the how wide can I go debate

63XL500

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I have factory 18 inch polished wheels on my 07 GT/CS. One tire shop told me the widest I can go is 255. But I think 275s will fit and seems like several on here are running 275s on their 18 inch stockers. If anyone has pics I would love to see them. Has anyone running 275s had any problems?
 

stkjock

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275s buldge, search some, the size has been covered on the 18x8.5" stock rim.

255s is the largest size "spec'd" for 8.5"

265/40 also,fits but is short.
 

1fastTbird

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Correct. While a tire shop certainly can "mount" a 275, your contact patch is not improving because the tread will be concave instead of flat against the road due to the bulge.
 

noldevin

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Correct. While a tire shop certainly can "mount" a 275, your contact patch is not improving because the tread will be concave instead of flat against the road due to the bulge.

This. SO many mustang people make this mistake with various size wheel and tires, but they don't seem to care as long as they have the widest tire possible.
 
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There's a lot of different opinions on this. I tried the BFG Rival in 275/35 for a year and they were OK. I switched to the Bridgestone RE-71R 265/35 and they had a much better feel. Don't know if it was the tire size or just the switch to Bridgestone (or a combination of both).
 

tjm73

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I've come to the conclusion that tire sizing is basically this....

rim width + 1, then multiply by 25.4 and round up to the next closest tire width in the appropriate aspect ratio for the tire height you want.

Example:
18x9 wheel, 9 +1 = 10 x 25.4 = 254. Run a 255 tire (maybe a 265 tire).
18x10 wheel, 10 + 1 = 11 x 25.4 = 279.4. Run a 285 Tire (maybe a 295 tire).
 

stkjock

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I've come to the conclusion that tire sizing is basically this....

rim width + 1, then multiply by 25.4 and round up to the next closest tire width in the appropriate aspect ratio for the tire height you want.

Example:
18x9 wheel, 9 +1 = 10 x 25.4 = 254. Run a 255 tire (maybe a 265 tire).
18x10 wheel, 10 + 1 = 11 x 25.4 = 279.4. Run a 285 Tire (maybe a 295 tire).

problem is that doesn't account for aspect ratio

M&H 325/40/18s on my 10" rims works great
 

frank s

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problem is that doesn't account for aspect ratio

M&H 325/40/18s on my 10" rims works great

problem is that doesn't account for what "works great" means to various users; your "...mustang people make this mistake with various size wheel and tires, but they don't seem to care as long as they have the widest tire possible", people say it works for them.
 

stkjock

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Ok, better to have said fits great, which it does.

DSCN2928_zps33d436ee.jpg
 

tjm73

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I think we all know M&H tire sizes are notorious for being loosely related to there actual sizes. Unless they changed them.
 

63XL500

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With my work schedule I will only be making it to the track a couple times this year so the car is mainly my fair weather daily. Those 325s do look just about perfect on the 10" rim.
I like 275s just because they seem more common but don't want the bulge. In my earlier Fox body days I had a friend running 265s on stock '87 LX 10 holes. They bulged A LOT.
Thanks for all the info. Does anyone have a pic of 275s on their 18" stockers?
 

stkjock

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M&H recommends 12" wide rims for that size, and minimum is probably 11" . . . just sayin'.


Norm

well I spoke to M&H before I ordered the tires and was told the fitment on a 10" rim was fine and widely used.... just sayin'
 

Norm Peterson

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↑↑↑ but like Frank said, the Mustang world is filled with people who don't think much past getting wide tires and you're at least partly taking their word for it. An 11" vs 10" shootout, same day, same car could prove enlightening whichever way it might favor.


Norm
 

stkjock

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Yes, the tire would likely perform marginally bettter on a 11" wheel.
 

oldVOR

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General rule is to stay within 1/2 inch +/- of the tread width (not section width) of the tire. Considering most 275's float around 10 inches of tread width, wheels ranging from 9.5 to 10.5 inches would work best.
 

Norm Peterson

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Agreed, at least for most uses.

Drag racing, specifically, probably does benefit from narrower rim widths by softening the initial 'hit' of power on launch (the tire's vertical stiffness being reduced means you get a little more shock absorption). One question here might be how narrow can you go before directional stability issues at the big end start showing up that might be better addressed with less inflation pressure on wider rims than higher pressure on the narrower ones.


Norm
 

63XL500

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My car has 255s and they just look skinny, Continental DWS. They just look skinny but I do notice that the sidewall is just about maxed out with the rim. Still trying to find a good side shot pic of these wheels with 275s.
 

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