Let's talk coilovers

[Rakuny]

You don't plan on specifying the valving at all? You're just gonna tell them you track it and hope for the best?

I will be specifying. What I meant was that I just tell them what I want and give them a few measurements off the car.. corner weights and a couple other things. They take care of the rest.

[anyonebutme]

FYI, it's no bilstein, but there are places that'll revalve megans (replace with their own cartridge)

Feal Upgrade

Thanks for the link, that may become useful someday.

[DG]

The Bilstein sleeve will fit a Bilstein shock - oddly enough.

The front is a little trickier, as stated. There are a couple of different ways for Bilstein to do struts. One way is an insert that fits into the OEM "foot"; the other way is a full-up replacement, like they do with the Cobra R shocks.

If it is a full-up replacement, the OD of the foot is - again, like they thought this through or something - the same OD as a "regular" shock, so the sleeve fits over it.

The snap ring that supports the sleeve is also used to support a rigid spring perch that adapts the OEM spring to the shock body, and it is placed at about the same place it would be on the OEM shock. Sometimes this means the snap ring is not well placed to support the coilover sleeve, so you have to cut a new groove in the shock body. This is a trivial operation on any lathe.

Securing the spring on the top end can go a couple of different ways. Sometimes you can get away with just resting it in the OEM spring perch, sometimes with the aid of a rubber pad to help with the different interface. The proper way is to do a coaxial upper hat. See my design here: Autocross.dsm.org - Build Your Own Konis You substitute in the Bilstein upper hat for the Koni, tweak the dimensions of the upper standoffs slightly to fit, and the bolt spacing on the plate probably needs to change to fit a 3S, but you get the idea.

On the front, you want a bearing to take up the steering axis so my DSM design won't quite work, but by examining the OEM design and mine you should be able to figure out a hybrid.

This gets you, effectively, a set of NASCAR Cup car shocks - far, FAR better than anything else out there at a tiny fraction of the cost.

GC probably has a setup that figures out sleeves over OEM shocks. Their upper spring mount solutions can sometimes be wonky, but are usually good enough for street cars (except on 2G DSMs, where it is outright shit)

I'm sure someone must have done this setup before...

What's wrong with doing your own R&D? Hell, I designed about 75% of the parts on the race car. I did my own intercooler, intercooler piping, shocks, wheels (fitment - I had the third set of TE37s in North America) intake piping, hood vent, exhaust, prototyped 3 different turbos, was the second standalone EMS in a DSM, seat mounts... just a ton of stuff. If I had to wait for someone else to do it, it would never get done. SO why the reluctance to buy some parts and figure shit out?

will be specifying. What I meant was that I just tell them what I want and give them a few measurements off the car.. corner weights and a couple other things. They take care of the rest.

They'll get it wrong.

As much as we like to think that vendors understand cars, most aftermarket shock development is smoke and bullshit. Most don't even have a dyno to test their own shocks, never mind the ability to design damping curves.

Ask them where the roll centre on the front suspension of a 3S is. Ask them what the motion ratio is.

99% of them just go "stiff" with a wide adjustment range, and hope that there's a setting in there somewhere the customer likes.

I had customers bring in some shocks, we dynoed them, then they went off to the "tuner" for revalving - and came back exactly the same. MAYBE they got fresh oil and seals, but the valving didn't change (when I did revalves you got before and after dyno plots so you could see the difference)

It's bad enough with popular cars; with rare and old stuff like a 3S - forget it.

DG

[Rakuny]

They'll get it wrong.

As much as we like to think that vendors understand cars, most aftermarket shock development is smoke and bullshit. Most don't even have a dyno to test their own shocks, never mind the ability to design damping curves.

Ask them where the roll centre on the front suspension of a 3S is. Ask them what the motion ratio is.

99% of them just go "stiff" with a wide adjustment range, and hope that there's a setting in there somewhere the customer likes.

I had customers bring in some shocks, we dynoed them, then they went off to the "tuner" for revalving - and came back exactly the same. MAYBE they got fresh oil and seals, but the valving didn't change (when I did revalves you got before and after dyno plots so you could see the difference)

It's bad enough with popular cars; with rare and old stuff like a 3S - forget it.

DG

Even Bilstein will get it wrong?

[DG]

Well... not so much wrong as iterative.

Koni and Bilstein have an advantage over most other shock manufacturers in that they are frequently the OEM supplier. They may have access to the OEM design documents and so know what a "stock replacement" looks like from a curve design perspective. So when you get one of their shocks, you get something that either has a pretty good duplicate of the OEM design curve somewhere in the adjustment range, or is the OEM curve plus some reasonable amount extra.

So better than a pure WAG, or the same valving spread across different part numbers like many Japanese shocks are.

But that information doesn't necessarily trickle down to the performance division. Koni and Bilstein don't have models of the car's suspension that they can pull and run to make changes. Instead, they have "rules of thumb" based on experience with other cars that they'll apply.

And they'll hedge their bets somewhat to keep from getting too extreme.

So what you get when you send the shocks to Koni or Bilstein is a revalving that is a little softer/stiffer in compression/rebound based on what you tell them, and they'll iterate around that as much as you want until you're happy.

You'll get what you ask for, in that if you ask for 10% stiffer low speed compression the shock will (probably) be dynoed to verify, or at least they'll pull a shimstack out of the catalogue that mostly does what you want (and they've done it so many times they trust the notes to be right) - which again, is far better than the "revalves" from the Asian stuff I saw that didn't actually change forces. But it is doing it the slow way and it is only as good as the information you send them... which typically isn't very good.

The right way to do it is to measure and model YOUR CAR, from that derive a spec curve that you want, and then get Koni or Bilstein to match your spec curve. If you are lucky, there is an off-the-shelf valving that matches. Otherwise, you get to pay by the hour for cut and try to generate a curve that matches your spec.

Of all the custom Bilsteins I did, I never had an OTS Bilstein exactly match my calculations. They tended to be a little bit stiff in low speed rebound - not outrageously so, but a little bit. And depending on when they were designed, it wasn't unusual to see older designs have symmetric bleeds (later stuff used the COB pistons that lets compression and rebound bleed be set independently)

An OTS Bilstein HD valving is a good place to start.

But if you expect to give Bilstein a set of corner rates and spring rates and get back of perfect shock... nope, won't happen.

DG

[Rakuny]

Thanks DG, looks like I'll be modeling my car in a couple months.

[IPD]

everyone glows over ecs...and completely misses the fact that some of us don't have ecs, never had ecs, and never will have ecs.

[DG]

Have you missed the several pages of discussion on the merits of Bilsteins?

Seriously dude... if you don't have anything constructive to say, how about you stay silent?

DG

[DG]

More discussion here: http://www.3sgto.org/f17/options-ecs...erns-7618.html

DG

[J. Fast]

They'll get it wrong.

As much as we like to think that vendors understand cars, most aftermarket shock development is smoke and bullshit. Most don't even have a dyno to test their own shocks, never mind the ability to design damping curves.

Ask them where the roll centre on the front suspension of a 3S is. Ask them what the motion ratio is.

99% of them just go "stiff" with a wide adjustment range, and hope that there's a setting in there somewhere the customer likes.

I had customers bring in some shocks, we dynoed them, then they went off to the "tuner" for revalving - and came back exactly the same. MAYBE they got fresh oil and seals, but the valving didn't change (when I did revalves you got before and after dyno plots so you could see the difference)

It's bad enough with popular cars; with rare and old stuff like a 3S - forget it.

DG

Damn, you're so jaded DG. You don't trust Bilstein to build a spec shock?

Even Bilstein will get it wrong?

Fuckin geeze, no they won't. That's all opinion. You don't think they have Q.C.?

Well... not so much wrong as iterative.

Koni and Bilstein have an advantage over most other shock manufacturers in that they are frequently the OEM supplier. They may have access to the OEM design documents and so know what a "stock replacement" looks like from a curve design perspective. So when you get one of their shocks, you get something that either has a pretty good duplicate of the OEM design curve somewhere in the adjustment range, or is the OEM curve plus some reasonable amount extra.

So better than a pure WAG, or the same valving spread across different part numbers like many Japanese shocks are.

But that information doesn't necessarily trickle down to the performance division. Koni and Bilstein don't have models of the car's suspension that they can pull and run to make changes. Instead, they have "rules of thumb" based on experience with other cars that they'll apply.

And they'll hedge their bets somewhat to keep from getting too extreme.

So what you get when you send the shocks to Koni or Bilstein is a revalving that is a little softer/stiffer in compression/rebound based on what you tell them, and they'll iterate around that as much as you want until you're happy.

You'll get what you ask for, in that if you ask for 10% stiffer low speed compression the shock will (probably) be dynoed to verify, or at least they'll pull a shimstack out of the catalogue that mostly does what you want (and they've done it so many times they trust the notes to be right) - which again, is far better than the "revalves" from the Asian stuff I saw that didn't actually change forces. But it is doing it the slow way and it is only as good as the information you send them... which typically isn't very good.

The right way to do it is to measure and model YOUR CAR, from that derive a spec curve that you want, and then get Koni or Bilstein to match your spec curve. If you are lucky, there is an off-the-shelf valving that matches. Otherwise, you get to pay by the hour for cut and try to generate a curve that matches your spec.

Of all the custom Bilsteins I did, I never had an OTS Bilstein exactly match my calculations. They tended to be a little bit stiff in low speed rebound - not outrageously so, but a little bit. And depending on when they were designed, it wasn't unusual to see older designs have symmetric bleeds (later stuff used the COB pistons that lets compression and rebound bleed be set independently)

An OTS Bilstein HD valving is a good place to start.

But if you expect to give Bilstein a set of corner rates and spring rates and get back of perfect shock... nope, won't happen.

DG

Of course you won't get back a "perfect shock". They'll atleast get you in the ballpark. And a hell of a lot closer to where you need to be than some tuner shock could come. Geeze man, what do pro shock builers and company's like Bilstein use Critical Dampening Analysis programs for? You fill out their info sheet with your vehicle specs, they customize for you, and send it back with a dyno sheet for each shock. For some of this stuff you're opinions and distrust for others is waaay ot there. Some of your opinions come from years and years of seeing things totally fucked up and it sucks that it had to be that way, but what about the shit that was right.

Having spec'd a few suspensions on my own now I trust the quality control of Bilstein and I trust pro MFR's and builders to do as they say. I always check everyones work and odly enough it's always as advertised. It sucks that you weren't so lucky because now you don't trust anyones work but your own and it's got you jaded.