.5 wheels. It’s not lowered. Will these tire sizes fit fine?

Front 245-45-18
Back 285-40-18
 

Norm Peterson

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Front, yes.

Rear, no. 285/40's need to be mounted on rims that are at least 9.5" wide (but not wider than 11").

Maximum tire sizes for 8.5" wide wheels depends somewhat on tire profile (any wheel diameter). That would be 265 in 45 profile or 255 in 40 profile.


Norm
 

Dennis Thomas

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So 245-45 upfront and 265-45 in the rear would work fine? Probably should get different wheels but I really like the look of them.
 

Norm Peterson

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I would suggest 255 all around... That's what I have and the tires fit the wheels very well. Anything more is too much for an 8.5 wheel.
As far as most peoples' street driving goes, that would be the better choice for a number of reasons.

Plus, availability of 255/45-18 is far better (48 possibilities at Tire Rack)than trying to get the 245/45-18 and 265/45 combination in the same make and model tire (only 3, with one size or the other in all 3 being in limited supply).


Norm
 

Dennis Thomas

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Thanks for all the help. Think I will go with 255’s looks perfect. Those 235 stock size never looked right. Didn’t consider availability and price. Good advice, thanks guys
 

Gabe

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If you don't mind the meaty-tire look, consider 255/50/18 with those wheels.
This size is 28" tall versus the 27.2" height of the factory 235/50/18 tires, and it will have a thicker sidewall.
 

Dennis Thomas

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Anyone have picture 255 50 18’s on the 2004-2009? Just curious on how it looks. Looks is the main reason I want different tires. I put little cash in the rear suspension, so traction’s not my main concern.
 

Pentalab

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Anyone have picture 255 50 18’s on the 2004-2009? Just curious on how it looks. Looks is the main reason I want different tires. I put little cash in the rear suspension, so traction’s not my main concern.

A 255-50-18 will be 28.04" diameter..which is big. The sidewalls will be 5.02".... which is getting silly.
They would look 'off roadish'.

The 255-45-18 is a popular size... and made by every tire maker.
27.04" diameter. 4.5" sidewall.
 

Anti

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Yea, I have that on mine now. Perfect tire size and cheap too. I run some kumho ecsta's. Love'em.
 

06 T-RED S/C GT

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If you're into hard cornering at all, 255/45's on 18x9.5" is a very do-able combination (the 2008 GT500 wore that exact wheel/tire combination up front, stock).


Norm
I know that to be true from personal experience, as I have the stock 2007-09 GT500 wheel/tire combo on my car up front. Also have the stock rear combo as well lol.

IMG_20190811_1643408.jpg
 

Dennis Thomas

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New question I just bought new rims. Front 18*9 and rear 18*10. What would be biggest without rubbing. And would an adjustable panhard bar be required?
 

Norm Peterson

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New question I just bought new rims. Front 18*9 and rear 18*10. What would be biggest without rubbing. And would an adjustable panhard bar be required?
265/40 is as wide as you should go on 9", and 295/35 is the widest true street tire size I could quickly find for 10". Don't be surprised if turning in on corners feels a bit soft and steering in general to be slightly 'numb'. IOW, not quite up to what the tire sizes themselves might be leading you to expect.

I can't offer much help on the matter of rubbing because that's also controlled by wheel dimensions not specified (offset & backspacing).

Nor on any need for an adjustable PHB, as that's controlled by offset and also by how accurately the axle is centered in the chassis. If you needed an adjustable PHB with 10" wheels of anywhere near the right offset it'd be because only one tire was rubbing.


Norm
 

Norm Peterson

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I know that to be true from personal experience, as I have the stock 2007-09 GT500 wheel/tire combo on my car up front.
Nice. I tried to get my dealer to get my car delivered with a pair of GT500 front sets when I put in my order but he wouldn't go for it.

Always did like those wheels, and since I always intend to keep my '08 normally aspirated I basically did the GT500 front wheel and tire size thing at both ends for the first wheel/tire upgrade. I went with the original GY Asymmetrics, though.

IMG_0872b.jpg


255 45 18 95 45 web.jpg


The second set of tires for the GT500 wheels are Michelin PSS in 265/40-18. Better grip, but it makes me wish that the GT500 wheels were 10's. If you look closely, slightly more sidewall bulge is visible, and I think that while the grip may be a little higher than with the Asymmetrics, response is a tad softer. Not a huge issue in street driving, but still noticeable in harder driving.

265 40 on 18 95 +45 web.jpg


Norm
 

06 T-RED S/C GT

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Perhaps your dealer had to go by what options were available for an "08" GT coupe when ordering would be my guess? I also noticed the slight bulge from the images and can't quite understand how a 265/40-18 tire would have any bulge at all when mounted on a 18x9.5" wheel with 45mm offset? According to TireRack and Discount Tire specs, the optimal tire size for a 18x9.5" wheel with 45mm offset is 275/40-18. Until reading your post along with looking over your images, I was actually considering either the Firestone Firehawk Indy 500 or General Tire G-Max RS in 275/40-18 both front and rear as a square setup for my next set of tires. However after seeing your images, it appears that I may have to end up going with 255/45-18" tires in order to run a square setup. At present, I'm still running the stock Goodyear Eagle F1 285/40-18 (rear) and 255/45-18 tires (front). Anyhow I always liked the stock GT500 wheels as well and bought the set from a friend of mine that no longer needed them after getting his car delivered back from Shelby Automotive, as he ordered the Super Snake option package on his "08" GT500. On a lighter note, the GT500 wheels definitely look really awesome on your "08" GT coupe :waytogo:
 

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