Corvette-FIN

Hi guys! First of all I'd like to say I'm from Finland to sorry for my English, it's not perfect but I hope you can understand what I'm trying to say.

So I bought a C4. Like in every vehicle, first thing you want to do is lower it a bit to give it more aggresive look. So I started with the rear end, as it seemed simple. So when I assemble the rear with 1.5" longer bolts, the spring is so straight that it wont touch the rubber isolators. Why is that for? Or is it normal that the isolators come loose when I jack one corner at a time up?

And if I want to lower the front, is the z51 option spring a direct fit and will it lower the car?

Mine is a 1984.

kael

Check, are the rear hubs sitting on the bump stops? The rubber bit on the body above the hub. If so, that's bad, you're way too low.

Have a pic we can see?

kael

Also, did you get a kit? It will include shims for the spring, to adjust it's height.

Corvette-FIN

I bought just the bolts and nuts.

The problem is not that I'm hitting bump stops - I haven't adjusted it that low, the problem is if I fit the new bolts, they are so long, that my spring is loose.

Also I had bushings between the hub and spring, has someone added those or should I have them?
The way it was:

https://ardhu.kuvat.fi/kuvat/Corvett...pg?img=smaller


And how I assembled it:

https://ardhu.kuvat.fi/kuvat/Corvett...pg?img=smaller

Corvette-FIN

No they are not hitting bump stops, The problem is that when I jack the car up, the rear spring comes loose from the bolts that adjust the ride height. Should they? Or should they stay in contact with the isolators in the bolts. I cant upload a picture for some reason...

kael

If the spring applies no tension when jacked up, that says two things to me. Either your rear shocks are too long compared stock, so the rear hubs sink much farther down than typical. Or, something is wrong with your spring, either it's cracked or mounted incorrectly.

I could be wrong, I haven't tried lowering my Lady yet.

kael

Hmm, checked your pics, that spring seems awfully thick. Maybe the spring was changed to a super stiff to allow for really low rear. In that case, it wouldn't travel much and the loose bolts would make sense.

Here's how my spring looks on jacks.



FYI, you have to have so many posts before you can paste images.

Corvette-FIN

Hmm... Searching rockauto, the shocks should be about 14” long extended lenght? Need to measure that, thanks for advice!

should there be bushings between the hub and spring? Looking throught internet, my rear end looks odd

WVZR-1

Your first snapshot "HOW IT WAS" is what I'd expect for an '84 or '85 except for the washer stack at the nut and I believe it's missing a bushing likely on top of the spring so the washer stack was used to fit it.




In this image look at 42, 44 and 46



Maybe a previous owner removed the one bushing to let the spacer drop to the lower bushing through the spring in an attempt to lower it. I've no idea!

I don't have a 'hands on' to an early rear spring so I can't tell you where to look on it for code.

Is there maybe a SPID/RPO label in the rear storage compartment? It might be interesting to see the suspension options.

Corvette-FIN

I can tell you the rpo codes when I get to the car So it seems that there's nothing wrong with my rear leaf? If I wanna lower this thing, I put on new bushings like it was (both sides of the hub and spring, right?) and then make a new steel bushings(number 46 on your photo) that is equally longer to the bolt that I have already bought? Correct me please if I'm wrong cause this is how I see this thing now

WVZR-1

Can't tell you that - only a close inspection answers that question. Early cars (no personal experience) I don't believe respond to the longer bolt lowering procedure.

I don't get the 'he!! bent on lowering'

Have you bought new bushings? How many?

MatthewMiller

No, your setup is okay. My car is lowered on longer bolts as well, and when I jack it up the springs don't stay in contact wiht the rubber busings/isolators either. That's just because the bolts are longer and the spring doesn't have enough droop. Different rate springs will do this to different degrees, of course. I have very stiff aftermarket springs (550lb/in in back), so they droop less than a stock base-model spring would.

This is no different than a car with conventional coil spring that are lower and stiffer than stock: sometimes they can get loose in the spring perches when the suspension is at full droop. Anyway, don't worry about it. As long as the spring ends are contacting the isolators when the car is at normal ride height (i.e., it isn't resting on the bump stops), you're in good shape.

PS - What WVZR-1 wrote about the missing rubber bushing and metal sleeve:
...is true. #46 and 44 in the diagram seem to be missing from yours. Those would have kept the spring in captured in snug contact even when jacked up. The only thing that provides is less suspension droop when the car is off the ground. But when you're driving (as opposed to jacking it up), the only way that will ever come into play is if the car is literally weightless on one or both of the rear tires - like you're jumping off a ramp! So I really can't see how it can cause a problem. And like I said, mine is the same way and I both race and street-drive it with no problems whatsoever.

WVZR-1

The sleeve/spacer isn't missing in the OP's car, if the sleeve/spacer were missing there would be "nothing" to keep the bushing snug to the suspension support/knuckle. The "washer stack" hints that maybe the bushing above the spring is missing but there ain't no snapshot confirming.

The OP's configuration I believe hints a FE7 build '84 & '85 only and not present on base build, also '86 and later didn't use 4 cushion & spacer configurations.

Ideally I believe you put the car back to it's original configuration and move forward. Modified by a PO I'd say for sure. Why and for what purpose? Who knows.

The OP could maybe check the other side to confirm both sides are the same. OP needs to ID the rear spring in the car also I'd think.

MatthewMiller

I was referring to his second photo, the "after" shot of how he reassembled it after lowering. Maybe I'm missing it, but I don't think I see a sleeve or the rubber bushing on the bottom side of the knuckle. There is also not one on the top side of the spring in that photo.

Again, my car is the same way. And I believe any lowered C4 would be the same, unless someone goes through the trouble to make a new sleeve from tubing or pipe stock. And if you do that, then it won't have adjustable ride height - just a fixed lower ride height. You wouldn't be able to make adjustments for cornering weighting or other needs. I don't see any reason that there has to be a sleeve and either of the two inside bushings. Again, as long as there is any load on that tire, there will be tension on the bolt.

kael

ID for the spring should be a sticker on a tip, facing up.
Like so:

Corvette-FIN

The spring is BMH 004588. The RPO wasn't in the center glove box or rear boxes.
The rear shocks were 14" extended like they should.

I assembled the car with longer bolts, all is good! Ride height went down like I have hoped and there is still room between hub and bump stop.

Now it's just me to decide do I want to make a new metal bushings between hub and spring... And then I need to bought a set of bushings to those bolts

Thanks everybody very much for the help, you all have been really helpful!

WVZR-1

Yes spring is '84 FE7

Corvette-FIN

Okay so the rear end is sorted, and I'm happy for it. So it's now time to move to front end, right?

If I want to lower it, lets say an inch... I came across ZR1 front spring, that is relatively cheap. Would it lower my car, since it has the FE7 suspension according to you guys? Would I need to change the center hanger type things?

Or do I just buy the lowering hangers and then slice the majority of the rubber bushing away from the original front spring?

Where do I need to post my VIN code to get the RPO list? I have understood that some corvette club(?) offers that?

Thanks again

MatthewMiller

I don't have direct experience with this because I bought my car with a Vette Brake Products Extreme front spring already installed, and it has adjustable end links on the spring so it can be adjusted like the rear spring. But I do know that most people are happy with the amount of lowering they get from just slicing most of the rubber bushing away. I friend of mine has a Challenge front spring on his car with the bushing pad gone, and it sits pretty low. I don't think you'll need to change anything with the center hangers.

WVZR-1

If you've actually come across a ZR-1 front spring it won't fit.

You need '87 or earlier for a 'fit' - if the spring you've found is a ZR-1 it's a later suspension configuration.

Since you have an '84 missing the SPID label it would be interesting to look near the 'right side' hood latch and see if your car has the earlier riveted TRIM TAG. It won't have a RPO list but limited information.