Suspension Feedback - ZR-1 Net Registry Forums

Okiedoke · 01-20-2017

My suspension feels quite bouncy/floaty, almost like a boat rolling over the waves. This is very obvious on Tour mode to the point I'm not comfortable driving through mountain highways. On Perf mode, the ride is pretty harsh as expected but I can still feel some of the bouncing/floating. Since this is the only ZR-1 I've driven, I don't have any point of comparison or know what it would have felt like when new. Any ideas on whether this is normal or what parts I may need to replace or rebuild?

Thanks,
Harry

DRM500RUBYZR-1 · 01-20-2017

Mileage?

Okiedoke · 01-20-2017

Quote:

Originally Posted by DRM500RUBYZR-1

Mileage?

Just passed 27k miles.

DRM500RUBYZR-1 · 01-20-2017

OK, That is odd.
It should not feel that "floaty" with those miles.
Does the ride height appear normal?

Logically, shocks or springs.
Get car in the air, and check both front and rear springs for any splitting or cracking of the spring itself. Typically, the car droops noticeably if there is an issue with the spring.
Next, do the usual bounce test at each corner to see if one or more shocks has too little resistance in either direction.
Check the condition of all of the suspension bushings, front and rear.
Alignment, if all of the other check out, then check the alignment of particularly the rear wheels and the camber settings. If too positive, the car can seem twitchy, which sometimes is described as unstable. Refer to Vette Brakes and Products for their suggested street settings as a good reference.

My first suspect would be the shocks might need replacement, although the mileage seems low for that.
Most often, that causes the sea sickness symptoms.
Let us know what you find.

Marty

Okiedoke · 01-26-2017

Quote:

Originally Posted by DRM500RUBYZR-1

OK, That is odd.
It should not feel that "floaty" with those miles.
Does the ride height appear normal?

I think it's the stock height. Here's a picture that I took today:

Quote:

Originally Posted by DRM500RUBYZR-1

Logically, shocks or springs.
Get car in the air, and check both front and rear springs for any splitting or cracking of the spring itself.

I had the Z checked out by a Corvette shop when I got it 3 years ago. The only issue was a delaminating rear leaf spring, which I replaced right away from a Corvette salvage yard. I don't know the miles on the spring.

Quote:

Originally Posted by DRM500RUBYZR-1

Next, do the usual bounce test at each corner to see if one or more shocks has too little resistance in either direction.
Marty

So I drove the Z to work today and went over speed bumps at 3 MPH. I don't think I felt the rear bounce. However, the front very noticeably bounced twice.

I have a right front actuator time out code that comes up once in a while, which I assume is an issue in itself, but is unrelated to the bounce?

Thanks,
Harry

mike100 · 01-21-2017

It is the stock valving on the shocks. I got my car with exactly the same mileage (27k) and i felt the rebound was 'loose' or bouncy. Compression was ok, but could have been stiffer too. I ended up sending (dropping them off at their shop in person) my shocks to Bilstein to get slightly more aggressive valving, but not race valving or anything like that.

I ended up with the request to increase rebound 20% and compression 10% if I recall correctly. I didn't alter compression much because it would be possible to program the shock controller to stiffen the setting at a lower speed...it was the floaty rebound that needed the correction. If you search my name here and 'bilstein' the post should come up.

I hear they aren't keen on rebuilding these shocks anymore, but might custom valve brand new unit$.

Okiedoke · 01-26-2017

Quote:

Originally Posted by mike100

It is the stock valving on the shocks. I got my car with exactly the same mileage (27k) and i felt the rebound was 'loose' or bouncy. Compression was ok, but could have been stiffer too. I ended up sending (dropping them off at their shop in person) my shocks to Bilstein to get slightly more aggressive valving, but not race valving or anything like that.

I ended up with the request to increase rebound 20% and compression 10% if I recall correctly. I didn't alter compression much because it would be possible to program the shock controller to stiffen the setting at a lower speed...it was the floaty rebound that needed the correction. If you search my name here and 'bilstein' the post should come up.

I hear they aren't keen on rebuilding these shocks anymore, but might custom valve brand new unit$.

This being a Corvette and ZR-1 at that, I was thinking it couldn't possibly have bounced this much when new. My plan in general is to keep this Z stock but also will be doing more autocross and track days with it. Do you think stock valving/rebound/compression would be sufficient? It must be much better than what I'm experiencing now.

mike100 · 01-26-2017

Quote:

Originally Posted by Okiedoke

... Do you think stock valving/rebound/compression would be sufficient? It must be much better than what I'm experiencing now.

New stock replacements sufficient or adequate? Probably yes.
Could it be better? ...Absolutely.

The LT5 is heavy and I think it wears out the front shocks as there isn't a special part number for it- I think all FX3 shocks were the same for all vettes.

Not sure how hard it is to get a modified shock controller these days, but that is another way to make them stiffer/sooner (at lower speeds). Even so, I liked the amount of rebound control my car has now.

mike100 · 01-26-2017

Quote:

Originally Posted by Okiedoke

This being a Corvette and ZR-1 at that, I was thinking it couldn't possibly have bounced this much when new...

I haven't driven a new one since 1993, but you are right- they didn't wallow and bounce much on the stiff setting.

DRM500RUBYZR-1 · 01-26-2017

Your rear spring already had delaminated and has been replaced.
Please make sure you inspect that front spring for the same delamination, or splitting, cracking, whatever you want to call it.

As these fiberglass springs delaminate, they lose their ability to react properly to suspension travel, i.e. they cannot control the movement.

Back went; front may be going too.
Easy to see; It looks like it is shredding.

I remain equally convinced that due to age, you most likely need shocks, certainly front ones based on your description.

Check the spring.
Replace the shocks.
AND check those actuators.

Keep us posted.

Marty

01-20-2017	#1
Okiedoke Join Date: Nov 2013 Location: San Jose, CA Posts: 132	Suspension Feedback My suspension feels quite bouncy/floaty, almost like a boat rolling over the waves. This is very obvious on Tour mode to the point I'm not comfortable driving through mountain highways. On Perf mode, the ride is pretty harsh as expected but I can still feel some of the bouncing/floating. Since this is the only ZR-1 I've driven, I don't have any point of comparison or know what it would have felt like when new. Any ideas on whether this is normal or what parts I may need to replace or rebuild? Thanks, Harry __________________ 1991 ZR-1 #405 (white/black with blue pin stripes)

01-20-2017	#2
DRM500RUBYZR-1 Join Date: Sep 2008 Location: Mullica Hill, New Jersey Posts: 2,614	Re: Suspension Feedback Mileage?

01-20-2017	#4
DRM500RUBYZR-1 Join Date: Sep 2008 Location: Mullica Hill, New Jersey Posts: 2,614	Re: Suspension Feedback OK, That is odd. It should not feel that "floaty" with those miles. Does the ride height appear normal? Logically, shocks or springs. Get car in the air, and check both front and rear springs for any splitting or cracking of the spring itself. Typically, the car droops noticeably if there is an issue with the spring. Next, do the usual bounce test at each corner to see if one or more shocks has too little resistance in either direction. Check the condition of all of the suspension bushings, front and rear. Alignment, if all of the other check out, then check the alignment of particularly the rear wheels and the camber settings. If too positive, the car can seem twitchy, which sometimes is described as unstable. Refer to Vette Brakes and Products for their suggested street settings as a good reference. My first suspect would be the shocks might need replacement, although the mileage seems low for that. Most often, that causes the sea sickness symptoms. Let us know what you find. Marty Last edited by DRM500RUBYZR-1; 01-20-2017 at 10:45 PM.

01-21-2017	#6
mike100 Join Date: Feb 2011 Location: San Marcos CA Posts: 1,802	Re: Suspension Feedback It is the stock valving on the shocks. I got my car with exactly the same mileage (27k) and i felt the rebound was 'loose' or bouncy. Compression was ok, but could have been stiffer too. I ended up sending (dropping them off at their shop in person) my shocks to Bilstein to get slightly more aggressive valving, but not race valving or anything like that. I ended up with the request to increase rebound 20% and compression 10% if I recall correctly. I didn't alter compression much because it would be possible to program the shock controller to stiffen the setting at a lower speed...it was the floaty rebound that needed the correction. If you search my name here and 'bilstein' the post should come up. I hear they aren't keen on rebuilding these shocks anymore, but might custom valve brand new unit$.

01-26-2017	#10
DRM500RUBYZR-1 Join Date: Sep 2008 Location: Mullica Hill, New Jersey Posts: 2,614	Re: Suspension Feedback Your rear spring already had delaminated and has been replaced. Please make sure you inspect that front spring for the same delamination, or splitting, cracking, whatever you want to call it. As these fiberglass springs delaminate, they lose their ability to react properly to suspension travel, i.e. they cannot control the movement. Back went; front may be going too. Easy to see; It looks like it is shredding. I remain equally convinced that due to age, you most likely need shocks, certainly front ones based on your description. Check the spring. Replace the shocks. AND check those actuators. Keep us posted. Marty