71 coupe, 454. New Bilsteins Sports on all 4; VBP 320 in rear; unknown springs in front. Rear spring set to 1 1/4" thread showing below adjusting nut. Was at 2" but my spine couldn't handle it.
I'm 69 years old & have developed a painful back from the jolts I feel when going over bumps; but the real surprise is how it reacts to smooth dips in the road. Both compression & rebound are pretty immediate. I'm familiar with " making great time but traveling in the wrong direction " so before I begin making adjustments I have 2 questions:
1. Are my settings with the existing components about as goods as its going to get ?
2. Is there a considerable improvement in ride quality & suspension action with coil overs ?

Thanks for your help, Tim

 

at 69 yrs old with a bad back why would you buy the stiffer Bilstein sport shocks?

 

I don't believe coil overs will help your ride much/any. Bilstein HDs are generally the better ride quality choice than the Sports.

 

1969 Corvette has huge wheel base at 108 inches. With IRS front and rear you should be able to make the car ride smooth ( at the cost of handling though ).

Stiff springs and stiff sway bars has a much bigger effect that shocks for a jarring ride.

What size tires and rims do you have? If you 18 inch rim with a low profile maybe you drop down to 16 inch rim with higher tire profile this will make the car much less jarring.

Seats make a huge difference for back pain over longer drives.

 

 

I agree tire size makes a huge difference. i went from 15" to 17" and lost a lot of ride quality, but it was worth it for looks

 

 

You are right. Thats what I get for using google and taking the first number I got back.

98 inch wheel base is still huge.

 

response to questions:
1. Regarding Meatheads question about Bilsteins. My experience is that shocks do not alter the ride quality as much as springs do. With the VBP 320 (360? ) spring, there is a need to control the additional spring load with a corresponding increase in damping. Shocks control both the compression & rebound energy created by the spring. More spring pressure; more damping required. High school physics: action/reaction. Simple stuff.
2. I'm running new BF Goodrich Radial T/A 245-60-15. Would appear to provide a good cushion from road irregularities.

Any additional suggestions appreciated, Tim

 

I'm running coilovers and with the shock adjustments can make it ride like a soft old Cadillac or a stiff go cart.

500 pound front springs and 450 rear springs.

Changing springs and ride height is also simple.

 

I am not sure about that. I changed my truck shocks from the cheap Monroe to the bilstein HDs and the ride changed appreciably. It rides on air on smooth roads ( a rarity where I live), but as soon as I get on a rougher surface it rides like a buckboard. I am going back to the Monroes.
You and I are in the same boat: old guy with a 73 454 that I want to ride smooth. I am finishing the frame off, but here is what I did so far.
1. Changed the Gymkhana front springs back to the stock springs,. You can get an idea of the spring you have by the number of coils.
2. Replaced all rubber components with RUBBER components. Based on my truck experience, this probably had the greatest impact on improving ride quality.... something I never would have expected.
3. Went with Koni adjustables.
4. Tires, I am going to start with the 225 70 15s so I have as much sidewall as I can get. Many on this site are going to tell you that the ride quality of the new technology low profile tires is better than the old technology tires I am starting with, so I am keeping a tire swap on the table. .
I will be following this post closely to tweak my setup.

 

All the above suggestions are valid. And shocks can have a huge impact. It depends on how adjustable they are, and how closely matched to the spring they are. Most single adjustable shock I know of only adjust rebound, but there may be some exceptions. This can have a huge impact on handling, po-go effect, etc. by how many times the suspension oscillates before it calms down. For extreme use it just does a half-bounce and settles slowly back to ride height, but it will spill your coffee on the ceiling. Mostly only double adjustable shocks let you adjust your compression. This is the one that needs to be set close to your spring rate to control it, and has a huuuge effect on ride quality vs rebound. (This compression valving change is why the Bilstein Sports control the fiberglass spring better than the HDs,) Also the range of acceptable adjustments is very narrow for compression, vs rebound where you can make huge changes. Most Konis are single adjustable, and for rebound only. But they can have as many as 3 models that all have different compression settings for the same car, for some car models. Standard vs Sport etc. Even fairly stiff springs like the Gymkanna springs can be tamed by careful shock tuning and ride very well. But they will never ride as well as the same careful shock tuning on a softer spring.

Also both Konis and Bilsteins can be custom valved. Tru sports racing in Ohio does Konis. For the ultimate best ride for a bad back I would recommend contacting them and getting some valving reccomendations to go with some soft springs.

If you get some feedback from them, please share it with all of us, none of our backs are as good as they used to be!

For an easier stock tuned setups I would stick with stock springs and Delco or KYBs. But check with members to see if that works with the VB&P spring.
(Ex Pro-Solo racer)

 

I wrote to both Koni and bilstein requesting information, Koni got back to me with this:
Unfortunately, we do not have dyno graphs readily available for distribution. What I can give you are the compression and rebound specs of both the front and rear dampers. That information will be included below. As for the adjustment, you are only adjusting the rebound. Compression is made at the foot valve of a twin tube shock absorber, and the rebound at the piston valve stack. When adjusting the shocks you are only tightening the valve stack, by way of a preload spring and adjust nut. The foot valve of the shock remains unchanged. Normal wear from age is not covered by the Manufactures Warranty.



8040 1019 & 8040 1020 are both valved the exact same.

Test run with shocks at full soft setting, rebound approximately doubles at full firm.

Test @.33m/sec (13in/sec)

Compression - 750N Rebound - 1300N

Test @.13m/sec (5in/sec)

Compression - 420N Rebound - 750N

Bilstein got back to me a few months later but i already had these shocks and never followed up with them.

 

Im going to have to disagree with you but I went from 15in rims to 17 in and the ride was improved. I don't think its the size of the rims that make the difference its the tires you put on the rims.
I put nitto tires on the car. And that harsh ride were all used too was gone. The rubber on those tires are soft almost like a drag radical. That was my experience.

 

Great Koni data. Those are the Classic Red single-adjustable Konis. IIRC there is no Sport Koni for the Vette, only Standard/Classic. And even the Standards are valved roughly 10% stiffer on compression than OEM shocks and the compression is non-adjustable. The Sport shocks are another 10% stiffer than that, when available on certain models, but not C3s.
As the numbers show the rebound can be adjusted over a muuch wider range, like 100-200% but it affects ride quality much less than compression.
You may find a Koni Classic on full soft to your liking, which is still stiffer than a OEM shock, but not by much. You may need the rebound adjustment at the rear to control the fiberglass spring, which although rather soft, has much less friction that a steel spring, and needs different valving. You could adjust the rebound up on that end a little bit if you are getting the pogo effect.
FYI there is also a non-adjustable Koni Orange for C3s that I no nothing about, Much less expensive. But looks like it is also tuned slighlty stiffer than OEM.

Koni Orange / Street non-adjustable

If you go coil-overs and they are double adjustable you should be able to experiment and change them to your liking. But I would still call them first and have them suggest soft springs, and then make sure there is enough adjustment to make them as soft or softer than stock. It is possible the softest setting is still too stiff since these are usually a "performance" option.

 

Soft springs and stiff sway bars are usually the ticket for a nice ride that handles a bit better than stock.

 

Have you tried backing off on the rear spring bolt some more?
If going from 2" to 1.25" was an improvement.
go back another .5".

JMHO

R

 

UPDATE:
First, know that I bought this car 2 years ago with the equipment I listed except it had AC Delco shocks. With that setup, my head would hit the roof after a bump. Respecting the racer/tuner rule that only one thing should be changed at a time, I installed the Bilsteins in an effort to control rebound damping. Big improvement, but time showed that there were still adjustments needed.
1. Taijutsu: We must be channeling each other. I reduced the adjustment to 1/2" of thread below the adjusting nut & everything changed for the better. It appears that the 360 spring is better matched to the Bilsteins at that setting. Very nice ride & excellent control of both compression & rebound.
2. I don't understand why nearly all suppliers recommend the 320-360 rear spring on a big block car. The heavy lump is in the front.
3. Is it possible that rear suspension settings are more sensitive on a Corvette because we sit so near the rear wheels ? In most other cars, the driver is situated almost in the middle of the wheelbase.
4. The car is also less sensitive to steering inputs. Kinda twitchy before.
5. I finally feel that my 71 is riding & handling the way it is supposed to.

Thanks to everyone for their help & suggestions. Timj

 

I don't mean to be the barer of bad news but a C3 is never going to ride like a modern car when it comes to comfort. Yes sitting right over the rear Axel is a big part of it. For a softer ride I would copy what GM did for the Late C3's. A soft Fiberglass Spring ( think some of the 82's came with 220 lb springs ) and probably some adjustable Shocks. Then set the ride a height as high as You can stand the looks.

 

I've never understood the love for a wallowing non performance C-3. I never felt safe in them. Mushy springs...………. In the 80's I went to a VB&P one inch shorter 550# front and a 500# rear with the SS kit with some substitutions. I've never hit my head on the roof, jarred my lower spin, or pissed my pant's. always bought high performance tires. Jumped on the first 17 inch tires when they came out in performance vehicles.


My vette doesn't dive when braking or roll in a turn. Neither has any of the performance cars I have driven that might only have 2 inches of vertical wheel travel. I guess if you compare it to 70's Pinto wagon it rides rough