gleveric

I have a 77 Corvette L-82, I need to put wider tires on the car, and don't want them to stick out. After a quick glance under the car, it seems that i'm going to run into trouble with the rear leaf suspension. The leaf runs left and right instead of two forward and back. Right now the leaf only has about 1/2 inch clearance from the tire with 3.5 in backspace rims. Anyone have any idea what I need to do? or have any info on this? :confused:

Thanks for any info,
Gary

GrandSportC3

If you want to use rims with more than 4 inch backspacing - you need Offset Trailing Arms.. They are available at:
http://www.vansteel.com
or http://www.ecklers.com

:cheers:

Olivier

Schmucker

Although you will hit the frame before you hit the trailing arm then. 5.25 is the safest backspace with offset, you can get 5.5, but it is more risky. 6 I think is out of the question. With the stock trailing arm the ebrake cable bracket gets in the way. My dad said I have enough tire for anything I need so I'm opting not to go with offset trailing arms. I'll just go get some 17x8 TT D's and I'll be a happy boy :D

norvalwilhelm

I have both. A set of 5 inch offset and a set of 6 inch offset. I needed offset trailing arms to run the 5 inch offset and then I ran into the frame and the area just above where the trailing arm goes into the frame. After grinding and welding I got this area clearanced but I still run into the frame so I needed 1/4 inch spacer on the drivers side and 1/2 spacer on the passengers side. This kept the tires with 5 inch backspaced rims from rubbing the frame.
Next is the spring. I shortened the original steel spring about 2 inches. You can cut it with a saw and drill it with a good drill bit, slow speed and lots of oil. It is certainly drillable.
6 inch offset with 17 inch front wheels will not clear the outer tie rod end.
This is not from theory but from experience having both set of 4 rims in the shop.
This was on my 75. This is a shot with centerlines and 3.5 tires. The top is a little out because both upper and lower strut rods are off. I have 6 link suspension.

norvalwilhelm

This is a shot from the back. You can see both strut rods hanging down. The tire is resting on one of the strut rods. This is 5 inch backspacing with 1/2 inch spacer installed. The tire is 305-50-15 on a 8.5 inch rim.

GrandSportC3

I always thought that you can go with 10 inch wide wheels and 6 inch backspacing with the offset trailing arms :confused: :confused:

:cheers:

Olivier

gleveric

OK, cool, i think i am getting the idea. so... If I move the e brake braket to the top of the trailing arm, and shorten the leaf spring an inch or two on each side, I should be able to fit up to a 4 1/2 inch backspace rim on the car with the stock trailing arms? Also, is shortening the leaf spings as simple as cutting them off and drilling two new holes?

Also, maybe this is a better question. I put a motor combination in my vette that has run high 11's and low 12's in another car. What kind of rim / tire size would you guys suggest? I am trying to keep the diameter at 28 inchs or less. I was told that I am going to need a 12 inch wide tire with 10 inch rim to make it stick (and I had a 12 inch slick on the other car). And I want a DOT tire on the vette. :confused:

Thanks!
Gary

GrandSportC3

It depends a lot on the track that you are running on... I use 275/60R15 BFG Drag Radials.. and my ET's are in the low 12's.. hopefully will get into the 11's this Saturday... If you have a linelock to warm up the tires...275's should be big enough.. I'm planning to switch to 325/50R15 Drag Radials.. but I have to make sure that they will fit and not hit the frame...

:cheers:

Olivier

norvalwilhelm

? Also, is shortening the leaf spings as simple as cutting them off and drilling two new holes?

To shorten my spring I took the spring pack apart and cut one end off the main leaf. Then I drilled a new 3/4 inch hole in the cut off end. Exactly half way between the new end hole and the other hole drill a 3/8th hole for the assembly bolt. This still requires 2 holes to be drilled but only one 3/4 inch.
I also grease between my leaves to prevent binding and I do not use the plastic inserts.
Remember if you drill a leaf do it slowly with a sharp drill bit and lot of oil.

WA 2 FST

You _are_ getting the idea! :) You will definitely have to shorten the leaf spring if you have an aftermarket one (I have a VBP 'glass spring). I do not know about the stocker.

But after recently installing a set of 17" wheels, I can tell you that 5" BS is about all you're going to get, even with offset TA's, if you do not shorten the leaf spring. If I'd chosen to do that, I could have definitely run 5.25" BS with no spacers to negate some of the BS.

As it is, I mounted 285/40s on some 9.5" wide wheels with 4.75" BS. No issues at all, but I do have offset TA's. I'm not 100% sure the stock TA's would have worked even if I'd moved the e-brake cable/bracket assembly.

gleveric

Hey Olivier, so a 275 tire has a total width of about 10.8 inchs right? (275 / 25.4). What do you run for a rim width and backspacing? and did you need offset trailing arms to get this to work? :confused:

Thanks,
Gary


[Modified by gleveric, 7:45 PM 1/16/2003]

GrandSportC3

I use a 15 x 8 Torq Thrust II rims with 3.75 inch backspacing. This setup works with stock trailing arms with no problems..

:cheers:

Olivier

norvalwilhelm

GrandSportC3. It is not the trailing arms that are the problem. It is the frame. Just about where the trailing arms go into the frame pocket it on, which is modified for more clearance.
The main problem is around the shock area where the frame bends out. Looking at the back of the tire the frame is far away. Looking from the tire side say at 2 oclock lots of clearance but look at 10 o clock and there is the problem.
And guys I am not talking about 10 in the morning and looking again at 2 in the afternoon..
I have pushed this for years always trying to get bigger tires in the wheel well.
With Mickey Thompson 12.5 wide by 28 high I pushed every dimension. They occassionally rubbed on the polished frame and just cleared the modified out lip. Never a problem with my trailing arms.
I could of made the 6 inch offset 17 inch rims work on the back with a wheel spacer but not a hope for the from. It even hit the upper ball joint plus the outer tie rod end.

gleveric

Hey Norval, I was actually looking at the Mickey Thompson 12.5 wide by 28 high's on the back. I was going to try them with 4.5 inch backspacing, my stock TA's, and just moving the e brake and shortening the leaf. What do you think about that?

The Money Pit

The 295's are 10" wide at the tread,and stick fairly well.Still no problem smoking them off the line if I want to,but I've learned to ease into it,then let em have it. I tried 10" rims and they stuck out way past the fender lip.Check out my website for a picture of the tires.