Question: bracing c-4 frame

[Bobs1977]

the chassis on my 91 coupe is too flexible with the top off. I was wondering if anyone has used the convertible bracing and if so does it bolt up with out modification to the frame or the brace..i love to drive this car without the targa top but get way too much chassis flex..

 

[Toms007]

There are some who buy a "brace" that bolts directly behind the seat backs across the halo, apparently this stiffens the chassis considerably as the AutoXer's and road race people use them. I don't recall who makes them but I'll try to figure it out and post back.

OK I did a search and came up with R-D Racing as the manufacturer of the braces. But they aren't exactly like I was thinking. They have a camber brace that mounts in front of the engine, and the Targa Brace which fits in place of the top to brace the body. The mount they have behind the seats is a camera mount, so I don't know if it does much to brace the body.

http://www.r-dracing.com/

 

[G Winter]

I haven't been under my 90 for a few months but if I remember right the brace bolts to the body on 4 places as well as to the frame.
Look at the frame just before it curves in under the front of the door and see if there are two 3/8 in holes there.
After thinking about it it might be just after it curves in .

Glenn


after some more thinking it is after it curves in because the fuel filter is just above where the X brace bolts on .

 

[Ugolino]

There is an aftermarket x-brace available for c4 coupes, I don't want to mention the company or product because I don't want to look like a shill, but a web search should reveal it. If I understand correctly, the front bolt holes are already there, but you need to drill into the rear part of the frame to attach the back part of the brace. I would have made this mod to my old c4 if I had kept it, as I have heard it stiffens up the chassis considerably.

 

[6 Shooter]

C4 frame flexing was one of the leading issues for me selling my LT4 and moving up to a C5.

The corners of my targa top had stress cracks in them per the flexing issue and if you took targa top out, frame shudder was ridiculous.

Hopefully the brace will help.

Later . . . . . .
6 Shooter

 

[Hib Halverson]

The X-brace-on-coupes question has been asked many times.

In short, adding the braces does little or nothing. This is because the coupe is already stiffer with the top out than the convertible is with the braces on. It's a "diminishing returns" kind of thing.

Yes, the x-braces can be fit to a coupe but, no, they will not dramatically change the trouble you have with the roof off.

The "shake problem" with the roof off is an inherant problem with the C4's weak structure and cannot be easily remedied short of putting a partial or full roll cage in the car.

Some believe that installing one of the many "harness bars" can help, but I suspect that won't make much difference either as the small amount (if any) stiffening a harness bar lends is not in the right place to make a difference in the shake.

The easy solution is, when you're going to drive the car hard, put the top on and make sure the top bolts are tight.

 

[wannaC6]

Purchased a used R-D Racing Camber Brace. Came with 2 bolts and no instructions. Anyone have install docs? I have been unable to find website with instructions and my e-mails to manufacturer have gone un-answered.

 

[CorvetteArchives]

One of the major Vette magazines did an install of this years ago. I cant recall which one though!
There are pics at the manufacturers website that show it installed. From what I remember about the install is that you dont actually drill the rear holes to final size. You need to use a punch since they dont hold by any internal fastener...but by self tapping/threading into the frame itself.

The same company also sells a targa truss that allows open air driving with proper structure. Like GM should have done to begin with...make it a T Top. Unfortunately, a top doesnt fit over targa truss which seems kinda lame IMHO.

 

[wannaC6]

The camber brace I have is used to tie the shock horns together. It mounts in front of the engine. If anyone has a copy of the installation instruction please let me know. Thanks!

 

[Paul Higg]

the chassis on my 91 coupe is too flexible with the top off. I was wondering if anyone has used the convertible bracing and if so does it bolt up with out modification to the frame or the brace..i love to drive this car without the targa top but get way too much chassis flex..

Yeah, but it's fun to be driving a car that seems as if it has square wheels with the top off!!! Actually I don't mind it, it's STILL a Vette!

 

[road agent]

Buy a C5! Your too wimpy for a C4!

 

[Paul Higg]

Buy a C5! Your too wimpy for a C4!

I'll buy it if you give me the money!
otfl