wheel/tire question--Ken, Injuneer, anyone?

[00 Ragtop Z]

wheel tire question--

What is the alrgest tire that should be mounted on a 17x8.5 wheel? What is teh largest tire that should be mounted on stock 16 inch wheels? My goal in this case is to not screw up the speedometer.

Also, in general I have heard through this board that with 17 inch wheels, we should use 275/40 tires.

What diffenrce would using 275/50 make?

My goal here is to find a compromise between harder ride versus better handling/cornering before I make my investment in wheels and tires--badly needed at this point.

[00 Ragtop Z]

added comment

the 17 inch wheels mentioned in teh second half of my question assume 17x9 or 17x9.5--sorry for teh confusion.

[Joe 1320]

some answers

*A 255/45/17 is about as wide as you want to go on a 8.5 inch wide rim.

*A 275/40/17 or 285/40/17 is the max on a 9 or 9.5 inch rim, respectively.

*A 255/50/16 is the largest you should mount on a stock 16x8 wheel. (rear only)

*The stock 245/50/16 is the same height as a 275/40/17.

You can use whatever you want and the speedo can be corrected via a programmer or speedo adjuster module.

I am really happy with my combo of Borbet 17x9.5s with 285/40/17 Firehawk SZ50s on all four corners. Excellent grip, ride, noise and value.

[wolfdogs]

remember.. "ride comfort" and "handling" are a trade off... just like "traction" and "treadwear"... the 40 aspect ratio tires make these cars handle much better than the 50 aspect ratio..thats why the Camaro SS, Ws6, Firehawk, and CompTA's got the 275/40r17's.........which..like Joe said..is the same O.D. as the 245/50r16.

k

[Injuneer]

Follow the tire manufacturer's recommendation. And, surprisingly, for any given size a particular manufacturer might have a slightly different width than another, and even within the one manufacturers catalog, different models of the same size tire may have a slightly different recommended wheel width.

16x8:

The "limit" of 255/50-16 is imposed more by the fact that its the largest size available in "high performance" street tires. You can use a wider tire on a 16x8, but you would have to select from something like a Hoosier road race tire with soft tread compound and limited tread depth.

Hoosier makes a 275/45-16 that will fit on a wheel width of 8"-10". But they even put the disclaimer "not for road use" on their website.

17x9.0 or 17x9.5:

A 275/40-17 is the max width on a 9" wide wheel. 285/40-17 on a 9.5" wide wheel. May seem like a very small difference.... 1/2" but being the anal "engineer" (yes, I am one... ) I like to follow the manufacturer's recommendation. If they wanted to just sell tires, they would tell you any size fits on any wheel, but when they take performance and safety into account, they make the recommendations they do.

A 285 is 4/10th's of an inch wider and in diameter than a 275. In many lines that offer both sizes, there is even less difference in the tread width. And you can't tie "width" rigidly to performance... I'm sure there are some 275's with narrow tread that will out perform some 285 with wide tread. To me 285 vs. 275 isn't worth the headaches.

275/50-17:

First, as far as I can tell, no one makes that size. If they did, it would be more than 2" larger in diameter than the stock tires, and since it would be 27.83" in diameter, it would look similar to my 28" Hoosier QTP slicks....

And, that would throw your speedo and odometer off by more than 8% (speedo would read 55mph at a true 60mph) and it would be like switching a set of 3.42 gears to a set of 3.15 gears.... not good for performance.

You need to match the outside diameter of the tire to stock (about 25.65") to avoid speedo problems, steering geometry problems, lifting the car further off the ground, pushing the tires further up into the wheel wells and rubbing, etc.

[JL8Jeff]

Just as a side note, my 91 SS454 pickup runs 275/60R15 tires on 15x8 wheels. These are the factory tires/wheels and there is a lot of bulge to them. I believe that the factory Impala SS wheels are 17x8.5 and they have 275/40/17 tires on them so look for something in the 17x8.5-9.5 range and either the 275 or 285 width.

[Joe 1320]

Originally posted by JL8Jeff
I believe that the factory Impala SS wheels are 17x8.5 and they have 275/40/17 tires on them so look for something in the 17x8.5-9.5 range and either the 275 or 285 width.

Close, but not quite. I owned an Impala SS and they came with 255/50/17 BFGs....... Taller than the 255/45/17 on the front of my LT1 Vette.

[wolfdogs]

as of 2002 Tire and Rim Yearbook , the largest 50 aspect ratio 17" tire is a 255/50r17.

drop to a 45 aspect ratio and it goes all the way to 315's.

[00 Ragtop Z]

Thanks for all teh inout. You guys helped tremendously. When I get he new wheels/tires, I'll post pics to see what everyone thinks.