10/90 Shocks for C2, C3

[Mark E.]

Any credence to these claims? It looks like the verbiage from these two sites were written by the same person (supplier?) so I don't consider this as two corroborating sources. My car rides stiffer than I'd like with gas shocks and wonder if these shocks would help. Very pricey though.

From ZIP https://www.zip-corvette.com/63-82-f40-41-fe7-replica-shock-package.html

All 1963-1982 Corvettes came from the factory with oil filled shock absorbers. These shocks were often referred to as 10/90, as the compression when going over a bump was 10% resistance on the down and 90% resistance on the way up. Designed to keep your Corvette's springs from bouncing up too fast.

In the 1980's shock manufactures eliminated oil filled shocks as most new vehicles were designed with gas shock applications. High pressure gas shocks dampen 50/50 - equal on both the compression and rebound. Perfect for new models, but that's not the way your C2 or C3 Corvette's suspension was originally designed.

These new 1963-1982 Corvette heavy duty suspension replica shocks are designed just like the original factory shocks. Oil filled with same internal design as original. Now you can finally get the factory ride you've been looking for!


From CC https://www.corvettecentral.com/c3-68-82/suspension/suspension-packages/63-82-standard-suspension-delco-replica-shock-572163 :

All 1963-1982 Corvettes came with oil filled shock absorbers from the factory. These shocks were referred to as 10/90 shocks because as they compressed when you car went over a bump, they had 10% resistance on the way down and 90% resistance on the way back up so the springs did not send you bouncing up too fast. The suspension was designed with this type of dampening.

These reproduction shocks are an exact replica both internally and externally of the original Delco brand shocks, which will once again help in your Corvette driving experience the way it was designed from GM.

[Duke W.]

Re: 10/90 Shocks for C2, C3

I don't agree that all gas shocks are 50/50. It's all based on the valving and can be tailored to each application. I also don't think that 10/90 is necessarily the best setup although in general rebound damping should be greater than jounce damping to allow the suspension to absorb a bump without the body over-rebounding.

The gas pressure keeps the fluid from cavitating. When worked hard fluid cavitation can cause the shocks to go limp.

The guy wrote "dampening", which is a sign or moronism. The proper verb is DAMPING

Most reports I've heard about the current Delco off the shelf replacement shocks are good for normal road driving. I have no idea who actually manufacturers them.

I recommend rebound adjustable shocks like Spax and QA-1, so that you can tune the rebound damping to your road conditions and driving style.

BTW, I think the OE shocks on my SWC were way too limp for my driving style, at least back when it was new, I was young, and I drove a lot more aggressively than I do now.

Duke

[Gary R.]

Re: 10/90 Shocks for C2, C3

I thought they were 50/50 as Duke mentions. We did run 90/10's which are drag shocks but not the best for a street car.

[Mark E.]

Re: 10/90 Shocks for C2, C3

I thought they were 50/50 as Duke mentions. We did run 90/10's which are drag shocks but not the best for a street car.

Gary,

The shocks in question are 10/90 shocks: soft on compression; firm on rebound (the reverse of 90/10 drag racing shocks).

I'm asking about this because the rear suspension feels stiff on compression (too much damping) and too fast on rebound (too little damping). The result is a stiff, buck-board rebound feeling. My sense is ride quality would improve if rebound was slower (i.e. damped more).

Would a 10/90 shock be softer on compression and slower on rebound compared to what I've tried (KYB and Delco gas)? The rear suspension is stock with new rubber bushings but with a 330# composite spring (the lightest recommended by the vendor for a big-block). Also, my sense is the composite spring naturally rebounds more quickly than the stock spring which may be contributing to the problem.

My goal is a nice compliant ride for cruising.

I like the feature of the QA1 shocks of being adjustable while installed, but does this adjustment change both compression and rebound? Again, I think I need less damping on compression, more on rebound.

[Mark E.]

Re: 10/90 Shocks for C2, C3

I like the feature of the QA1 shocks of being adjustable while installed, but does this adjustment change both compression and rebound? Again, I think I need less damping on compression, more on rebound.

Update: I called QA1 and learned about their "Stocker Star Double Adjustable" shock, SKU: TD403 for Corvette. Double adjustable means the compression and rebound valving can be adjusted separately which may be what I want. The only downside is they're $288 each. They also sell non-adjustable and single adjustable (increase or decrease compression and rebound the same amount).

[Tom B.]

Re: 10/90 Shocks for C2, C3

I had a leaking original shock on the '81 so I bought the Delco gas shock listed as replacement for the car and replaced all four. These may not be fancy adjustable shocks or the best for autocross or track days but for a car you drive every day they are great. The sharp pounding of jounce is gone and they ride and handle better than the car ever has and we have had it since new.

Tom

[Mark E.]

Re: 10/90 Shocks for C2, C3

Tom,

Thanks for the input. The car has virtually new Delco Gas shocks now and I have the issue described above. I was hoping moderately priced would be fine for this street cruiser, but no luck after trying two different brands.

[Bob I.]

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[Don S.]

Re: 10/90 Shocks for C2, C3

As a retired, 27 year employee of Monroe shocks, the 90-10 / 10-90 ratio claims referenced in the first posting are pure BS. Original shocks on all vehicles were valved for the best ride possible without sacrificing control, could be most any ratio like 55/45 -70/30 - 60/40 etc. Important to understand that they shocks were built and valved for the particular application. Aftermarket OE style shocks for sale today still have the correct valve ratios in them. I believe Delco replacement units are made by Monroe and naturally Monroe branded units retain the original valve specifications. Low pressure gas charging of OE style shocks perform one function which is to eliminate the shock fluid from foaming and has zero affect on the valving ratio's. It also will not change ride height. If you want original ride and handling go with the Monroe or Delco replacements. If you want performance handling pick one, but understand you will sacrifice ride.

[Chris H.]

Re: 10/90 Shocks for C2, C3

The original F41 shocks (drivers rear) finally gave up the ghost and pumped all its oil out. After lots of research for replacements, I settled on the Bilstein HD B6s. Unfortunately they must all be on a container ship out in the Pacific because no one has them in stock.

So I settled on the Delcos supplied from Corvette Central. They seem to ride the same, no better, no worse, than the F41s. The ride height is spot on and they were less than half the price of the Bilsteins. And they will judge as service replacements.

[Mark E.]

Re: 10/90 Shocks for C2, C3

Bob,

Thanks for the heads up; I won't be getting these front shocks if this hasn't changed. My ride issue is with the rear suspension so hopefully installation of those is more straight forward. I will definitely check before purchase.

[Mark E.]

Re: 10/90 Shocks for C2, C3

Don,

Thank you for this insightful information. Rebound changed with the composite spring installed. It feels like it needs more damping on rebound but not compression. That's why I'm considering double adjustable shocks.

Your thoughts? Maybe I should just restore and install the stock spring and use regular shocks...

[Duke W.]

Re: 10/90 Shocks for C2, C3

Mark,
I purchased QA1 years ago, when it was time to install them. I didn’t know that front shocks were designed to install on top of the lower a arm. And it uses 3/8” bolts, the shock won’t pass through the existing shock hole in the a arm. By now I lost interest.

To install the front shock, it requires dropping down the lower a arm and taking the coil spring out. Attaching the shock to the a arm and installing the spring over the shock. Each time I read Duke commenting on adjustable shocks, the thought of installing them rises to the surface.
I did make spacers for the bolts, so I could use a 5/16” bolt.

Bob

That's the first I've heard of this problem, Bob, but maybe the design changed. It looks like the adjustment knob is what won't clear the shock hole in the lower control arm. Is it possible to remove the knob for installation?

The Spax rebound adjustment at the base of the shock is just a small slotted projection that you access with a small screwdriver.

Duke

[Duke W.]

Re: 10/90 Shocks for C2, C3

Gary,

The shocks in question are 10/90 shocks: soft on compression; firm on rebound (the reverse of 90/10 drag racing shocks).

I'm asking about this because the rear suspension feels stiff on compression (too much damping) and too fast on rebound (too little damping). The result is a stiff, buck-board rebound feeling. My sense is ride quality would improve if rebound was slower (i.e. damped more).

Would a 10/90 shock be softer on compression and slower on rebound compared to what I've tried (KYB and Delco gas)? The rear suspension is stock with new rubber bushings but with a 330# composite spring (the lightest recommended by the vendor for a big-block). Also, my sense is the composite spring naturally rebounds more quickly than the stock spring which may be contributing to the problem.

My goal is a nice compliant ride for cruising.

I like the feature of the QA1 shocks of being adjustable while installed, but does this adjustment change both compression and rebound? Again, I think I need less damping on compression, more on rebound.

Do you understand that your aftermarket composite spring rate is more than DOUBLE the base OE suspension spring rate? In fact, it's even greater than the F-41 rear spring rate of 305 lb/in. No wonder it has a stiff ride. Suspensions need compliance, and the OE base suspension spring rates are right on for normal road driving. And the reason it over-rebounds is that composite springs have less internal damping than the OE multileaf steel spring. There is no off-the-shelf non-adjustable shock that will control that spring.

Did the morons who told you that was the lowest rate spring they recommend tell you that? I don't see how some of these aftermarket outfits stay in business given the junk a lot of them sell. They don't know jack sh...t about suspension design and tuning.

Your best course of action to keep from digging yourself deeper into a hole is to obtain a serviceable or rebuildable OE rear spring and install it with a set of Delco replacement shocks. That will restore ride quality to OE configuration, which was quite well thought out by those long gone engineers back in the early sixties.

Duke

[Mark E.]

Re: 10/90 Shocks for C2, C3

Duke,

Thank you for your erudite and encouraging response. It's odd that the softest composite I see for sale online is 300#, with 330-340 the most commonly recommended for a "stock" ride.

I have some decisions to make...