Questions on changing rear spring... - ZR-1 Net Registry Forums

KILLSHOTS · 05-22-2014

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 · 05-22-2014

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

GOLDCYLON · 05-22-2014

Good time to move up to coil overs

batchman · 05-23-2014

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 · 05-23-2014

Quote:

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 · 05-23-2014

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 · 05-23-2014

Quote:

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 · 05-23-2014

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 · 05-25-2014

Quote:

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!

05-22-2014	#1
KILLSHOTS Join Date: Feb 2014 Location: AZ Posts: 860	Questions on changing rear spring... 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!

05-22-2014	#2
PhillipsLT5 Join Date: Aug 2005 Location: Scottsdale, AZ Posts: 2,450	Re: Questions on changing rear spring... I seem to remember something about the numbers or letters on spring designated the poundage, VBP is good

05-22-2014	#3
GOLDCYLON Join Date: May 2007 Location: Peoria, AZ Posts: 9,154	Re: Questions on changing rear spring... Good time to move up to coil overs __________________ GOLDCYLON - 91 ZR-1 #2014 GOLDCYLON - 90 ZR-1 #2794, 4L60e (Formerly Schrade's) GOLDCYLON - 11 CTS-V Arizona State Director 91 WHITE/BLACK #2014. 380 P&P&PCed,Ported Heads, Jeal Long tubes, Corsa Exhaust/FIKSE FM-5s /LED TLs, LED Headlights, Front Wilwood 6 piston narrowlite calipers and rear Wilwood caliper street shop mod,CNCed Coolant Pipes,TPI Cvr,Filter cover,Stainless Bolts, DRM/DOM PROM /ZFDOC mod build #102,DRLs,BMAD with stainless Debris Screen,Coplan Air Blaster, Pioneer APP Radio 4,Brey-Krause HB,Sub Bar,Fire extinguisher seat mount,DRM Coilovers,LEDs everywhere,Compass mirror (orange),V1 DIC hidden display, Homelink sun visor, Carbon Fiber top x3 and APSIS Carbon Fiber interior, APSIS CF Steering Wheel/NAPA Leather, Banski trailing arms, Guldstrand front suspension,urethane bushings from Prothane (total suspension) ZFDoc drive shaft safety loop, raptor shift light (orange),AO engineering louver front plate, Console seat cushion, 96CE seats with black custom Sheepskins, ss billet catch can,Viper remote entry/alarm,Cragar Rear Louvers,LED side louver lights, Dewitts Radiator with SPAL fans and a Woods 160 T-Stat 90 RED/BLACK #2794. 4L60e Automatic Stage V by RPM Transmission, TCI Dedicated TCM, OBX Stainless Headers, Corsa Exhaust, SAN Secondaries and Haibeck PROM, Exotic Muscle Coil overs, LED Interior Lights, LED Tail Lights, LED Headlights, 94 Sport seats with black custom Sheepskins , Cragar rear louvers, GS Front calipers, Banski Trailing arms, APSIS Carbon Fiber steering wheel, Front and Rear Baer Eradispeeds, DRLs, Guldstrand front suspension,urethane bushings from Prothane (total suspension), Dewitt's Raditor with Dual SPAL fans and a Haibeck 170 T-Stat 11 RED/GREY CTS-V

05-23-2014	#4
batchman Join Date: Jun 2009 Location: I live at Devens, one run at a time Posts: 455	Re: Questions on changing rear spring... 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 __________________ [I]91 ZR-1 #1840, autocrossing in SCCA BSP. FIC S/S's DRM chip/Watson/Borla/lid/LW batt&headlights, springs, shocks, pads & lines, quick rack & Turn One, camber brace, 32/22mm sways, A/C halfway deleted 17x11 & 12 CCW's, 315 & 335 Hoosier A6s [/I]

05-23-2014	#6
batchman Join Date: Jun 2009 Location: I live at Devens, one run at a time Posts: 455	Re: Questions on changing rear spring... 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 __________________ [I]91 ZR-1 #1840, autocrossing in SCCA BSP. FIC S/S's DRM chip/Watson/Borla/lid/LW batt&headlights, springs, shocks, pads & lines, quick rack & Turn One, camber brace, 32/22mm sways, A/C halfway deleted 17x11 & 12 CCW's, 315 & 335 Hoosier A6s [/I] Last edited by batchman; 05-23-2014 at 01:08 PM.

05-23-2014	#8
mike100 Join Date: Feb 2011 Location: San Marcos CA Posts: 1,802	Re: Questions on changing rear spring... 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.