Questions on changing rear spring...

[KILLSHOTS]

Hey guys,

When the shop did the new gears, they found that my OE rear spring was starting to splinter very slightly, so I need to start looking for a replacement. A few questions...

1. Does anyone know exactly what the the stock tension was (in lbs, not NM) for a '90 ZR-1 with Z51? I've been told 490-500lb but I didn't think it was that high. That's the only part that I intend to replace, so I want it as close to OE as possible.

2. Do I need to purchase anything other than the spring itself? Will the replacement spring come with the required bushings, etc.? (I think I'm gonna order from VB&P)

3. How difficult is the install? I generally don't work on my own car unless it's REALLY simple, but I'd like to do it myself if I can. Can anybody give me a breakdown of the procedure? Is it a 1-person job?

Thanks for all your help, brothers!

[PhillipsLT5]

I seem to remember something about the numbers or letters on spring designated the poundage, VBP is good

[GOLDCYLON]

Good time to move up to coil overs

[batchman]

ISTR the Z51 was about 375lbs, I find it to be a good match for the VB&P 750lb front. I got the z51 Hyperco (sp?) and z51 Bilstiens from Ecklers I believe.

You'll want the long bolt kit commonly available, everything should be fine with possible exception of the rear sway bar body bushings, which you'll see because I think I remember having to drop the rear sway bar to do the spring. It was all pretty easy, and that's using hand tools without a lift - I think it was a 2 beer job.

FWIW I wound up going with a lighter rear sway bar.

Cheers,
- Jeff

[KILLSHOTS]

Originally Posted by batchman

ISTR the Z51 was about 375lbs, I find it to be a good match for the VB&P 750lb front. I got the z51 Hyperco (sp?) and z51 Bilstiens from Ecklers I believe.

You'll want the long bolt kit commonly available, everything should be fine with possible exception of the rear sway bar body bushings, which you'll see because I think I remember having to drop the rear sway bar to do the spring. It was all pretty easy, and that's using hand tools without a lift - I think it was a 2 beer job.

FWIW I wound up going with a lighter rear sway bar.

Cheers,
- Jeff

Thank you, Jeff! I appreciate you taking the time to answer the specific questions I asked!

Glad you mentioned the lowering kit with the longer bolts. I was planning on doing that, if only to achieve the height I currently have now, as I figure my old spring must be sagging a little bit.

Can the exhaust stay in place? Any jacking of the differential involved, or does the spring just sort of pop out and pop back in?

Thanks again!

[batchman]

Hi Chris,

The longer bolts actually buy adjustment space to lower the car, raise I am not sure. They are easy to change if you want to target stock height with the stock bolts and change your mind later.

No worries about the diff. I can't recall if i had to drop the tailpipes, I think maybe I had to drop one to get better angles to get the sway bar out? I don't recall the specifics (and am somewhere between a week and 6 months of doing it again) but it was all just on the driveway with jack stands and hand tools. I recall being surprised how easy it was - one simple afternoon.

I should add that when my wife called VB&P and asked them for an autocross spring/shock package, with the 750lb front was a rear 500-550lb spring and Morocca shocks that were a hopeless mismatch in back. I softened the rear to Z51 (which was not available with ZR-1) and it's worked fairly well. Presumably not the fastest for my application, but it made the car work (where it didn't with the VB&P desk gal setup)!

on edit - I am no longer sure if my addled mind is mixing up or merging the projects of spring and/or bar swap - take my instructions with boulders of salt please!

Cheers,
- Jeff

[KILLSHOTS]

Originally Posted by batchman

Hi Chris,

The longer bolts actually buy adjustment space to lower the car, raise I am not sure. They are easy to change if you want to target stock height with the stock bolts and change your mind later.

No worries about the diff. I can't recall if i had to drop the tailpipes, I think maybe I had to drop one to get better angles to get the sway bar out? I don't recall the specifics (and am somewhere between a week and 6 months of doing it again) but it was all just on the driveway with jack stands and hand tools. I recall being surprised how easy it was - one simple afternoon.

I should add that when my wife called VB&P and asked them for an autocross spring/shock package, with the 750lb front was a rear 500-550lb spring and Morocca shocks that were a hopeless mismatch in back. I softened the rear to Z51 (which was not available with ZR-1) and it's worked fairly well. Presumably not the fastest for my application, but it made the car work (where it didn't with the VB&P desk gal setup)!

on edit - I am no longer sure if my addled mind is mixing up or merging the projects of spring and/or bar swap - take my instructions with boulders of salt please!

Cheers,
- Jeff

Boulders of salt or not, the info is VERY helpful and greatly appreciated!

Thanks again brother!

[mike100]

You may find dropping the mufflers and tailpipes halfway down will make reaching the rear spring diff mounting point a lot easier. Once you first de-tension the spring ends, the spring itself pretty much just unbolts and falls off. pay attention to the spacers as you will want to put them back on the same way.

as far as de-tensioning the rear spring: get a block of wood or something soft to put on a floor jack and push up on the spring near the end until the end bolt shows slack. probably as the first step you will need to jack up the rear on jackstand and remove the rear wheels to give yourself a little space. You would have already done this if you dropped the mufflers first.

it is easy- the front one is a mother though.

[KILLSHOTS]

Originally Posted by mike100

You may find dropping the mufflers and tailpipes halfway down will make reaching the rear spring diff mounting point a lot easier. Once you first de-tension the spring ends, the spring itself pretty much just unbolts and falls off. pay attention to the spacers as you will want to put them back on the same way.

as far as de-tensioning the rear spring: get a block of wood or something soft to put on a floor jack and push up on the spring near the end until the end bolt shows slack. probably as the first step you will need to jack up the rear on jackstand and remove the rear wheels to give yourself a little space. You would have already done this if you dropped the mufflers first.

it is easy- the front one is a mother though.

Thanks for the tips, Mike!