I am about to buy a new set of wheels and tire for my 76 vette and need some help.
What should the backspacing be if I want to use 17" wheels, 9.5" wide ,without having to change f.e. the trailer arm, as my rear wheels.
Tire size either 275/50/17 or 285/45/17.
For the front 245/50/17 or 235/55/17 on 17" wheels and 8" wide.

 

If I had it to do again, my front wheels would be 7" wide, I am running 17 X 8 with 4.5 " backspace TT2"s . All new front suspension and the car still wants to wander.

 

What size of tires in front and what size of wheel/tire in the rear?

 

Are you looking for the "look", performance or both? I run SLP's 255/45/17 ZR's in front and 255/50/17 ZR's in the rear. No wander, incredible handling, and excellent ride with Kuhmo Ecsta tires and everything fits perfectly on the stock suspension. I like the look and a ZR tire most of the time will outperform by a large margin wider tires with lower speed ratings (softer sidewalls which hurt performance and contribute to wander by allowing way to much sidewall flex. A Z rated tire has the strongest tire construction and usually the best rubber for traction as well.

 

Just putting on ZR rated ultra high performance Toyo T1R's turned my Vette into nice handling sports car from feeling like I was driving a dump truck

 

I would llike to put some more rubber on the road since I am running a 496 with a 8-71 blower. That's why I was looking at 275 in the back

 

I am running 275-40-17 on 17"x9" wheels with a 4.875" backspace. These fit fine in the front but on the rear they will not clear the stock size or aftermarket sway bar if you have one. Also I have offset rear trailing arms, but this size wheel and tire should clear the stock trailing arm. I might later use a 1/2" spacer on the front and rear, so if you had a choice of backspacing I would choose 4.5" on a 9 inch wheel and maybe 4.75" on a 9.5" wheel. I also have the VBP bump steer kit on front. Without it my wheels look like they would rub the outside tie rod ends. Same wheels with 4.5" backspace would not rub on tie rod end. These are on a 1980 C-3.

 

My 78 was not too bad with the stock 255/60/15 S rated BFG Radial T/A's but I just did not feel that I was getting the most of all my modifications to the stock suspension running those tires. I have poly sway bar bushings on the OEM 1 1/8inch front bar. poly upper and lower control arm bushings, poly top shock mount bushings on the Bilstein Heavy Duty shocks, and 550 springs lowered 1 inch in the front. In the rear, I run a 360 composite spring with poly mounting cushions, Bilstein Sport shocks (30% stiffer than the HD Bilsteins), Heim joint competition strut rods, and a 3/4 inch rear sway bar with poly mounting bushings. The ride witht the ZR tires is actually BETTER than the BFG's and the handling and steering response is way superior-no wandering! I am getting ready to pull the steering box to have it rebuilt and blue printed (which it was never done from the factory) and looking forward to even better steering. I read of many folks using wider tires and lower profile tires but they run very low speed rated tires which, to me is self defeating, if they are looking for more dramatic performance, not just looks! I will take a 255/45/17 ZR tire all day over a 275/40/17 S/H rated tire, as an example.

 

I don't know if your stuck with 17 inch wheels already but if not when
you go bigger, 18'' or even 20'' the trailing arms are no longer a problem.
When running smaller rim sizes with tires that have thicker side walls, that
is when the trailing arm becomes a problem, larger rim diameters clears
most, if not all trailing arm problems. For wider tires you will have to move
the E-brake cable bracket from the side of the control arm to the top.

I am running 18x10 with a 5.5 back space wheels rolling on 285/40/18 Toyo
T1R Proxy's tires on the rear and up front I am running 17x8 with a 4'' back
space rolling on 245/45/17.

Some forum members are running a 295 on some 18'' and some 20'' wheels
and don't seem to have any problems. When you start running wider tires
on the rear of these cars you really have to pay attention to you back spacing.
20''wheels on the back seem to be the easiest to run the wider tires on do to
the reduction of the side wall flex, not to mention if the right design for a wheel
is picked out the 20'' wheels look really nice on these cars but with the wrong
choice, 20'' wheels can also kill that special look one might be going for.

If you haven't already, do a search here on the C3 forum for wheels and their sizes,
there is a lot of info already here.

Hope this helps,

Riggs.