suspension gurus, lend me your ears....

[captain awesome]

So I somehow messed up and ordered B6 Bilsteins for a GTI instead of the proper B8 sports with better travel. Why it took me a month or so to figure this out is beyond me. Anyway, I am trying to see if these will work for my intended use or whether I need to just unload them at a fire sale price and get the proper gear.

I have found the following measurements that Tom D has posted previously rather helpful as it at least gives me some numbers to compare to:

* 320I struts tubes are - 40.13 mm i.d. 457.2 mm deep

* bilstien stock / alpina - 38.32 mm o.d. 460.38 mm long 114.30 mm travel

* bilstien vw mk1 - 38.32 mm o.d. 317.50 mm long 158.75 mm travel

From my measurements of the B6 Bilstein (HD) dampers: 38.32 mm o.d. 317.50 mm long ~127 mm travel

I could potentially trim the bump stop one knuckle and gain another ~19mm of travel for a total of 146mm. I've done this on my 318is and it was a relatively simple process.

I'm not putting this car in the weeds, as it is planned specifically for local autocross. From what I gather the total drop of suspension will be about 1.5" - 2" max, and I have every intention of raising the front cross member 1" to help restore some roll center which will also effectively restore some suspension travel(I believe).

So, now that all that information is provided, do any of you performance minded folks have an opinion on what I should do? On one hand I got a really good deal for at least one of the B6 dampers, so I could sell them both and be right side up. On the other hand if these will work just fine for what I have planned, there is no sense in buying the B8s and I can carry on with my initial plan.

[m60b30530i]

What spring rate are you planning on running ? This year I ran the vw Bilstien sports, I really dont like them. Will be putting my Koni adjustables back in over the winter.

The Bilstien sports on the soft side, mind you I have a m20 up front and running 400lb springs.

[autox320]

Don't quote me but off top of the head. B6 and B8 valving is identical. Only difference even if trim the stops is the shaft is physically longer on the B6 (old HD) vs the B8 (sport). If can fit them height wise and not bottom then basically same performance. The shorter shaft B8 works better with shorter springs obviously if limited shaft travel, but that's it.

When setup my B8 VW ones they are way shorter than stock inserts. I think shortened my strut housings 2 inches. Still required a piece of tube as an insert below the strut to fill the gap when tightened in the housing. This gives me full travel of the shock at much lower ride height. Yes adjusting roll center in the front helps keep things in check. It may become obvious if look and put a bubble level on the control arms as you lower the car body using the coil over sleeves. Once past parallel you'll see the inner pivot or subframe holes need to move up, or/and the hub side needs to move down; to make the arms sit near parallel again or angled up toward the subframe like stock. Keeps the front roll center higher which is what your after.

[captain awesome]

What spring rate are you planning on running ? This year I ran the vw Bilstien sports, I really dont like them. Will be putting my Koni adjustables back in over the winter.

The Bilstien sports on the soft side, mind you I have a m20 up front and running 400lb springs.

364# is what I have planned for the moment, but I'm planning to get them revalved to 450-500 range after the GRM Challenge.

If you decide to sell the Sports, let me know and maybe we can work out a deal.

[captain awesome]

Don't quote me but off top of the head. B6 and B8 valving is identical. Only difference even if trim the stops is the shaft is physically longer on the B6 (old HD) vs the B8 (sport). If can fit them height wise and not bottom then basically same performance. The shorter shaft B8 works better with shorter springs obviously if limited shaft travel, but that's it.

When setup my B8 VW ones they are way shorter than stock inserts. I think shortened my strut housings 2 inches. Still required a piece of tube as an insert below the strut to fill the gap when tightened in the housing. This gives me full travel of the shock at much lower ride height. Yes adjusting roll center in the front helps keep things in check. It may become obvious if look and put a bubble level on the control arms as you lower the car body using the coil over sleeves. Once past parallel you'll see the inner pivot or subframe holes need to move up, or/and the hub side needs to move down; to make the arms sit near parallel again or angled up toward the subframe like stock. Keeps the front roll center higher which is what your after.

My biggest worry is that these are the same size and length as the B8 VW Sports from comparing Tom D's measurements to my own, and the valving isn't the same. I know it's often stated for e21 Bilsteins that the HD and Sports share the same dampening characteristics, just a different length for shorter springs, but I have no idea if that's the same for the VW inserts considering they physically look the same.

I'm thinking for now I will get the suspension setup with the m10, roll around my neighborhood a bit with some zip ties and measure travel with a loaded suspension. I'll check sag as well, which should let me know where in the stroke my travel will be with the two numbers. In the mean time I'll try to get info from Bilstein on valving to see if they are in fact the same.

Anyone wanting to unload some used front B8 sports for the GTI feel free to PM me.

[captain awesome]

So I've spent a few hours pouring over data in a VW Vortex thread that essentially involves testing every well known aftermarket damper and comparing the data between them. From Koni, KYB, Bilstein etc. This is some of what was posted about the Bilstein HD vs. Sport. There may be more, but for some reason the site just went down so I'll have to revisit the remainder of the thread to see if there were any follow up posts comparing the nuances between the two. There was also a lengthy post on the differences between Bilstein HD and the Koni Sport adjustable. Definitely proof positive at least with the shocks tested that the HD and Sport are in fact different.

Just got the results from the dyno and have to say that the valving (or whatever else that affects the numbers that the damper makes) may not really be the same! We compared a rear HD with about 1.000 miles on it against a rear Sport with more than 100.000 miles on it and the Sport showed still considerably stronger at all speeds! And it is stronger on both compression and rebound. We are talking about 30 lb difference on some speeds...... Now, from the graphs it looks like the shape of the curves is similar, so they both would offer similar driving "feel" (character), but at the end the Sport will be less comfortable, as the difference is well visible even at very low speeds and most of all, as soon as the damper moves. Of course, the graph would show more than the words, but as I said, no graphs for now, as I simply have no time to elaborate them.
However, for the real final answer on this, I have to find relatively new Sport and dyno it again, as we have to see how much those curves got "weaker" for the 100.000 miles, as to determine better by how much the valving makes those two dampers different. I will also open the Sport and do a complete modeling later in the month, so we can explore it better and understand more in depth how it works and what opportunities it offers for revalving.

After spending some time exploring the HD vs. Sport dyno plots, it is even more obvious that these two dampers are valved differently! The big difference is in the low speeds (from 2 in/sec to about 10 in/sec) where we have:
1. Much more pronounced "knee" in the Sport.
2. Much higher value of the force after the knee in the Sport.
Just to give some idea of the difference in values here - For example, the curve that the Sport provides at 2 in/sec is almost identical to the curve that the HD provides, BUT at double the speed (4 in/sec)! And the same goes with all the speeds until 10 in/sec where the difference gets little bit less..... and as a reminder, we are talking about a damper that has 100.000 miles versus almost new one!
There is really no way in the world these two dampers have the same valving! Or, if indeed the actual washers are exactly the same inside, then there is design changes in either the piston or somewhere else, that affect the way the washers perform. I do not know yet who exactly these are assembled inside, but from the way the curve look and from the way it acts (big difference in low speed, less difference in high speed) may as well be just different preload on the washer stack (if that is possible in these dampers). In fact, the curves of the Sport vs. HD look very similar to the comparo we had time ago when trying different pre-loads on the Konis...... I will try to get some graphs soon, but till then just have to take the words here. I would do my best to locate a brand new Sport and dyno again, so we compare apples to apples.
Omar, I will send you an IM later, so we talk in details, but I am more interested in A4 Bilstein Sport with low miles, so we can see by how much different they are.....
Winston, I am discussing your theories about the linear dampers and your calculations with Phil as we speak. I will tell you more later on his take, but my guess is that you are absolutely right on the money, as in reality this damper performs very well on my car, plus it had been Phil's way of preventing bottoming in the bikes for years. More later, but thank you very much for your (as always) very detailed explanations and for the write-up on the Reds! Hope all this work you have done will help many here to make the right choice for their application.

[autox320]

Good to know. Proof don't believe everything on the interwebs. Said don't quote me

[captain awesome]

Good to know. Proof don't believe everything on the interwebs. Said don't quote me

I thought the same thing, but it's hard to tell what's fact or fiction sometimes. If you read almost every forum post that mentions the two together, it is often said that the two are valved the same, regardless of the model car. What I do find interesting in this scenario though is that the stroke length I believe happens to be the same for both, just a more aggressive valving. If that's the case, these MAY work in a shortened housing situation, just won't provide quite the performance package.

[Tom D]

..... it's hard to tell what's fact or fiction......

easier to just call bilstein N.A., i'm sure if asked politely they would tell you the difference. 1-800-537-1085

[captain awesome]

easier to just call bilstein N.A., i'm sure if asked politely they would tell you the difference. 1-800-537-1085

I’ll give that a shot tomorrow. Thanks.

[OLD MAN]

Derrick something to keep in mind - when set up/cutting and welded is done correctly - the only travel difference should be in droop between the E21 and VW inserts. Ride height and up travel with the VW inserts will be all you need for track and auto-x. Which also means you do not have to jack the car up so high to change the tires -

Valving can be custom re-set by any manufacturer if the right ones are bought to begin with.

I have not done any work on raising the front mounting for the lower control arms - and our car works pretty good. Not sure lower (too low) is better for auto-x as they are held in parking lots which can get bumpy!

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easier to just call bilstein N.A., i'm sure if asked politely they would tell you the difference. 1-800-537-1085

I have always found them very helpful - my have to leave a number for them to call you back though. Not sure which office is doing the stock insert re-builds now though.

[captain awesome]

Derrick something to keep in mind - when set up/cutting and welded is done correctly - the only travel difference should be in droop between the E21 and VW inserts. Ride height and up travel with the VW inserts will be all you need for track and auto-x. Which also means you do not have to jack the car up so high to change the tires -

Valving can be custom re-set by any manufacturer if the right ones are bought to begin with.

I have not done any work on raising the front mounting for the lower control arms - and our car works pretty good. Not sure lower (too low) is better for auto-x as they are held in parking lots which can get bumpy!

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I have always found them very helpful - my have to leave a number for them to call you back though. Not sure which office is doing the stock insert re-builds now though.

Yeah I'm torn on the subframe raising. My main train of thought is that I have the means to raise it without much fuss. I am already making some new motor mounts for the m42 swap, so it seems like a good idea to just go ahead and do it. If I raise the rear subframe just by flipping the mounts with no extra effort, it should help keep the driveshaft aligned to help balance everything with a 23mm, so only the CSB will need raised. The only grey area is how much clearance the oil pan will need. I'm halfway temped to snatch up a spare front subframe so I can try them from one autocross meet to the next and see how much it's helping or hurting. Another thing worth mentioning that I never really put much thought into before, is that the future set of 13" tires are going to give me 1" of drop without any penalty to the suspension geometry. Either way, there are a ton of people that have successfully ran competitive e21s without doing either of those subframe options. I'll probably know for sure if I want to commit to the front subframe once I have all the parts in the same place. For now it's all just speculation and no real world experience.

[OLD MAN]

I set up the car with the front lower control arms just off of parallel to the ground (level). They angle up from the wheel to the sub-frame about 1 to 2 degrees, then I set the rear to be 3/8" to 1/2" higher then the front measuring from the ground to the pinch weld at the bottom of the body.

Lowering the car has more bad effect on the rear suspension then the front in my opinion. That's why I raise the rear sub-frame as much as I do, too much you lose forward bit that can end up with lots of wheel hop during take off.

[autox320]

If can't adjust roll center, then it's all in the ride height. Best setup IMO is setting heights and weight then alignment completely around the roll centers. I tape bubble levels on the front arms and raise till parallel or taper to subframe as Daryl mentions. If can't adjust the front roll center the ride height will determine where this is. If adjust the front roll center (up at subframe, down at hub) you'll notice can use lower ride heights.

In the rear it's easier to go up on subframe to raise the roll center. I tape bubbles on the axles and keep parallel or taper to the diff as you would the front arms. I went opposite and it is much harder to go lower rear roll center. The lower the rear roll center the more static camber. This is the limiting factor unless have a way to adjust it. Seems to negate doing it cause camber and roll center are related, but does work. Another limit is the axles will fold in so the diff has to be separated from the subframe and placed high as possible. Lower the rear roll the more it sticks and is hooked up to the road. Higher will loosen the back. Can raise and lower the subframe to change a small amount as another way to tune for understeer/oversteer. Best suggestion I'd give is just use bubbles on the axles and set height based off the axle angle limit.

There's tons of info on this in my build thread btw.

[captain awesome]

Sounds like I need to just leave the subframes in the stock positions for now and can later test effectiveness on handling. I think the subframe adjusters will get me the proper alignment specs, which I think should be around 2.5-5 degrees camber up front and 1-1.5 in the rear.

[OLD MAN]

Sounds like I need to just leave the subframes in the stock positions for now and can later test effectiveness on handling. I think the subframe adjusters will get me the proper alignment specs, which I think should be around 2.5-5 degrees camber up front and 1-1.5 in the rear.

Best front end money to me are GC camber caster plates in my opinion. And for auto-x I found that less camber more caster works a little better - with lots of front camber you angle the tires so that only half the tread is on the ground when going straight. Which means less tire on the ground for braking before a corner, we use to light up the tires all the time until I took out some of the camber I had added. With caster you gain camber in corner where you need it when you turn the wheels for the corner. We have tested all the way down to only .5 degree of camber in the front trying to increase stopping performance. We now run 1.5 degree front camber with 4 degrees of caster.

[autox320]

You could for less work and always dive more into it later. A good setup is still a good setup no matter how you achieve it.

Just a thought reference; ours is setup with camber -2.5 up front and -3 in back.

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Best front end money to me are GC camber caster plates in my opinion. And for auto-x I found that less camber more caster works a little better - with lots of front camber you angle the tires so that only half the tread is on the ground when going straight. Which means less tire on the ground for braking before a corner, we use to light up the tires all the time until I took out some of the camber I had added. With caster you gain camber in corner where you need it when you turn the wheels for the corner. We have tested all the way down to only .5 degree of camber in the front trying to increase stopping performance. We now run 1.5 degree front camber with 4 degrees of caster.

sheesh 4deg caster turns faster than a honda or grocery cart; ours is 10 deg. A lot of factors play into setup and not all are the same. Neat to see how much alignment settings can be apart from one car to another depending on how it's configured.

[OLD MAN]

You could for less work and always dive more into it later. A good setup is still a good setup no matter how you achieve it.

Just a thought reference; ours is setup with camber -2.5 up front and -3 in back.

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sheesh 4deg caster turns faster than a honda or grocery cart; ours is 10 deg. A lot of factors play into setup and not all are the same. Neat to see how much alignment settings can be apart from one car to another depending on how it's configured.

We are still working on the front end alignment - due to not being able to go out for awhile we never finished dialing in the front caster - thanks for the numbers Jody, we will have to try the 10 degrees or maybe even more....LOL, More is always better RIGHT!?

And 4 maybe incorrect - it has been awhile since I did the work - 6 sounds more like it now that I think about it.

The big thing to us is being able to brake hard and not light up a front tire for 50 ft or so.

[captain awesome]

I didn't know the GC plates did caster as well. For the GRM Challenge I have a pair of cheap $35 ebay camber plates meant for an e46 that will require some drilling to fit. It's a temporary setup that will eventually find the trash bin.

[autox320]

We are still working on the front end alignment - due to not being able to go out for awhile we never finished dialing in the front caster - thanks for the numbers Jody, we will have to try the 10 degrees or maybe even more....LOL, More is always better RIGHT!?

And 4 maybe incorrect - it has been awhile since I did the work - 6 sounds more like it now that I think about it.

The big thing to us is being able to brake hard and not light up a front tire for 50 ft or so.

For sure it's fun to do test and tunes. I try as you say to stay under or at 2.5 degrees camber cause braking does get sacrificed too much especially at higher speeds. Caster I played with 5 and then just 10 like the M3 stays near. Just feels more stable high speed so left at 10deg. Slightly longer wheelbase with extra caster. Usually anything we change or throw at it can make oversteer again with a touch more rear bar and go pedal

Good to hear your using the car again man. I feel pretty good with dialing ours in more. It has been a lot of fun.

[OLD MAN]

I didn't know the GC plates did caster as well. For the GRM Challenge I have a pair of cheap $35 ebay camber plates meant for an e46 that will require some drilling to fit. It's a temporary setup that will eventually find the trash bin.

The GC plates adjust caster where they bolt to the strut tower, three stock mounting bolts. You will have to cut the inside of the strut mount out to allow for adjustments.

[hdx]

I feel the e21 has to much caster . It’s nice for high speed and street . But for auto x or smaller tracks less caster is better.

I like the front end alignment toed out about 5mm total.
Rear toed in 4mm total.

I run 2deg negative camber rear
And 2.5 deg in front .

I don’t know the exact caster angle I am running but I moved the strut up to the maximum I could with the plates I have .

I have always use the gti race shocks out of the box . With a 450 500 lbs springs in front. I recall I cut 50mm or more out of the strut and just a small spacer in the bottom to tighten it up.

[OLD MAN]

HDX has a good set up - He always bets me at events!

[captain awesome]

I feel the e21 has to much caster . It’s nice for high speed and street . But for auto x or smaller tracks less caster is better.

I like the front end alignment toed out about 5mm total.
Rear toed in 4mm total.

I run 2deg negative camber rear
And 2.5 deg in front .

I don’t know the exact caster angle I am running but I moved the strut up to the maximum I could with the plates I have .

I have always use the gti race shocks out of the box . With a 450 500 lbs springs in front. I recall I cut 50mm or more out of the strut and just a small spacer in the bottom to tighten it up.

No re-valving with the heavier springs up front needed?

What sways and rear springs are you running?

I may have scored a set of lightweight 13x9 wheels from a local autocrosser running a GTI in FSP. He thinks they are around 10 lbs each, but my biggest worry is clearance with 9" wide rims. Any thoughts on that size?

[hdx]

No revalveing on the shocks needed with a 450 -500 spring.
The 13 x9 wheels are maybe a bit wide depending on the backspace . A 205 60 13 on a 9”wheel is going to be stretched a bit but ok .
I prefer a 13x8 with a 205 60 13 tire.