C4 X Frame brace

[gman35]

Does anyone have a picture or diagram of a OEM X frame brace that comes on the C4 corvettes. I recently aquired a very nice oem one. I don't have a clue where it fasten's in the rear.. it came with four spacers about 1.5 inches tall and the mounting hardware. Maybe some one has a factory manual with a diagram, thanks. gary

 

[Huskerman]

I don't think they were OEM X braces. I thought they are all aftermarket. Might be wrong.......I have heard that the Targa brace works very well and you don't have to worry about it dragging on stuff undernieth.

 

[gman35]

oem

I don't think they were OEM X braces. I thought they are all aftermarket. Might be wrong.......I have heard that the Targa brace works very well and you don't have to worry about it dragging on stuff undernieth.

The one i just purchased is in like new condition, it came with all the hardware and was oem from the factory installed on a convertible. I have found two more since i bought this one, they say they are hard to find. I have a targa truss on the car now... and soon will have the camber brace on.. thanks gary

 

[G Winter]

They came on the convertibles. My 90 has one. it bolts with 2 bolts at each corner plus there are two on the body.In the front it bolts to the frame just where it turns in.
It is right where the fuel filter is on the passenger side.If you can get that corner located the rest should fall in place.If memory serves me right the frame is threaded for the bolts.
I have the service manual and could look it up later tonight but right now I have to be leaving.
concerning dragging, it is only about 3/4 thick in the center, actually helps protect the floor pan if you would scrape.

 

[gman35]

thanks

Great and thanks, I really would appreciate those pics or diagrams. I am hoping to begin the install of the X brace today,, i have already installed the targa truss.. and still need to install the camber brace. my email is g_jorgensen@msn.com it should be listed in my profile here also. Thanks so much for the reply and the help,, gary

They came on the convertibles. My 90 has one. it bolts with 2 bolts at each corner plus there are two on the body.In the front it bolts to the frame just where it turns in.
It is right where the fuel filter is on the passenger side.If you can get that corner located the rest should fall in place.If memory serves me right the frame is threaded for the bolts.
I have the service manual and could look it up later tonight but right now I have to be leaving.
concerning dragging, it is only about 3/4 thick in the center, actually helps protect the floor pan if you would scrape.

 

[Hib Halverson]

If you're putting those X-braces on a coupe, when the roof is on, they won't do anything but decrease ground clearance (that's why C4 convertibles had higher trim heights) and increase vehicle weight.

With the roof out, they might make a modest contribution to stiffness in torsion/bending but probably not solve the car's problem with cowl shake.

 

[gman35]

roger that

Roger that, i have a targa truss bar insstalled for when the roof is out... the x brace and the camber bar will just stiffen it up even more i hope.. never relly had any problems yet with the frame flexing. ground clearance should not matter,, car has been allways drivin on smooth roads,,, i have a 1978 step side silverado 4 wheel drive with a built 454 for the ruff stuff. thanks, gary

If you're putting those X-braces on a coupe, when the roof is on, they won't do anything but decrease ground clearance (that's why C4 convertibles had higher trim heights) and increase vehicle weight.

With the roof out, they might make a modest contribution to stiffness in torsion/bending but probably not solve the car's problem with cowl shake.

 

[Hib Halverson]

Might have misunderstood my post.

The convertible X-braces don't do anything on a coupe except add weight and make service of driveline pieces even harder.

The convertible is so "flexible" compared to a coupe, just to get the convertible's stiffness in torsion and bending close to the coupe, GM had to use those braces. On a coupe, which is already stiffer than a convertible, they make no contribution to stiffness.

 

[gman35]

roger that

roger that and thanks, I figure i will install it and then assess what the results are. with the x brace and camber brace.. i figure my coup will be tighter with the targa truss out. normally if the truss will be out the solid top will be in. but sometimes i put in the astro top. So i figure at that time the x brace and camber brace will help for more rigidity of the frame.. thanks gary

Might have misunderstood my post.

The convertible X-braces don't do anything on a coupe except add weight and make service of driveline pieces even harder.

The convertible is so "flexible" compared to a coupe, just to get the convertible's stiffness in torsion and bending close to the coupe, GM had to use those braces. On a coupe, which is already stiffer than a convertible, they make no contribution to stiffness.

 

[gman35]

pics update

Hello again, just doing a follow up on the pic's.. any luck on taking them yet..? I will be installing tomorrow if all goes right,, thanks and i hope your night is good,,Gary

They came on the convertibles. My 90 has one. it bolts with 2 bolts at each corner plus there are two on the body.In the front it bolts to the frame just where it turns in.
It is right where the fuel filter is on the passenger side.If you can get that corner located the rest should fall in place.If memory serves me right the frame is threaded for the bolts.
I have the service manual and could look it up later tonight but right now I have to be leaving.
concerning dragging, it is only about 3/4 thick in the center, actually helps protect the floor pan if you would scrape.

 

[C2C3C4]

If you're putting those X-braces on a coupe, when the roof is on, they won't do anything but decrease ground clearance (that's why C4 convertibles had higher trim heights) and increase vehicle weight.

With the roof out, they might make a modest contribution to stiffness in torsion/bending but probably not solve the car's problem with cowl shake.

Don't want to argue with an expert such as you Hib but I was at a Chris Petris C4 class and he thought it would help. We were at a Chevy dealer in St Charles and had a C4 coupe up on a lift. The car was owned by a gentleman who would do some road course events a few times a year. He showed us how to do this. There are threaded holes toward the front of all 86 - 96 Corvettes that you can bolt the front of the X brace to. You then place the rear of the X brace in place and mark the frame where the holes line up. Then drill the frame and put in the proper sized nut (it has a special name but cannot for the life of me think of it). This nut (maybe a well nut?) will expand and hold itself into the hole you drilled. Then bolt the back of the X brace into the nuts. I bolted in a set of No Flex frame braces from www.vette2vette.com and love them. I do not have any empirical data to back these up but my car handles like new instead of felling its 107,000 miles - even with the targa off. These bars allow full access to the exhaust and driveline. You can search for the article I had published in Auto Enthusiast magazine. The title is "Do The TIghten Up". Note that I do not work for Vette2Vette or receive any payment for any of his sales - I am just a happy customer. I will see if I can scare up a pic here in a bit.

 

[C2C3C4]

 

[Hib Halverson]

I work for "Auto Enthusiast" occasionally and I recall that story.

The braces you speak of are an aftermarket product and quite different from the stamped X-braces used by the factory on C4 Convertibles. I base my statements about the OE convertible X-braces on conversations I had with GM engineers who worked on Corvette during the C4 era. The stock X-braces made a significant contribution to the C4 Convertible's stiffness in torsion and bending. This is because the C4 convertible's structure was absolutely terrible.

One a coupe with the roof on, the OE braces will make no practical improvement.

As for the aftermarket pieces you talk about, above I have no information about them like I do for the OE braces. If you say the car feels different, it's probably because those braces are stiffer and have a better mounting so they can make a useful improvement which you may feel.

Looking at your images, I would imagine they make an improvement in bending but not in torsion.