Topic: Tire Question
in Forum: C3 Handling Components
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Time for my second noob question, I <obviously> want to be faster, and the first step is rubber. What is the biggest hunk of rubber I can jam into my 79? it has stock suspension and original ralley wheels. I am thinking its 275/60/15 but I am not 100% and would like some feed back, I only will be replacing the rear tires since my fronts (and rears) are still good. I was thinking the BF Goodrich DOT Drag tire. I dont do very much distance driving, and honestly the farthest I drive is to the track anyways or to cruise the strip ;)
Also would anyone have some good suspension tips. Im not looking for anything to over the top (the sharkbite coilover system does make me giddy though) but would like to correct some of the "drift" I experience going hard into corners. also sitting a little lower wouldn't hurt my feelings to bad.
Thanks again for great info ahead of time.
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Frederick, MD - USA
Joined: 9/8/2003
Posts: 3398
Vette(s): 1969 convertible L71 427/435 4-speed black interior
For your '79 the biggest tire authorized by GM is a P255/60R15. Now, that doesn't mean it's the biggest tire you can fit under there, but you can run into problems. To put a fatter tire under the rear end might require the use of offset trailing arms. You said you have a stock suspension so that might limit your choices.
For practical purposes, the biggest limiting factor you have is the 15" wheels and tires. Today the 15" size has pretty much been passed by when it comes to tire technology. Everything of real improvements in that starts at 16" or even 17" and bigger. 15" tire technology is simply not up to available tires in larger diameters. Tire makers make 15" mostly to service an older market that is declining in sales, so they don't invest their best technology for C3 Corvette tires and other cars of earlier generations. Even C4 drivers are complaining about the lack of tire choices for their cars now.
That's not to say you can't find good tires...just it's very difficult to find tires for our cars that are significantly better than original replacement type for them. It's a shrinking market and many tire makers are cutting back or eliminating production for slow moving lines and letting the specialty market handle it.
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I have 285/40/18ZR tires for the rear. To make things work I installed the reverse offset trailing arms. The wheels are American Racing Torque Thrust 2. They are 9.5 inches wide with a 4.75 backspace...........which means the center of the rim is in the very center of the wheel. The suspension has been modified here is the kit:
corvette440hp
Lifetime MemberManteca, CA - USA
Joined: 11/20/2005
Posts: 3623
Vette(s): 1978,two tone,Metalic Rootbeer & gold
1975 L48 4 speed
For the stock 15" wheels you immediately run into clearance issues with the 275 /60. Every vette is a little different but I found mine rubbing (like brakes) the E-brake cable. I have a buddy with the same size tires and all he did was draw the cables up against the frame with large hose clamps, mine won't be so easy.
Stock leaf spring bolts are 6", the aftermarket springs usually include 8" bolts to allow a little height adjustment. At full length the rear might sit just slightly lower.
Jimmy B.
Just can't wait to get on the road again. 
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I have 275/60/15 on the rear of my 68 which has flared fenders. They will stick out on a stock vette. They are also a taller tire which will raise your back end unless you install longer spring bolts or modify the suspension. They also grab better than a 255/60/15. This puts a big strain on a stock drive train & can lead to breakage. I know first hand & without drive shaft safety loops you will be just asking for trouble. Anytime you make mods to these cars it will lead to other problems. So plan ahead carefully or it can be a costly experience.
Alan
in Forum: C3 Handling Components
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