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Help! C4 flex with top off is beyond bad.

NewGuy

Active member
Joined
Aug 30, 2002
Messages
33
Location
Diamond Bar, CA, USA
Corvette
1996 LT4 Collectors Edition
I recently purchased a 1996 LT4 CE. Great car, previously owned a 1998 C5.

Took off the top and thought the car was going to self-destruct from the body flex.

Found TTR Performance at http://www.ttrperformance.com/ and they sell an under chassis cross brace similar to but better to what C4 convertibles have and claim it can bolt under a coupe. (understand the front holes are there but need to self tap the rear braces)

I am not interested in getting the top cross brace that goes where your top should since I just want a firm car with the top off once in awhile.

Here is the question: If this under chassis brace is similar to what a C4 convertible has, is there someone out there who is familiar with driving a late C4 coupe without a top and a late C4 convertible? Is the convertible a firmer vehicle, considering it comes from the factory with an under chassis cross brace????

Can you describe your opinion of the body flex of: Coupe with top on, coupe with top off and convertible?

Thanks in advance
 
F

Fugitive

Guest
Yo need to also consider R& D Racing. Dave Cooper is his name very knowledgable! I bought the "Truss" from him. It's like the TTR Anit-flex bar only I like Daves much better! Anyway I recommend getting the "Truss" because it corrects body flex from the point of weakness. He also sells a camber-brace which completely eliminates front end felexing! Check out his web site: www.r-dracing.com
Now I never drove a C4 convertible but everything I have ever herd or read suggests that the convertible has body flex problems to a lesser degree, but no doubt has flexing issues as well. I strongly reccomend getting the "Targe Truss." Your coupe convertible will ride much better than any C4 convertible with the top down. It's easy to put on and fits in the back of the car. Good Luck! Scott
 

Gary04Z06

Well-known member
Joined
Nov 15, 2000
Messages
109
Location
St. Louis, MO.
Corvette
2004 Z06
Dave does have the Targa-Truss and it is real nice, BUT....he is developing an underbrace like the verts have only Daves will be much more rigid. He makes great products. I have his Camber-Brace and Cross-Bar and both are great improvements to the handling!!!! I say wiat for Dave to complete his X-Brace!!
 
Joined
Jun 20, 2002
Messages
2,509
Location
Tallahassee, FL
Corvette
none right now :(
The bodies definitely flex on all C4's... I think it really depends on where you drive the car though... I hardly noticed it on the flat roads of melbourne FL, but in Tallahassee, the flex is very noticable... The underside cross bar will definitely help. I have wanted to add the convertible brace to my Vette, now I am looking at the link you posted. It is pretty reasonable considering it should really help the chassis flex... just keep in mind that the bar that bolts where the top should be would help more... it is a physics thing... but I won't buy the targa truss because i think it looks stupid, and i don't feel like a 12 step process to get the top on and off my car.
 

NewGuy

Active member
Joined
Aug 30, 2002
Messages
33
Location
Diamond Bar, CA, USA
Corvette
1996 LT4 Collectors Edition
Spoke to Dave at RD racing. Really nice and helpful. Ordered the camber brace and he has me on his list for the underbody brace that he developed. From the sound of it, he has a better brace than TTR and he is working on a better bolting system for the rear supports (the front has bolt holes like a convertible but the rear does not)

Like Vettelt193, trying to avoid the truss that replaces the top. These cars are a pain to remove the top as it is and I do not want it to look like I am going to an off-road race.

Will post the results of each part after I receive them and install on the vehicle.
 

Gary04Z06

Well-known member
Joined
Nov 15, 2000
Messages
109
Location
St. Louis, MO.
Corvette
2004 Z06
You'll love the Camber-Brace, really improves the handling!!!!:cool
 
F

Fugitive

Guest
Yeah Dave is the Bomb! And it's no big deal to put the Truss on! I got rear bolts on the one he sent me! Works great and looks great to! Waiting for my car to get painted, when it's finished I'm going to put the camber brace on!
Yo Gary how does the camber brace feel? Does it eliminate front end flexing? Improves overall tightness? If it's as good as the Targa Truss I know I won't be disappointed! Later Scott
 
B

Black Ice

Guest
Oh for heavans sake join the club. Thats how C4s are try driving a 1992 Camaro Vert talk about scary.
 

Gary04Z06

Well-known member
Joined
Nov 15, 2000
Messages
109
Location
St. Louis, MO.
Corvette
2004 Z06
Fugitive said:

Yo Gary how does the camber brace feel? Does it eliminate front end flexing? Improves overall tightness? If it's as good as the Targa Truss I know I won't be disappointed! Later Scott

Scott,
The Camber Brace is great!! The front end feels tighter. I could feel the most improvement at the track. I autocross every chance I get and my times are definitaly better with the brace. You won't be disappointed with this bolt on!!:beer
 
Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Dang! I just passed on a new in box one for $100 from another forum :( .

My 86 had a lot of top-off flex when I first got it. Replacing the tires and especially getting an alignment helped a lot. I've got a Cross-bar as well, but still had the shaking/flexing.

[RICHR]
 
R

RubyDropTop

Guest
Having a convertible, I will say that they are sloppy in the cowl area for sure. There is a remarkable difference between driving the car with the soft top up (car feels like jello) and driving the car with the hardtop bolted on (car feels like concrete). When I purchased my car it had the hardtop bolted on, so I was able to drive it for a while with the hardtop. Once I took that top off and drove it as a convertible, it felt like a different car - not nearly as stiff.

Yes, the extra cross-bracing is there, but the car does flex quite a bit in my opinion.
 
F

Fugitive

Guest
Yeah I'm excited to get my LT4 back! Can't wait to put the camber brace on! Just wondering Gary how hard it was to put the camber brace on? Glad you like it! Scott
 

Gary04Z06

Well-known member
Joined
Nov 15, 2000
Messages
109
Location
St. Louis, MO.
Corvette
2004 Z06
Fugitive,
The Camber Brace is pretty easy to put on. Some people have to take off the serpintine belt and some don't. Takes a little patients to feed through to get it in. If you can change your oil, you can put the brace on pretty easy. Also, depends on the year of Vette, L98 are easy, our LT4's aren't to bad. Dave is always ready to help, if your having a problem, just call him and he will be happy to help. He has great customer service.
 

timmb001

Well-known member
Joined
Oct 15, 2002
Messages
114
Location
San Diego, CA
Corvette
1996 Black LT4
So has anyone heard if the undercar barce from Dave is done yet. If so I would like to know how it turned out.
 

NewGuy

Active member
Joined
Aug 30, 2002
Messages
33
Location
Diamond Bar, CA, USA
Corvette
1996 LT4 Collectors Edition
Here is the solution

First, had the camber brace on the car and immediately took it off. It eliminated 100% of the flex of the front suspension so it was a horrible street driver. Great if you are racing but you will hate it for every day driving.

Finally installed Dave's under carriage cross frame. This is what we have been waiting for. My C4 now rides like a C5 (yes, I owned a C5 and sold it awhile back - the C4 is much more fun).

Totally eliminated body flex without any adverse changes to the handling or ride. No more squeeks, rattles and shimmys when going over normal road imperfections, great feel. No kidding, you can tell the difference immediately. Best way to put it is that the car just handles, rides and feels more solid.

Dave gets my recommedations for customer service and support. He called me before I even tried to install the brace to make sure he shared some shortcuts he discovered.

By the way, this is not a job for your home garage. Would not try this without a car hoist. Just too bulky and tight to try on axel stands.

Only drawback is that it hangs pretty low. Already scraped the it on a driveway and if you want to rack the car, you will want to use a drive on lift since the brace would hit most regular center lifts.


:beer
 

Gary04Z06

Well-known member
Joined
Nov 15, 2000
Messages
109
Location
St. Louis, MO.
Corvette
2004 Z06
Yes, the Cross Frame is ready to ship!!
http://r-dracing.com/CROSS-FRAME.htm

I don't have one yet, but I saw one at his shop a few weeks ago, it looks great. I'll have one before to long.

I drive my Vette everyday and have not noticed any negative affects from the Camber-Brace. It dosen't "kick in" unless you hit a turn fast then it does its job.

Don't forget guys, the Camber-Brace and Targa Truss take care of two diffenet things. The Cabmber Brace improves the steering by connecting the upper A-frames and the Targa Truss goes in place of the roof panel to strenthen the car with the top removed so you reduce body flexing, front-end noise, steering wheel vibration and shimmy, as well as stiffen suspension while cornering.
 

kingman

Well-known member
Joined
Jan 1, 2003
Messages
1,533
Location
Georgia
Corvette
2002 Torch Red Coupe
Cross Frame

Hi New Guy

Who installed your cross frame and how much did they charge you. I e-mailed Dave to see if he shipped it to anyone in New Jersey yet, and if he did, l asked him to get us together.

Was it a bolt on or was it more complicated? l would hate to spend the money to find out that l couldn't find anyone to install it.

Every mechanic thinks he can walk on water, but we different.

To find out that it would cost a lot of dough to install, would turn me off.

Thanks

Alan
 

NewGuy

Active member
Joined
Aug 30, 2002
Messages
33
Location
Diamond Bar, CA, USA
Corvette
1996 LT4 Collectors Edition
The cross frame brace install is pretty straight forward but takes a lot of steps. Understand there are bolt holes in the front of the C4 coupe frame where a convertible cross frame would go but there are no holes in the rear. (I do not know why, ask GM)

For the rear bolts, Dave supplies 6 "Nutserts". These are best described as "hollow wall anchors" for steel plates. These come with instructions and a crush plate to facilitate their use. They "Crush" against the hole and form a permanent thread in the frame.

Step one: bolt the front of the cross piece that goes from the passagenger front to the driver rear. Use four bolts in the front of this brace to your car frame's existing bolt holes. (Dave supplies these bolts)

The rear brace plate has three pre-drilled holes. Position the brace to fit into the pocket of the frame and centerpunch the center hole. Then drill a hole in the center bolt hole only. Use something less than 1/2 ''.


Unbolt the front of the brace, drop the brace and expose the hole you drilled. Then drill this hole out to 17/32 to accept a "Nutsert". Insert a nutsert and crush it in place with the supplied steel plate.

Now bolt the front of that brace back to the frame and bolt the single center hole. Mark the two other holes in the rear plate. Drill a hole smaller than 1/2'', unbolt and drop the brace again, drill these two holes to the proper size, insert nutserts, rebolt that brace in the front and rear middle then crush the two remaining rear nutserts. (do not put heavy torque on it yet, just enough to get a grip and stay in place without spinning.)

Note: You should not try to drill and install all three nutserts at once since they will move off center as you crush them. This is why the first, center, nutsert is done in a way to guarantee you can get your bolts in place.

Repete the process for the other brace that goes from front driver to rear passenger.

Bolt the middle of the brace together, torque all bolts (no idea how much - maybe Dave can give specs - I just used a good amount of shoulder and hoped it did not go beyond its limit) and you are done.

Give it 2 - 3 hours for your first one. I could probably do another one in an hour or so. Bet Dave can install one in 20 min.

I slipped a friend $100 for the lift and help.

Last, I took it back after a week to check all the bolts. Sure enough, needed to retorque a few.
 

kingman

Well-known member
Joined
Jan 1, 2003
Messages
1,533
Location
Georgia
Corvette
2002 Torch Red Coupe
Thanks

Thanks for the instructions, if Dave has nobody within 150miles of New Jersey, l will show it to the members of my Corvette Club and see if something can be worked out.

I would rather pay somebody, then rely on a part time mechanic.

Alan
 

timmb001

Well-known member
Joined
Oct 15, 2002
Messages
114
Location
San Diego, CA
Corvette
1996 Black LT4
So Im glad i was able to bring this up again. Looks like I need to get intouch with "Dave" for a X-brace.
 

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