biggest tire?

[dannyho]

I am in the planning stages of building up a 71 roadrunner and I have some questions about wheels and tires. Things are partly being dictated by a small budget so with the look I want i have only been able to find tires up to 17x8 and 18x9 widths, this would dictate 245 and 275 mm tires. is 275 too wide a tire for a 9 inch wide rim. The spec sheets the tire companies put out say it will work (I'm looking at yoko avs es100's ) but is that pushing it? Also, Would it make sense to step it up in the front as well. I know I'd have to make it fit, but would it be worth the trouble to have the same size tire front and rear, or would it make more sense to have a 245/275 combo?

[dannyho]

anybody? is having a 275/275 combo much better than a 245 combo. I'm not afraid of doing the work, just don't want to be too much of my time in the wrong place if it isnt necisary

[astroracer]

Is this a race car? A 255/275 combo would look good and either of those will work with your 8 & 9" rims. What aspect ratio are you looking at? 40? 50? I am running Nitto 255/50's and 275/50's on 17x8 and 17x9.5 inch rims respectively on my truck and they look good and fit the rims fine.


Where you really need to spend the time is measuring for backspacing and offset. Do a search on the site. There is alot of discussion and direction concerning this and I know I and a number of others have posted links in a few other threads.
Mark

[dannyho]

my question isn't about looks, its more of a performance question. I've read it's ideal to have your tires both the same width, and wider is better, for a given condition , ie scrub radius, etc, but I'm curious as to how much it's actually worth in the numbers game.

[astroracer]

my question isn't about looks, its more of a performance question. I've read it's ideal to have your tires both the same width, and wider is better, for a given condition , ie scrub radius, etc, but I'm curious as to how much it's actually worth in the numbers game.

I'll ask the question again, with a modifier... Is this (strictly) a race car? If it is you would be good to match sizes front to rear. If it isn't there are a lot more "things" you need to do to the suspension as a whole before tire size becomes a limiting factor...
Mark

[gearbanger]

I don't agree on it being the best to have the tires the same size. I think it is dependant on weight distibution. Corvettes have wider tires on the rear than the front because they have an aluminum motor and a 50-50 weight distribution. They don't need as much grip in the front. Also the Porche Carreras are the same way. Rear engine and more weigght on the rear requires less grip in front.

The Trans Ams and Camaros however have cast iron blocks and engine mounted trannies, so they have 275's all the way around to provide more grip in front.

Our cars probably would be better with same size front and rear, but I don't think you will find many going over 275 in front. The big tires in front can really point out the shortcomings of your front suspension setup. Also, with the power some of these cars are putting down, 275's aren't even close to enough on the rear.

Ihave 245's on an 8 in front and 295s on a 9.5 in back. My opinion they look perfect. They don't pooch and they are not stretched out either. If you like the flattened out look or feel that they perform better, then you may want to put the 245 on an 8.5 or a 275 on a 9.5. On the rear you can put a 275 on a 9.5 or a 295 or 305 on a 10.5 or 11.

[68Formula]

Sure the more contact patch you get, the higher the traction potential. But you're trying to balance out cornering traction front and rear. So, it really depends on if the the car presently oversteers or understeers and your driving preference, whether it's worth the effort.

Plus there are alot of other things that could be tuned (weight distribution, torsion bars, leaf springs, anti-roll bars, tire design, geometry, alignment, etc.) in addition to tire width. So the answer is "it depends."

FYI,tons (if not most) people are running different front/rear widths with success. I wouldn't be hung up on it.

[dannyho]

thanks for all the input. Looks like i'll probably be running a 245 on an 8 inch, and 275 on a 9 inch rim.