Transverse leaf spring question

[Scrrem]

Originally Posted by secondchance

Which one? Early or later one.

The early one.
Rich

[WVZR-1]

Originally Posted by secondchance

Hi, David,

Looks like I need to rework my spring. Rates are different between 91s and 92+ cars.

Like I added to my other post. I believe the spring rate could be a +!

[secondchance]

Originally Posted by WVZR-1

Like I added to my other post. I believe the spring rate could be a +!

I hear you David. If I go with early front (stiffer) the shouldn't I replace rear w/ early also (stiffer). Otherwise, I could be introducing oversteer (or did I get it backwards)?
Also, do you think Chevy engineers respecified shocks in compression/rebound when they went to softer springs? I wonder if they stiffened up the shocks to counter softer spring somewhat...

[batchman]

My two cents - if you lower you want more spring rate to minimize running out of travel.

I *think* any factory-spec shock should work with any factory spring rate, while it won't be optimum it should work for street driving. The more aggressive the driving the further from optimum it will become. Worst that should happen is back shocks may not fully control rear spring rate and you get an "echo" or hobby-horse effect.

FWIW I went from stock 91 to 750/375 (front/rear) and it ain't enough for autocross on slicks - next stop coming soon (I hope) is 1k/500 with Penske double adjustables.

Cheers,
- Jeff

[mike100]

when you cut the bushings and/or remove the shims, you effectively lower the spring rate so you might be better off with the early spring. Another way to put it is you reduce the spring preload so the car sits lower. you probably don't approach the stock tension until you are near the bumpstops. Doing the lowering wedges makes the car softer imo.

You might consider taking out one or both bushing shims as that will get you some drop without having to remove the spring 100% (it is easier and about 2/3rds the work). The ZR-1 (early cars at least) has two shims presumably due to the weight of the LT5, whereas the coupe/vert came with just a single shim or no shim.

[USAZR1]

Originally Posted by mike100

when you cut the bushings and/or remove the shims, you effectively lower the spring rate so you might be better off with the early spring. Another way to put it is you reduce the spring preload so the car sits lower. you probably don't approach the stock tension until you are near the bumpstops. Doing the lowering wedges makes the car softer imo.

You might consider taking out one or both bushing shims as that will get you some drop without having to remove the spring 100% (it is easier and about 2/3rds the work). The ZR-1 (early cars at least) has two shims presumably due to the weight of the LT5, whereas the coupe/vert came with just a single shim or no shim.

Sorry for bumping this thread back to the top but I haven't heard the results of Yun's changes and what changes he settled on with his car. I want to lower our 94 1.5"-2" without having to install coilovers. Have talked with Vette Brakes & Products about one of their adjustable front springs like Jeff Moore has on his 91 ZR-1. Only possible downside I can see with one is the 900-1K spring rate but the ability to adjust the ride as easily as a C5 is a bonus.

Mike,can you post a photo of the bushing shims you're referring to in the above post?

[secondchance]

Originally Posted by USAZR1

Sorry for bumping this thread back to the top but I haven't heard the results of Yun's changes and what changes he settled on with his car. I want to lower our 94 1.5"-2" without having to install coilovers. Have talked with Vette Brakes & Products about one of their adjustable front springs like Jeff Flint has on his 91 ZR-1. Only possible downside I can see with one is the 900-1K spring rate but the ability to adjust the ride as easily as a C5 is a bonus.

Mike,can you post a photo of the bushing shims you're referring to in the above post?

I will be installing a pair from 91, front with shaved wedges, after engine is reinstalled.

[mike100]

The ZR-1 front spring color code is green- it's a square ink spot on the top face near the end.



recently completed: stock spring back in because I couldn't stand dragging the car over speed bumps any longer- control arm out because nobody owns the special transverse leaf compression tool.

[mike100]

Here's what the shims look like when not installed above the spring bushing. my car was slammed and the two aluminum shims are shown here going along for the ride (at least they didn't toss them).

[WVZR-1]

I checked two springs I have here, a '91 removed at 16K from a ZR-1 with the "green ink" and a code of FHA with the molded pad as in Mike's image. I have another from a '93 that is assembled with the riveted on metal reinforcement and the 1 1/4" square pedestal cushion like I believe all '92+ cars are assembled with and they both have the same FHA code. That tells me the spring rate is the same and if there are differences in any of the publicized specifications then the assembly procedure at the control arm ends is responsible for that variance.

Mike - What are the actual codes stamped/molded/branded in your two springs?

The code can be checked from underneath easily, it should be maybe 2 - 4" inboard of the control arm contact area.