massiveB

anyone else feel like the car is gonna rattle apart when they take off the roof panel? my car is tight as a drum with the roof on, as soon as i take it off i feel like the winshield is gonna fall off and the steering wheel gets a half a foot of side to side play(exagerating of corse) but very loose feeling none the less. anything can be done to correct this?

RollaMo-LT4

Lots of people will say that its normal.
But I don't experience that feeling in my '96.

Midnight 85

This was discussed at great lengths here a few years back and IIRC it went unresolved, some cars do it while some don't. My '85 never did do it. I did do some mods for better handling that should stop your problem. I bought a used x-brace off a convertible then I boxed it all in using 1/8 in. flat stock. I also installed a camber brace. my car is solid as can be and handles great. I doubt if the camber brace would solve your problem but the x-brace was reported here that it did stop the shakes.

pianoguy

It was the same with my '96 - I was shocked at how loose it was with the targa off, thought the steering wheel was gonna fly out of my hands. I installed an R-D Racing Camber-Brace, which helped quite a bit. Then I added a Cross-Frame from them, which helped a bit more. Finally, I bought an AFSB Targa Bar, (got mine used, but new they are sold by Pro Street Customs) which makes the car as solid, if not more so, than with the roof in:



The latest solution appears to be these braces:

http://forums.corvetteforum.com/c4-g...me-braces.html

CRUZN C4

Never had any problems with my 84 and no problems with my 90.

RustInPeace

I notice a difference on rough roads with the top off in my 94, not so much in my brother's 88 though

8valve

No issues whatsoever with my 87. I live in the mountains and lots of rough roads. She is as solid as you could want. My top is never on during the entire summer fall. I carry it in the back just in case of rain.

8Valve

jrzvette

The tops of the C4 were an integral part of the body structure, that's why they bolt in rather than use the clips like the C3s. Originally the C4 was to have a T-Top like the C3s but someone up the food chain wanted a single piece top, which required a chasis redesign. This is one of the reasons for the high side rails and the delay in bringing the C4 to market (no 1983 model).

wnafly

When I have the top off my 96 the body flexes a little on big bumps but my steering wheel isn't affected at all.

8valve

In the past, I have done a search on this top on/off issue. I have read every post that search turns up. I have years of fab'ing and strength of materials as experience.

Simply put, I do not believe the Targa top stops all the flex and vibrations like many feel it does. Consider this;

In many of the searched posts I read, the poster's tell of serious body flex, windshield vibrations, steering wheel jumping back and forth. For this to happen, there is serious body flex !

Many of the C4's have the acrylic or glass tops with a small aluminum frame around the acrylic or glass. Consider the forces imposed on the Targa top as the car flexes. If this was all a real fact, that top would crack and break in a heartbeat. No way Acrylic or glass bonded in a aluminum frame is going to stiffen up the body an not break. There are other issues in play here, some cars have it while others dont with the top off. I would sure like to ride in a C4 that behaves poorly with the top off, then figure out why some do and some dont.

And if the flex was so bad without the top, GM for safety would have made the top not removable and had extra steel in the top for support.

8Valve

Vette Daddy

Without the top there is flex. With it, much less. Only makes sense to me.

I will say that my 96 had very little at all.

r15

I have it at times in my 92. It's mostly on rough patches of road. Any shaking at other times is probably a different issue (tie rods, tire balance, etc)

darkstallion_69

my 94 with the top off is a much different car. There is some sort of side to side movement when it hits bumps.

romankrzy

I plan to take advantage of the deal on these frame braces to tighten my 93 up. There has been lots of positive feedback on them so far.

http://forums.corvetteforum.com/c4-g...me-braces.html

ddahlgren

Following the thread offered here said the 'frame' is spot welded sheet steel... I would think doing one or all of the following might be the real fix. Do some stich weld between the spot welds to join the parts better or build a L shaped stiffener to go along side the frame as a 'fishplate' of sorts used to repair truck frames or fill the frame rails with structural foam as used in some airframes. I am thinking 20 years of flexing stop welded steel the structure is not neary as stiff as it once was and why some cars are better than others. Has anyone ever used the foam I remember seeing a thread about it a while back.
Dave

Itshakes

See my Avatar----

8valve

Yes, I agree. You may even find broken spot welds. Lots could be done to stiffen up the frame. It all depends on the application you use your vette for. I sincerely believe tht any C4 Owner who experiences this awesome flex/rattle/shake should get to a good frame shop and have the entire underbody/frame inspected. You....could....be dealing with life threatening issues, it needs to be checked by competent people.

May I suggest using any type of foam in the frame is not a good idea. This will allow water to collect, and promote internal rust. Then with the foam, its nearly impossible to repair properly. Welding on the frame with internal foam could easily start a internal fire inside the frame.

Its my bet that if you had a chance to drive a brand new C4, zero miles, you would not experience these issues we discuss.

As I mentioned, my 87 has none of these issues, as some others also report. Maybe these cars were really babied and never stressed and flexed over all their years.

8Valve

ddahlgren

You have some good points 8valve. I would do welding first not last. I know my 91 would be totaled if later welding was needed from a crash. If the foam is made for this application I would think it is formulated to adhere to the metal so there would be no room for moisture. If it did not adhere it would be useless as a stiffener anyway. Has anyone done a frame off project on one of these cars. What holds the plastic body on and could you remove it to actually get to the frame?

Frizlefrak

My 84 exhibited a lot of body flex with the roof off. I've never driven Marco with the top off....guess I need to try that. But it's gonna need to drop about 25 degrees before that will happen.

I remember the C4 used to be called the "Flexible Flyer" back in the 80's for this very reason. I've never seen any harm come from it.

8valve

You just hit another good point. The FSM says the body is bonded to the frame. Ok, what if over time and wear and tear the rear part of the body, somewhere, became unbonded in places. Now we have the body (much lighter) hopping around. I wonder in that case, by tying in The Steel Windshield frame, via the Targa top (fore/aft) if that would tame the body. In this case much less stress would be handled by the Targa, compared to trying to tame the frame flex ???

Consider this; If brand new C4's misbehaved so badly with the roof removed, there would have been recalls and people suing.
If the GM answer was that the Targa top must remain on the car, again people suing and forced buy backs. No, I truly believe this is a problem that developed with age and maybe certain types of usage.

8Valve