WA 2 FST

Alright, someone correct me if I'm wrong but the stock wheels on a '69 are 8" wide with 4" BS from what I have gathered.

I am wanting to run a 285/40-17 tire in the rear and I believe I will need at least a 9.5" wide wheel to accomplish this. I know that if I go with a 5" BS that it will push the outside wheel lip out .5". I think this will be ok, but if someone has tried this (moving the wheel out) and it didn't work out, please let me know.

I would rather not have to do offset trailing arms and I believe I can get away with a 5" BS and be ok.

What about the sway bar/sway bar mount? Am I going to have problems there? It looks like it will be tight, IMHO, but I hear of people running 295mm wide tires and getting away with it.
:confused:

Magnet

I am running 17"x 9.5" on stock trailing arms for my 1980 :thumbs:

WA 2 FST

Magnet,

That sounds great! Now, can you help me with what backspacing you run? What size tires do you run, and does the wheel/tire stick out much past the fender lip?

Thanks for the reply!! :)

Stingraycrazy

Hey "WA 2 FST"

I put one of my 20's on the back for ya. This is one of my front wheels but you should get the idea. It's a 20X8 with 4.5" back spacing. I have 1.5" of clearance before I hit my sway bar. That would give you about an inch of clearance with a 5". You would need to pick a tire with less than 10.75" total width. You could have more tire if you went for the 4.5" I have the VB&P rear arms but if you move the emergency brake cable you shouldn't have a problem there. Good Luck... :crazy:

mrvette

I don't see how any 17 inch wheel with more than 4.5 inch net backspace will fit on a stock C3 t-arm, even with moving the ebrake tab....assuming of course i'ts a 275 tire...that makes the tire about 1/4 inch from the t-arm flat surface....a 5 inch backspacing puts the tire touching the t-arm...

GENE

WA 2 FST

Stingraycrazy...thanks for taking the time to take the pics!

I don't have to have 17s, but I was thinking that if I run wider 15" wheels that have more than stock BS, then I will hit the spring (way before the T-arm).

If I run 15s, then I want to run 295/50s on there. A 295 really needs a 10" wheel, but at the very least a 9" wheel. A 9" with 4.5" BS would probably be fine and keep the tire inside the outer fender lip, but a 9.5 would need a 5" BS, IMHO.

Thanks again. I'm making educated guesses at this point, but that's better than haphazardly jumping in! :)

Stingraycrazy

I've found that the larger diameter wheel you go with the more back spacing you can have. My spring is actually inside the diameter or the rim for the 20's. The sway bar on my car would be my only clearance issue. If I removed it I could go with 6" of BS. If you decide to go with new wheels check availability of rubber before you make a purchase. I bought a set of 18's and ended up buying the 20's just because of the available tire options. Check out EBay for rims. You won't be disappointed. Tons of deals! :crazy:

Magnet

I have 5" backspace, which requires me to use a custom 3/8" spacer so the wheel clears the brake caliper

Stingraycrazy

Clearing the caliper depends on the design of the wheel. My 20" rims clear the calipers with about a 1/4" to spare. I think it's just a matter of trial and error. :crazy:

PROSOUTH

Thanks for the pic's. I wish someone would do a "Tech Article" on this subject and give specific measurements on a C-3 system with stock T-Arms and with Offsets.

I am planning on using 17'x 9.5 with a 5" BS at least and more if I can make it work with my VanSteel OSTA's like yours. I also wonder what the total dimensionis from the Rotor face to the Inner Wheelwell? This seems to be the real limiting factor. JIM

terryrudy

Wes, check out this link (requires Adobe Acrobat)
Hopefully it will help you out (or give you more to think about) http://www.corvettefaq.com/redir.asp?site=156

-terry

Stingraycrazy

Thats where my ZL1 flares come in. :yesnod: I just got to mount em... Know anybody in the Syracuse area that's good with fiberglass? :crazy

PROSOUTH

Well Stingraycrazy I was refering to Backspacing but I have to agree if you can't go one direction go the other. I would like to put an 11" Wheel under my car. I have the offset Trail-arms and would change rear sway-bars if necessary to use them. I am ordering my wheels (when the time comes) and a Custom BackSpace is available. Does anyone have 11' wheels under a "Stock" fender?

I am not planning on using the ZL-1 flares on my car. I do like the looks of them on certain cars. There are many on this forum that the ZL-1 flare puts the finishing touch too.

I would almost consider and "Expanded " quarter for lack of better term. I want to think I saw them on a car some where and they were so well blended that they looked like the factory original quarters, just bumped out a little more. This I would consider changing quarters for. .........well almost . LOL JIM :yesnod:

norvalwilhelm

I have 5 inch back spaced 15 inch wheels and run into problems with hitting the spring. I had to run a shorter spring. I also had to run offset trailing arms. I also polished the frame just above the trailing arm pivot point. I ran MT Sportsman pro 12.50 x 28 wrinkle walls at the time.
I feel with stock trailing arms that 5 inch backspacing is too much.

Stingraycrazy

Your right about the 15's but if you were to go to a larger diameter wheel say 17" or higher you would be able to fit It. The rear arm is not straight it angles away from the wheel before it connects to the frame. :crazy:

WA 2 FST

I concur with this...although obviously _I_ haven't actually strapped a set on yet. :D

Stingray...think I'm safe with a 4.75" BS w/ 17" wheels? I believe I will be.

Stingraycrazy

Yea, I think that would do it... Just mount the wheel and measure for how big a tire you could fit before you buy. Also if needed small spacers will help the caliper problem. 1/4" or less is all the difference sometimes. I have friends that run them on there daily drivers without a problem... :crazy:

WA 2 FST

I guess I don't understand why there would be a caliper issue with a 17" diameter wheel. :confused:

Granted, I have not studied these calipers that much, but the taller wheel should clear the caliper...especially if a 15" stock wheel will. Do these calipers stick "out" pretty far, so we get into an interference issue there?

I want to build a wheel that fits without a spacer. If I need a spacer, then I need to have the manufacturer build more backspacing into the wheel to begin with.

Stingraycrazy

The clearance issue is not with the hoop or diameter of the wheel it's the backside of the wheel that the studs go through. If you look at the pictures posted you can see the caliper has raised areas behind the pistons on both sides. The front calipers are larger and interfere the most with the back side of the wheel. If you have a problem with your new wheels you can use spacers between the wheel and the brake rotor to move the wheel away from the caliper if needed. :crazy:




[Modified by Stingraycrazy, 1:57 AM 12/3/2002]

Stingraycrazy

Here's a good picture that shows how the brake caliper protrudes over the rotor to wheel mounting surface. :crazy: