Shock valving/shimming suggestions

[draxxus131]

Hi everyone,

Been quite a while since I last posted on the forum. Got some coilovers coming in that are in need of freshening up and well I have a project in mind. I'm undertaking the research of compression and rebound shimming to create a digressive valve within the coilover. A fair bit of math is involved of course to locate the proper frequencies to pick the correct shims and piston.

Why I'm posting on here for this is because it is very difficult to find good reading on this subject, so far just off-road shock tuning. Would anyone happen to have any insight on this subject and could potentially point me in the direction of perhaps some literature? I'm also very interested in relaying my findings back onto this forum, therefore current/future members can also benefit from the evidence gathering.

My only found sources have been very tiny bits of Bilstein valving diagrams and off-road technology (doesn't fit the profile as well). Found an amazing write-up on clublexus.com on going about the mathematics portion to decipher frequencies.

https://www.clublexus.com/forums/gs...shock-revalve-parts-1-3-a.html?ispreloading=1

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[draxxus131]

Does anyone have any shock Dyno's they could offer up for research?

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[Fusion Works]

You aren't going to find anyone willing to share shim stack secrets. That is how shock builders make money. Also the piston is probably digressive to begin with on the Bilsteins. If you want to send me the shocks I can dyno them and tell you what the curves look like and what piston is in them, whether it is linear, digressive, or CBP (probably not on a stock shock).

Shock dynos won't tell you a whole lot as most builders will zero out the dyno so you can't really see what is going on anyways.

Gotta pay to play. Bilstein did tell me the rear B8 and B14 shocks are the same part number and they are not crimped though, so they can be taken apart by a proper shock builder.

 

[kevinatfms]

Gotta pay to play. Bilstein did tell me the rear B8 and B14 shocks are the same part number and they are not crimped though, so they can be taken apart by a proper shock builder.

Not from what i heard from Bilstein. The G572 part number for the rear B14 damper has different valving according to their tech line. The TUV information also states the same but also misdirects the damper as a monotube even though its certainly a twin tube like the B8.

So unless we could dyno both who knows. Do you feel the B8 could handle the rear spring rate of the B14 kit?

 

[Fusion Works]

The guy on the phone at Bilstein says they are they same part number and they are both Monotube. What makes you think its a twin tube? The front B8 strut is a cheapy twin tube, but the B14 fronts are not twin tube. They are a standard inverted monotube like I use in motorsport applications.

Without dynoing, I can't say for certain, but the B14 rear spring rate isn't that high. Its 228lbs/in. My ST springs are higher. I will be getting into shocks shortly, but first have to finish the current projects on the car.

 

[draxxus131]

You aren't going to find anyone willing to share shim stack secrets. That is how shock builders make money. Also the piston is probably digressive to begin with on the Bilsteins. If you want to send me the shocks I can dyno them and tell you what the curves look like and what piston is in them, whether it is linear, digressive, or CBP (probably not on a stock shock).

Shock dynos won't tell you a whole lot as most builders will zero out the dyno so you can't really see what is going on anyways.

Gotta pay to play. Bilstein did tell me the rear B8 and B14 shocks are the same part number and they are not crimped though, so they can be taken apart by a proper shock builder.

Do you personally possess a shock Dyno?

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[Fusion Works]

The shop beside me has one that I use on a regular basis. Its a Roehrig.

 

[Old Mike Emerson]

Interesting, it's nice to see someone besides me that asks questions and does R/D type work.

 

[kevinatfms]

The guy on the phone at Bilstein says they are they same part number and they are both Monotube. What makes you think its a twin tube? The front B8 strut is a cheapy twin tube, but the B14 fronts are not twin tube. They are a standard inverted monotube like I use in motorsport applications.

Without dynoing, I can't say for certain, but the B14 rear spring rate isn't that high. Its 228lbs/in. My ST springs are higher. I will be getting into shocks shortly, but first have to finish the current projects on the car.

I'm nearly 100% certain the rear B8 is a twin tube. No idea how the rear B8 or B14 damper is a monotube if the diameter of the damper is the exact same as the OE twin tube. IN nearly every application ive ever seen the 46mm+ piston is used. The B8 and B14 arent even that diameter to begin with.

As you stated the front B14's are significantly larger than the B8 fronts and are of motorsports grade(inverted monotube). That is the biggest difference in the B14 kit versus the B8 dampers.

The ST springs....yeah, i dont believe that. They tried to state that the rear spring rate is 250lbs/in yet when i asked KW(who makes them) it came out as being just slightly higher than OE rate of 137. I think it was 144 or so for the ST springs. I highlighted this in the spring rate thread under the track/autocross portion of the forum. So im not sure who is correct.

 

[Fusion Works]

Bilstein makes a small body monotube. The most common one used in a motorsports application is the GM Monte Carlo small body shock for circle track racing. So yeah its no problem to make a small body monotube shock.

A twin tube shock uses a very small piston. I will have to measure the diameter of the small body piston.

I am only working off the info from Bilstein. The guy on the phone pulled the part numbers and drawing dimensions for me.

I guess since my car isn't doing anything but sitting on the lift I can pull a spring and rate it. Then we will know the rear spring rates. I was told by ST the springs were: 245fr/250/r

 

[kevinatfms]

Bilstein makes a small body monotube. The most common one used in a motorsports application is the GM Monte Carlo small body shock for circle track racing. So yeah its no problem to make a small body monotube shock.

A twin tube shock uses a very small piston. I will have to measure the diameter of the small body piston.

I am only working off the info from Bilstein. The guy on the phone pulled the part numbers and drawing dimensions for me.

I guess since my car isn't doing anything but sitting on the lift I can pull a spring and rate it. Then we will know the rear spring rates. I was told by ST the springs were: 245fr/250/r

The more info the better. If you can, could you dyno the B8's? Would help a lot of us understand the valving and what they were built to do.

 

[Fusion Works]

I don't have any B8s or B14s here. I was planning on building my own rear shocks probably based on an aluminum body. I have some old ASNs laying around that should work great for this.

Based on other vehicles B14 dampers I have run, they are still REALLY mild as far as valving goes. Bilstein is not super agressive on their street applications. The B8 might even be softer than the stock valving. I am going to dyno my 50Kmile old stock dampers just for shits and grins. Have to make an adapter for the struts first.

 

[draxxus131]

Thank you for informing us that you have access to a brand name shock Dyno. I've been going over the templates from Bilstein on their valving suggestions. Been reaching out to a couple low-end suspension companies requesting information on compression/rebound ratios, no bites so far. Many of the items came in already, N2 air tank, needles, Maxima oil. I really need to start searching for shim kits, the prices I've seen are astronomical though, they aren't made from mild steel so that probably explains a lot.


Still need to source the seals for the socks still.
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[Fusion Works]

What are you trying to do? Build Bilstein shocks?

 

[draxxus131]

What are you trying to do? Build Bilstein shocks?

Currently BC racing coilovers OR quite possibly the ugly ass godspeeds I have installed; they lasted a while. After attending an upcoming event the BC coils will be getting ripped apart and fully refreshed. My goal is to create a digressive stack, although it may not be a successful stack configuration for this chassis, I still want to succeed in the failure. Yes, I'm aware of what I said there.

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[Fusion Works]

Digressive shocks are fine and we use them all the time for road race applications and even street applications. How are you gonna make sure you are achieving the forces you want without dynoing the shocks?

 

[draxxus131]

I would need to Dyno the shocks after refreshing and make adjustments from there. I've found programs that allow you some insight into the shim stack configuration like Restacker.

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