what if my rim is narrower then the tire's recommended rim width range?

[c55m8o]

Mirroring this question over here too as there's a lot of good knowledge spread btw'n all you. (please forgive if you read this on another board). Did a search; wasn't discussed with the terms I used

255mm wide tires [17" diameter rim] all have a recommended [or approved?] rim width of 8.5" - 10"; I never find good performance tires at a 255mm width spec'ed approving an 8" wide rim.

So what would happen if I try to put a 255/40-17 rim onto a 8" wide rim? I know the sidewalls will roll in more then the manufacturer recommends. But...
- will it adversely affect grip / performance in a noticable way?
- will it adversely affect life of the tire in a substancial way?
- will it look like crap, or at least 'odd' in a noticable way?
- will it not seal well? (this one I doubt but hey, I don't know)
- will the center of the tire get worn faster then if I did a 245mm wide tire?
- any of you running it?

Thanx for your thoughts...

[Denlasoul]

This will not answer most of your questions, but may shed some insight. (http://www.tirerack.com/tires/tiretech/tirespecskey.jsp)

[c55m8o]

Lol ... Thanx. That was posted by Luke on Mercedesshop.com, but I only scanned a few sentences of each paragraph to determine if what I was looking for was covered. You're right, it's not exactly there, but the "rim width" sections help.

I'm leaning towards going ahead and putting 255s on the 8" wide rims. Or ... I can buy 18"x9" rims for the rear and run 17"x8" in the front. [!] Hey, the right tire choice and the outer diameter's still the same.

BTW, if anyone is wondering why, it's cus I want to use my super light OZ Superleggera rims with ultra hi performance, light, summer tires. The Michelin Pilot Sport PS2 is a few pounds lighter then all the others, so I think that's going to be it now. (regarless of the fact that I said I'd never use Michelins again after I slid the car into a curb on the stock Pilot Sports when they were cold that originally came on the car when I only had 5K miles on it :o )

[martattack]

It should work fine. It'll just look meaty.

[Chupa]

You're little project is starting to concern me a little since you don't seem to understand tire and wheel specs too well. I understand that you're trying to go superlight on the wheel/tire combo, which is what is prefered for minimizing disturbances from the unsprung mass, but increasing the wheel diameter & width is only adding more weight to your system. Keep in mind also that your front and rear tires will be behaving quite differently and it's rather impossible to predict slip angles and inflation pressures to get the appropriate traction you need (also effecting your car's tendencies towards over/under steer). Also, does your 202 need that much rubber? Are you having traction problems or is this just for show?

[c55m8o]

Originally posted by Chupa
You're little project is starting to concern me a little since you don't seem to understand tire and wheel specs too well...Keep in mind also that your front and rear tires will be behaving quite differently and it's rather impossible to predict slip angles and inflation pressures to get the appropriate traction you need (also effecting your car's tendencies towards over/under steer). Also, does your 202 need that much rubber? Are you having traction problems or is this just for show? LoL .... Though I may not be a dumb as the question in the 1st post of this thread may lead a new reader to think, Yes, I'm always learning and willing to be humble about my ignorance. (though I don't know why wanting to go 10mm wider in the rear then stock, to keep the extra 90 ft-lbs of torque I run in check, would lead you to surmise I don't 'understand' tire specs).

Just so happened that I came to a similar conclusion you cite here after reading a little -- when also wondering if I could get away with a 17" diameter rim in front and 18" rim in the rear since the latter comes in 9" width (keeping the outer diameter of the tires 25") -- and posted it a number of days back in another thread:
http://www.club202.com/forums/showthread.php?s=&threadid=10149#post98089
( answer is a resounding -NO- )

I do also surmise you must know a few things about the concepts of handling even knowing about slip angle / grip angle (depending on who you talk to). ;) Looking forward to hearing some more around the forum.

BTW, I'm not about to use 255 tires on an 8" wide rim anymore if the manufacturer doesn't support that size. Luke of the Tirerack, was adamant that would cause catastrophic failure of the sidewall; as he stated it wasn't an "if" but a "when" with that in his opinion.

Put stock sized tires on yesterday on the 8" rims. Dunlop Sport Maxx 225/45-17 and 245/40-17, and though I haven't made a dent in the outer wax or whatever from the tire mold, already picked up a bit of washout from the fronts that I -hated- from the GY Eagle F1 GSD3s. So I hope that changes after 500 miles.

Do I need more grip? 5.4L engine swap, speedybenz suspension that I stress to the max since I tend to drive the car like I stole it ... so I'll leave that answer to the reader. I flew out to the west coast to take a drive with Jeff (speedybenz) before I bought the complete kit, and I know what 245mm tires up front and 275mm in the rear can buy these C43s with some great springs, shocks, and alignment, above the handling of a stock C43's tire sizes (you can read my review on this board). That's the long way of saying "no, it's -not- a look thing". :D

Also, going with the Dunlops, I saved a few pounds over going with my favorites, Bridgestone Potenza Pole Position SO-3. After seeing the weights on tirerack -- thank you tirerack for publishing tire weights -- I couldn't pull the trigger on them. I know what each pound of rubber spinning around outside the rims will do to Moment of Intertia. Michelin Pilot PS2s were the lightest in the category of tire I was looking for (great wet traction). But after the disaster I had on the original Pilots, I can't seem to ever look past that and give Michelins a try again.

...I've rambled enough ... thanx for reading. Welcome to the board.

[Chupa]

I'm glad to hear it's a project car with a lot of upgrades. FYI, I have both designed and built racecars, supercars, & production vehicles, so I do have some experience with the intricacies with all aspects of cars. I'm just here to occassionally inject some wisdom when it seems someone may be a little over their head (mostly if it seems they might be endangering themselves or others), and to pick up experiences of the 202 boards. I'm, of coarse, open to questions and I'm interested in how your upgrades work out. So for future reference ...

when you side wall gets shorter, the amount of lateral deformation to accomodate a rim is dramatically reduced (though this is also what gives it more stiffness for cornering). Also for rotational inertia, most people fail to look at the inertia of larger diameter wheels (it's NOT insignificant) ... so there are reasons why most OEMs will send out the sports cars in 17" at most.

[Proven Guilty]

i love me some nerdy tech talk. i thrive on it :D