Corvette Forum : DigitalCorvettes.com Corvette Forums banner

1 - 9 of 9 Posts

·
Premium Member
Joined
·
5,157 Posts
Discussion Starter #1
I finally got my Bilstein Sports installed today, and I learned some valuable lessons ...


1. Comfort is more important now than it was when I was 20.

If you're old, like I am, then crawling around on bare concrete is no fun. Fortunately, my dear wife supplied me with an old Mexican blanket, and it provided just enough cushioning to make the concrete bearable.


2. Holy Crap!!! My car is sitting up like a Monster Truck after I put these new shocks on! What happened?

I think I've figured out the "why has my ride height changed?" question. I carefully measured the ride height before I started, and and had figures varying between 27.375" to 27.75". When I was done, the ride height was close to 29 inches! However, after a quick 20 mile exercise, the ride height was a uniform 28" at each corner.

What's going on you ask? In all our discussions about this, I'd been assuming that gas shocks acted like "regular" shocks. However, they don't. The gas charging imparts a force to the suspension, acting to RAISE the car. Here's my empirical approach. When I got my Bilsteins, I took them out of the box, and intended to play with them by moving them through their range of motion. However, I found out it took a lot to get them started, and when I let go, they would return to the fully extended position. That led me to the theory that they are imparting a force in concert with the spring to raise the car to the desired ride height.

So, today, I took each new shock and measured the constant force needed to move it through it's full range of motion. The nominal force was around 71 pounds (varied between 70 - 72 pounds). As I removed the old shocks, I also measured that same force. The nominal force for the old shocks was around 42 pounds (one at 40 pounds, three at 42 pounds).

In summary, I think the new shocks, with their correct and higher force, then, contribute to the ride height. The increase you see is due to replacing the worn shocks, which no longer supply as much (or the correct) support force to the suspension.


3. Good tools are important!

I took a few pictures, and I intend to provide a full write up of how I did this little job (there are some things the FSM forgot to mention), and exactly what tools you'll want to have around before you start this little project. However, I'm exceptionally glad that I have a set of Craftsman ratchet wrenches. They helped immensely - I wouldn't want to try this again without them.


4. I don't like detailing things.

I had visions of spending time cleaning and detailing the wheel wells, the back side of the wheels, and the more reachable areas of the undercarriage. OK - I spent about 20 minutes on the rear driver's side, and it did look better. However, I was much more interested in actually getting the job done and DRIVING the car than I was in CLEANING the car so it could get DIRTY again.


5. If you have the base suspension, UPGRADE the Bilsteins!

The standard replacement Bilstein for an FE1 suspension car is the "Heavy Duty." The standard Bilstein for the Z51 and Z52 is the "Sport." If you need shocks for your FE1 car, then I highly recommend the Sport shocks. They make a world of difference. I drove a C6 with Z51 a while back, and my C4 feels a lot closer to that car with the Sports on it. Excellent compromise between the Z51 C4 "Kidney Killer" and the "Grandma Soft" FE1 in my opinion.

I'm hoping to have the installation write up done in the next week or so. No time tomorrow, as I'll be at the Jefferson Swapmeet in Southern Wisconsin.

Steven
 

·
DC PIT CREW BOSS
Joined
·
39,545 Posts
Roger that on the concrete, Stephen. Of course, at times it is easy to endure the concrete than is is to get up:laughing:
 

·
Premium Member
Joined
·
6,667 Posts
I had visions of spending time cleaning and detailing the wheel wells, the back side of the wheels, and the more reachable areas of the undercarriage. OK - I spent about 20 minutes on the rear driver's side, and it did look better. However, I was much more interested in actually getting the job done and DRIVING the car than I was in CLEANING the car so it could get DIRTY again.
:laughing: Sounds like me. Every time I "rotate" my tires, I tell myself "this would be a perfect time to...":laughing:
 

·
Premium Member
Joined
·
5,157 Posts
Discussion Starter #4
:laughing: Sounds like me. Every time I "rotate" my tires, I tell myself "this would be a perfect time to...":laughing:
If you lifted my hood, you'd see the driver's side wheel is cleaner than the passenger's side wheel - on the inside. It just wasn't worth it! Part of the reason was the poor method I chose to clean the inside of the wheels. Nothing like having the wheel on the ground, and me bending over trying to clean it. Next time I'll build a platform to work from at standing height. I'm too lazy to do this crap the hard way!

Steven
 

·
Registered
Joined
·
9 Posts
I put new Bilstein shocks on my '92 with FX3 several years back and noticed the ride height elevated slightly. Per Bilstein these shocks were "Euro Spec" where the shock controls more of the ride height Vs the springs on the stock setup. Bottom line - Very pleased. Also if you have any problems - They can be rebuilt by Bilstein.
 

·
Registered
Joined
·
428 Posts
Just curious, did you drive around for a while to settle the suspension back to what it was before the shock change? Everytime I have changed shocks, 3 times (one of the sets being adjustbales), the height never changes.
I have used Bilstein HD, QA1's and TPIS shocks.
The QA1'a being adjustable, not in height but stiffness, doesnt change height, just compression/rebound.
 

·
Premium Member
Joined
·
5,157 Posts
Discussion Starter #7
Just curious, did you drive around for a while to settle the suspension back to what it was before the shock change? Everytime I have changed shocks, 3 times (one of the sets being adjustbales), the height never changes.
I have used Bilstein HD, QA1's and TPIS shocks.
The QA1'a being adjustable, not in height but stiffness, doesnt change height, just compression/rebound.
Steve -

Yes. I measured post installation ride height after I took the car on a 15 - 20 mile jaunt. Refer back to section #2 of my original post ...

I think I've figured out the "why has my ride height changed?" question. I carefully measured the ride height before I started, and and had figures varying between 27.375" to 27.75". When I was done, the ride height was close to 29 inches! However, after a quick 20 mile exercise, the ride height was a uniform 28" at each corner.

It stands to reason that in my case, the ride height would change. Ride height is dictated by the force of the springs as well as the force of the shock absorbers. I measured a roughly 30 pound increase in force with the new shocks compared to the old ones (42 vs 70 pounds). The new shocks, therefore, should contribute something to the ride height that is greater than the old shocks (in this case, just over a quarter of an inch).

I don't know how much force a new Bilstein Heavy Duty shock would generate compared to the 70 pounds generated by the Sport shock. I'm assuming that some component of the change in ride height is caused by that difference in force. If the HD shocks had say a 50 pound force when new, then compared to my old HD shocks at 42 pounds, then I wouldn't have expected a significant change in ride height (except I would have expected the ride height to be uniform, in either case).

I made this comment due to the fact that there are many threads on here about significant ride height changes when going from "old worn out" Bilsteins to new replacements. I hadn't seen a good explanation of why that would occur, and am offering this to see what everyone thinks.

In your case, did you compare the old shocks with the new with respect to forces? If your old shocks were still generating good force (mine clearly weren't with respect to the new ones), then your ride height shouldn't have changed.

I had time to think through what I was going to do, and then tried to see if I could find a measureable difference between them. I did, and it seems reasonable.

Steven
 

·
Registered
Joined
·
428 Posts
The one thing that may contribute to the height change is the bushings in the shocks. My Bilsteins were soft rubber and the QA1's were hard rubber. Maybe the older shocks you had had worn bushings.
The Bilstein Sports shocks are supposed to be a compromise between factory Bilsteins and HD's. But then again, they dont tell you the number values either.
 

·
Premium Member
Joined
·
5,157 Posts
Discussion Starter #9
The one thing that may contribute to the height change is the bushings in the shocks. My Bilsteins were soft rubber and the QA1's were hard rubber. Maybe the older shocks you had had worn bushings.
The Bilstein Sports shocks are supposed to be a compromise between factory Bilsteins and HD's. But then again, they dont tell you the number values either.
I should have taken the new bushings into work and measured the durometer of them - I didn't think of that!

If you examine the Bilstein application guide, you'll find that the Heavy Duty shocks are the replacement units for the FE1 (Base) suspension. The Sport shocks are listed as replacements for the Z51 suspension.

I also discussed this with Vette Brakes & Parts before I ordered the shocks (they offer a 10% discount to DC members), and they confirmed that the HD's were stock replacements for FE1, and Sports were the replacement for Z51. They indicated that the Sport shocks would have an impact on roll stiffness compared to the Heavy Duty units, and my SOTP impression since the change confirms that. However, I don't know how the Sports would compare with a fresh set of HD's. If I could get VB&P to send me a set, I'd be happy to try it. I've got the method down for changing the shocks now!

I have a friend that has an '87 with the Z52 option. It was a nice compromise between the FE1 and the Z51. I like the way his '87 handles, so I'm doing a step by step conversion from my FE1 to my own version of a Z52. My next suspension mod will involve changing the rack from my FE1 unit to a Z51 unit (2 turns LTL rather than the FE1 2.25 turns LTL). Eventually, I'll upgrade the sway bars and replace the stock bushings with poly's.

Steven
 
1 - 9 of 9 Posts
Top