subtlez28

I just purchased an 84 Corvette. It has an LS1 in it, and I will be building it as a mainly road course car (though still streetable).

My understanding is that 84 suspension is different than 88 and later, right?

They change the front to reduce scrub, right?

88 and up cars require different offset, that much I do know.

What I want to know is what exactly was changed?
I'm wondering how much of a hassle it would be to upgrade to later year parts, so I can use the big brake kits and wheels (w/out spacers) of the later cars. Also, if the geometry is better on 88+ cars this should be a bennifit on the track.

So if someone could explain what parts are different, or will need to be changed to update. Or a link to another thread - although I did search.
Pics and/or diagrams would be great!

Thanks in advance!

subtlez28

I'm researching now.
My new toy hasn't arrived yet (should be here on 07-26-08).
It has Konis and 32/26mm sway bars already.
Here is a link to the Ebay auction I won it on:
http://cgi.ebay.com/ebaymotors/ws/eB...m=180255460141

I haven't decided if I will go crazy and gut it out and go all out track car or not.
But I am determined to put a T56 in it!

Solofast

The later parts (control arms, spindles ect) are all different. Not sure if they will bolt up to an 84, but if you did it you would have to do it as a package. Maybe somebody else will chime in on the what can be swapped out relative to frame mounts.

In low speed events in stock class, the earlier suspension has better camber at higher steering angles. With the later suspension you can't get enough caster to offset the high king pin angle (line between the ball joints when viewed from the front). Where the earlier cars had less kingpin angle and as a result didn't loose as much negative camber at high steering angles. That gave them more grip in autocross events, but at lower steering angles the difference is not as great.

If you are running high speed events there is much less of an issue, and if you replace the lower bushings with offset bushings there is no practial advantage to the earlier suspension. The later suspension has less "kickback" in the steering over nasty bumps, but as far as handling goes there isn't an advantage either way.

There are aftermarket brackets that will let you bolt up later brakes to the early spindles. These aren't legal in BSP, but if you are running track days that would let you get bigger front brakes onto the car.

The rear suspension of the later cars is better (less bump steer and different anti-squat) and there was a thread on that subject in this forum a while back that you might want to research if you wanted to go that way.

If you were to replace the suspension in the front, you ought to do the back end too. That way you will get equal offsets and be able to swap tires front to rear. If you change out one end of the car and not the other you will end up with a different front and rear offset.

Red Guts

Lots o' C4 suspension info here.

subtlez28

Thanks guys.
And yes, I would do both, I want to run 17x11s front and rear, and same offset is a big plus.

Anyone know if 36mm offset 17x11 GS style wheels will clear on the 84?

Bill Dearborn

People who run the wide wheels on the early cars use the ZR1 offset in the rear. The GS offset moves the wheel to far inward.

Bill

subtlez28

Ok, so the GS are the 50 (or 56)mm offset,
and the ZR1s are the 36 mm.... I guess I had that backward....
So I guess I would need spacers to run the stock narrower 84 suspension.

Not good news.

ghoffman

I just gave Brian Cunningham a C4 rear knuckle to do a Solidworks model for us. I have the first lower rear mounts fitted, and the production versions will be out soon for all brands of shocks. This prototype will be widened for QA1, Koni, Bilstein as well as the Penske mount shown. With this, you can safely run coil-overs without bending the cantilever stock mount.