Bilstein Science Experiment

[Mech_Mike412]

I’d also expect soft - Koni’s reputation is usually for softer than stock compression, and adjustable rebound ranging from quite soft to bonecrushingly firm. But good quality shocks that at least consistently produce the damping they claim.

The real question I have is, who rebuilds/re-valves Koni Yellows and can two way adjustability be added during a re-valve? If so, I'm sold

 

[Dialcaliper]

The real question I have is, who rebuilds/re-valves Koni Yellows and can two way adjustability be added during a re-valve? If so, I'm sold

Koni North America sells parts directly and will also do rebuild service on shocks. They can also be revalved for both compression and rebound (the latter essentially changes the adjustment range)

There are a few vendors (Koni Authorized) that will rebuilt and restore with proper gas charge:
https://www.koni-na.com/en-US/NorthAmerica/Products/Accessories/Parts/
https://www.performanceshock.com/product/koni-shock-repair-and-rebuild/

There are also plenty of others around or you can do it yourself that will do a rebuild/revalve without gas charging (which unfortunately means they’ll overheat and cavitate sooner). Sadly unlike Bilstein HD monotubes, you can’t usually install a a schrader valve to add gas post assembly as the chamber is in the inner tube.

If you want to be handy, one approach you could try is to rebuild yourself a couple times until you get the valving right and then have them serviced with a proper gas charge - the problem is that the machine required to charge+seal at the same time is fairly specialized.

Rebuilding shocks is actually pretty simple, it’s just messy and takes quite a bit of time, especially if you do it by trial and error. Some of the parts vendors including Koni will help with the technical info if you call.

 

[Volumetrik]

While you’re right that the sprung mass natural frequency is higher, the forces on the spring are not actually higher - they’re still based on the vehicle mass, and speed and subsequent force applied by either a bump or a steering input.

Most of what you “feel” in the suspension is not actually the bump you went over because the suspension absorbs most of it, but rather you feel the oscillation that happens afterwards as the energy is released. I say “most”, and not “all” because you’ll still feel the initial jerk from a combination of the seal friction and gas force that has to be overcome.

In practice what actually happens is that while the stiffer spring oscillates and settles more quickly following a bump, the amplitude is lower, and so the shock velocities are in a largely similar range - that’s why almost universally, the “knee” of most digressive shocks are somewhere around the 1-5 in/s range. Speeds below that are typically body roll, speeds above that occur on encountering bumps, dips and whoops on the road.

Some applications fall outside that range and there are various philosophies on where exactly to put the knee, but outside of high end racing, it’s less related to the spring rate chosen than it is other factors.

What’s more related to spring rate is the amplitude of the damping force, as ideally its tuned to accomplish some fraction of either slightly underdamped (some overshoot and trailing oscillation allowed after the first bounce) or near critically damped (just enough to arrest the first bounce without any overshoot. You never want an over damped suspension, as that means the suspension will take a very long time to settle and recover from a bump, at which point you’ve encountered another.

Because of the higher frequency, critical damping must arrest motion much faster to avoid oscillating (aka “Honda Bounce”) which means stiffer low speed damping. Because of how damper valving works, a higher knee always means high speed damping is always stiffer as well. Too much high speed damping is one of the causes of a harsh riding suspension.

There are two “common” schools of thought on critical damping ratio. (and many more uncommon/motorsort specific ones)

The first, like our stock suspension, many Japanese and cars with stiff “sporty” suspension as well as many,many aftermarket shock use asymmetric damping biased heavily towards or slightly past critically damped rebound to control body roll. This causes the car to hunker down (aka jack down) in corners, controlling body roll.

This typically produces an extremely harsh ride, and so it’s typically coupled with soft compression damping and a softer spring to mitigate harsh ride quality, and a tall progressive bumpstop that engages early to create a progressive setup to boost spring rate when cornering. When used with a stiffer aftermarket shock and spring or a coilover that is stiffer so as have linear springing without the aid of the bumpstop, the result is the typical brutal “racecar” ride quality.

The other approach which some call “old school” is stereotypically the “European” approach used in many German cars and luxury sports/GT cars and supercars. Think AMG Mercedes (but not Black Series) and some Porsches. A stiffer spring is chosen, with less damping that’s more symmetrical - compression damping is used to support the inside corner in addition to the rebound pulling the outside down. Ride quality is better due to less high speed damping, but this setup is harder to tune just right and get just enough low speed damping, and done poorly can produce a bit more oscillation and result in “floaty” feeling. If you haven’t guessed, the B14 uses this approach and might not have gotten it quite right (although much improved over the base model Fiesta which was the benchmark)

Neither approach is “wrong”, but factory “sport tuned suspension” has gravitated towards the Japanese approach, partly because it’s easier to get “right” and produce good handling, but also because consumers want a car that “feels” sporty and stiff regardless of how fast it actually is. Bad ride quality is actually a feature that sells cars…

Contrary to what you might think, ride quality is primarily a result of stiff damping and not stiff springs. The issue with stiff springs is actually getting enough damping to prevent the bouncy/floaty sensation, and the ball and chain is always that high speed damping is always baselined off the knee of the low speed, and with consumer grade shocks, you can’t make high speed damping flat (slope always goes up)

Just wanted to say that it's an absolute pleasure reading your posts on suspension theory. In this thread, yours (rally suspension) and the other (becoming silly unfortunately) "racecar handling" thread, I have learned so much. It aligns with my suspension books and other content by automotive engineers, especially regarding roll centers, etc. Thank you for taking the time to write in a neutral (I'd say professional, even) tone and answering the questions of many members. It has helped understand a ton of concepts, even though I have a degree in mechanical engineering and loved cars since I was a toddler.

 

[Mech_Mike412]

Koni North America sells parts directly and will also do rebuild service on shocks. They can also be revalved for both compression and rebound (the latter essentially changes the adjustment range)

There are a few vendors (Koni Authorized) that will rebuilt and restore with proper gas charge:
https://www.koni-na.com/en-US/NorthAmerica/Products/Accessories/Parts/
https://www.performanceshock.com/product/koni-shock-repair-and-rebuild/

I've heard the Yellows can have compression/rebound adjustment installed with a re-valve. Is this true?

 

[Dialcaliper]

I've heard the Yellows can have compression/rebound adjustment installed with a re-valve. Is this true?

Call up Koni. I think some can be modified but it depends on the shock configuration - the compression adjuster is usually at the bottom, so sometimes with an eye mount there might not be a good place to put the adjustment.

 

[M-Sport fan]

Call up Koni. I think some can be modified but it depends on the shock configuration - the compression adjuster is usually at the bottom, so sometimes with an eye mount there might not be a good place to put the adjustment.

The off the shelf, Koni Sport yellow double adjustable dampers on my Z28 had that little (adjusted with a slotted screwdriver, with ~10 'click' settings) dial compression adjuster at the base of the damper, directly above the mounting eyelet.

 

[Dialcaliper]

I tried to tell you it was not the MeisterR’s but you would not listen. You might stop to think some of us older forum members have been around and gone through stuff. My car is not built the way it is for nothing. 😂I have been running MeisterR’s for several years now and they handle and work great . Quite honestly the only other coilover i would consider for the car is the Fortune Auto specifically because like MeisterR they took the time to test out and valve their models for our car on our cars and did not just go and pull something off the shelf.
You really have to spend a lot more money to find better setups than these two brands. Bilsteins and Koni’s are off the shelf setups. They look at stock and valve according to stock and do not go further with any kind of testing. Neither are terrible but it’s the actual testing the other two companies took to get a setup that works well for our cars. Other brands do but they will cost you upwards of $2500.
So ya I could have told you tire noise on RE71r’s migHt be the cause .Just like someone running 888r’s or Federals 😂

One other thing that’s kind of interesting to mention is that MeisterR uses the same sort of “Euro” damping approach as Bilstein (specifically the B14) in the ZetaCRD and ClubRace series. Not sure about the GT1’s. “Close Ratio Damping” despite how fancy it sounds is actually just using more nearly symmetric low speed compression/rebound (at full soft) instead of a heavy rebound biased approach. I believe they do increase rebound bias with stiffer settings

Koni is typically the opposite - very soft, near stock compression, increased rebound even on full soft.

 

[Dpro]

One other thing that’s kind of interesting to mention is that MeisterR uses the same sort of “Euro” damping approach as Bilstein (specifically the B14) in the ZetaCRD and ClubRace series. Not sure about the GT1’s. “Close Ratio Damping” despite how fancy it sounds is actually just using more nearly symmetric low speed compression/rebound (at full soft) instead of a heavy rebound biased approach. I believe they do increase rebound bias with stiffer settings

Koni is typically the opposite - very soft, near stock compression, increased rebound even on full soft.

Bilsteins approach is perfectly fine. The problem with Bilstein is due to mass market they like Koni kinda of chase a stockish generic valving setup instead of really tuning the build for the car specifically with performance enhancements in mind.

Both companies do make some excellent race car applications but those do not carry over , of courise in the 240sx world we were buying. high performance double adjustable koni’s and putting housings together. to drop them into allowing us to tune the spring rates and adjustability it was not cheap though.

I believe its Motion Control that takes Bilsteins and just completely tears them apart and then he revalves them specifically for the application with a lot of testing and tuning .
For our cars in the affordable range the only two I know off that actually did that was MeisterR and Fortune Auto which is why I have respect for both companies .

 

[Mech_Mike412]

Call up Koni. I think some can be modified but it depends on the shock configuration - the compression adjuster is usually at the bottom, so sometimes with an eye mount there might not be a good place to put the adjustment.

The off the shelf, Koni Sport yellow double adjustable dampers on my Z28 had that little (adjusted with a slotted screwdriver, with ~10 'click' settings) dial compression adjuster at the base of the damper, directly above the mounting eyelet.

Ahh okay I thought they were only rebound adjustable in an off the shelf configuration. Thanks!!

 

[M-Sport fan]

Ahh okay I thought they were only rebound adjustable in an off the shelf configuration. Thanks!!

For our cars the Koni Sports (yellow) are only rebound adjustable.

For the 4th gen Camaros, they offered them in double adjustable, at least initially, when I bought mine in 2001.
(I only mentioned them to state where Koni put the adjusters on their double adjustable dampers. )

 

[Fusion Works]

I wonder if you compared valving on the Mk2 VW GTI and the Fiesta how far off the Koni Yellow valving is. HAHA. Koni yellows are one of the oldest damper valving philosophies in the market. Just buy OEM replacement dampers, they will be better. Koni is almost as bad as KW to deal with when servicing or upgrading their dampers. You get one or two shops that can "service" their stuff and no they won't sell you parts.

No MCS is all their own stuff, they do not take Bilsteins and do anything to them. If you want a 90% damper for a 90% application, Bilstein is pretty much the only way to go. If you need a more performance oriented damper, then you need to look beyond the Chinesium junk on the market. You can customize Bilsteins easily and there are a lot of shops that work on them. Otherwise I would be looking at an MCS, possibly a Penske, and maybe Ohlins on the high end of race dampers. AST makes some race shocks for the Fiesta ST240 Cup in Europe and I think Nitron also makes some race fitments, that aren't listed on their website.

 

[M-Sport fan]

I would feel a lot better about buying stock, off the shelf B6es, and pairing them with some Swift Spec Rs if they were at least actual monotube dampers with large diameter, motorsport style internals, even with/despite their valving not being 'ideal'.

 

[Dpro]

I wonder if you compared valving on the Mk2 VW GTI and the Fiesta how far off the Koni Yellow valving is. HAHA. Koni yellows are one of the oldest damper valving philosophies in the market. Just buy OEM replacement dampers, they will be better. Koni is almost as bad as KW to deal with when servicing or upgrading their dampers. You get one or two shops that can "service" their stuff and no they won't sell you parts.

No MCS is all their own stuff, they do not take Bilsteins and do anything to them. If you want a 90% damper for a 90% application, Bilstein is pretty much the only way to go. If you need a more performance oriented damper, then you need to look beyond the Chinesium junk on the market. You can customize Bilsteins easily and there are a lot of shops that work on them. Otherwise I would be looking at an MCS, possibly a Penske, and maybe Ohlins on the high end of race dampers. AST makes some race shocks for the Fiesta ST240 Cup in Europe and I think Nitron also makes some race fitments, that aren't listed on their website.

So you are basically saying that MeisterR and Fortune both of which specifically worked on valvling their dampers properly for our cars are worthless or you are lumping them into a category you call Chinesium junk? Both of which based on what you have said above you have no experience with .
Ya you lost credibility with that statement this is not 2000 this is not 2009
Things have come along way in the performance shock world 15 years it might be time to broaden one’s horizons.

 

[M-Sport fan]

I wonder if you compared valving on the Mk2 VW GTI and the Fiesta how far off the Koni Yellow valving is. HAHA.

I actually had a set of Koni yelllows on my first year here in the states ('83), A1 (Mk1) GTI paired with the factory springs. LOL

Otherwise I would be looking at an MCS, possibly a Penske, and maybe Ohlins on the high end of race dampers. AST makes some race shocks for the Fiesta ST240 Cup in Europe and I think Nitron also makes some race fitments, that aren't listed on their website.

The Penskes and Ohlins would have to have everything either sourced or fabricated in order to be fitted to our rides, correct (as they offer NOTHING 'bolt on' for our app, but MUCH for the Scoobies and other popular rides out there)??

 

[foodtruck]

AST makes some race shocks for the Fiesta ST240 Cup in Europe

Saw this on Whoosh the other day

 

[Fusion Works]

So you are basically saying that MeisterR and Fortune both of which specifically worked on valvling their dampers properly for our cars are worthless or you are lumping them into a category you call Chinesium junk? Both of which based on what you have said above you have no experience with .
Ya you lost credibility with that statement this is not 2000 this is not 2009
Things have come along way in the performance shock world 15 years it might be time to broaden one’s horizons.

Meister R and Fortune Auto are made of Chinese parts and in part or in whole assembled in China and sold by their respective manufactures here and in Europe. Fortune Auto has components inside that are Chinese copies of Penske components. Their valving is not specific to our cars unless you go with the Fortune Auto custom race dampers, which they assemble here in the US specifically for your application out of Chinese parts. Their off the shelf dampers are not different than Bilstein or Koni as far as valving philosophy, they just buy what ever 1-10 damper the Chinese manufactures offer. I get emails every couple of months from these companies offering to sell me "coil overs" cheap.

You are right things have come a long way in the performance shock world. The Chinese are making better copies of every good companies parts and shilling them out to the cheapest buyers. They will put anyone's name on their garbage and then let the seller convince you its "quality". If you want cheap coil overs thats fine, but lets not put the Chinesium garbage up on the same level as a company that has done all the engineering, research and production into making a good originalish product and standing behind it.

 

[Dpro]

Meister R and Fortune Auto are made of Chinese parts and in part or in whole assembled in China and sold by their respective manufactures here and in Europe. Fortune Auto has components inside that are Chinese copies of Penske components. Their valving is not specific to our cars unless you go with the Fortune Auto custom race dampers, which they assemble here in the US specifically for your application out of Chinese parts. Their off the shelf dampers are not different than Bilstein or Koni as far as valving philosophy, they just buy what ever 1-10 damper the Chinese manufactures offer. I get emails every couple of months from these companies offering to sell me "coil overs" cheap.

You are right things have come a long way in the performance shock world. The Chinese are making better copies of every good companies parts and shilling them out to the cheapest buyers. They will put anyone's name on their garbage and then let the seller convince you its "quality". If you want cheap coil overs thats fine, but lets not put the Chinesium garbage up on the same level as a company that has done all the engineering, research and production into making a good originalish product and standing behind it.

ah I call you on the comment of Fortune not being valved for our cars they actually worked with one of our forum members testing out the valving on his car and tweaking accordingly. MeisterR actually did that as well in the UK as they first started out marketing in the UK. I know this about these brands.

 

[Fusion Works]

ah I call you on the comment of Fortune not being valved for our cars they actually worked with one of our forum members testing out the valving on his car and tweaking accordingly. MeisterR actually did that as well in the UK as they first started out marketing in the UK. I know this about these brands.

Again, if Fortune was doing some "race type valving" yeah I would expect them to look at the off the shelf valving and make modifications to that. Those weren't the cheap bottom of the line. I expect those were double adjustable dampers. That is good, I would expect a company that is to be taken seriously to do this kind of development. Most of the Chinesium dampers are rebadged commonly available generic dampers rebadged for who ever is selling them. The Whoosh, Yellowspeed, ISC, Maxspeeding Rods, Megan, BC, Raceland, etc are all the same company's stuff, just in a different package.

If Meister and Fortune did this, props to them, they are trying to become a serious damper company.

 

[M-Sport fan]

Saw this on Whoosh the other day
View attachment 61483

Finally, some competition for the Reigers in top dollar pricing for an off the shelf suspension setup!

 

[foodtruck]

Since I have the Bilstein springs here I can measure the actual rate and is ramp up of linearity. The rears are most definitely progressive and won't be in the linear portion at ride height. The front "progressive" portion is at the top of the spring mount.

So did you end up dyno-ing those springs at some point? I'm really curious to see what the profile looks like.