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View Full Version : difference between 18x8 and 18.7.5?

ridgeback
11-20-2006, 02:27 PM
Are there any benefits of an 8" wide rim over a 7.5" other than the obvious wider tire possibility?

I am looking for some 18's and have been seeing increasing amounts of people only wanting 8" rims, to the point of letting ones they really liked go because they were 7.5.

Being relatively ignorant when it comes to these things I thought I would ask
whitetiger
11-20-2006, 02:38 PM
the ability to run a wider tire is the main concern here. people want to run a 235mm or wider tire witout having a sloppy sidewall.
ridgeback
11-20-2006, 03:08 PM
the ability to run a wider tire is the main concern here. people want to run a 235mm or wider tire witout having a sloppy sidewall.

That being said, will a 7.5" rim have a "sloppy sidewall" if running a 225 compared to a 8" rim?

After my Oe 215's are done I plan to go to 225 or 235, not sure yet.
whitetiger
11-20-2006, 03:35 PM
Im running a 225 tire right now on the stock 7" wide rim. so you will have no problems with a 225 on a 7.5" rim. i would go wider than 235 on a 7.5" wide rim.
ridgeback
11-20-2006, 03:57 PM
Thanks whitetiger
Han'sGT
11-20-2006, 04:04 PM
Im running a 225 tire right now on the stock 7" wide rim. so you will have no problems with a 225 on a 7.5" rim. i would go wider than 235 on a 7.5" wide rim.

you mean...you wouldn't go wider than 235 on a 7.5" rim.

a benefit of 7.5 over 8 is that the 7.5 will be lighter...given it's the same style wheel.
whitetiger
11-20-2006, 04:27 PM
you mean...you wouldn't go wider than 235 on a 7.5" rim.

a benefit of 7.5 over 8 is that the 7.5 will be lighter...given it's the same style wheel.

right. typos pwn me
urfsin
11-20-2006, 04:58 PM
Would 235 be ok with a 8" wide rim or would the tire be "streched" over the rim to much?
Xenonk
11-20-2006, 06:24 PM
the real question is: "why wouldnt you want to go wider?"

if you can have the room to go wider, go wider. Any tire that can fit on a 18x7.5 can fit on a 18x8.. in some cases, the tire just gets stretched over the larger rim, which will reduce sidewall flex.

You're not going to save a lot of weight from 7.5 wide vs 8. Price wise it's not as much per rim. Some times the 8" wide just fit and look better than a 7.5 would. If you do stretch a narrow tire over a wider rim, you could have a larger chance of having curb rash since your lip of the rim may be exposed without having the tire bulge to protect it.
Xenonk
11-20-2006, 06:25 PM
Would 235 be ok with a 8" wide rim or would the tire be "streched" over the rim to much?

it's ok.

Im currently running on a racing compound 225/40/18 on a 8.5" for street use
KartRacerBoy
11-20-2006, 07:48 PM
the real question is: "why wouldnt you want to go wider?"

I generally agree with you Keefe but there are at least a couple of reasons why you might not want to go wider: 1) If you stretch a stiff tire over a slightly wider rim, for any given sidewall stiffness, you will reduce ride quality since the the tire tread and sidewall will be stretched out a bit more and have less "give." 2) You may also introduce more tramlining since with a stiff tire construction the tire will want to follow the road more and pull your steering wheel along with it.

Those are the downsides I've noticed on several cars when going up to 8" wide wheels from 6.5 to 7 inch wheels. But it VERY MUCH depends on tire construction differences between the old tires and narrower wheels and wider rims and newer tires. I've never taken an existing set of street tires and mounted them on wider wheels, so I can't say definitively that my comments are true, but I think they're close to the truth. Or at least, that's my story and I'm stickin' to it. :icon_wink
Han'sGT
11-21-2006, 07:56 AM
narrow = better in snow
KartRacerBoy
11-21-2006, 06:27 PM
^As the Canadians say, "ayup."
Hanger
11-21-2006, 06:45 PM
i have the same question with 225 tires on a 7" as oppose to 225 on a 7.5

is there any difference?

the 7" just has softer sidewalls right? is there any other difference in performance or handling?

thanks in advance
KartRacerBoy
11-21-2006, 07:38 PM
Read the above. With narrower rim, turn in won't be as quick or precise, but ride will be better generally. The car will take a millisecond longer to take a "set" in a turn in a transition manuver, all else equal, than a car with the same tires and wider rims. Ultimate grip might be slightly lower.
Atroz
11-21-2006, 09:40 PM
^As the Canadians say, "ayup."

We do?
KartRacerBoy
11-22-2006, 12:38 PM
ayup.
EL PAALO
11-23-2006, 12:36 PM
Read the above. With narrower rim, turn in won't be as quick or precise, but ride will be better generally. The car will take a millisecond longer to take a "set" in a turn in a transition manuver, all else equal, than a car with the same tires and wider rims. Ultimate grip might be slightly lower.
also feels sloppy on a skinnier wheel, imo.