The Better Bilstein Ebay Coilover Thread
#821
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I disagree regarding going to higher spring rates with that valving on a commuter car. Yes, Spec Miata runs them, but only because they must because of the rules. And Spec Miatas make shitty street cars.
Get shorter bump stops or trim yours enough to allow good travel and get extended top hats to further assist with travel.
Since I'm on the mobile app, I can't scroll up to see what sway bar you are using, but a good aftermarket bar at least one inch in diameter will not affect your ride height negatively and will help to keep the car off of the bump stops in the curves.
Get shorter bump stops or trim yours enough to allow good travel and get extended top hats to further assist with travel.
Since I'm on the mobile app, I can't scroll up to see what sway bar you are using, but a good aftermarket bar at least one inch in diameter will not affect your ride height negatively and will help to keep the car off of the bump stops in the curves.
#822
So my next course of action is to order new springs and during disassembly take the spring out and find out how much bumpstop I really need to keep things from hitting each other. I should be aiming for about 3/4" shock travel before the bumpstop engages. If I cut the stops up to keep things from destroying each other and I still don't have enough travel in the suspension then I should look at ordering extended top hats?
Yeah I'm still running a stock front and rear bar for now just because of funds available. My plan was to grab an FM front bar and 949 endlinks as a "mild" sway bar upgrade as my spring rates weren't crazy enough to warrant going huge front bar. I don't know if that actually makes any sense logically though.
Yeah I'm still running a stock front and rear bar for now just because of funds available. My plan was to grab an FM front bar and 949 endlinks as a "mild" sway bar upgrade as my spring rates weren't crazy enough to warrant going huge front bar. I don't know if that actually makes any sense logically though.
#824
Continuing a discussion from the MCS shock thread (in Race Prep) in here so as to not keep bumping that thread (and understandably riling up the involved parties with commercial interests who probably don't want people mis-understanding comments about their products...).
The high speed forces are determined by the cover plate (and to a lesser degree the support plate(s) that they bend back against). How much force it takes to open (digress) the cover plate is dependent on the cover plate shim(s) dimensions and the dimensions of the pre-load shim. The shape of the curve below the digression is the result of the bleed shim and the sizes of it's ports.
Here's a diagram I labeled of how the shims interact to produce the force vs velocity graph we're used to seeing:
And from some kind of bilstein manual I found (would love to find the original doc):
I'm pretty sure I could get pretty close to the right shim stack if I had a given curve I wanted (or at least could work with someone who actually revalves them to get there). Have been looking at ReStackor too - quite tempted to buy a copy.
So what I'm interested in is finding the desired curve for a base revalve for say 700/400 springs, a 2200-2500lb car, with digressive damping somewhere close to, say, in the middle of their adjustment range (or insert any other known quantity quality miata damper that has proven damping in there).
Here's a diagram I labeled of how the shims interact to produce the force vs velocity graph we're used to seeing:
And from some kind of bilstein manual I found (would love to find the original doc):
I'm pretty sure I could get pretty close to the right shim stack if I had a given curve I wanted (or at least could work with someone who actually revalves them to get there). Have been looking at ReStackor too - quite tempted to buy a copy.
So what I'm interested in is finding the desired curve for a base revalve for say 700/400 springs, a 2200-2500lb car, with digressive damping somewhere close to, say, in the middle of their adjustment range (or insert any other known quantity quality miata damper that has proven damping in there).
#826
Allow me to be more clear - I understand which shims affect the nose and the knee of the graph. What I'm saying is that Bilstein's valving codes do not provide any obvious feedback on what you're getting for those values. A "300" linear stack will be producing 330 lbs of force at 10 in/sec (ish, I did a rule of thumb conversion) and, barring bleed and stuff, 165 lbs at 5 in/sec and so on - one number will tell you the whole theoretical FV curve. But a "190D" stack, that's not the case. I have a Bilstein digressive piston simulated in Restackor, but it's on my home PC so I can't really mess with it right now - it just annoys me a bit, especially since I haven't fully validated it.
I like the Ohlins X-Stack book (http://www.resuspension.com/assets/O...cks%20Book.pdf) because it shows a bunch of example shim stacks with different pistons and shows you what you get. And for that matter, I don't know that any of the off the shelf Bilstein stacks mess with ring shims. Oh yeah, check out the excel calculator linked here - Subaru Impreza WRX STI Forums: IWSTI.com - View Single Post - Suspension/Stiffening Weight transfer, spring frequency, damper, body roll calculator... and more! All the data for the NA/NB geometry is findable and with some work you can get shock forces into it too. The critical damping vs shock velocity plots shows some interesting things.
Now. The problem I'm seeing in a lot of Miata dyno graphs is that most of the shocks aren't built with enough compression. Compromises though - without a base valve, you have to fight cavitation with gas pressure alone, and that has its own tradeoffs, especially with as short as the rear shocks are. It's interesting how much more gas pressure the ND shocks seem to be running based on dyno graphs I've seen of them - once geometry for those gets analyzed by someone I'd like to characterize them and figure out what's going on. In short though, some of the more "ideal" shock graphs (I'm not naming names, but you can do research) aren't doable on Bilsteins without either big gas pressure, base valves or canisters with base valves / compression adjusters. But there's some stuff out there that are built basically the same as Bilsteins (albeit with clickers) and have been track tested that should be a fair starting point.
And yeah I'm hinting around a lot and doing the secret squirrel thing when I could just be more specific. I know. We're blessed with vendors that are far more willing to put shock data out there than most and I don't want to be the dick who spills the beans on other people's intellectual property on an open forum to where any fool can take stuff to a circle track shop and undercut them. I might be willing to share some of my stuff when I get to that point - have to get the new version shock dyno built first though.
I like the Ohlins X-Stack book (http://www.resuspension.com/assets/O...cks%20Book.pdf) because it shows a bunch of example shim stacks with different pistons and shows you what you get. And for that matter, I don't know that any of the off the shelf Bilstein stacks mess with ring shims. Oh yeah, check out the excel calculator linked here - Subaru Impreza WRX STI Forums: IWSTI.com - View Single Post - Suspension/Stiffening Weight transfer, spring frequency, damper, body roll calculator... and more! All the data for the NA/NB geometry is findable and with some work you can get shock forces into it too. The critical damping vs shock velocity plots shows some interesting things.
Now. The problem I'm seeing in a lot of Miata dyno graphs is that most of the shocks aren't built with enough compression. Compromises though - without a base valve, you have to fight cavitation with gas pressure alone, and that has its own tradeoffs, especially with as short as the rear shocks are. It's interesting how much more gas pressure the ND shocks seem to be running based on dyno graphs I've seen of them - once geometry for those gets analyzed by someone I'd like to characterize them and figure out what's going on. In short though, some of the more "ideal" shock graphs (I'm not naming names, but you can do research) aren't doable on Bilsteins without either big gas pressure, base valves or canisters with base valves / compression adjusters. But there's some stuff out there that are built basically the same as Bilsteins (albeit with clickers) and have been track tested that should be a fair starting point.
And yeah I'm hinting around a lot and doing the secret squirrel thing when I could just be more specific. I know. We're blessed with vendors that are far more willing to put shock data out there than most and I don't want to be the dick who spills the beans on other people's intellectual property on an open forum to where any fool can take stuff to a circle track shop and undercut them. I might be willing to share some of my stuff when I get to that point - have to get the new version shock dyno built first though.
#827
Great stuff you're sharing here, I'd like to get to the point that you're at but as I started investigating it became obvious that a dyno was needed as you've shown there just isn't enough documentation to be able to install pre-designed shim stacks. This is where I stalled out, I did take the time to see where the Hard S shock curves are in comparison to ideal critical dampening values and realized that the low speed valving isn't that far out for my particular springs.
I shelved the project at that point as there is lower lying fruit elsewhere to gather up first.....that and I'm winning with a setup that most on here would consider ridiculous.
I shelved the project at that point as there is lower lying fruit elsewhere to gather up first.....that and I'm winning with a setup that most on here would consider ridiculous.
#828
Possibly because I'm crazy and have to do everything the hard way, I'm working on building a servovalve controlled pneumatic shock dyno - should be able to do a lot more than just stroke the shock in and out at a constant frequency. The old version worked surprisingly well - it just had a variable regulator to put the shock at various forces and a directional valve. So cycle the shock back and forth at one force, measure velocity, drop the pressure, repeat. It had limitations at low forces though (which are the most important!) and I really needed to clean up the output. One of the earlier raw outputs looked like this:
#829
Allow me to be more clear - I understand which shims affect the nose and the knee of the graph. What I'm saying is that Bilstein's valving codes do not provide any obvious feedback on what you're getting for those values. A "300" linear stack will be producing 330 lbs of force at 10 in/sec (ish, I did a rule of thumb conversion) and, barring bleed and stuff, 165 lbs at 5 in/sec and so on - one number will tell you the whole theoretical FV curve. But a "190D" stack, that's not the case.
I have a Bilstein digressive piston simulated in Restackor, but it's on my home PC so I can't really mess with it right now - it just annoys me a bit, especially since I haven't fully validated it.
I like the Ohlins X-Stack book (http://www.resuspension.com/assets/O...cks%20Book.pdf) because it shows a bunch of example shim stacks with different pistons and shows you what you get. And for that matter, I don't know that any of the off the shelf Bilstein stacks mess with ring shims.
I like the Ohlins X-Stack book (http://www.resuspension.com/assets/O...cks%20Book.pdf) because it shows a bunch of example shim stacks with different pistons and shows you what you get. And for that matter, I don't know that any of the off the shelf Bilstein stacks mess with ring shims.
Oh yeah, check out the excel calculator linked here - Subaru Impreza WRX STI Forums: IWSTI.com - View Single Post - Suspension/Stiffening Weight transfer, spring frequency, damper, body roll calculator... and more! All the data for the NA/NB geometry is findable and with some work you can get shock forces into it too. The critical damping vs shock velocity plots shows some interesting things.
Now. The problem I'm seeing in a lot of Miata dyno graphs is that most of the shocks aren't built with enough compression. Compromises though - without a base valve, you have to fight cavitation with gas pressure alone, and that has its own tradeoffs, especially with as short as the rear shocks are. It's interesting how much more gas pressure the ND shocks seem to be running based on dyno graphs I've seen of them - once geometry for those gets analyzed by someone I'd like to characterize them and figure out what's going on. In short though, some of the more "ideal" shock graphs (I'm not naming names, but you can do research) aren't doable on Bilsteins without either big gas pressure, base valves or canisters with base valves / compression adjusters. But there's some stuff out there that are built basically the same as Bilsteins (albeit with clickers) and have been track tested that should be a fair starting point.
And yeah I'm hinting around a lot and doing the secret squirrel thing when I could just be more specific. I know. We're blessed with vendors that are far more willing to put shock data out there than most and I don't want to be the dick who spills the beans on other people's intellectual property on an open forum to where any fool can take stuff to a circle track shop and undercut them. I might be willing to share some of my stuff when I get to that point - have to get the new version shock dyno built first though.
#830
Possibly because I'm crazy and have to do everything the hard way, I'm working on building a servovalve controlled pneumatic shock dyno - should be able to do a lot more than just stroke the shock in and out at a constant frequency. The old version worked surprisingly well - it just had a variable regulator to put the shock at various forces and a directional valve. So cycle the shock back and forth at one force, measure velocity, drop the pressure, repeat. It had limitations at low forces though (which are the most important!) and I really needed to clean up the output. One of the earlier raw outputs looked like this:
#833
I actually was looking more at the published graphs for the DA Gen 1 Xidas than the SA ones - it was mentioned at some point that the Gen1 Xidas were only running a 40mm piston, so limited on compression. I like the MSM Bilstein's rebound side quite a bit, to be honest, but it could probably use more compression. Not that that's a theme for me or anything.
*quickedit* Oh yeah, and the first dyno was really kind of a hackjob effort - stuff I had laying around plus a few ebayed parts. I'll make a thread somewhere on the new one once my "fun stuff" budget recovers from buying an NA shell to turn into a race car.
*quickedit* Oh yeah, and the first dyno was really kind of a hackjob effort - stuff I had laying around plus a few ebayed parts. I'll make a thread somewhere on the new one once my "fun stuff" budget recovers from buying an NA shell to turn into a race car.
#834
Ok, so I now have in my possession a set of NA HD"s with less than 50 miles on them and a set of MSM"s off an 04 with 62k miles on them. Could you guys please explain in more simple terms how the valving reaction at high speed (one inch bump in the road?) and low speed (dip or undulation in the road?) would compare. I got that there is a hierarchy in the shock choices, I'm just trying to wrap my head around how they would feel and/or react on my car. 2000 SE full stock weight plus weight of turbo, exhaust, 04 MSM 17" stock wheels, (christ, are they heavy). Bought 600"s front 400's rear. I have yet to buy the RB front bar (1.25?). That's about it I think, Thanks, -JB
#835
I hate to keep running set ups by you guys.... but I'm about to pull the trigger and don't wanna f it up. I have just found some NB yellow sport bilstein take offs. Plan is 90% daily driver, maybe 4 track days a year and some autocross. Car is stock, but will get a front sway bar (not sure which) and 15x9 wheels with 225 Ventus RS-3s. Shopping cart is as follows:
- Allstar sleeves ALL64162 QTY4
- Allstar nuts ALL64180 QTY4
- Ride tech spring washers 70010828 QTY4
- Energy suspension coil isolators 9-6103G QTY2 (pack of two)
- QA1 7 inch 450 spring 7HT450 QTY2
- QA1 7 inch 350 spring 7HT350 QTY2
- I have honda bumpstops Ill cut to size, 30mm?
- ISC 1.5" top hats for the rear, stock front.
#838
Depending on weather you use stock criclip location or not, what size of wheel and tires, possible contact between wheel and liner if your springs are not stiff enough. Again, I don't know this for a fact, but read in other coilover threads/sites. I'm about to do Bilstein build myself and most people told me to use stock hats in front and back, but I feel like adding 1" for a bit of extra travel may be a good idea.
#840
Depending on weather you use stock criclip location or not, what size of wheel and tires, possible contact between wheel and liner if your springs are not stiff enough. Again, I don't know this for a fact, but read in other coilover threads/sites. I'm about to do Bilstein build myself and most people told me to use stock hats in front and back, but I feel like adding 1" for a bit of extra travel may be a good idea.
If you put NB shocks on a NA you'll find your rear bump stop ends up being less than 1/2" in height which makes for harsh engagement......add 1 1/2" top hats and you can now run a 2" bump stop that has a much softer engagement.