Custom Bilstein Coilovers

[03whitegsr]

Thought I would post up a little project I am about 80% done with. I wanted something with Bilstein inverted monotube struts up front but don't like the soft spring rates on the PSS and PSS9 setups. I decided to piece together something on my own instead.

I bought a set of cheap struts on ebay for ~$60 to use as the outer strut tubes. 3000GT VR-4 inserts are very short (giving a ton of travel at very low ride heights) and are valved fairly high due to the 3000GT being a pig. With the springs I have chosen, the 3000GT valving puts the car at about 60% of critical damping at 5in/sec and then they are digressively valved to provide better ride comfort. Add a coilover sleeve kit along with some machining of a couple piece to put it all together and you have an inverted monotube bilstein setup that can handle high spring rates for about $500.

Cut Open EBAY strut


Machining top hat for Bilstein shaft


Machining Bilstein insert outer tube to work with EBAY strut tube.


Add some camber plates with added caster. Still have to machine strut gland nut and cut down coilover sleeve.



Add to this some bimmer world offset LCA mounts, new LCAs with solid steel balljoints, tie-rods and everything up front is new.

Out back, I picked up the Ireland Engineering spring adjusters with some hyperco 2.25" springs. For shocks, I found an off-the-shelf Bilstein shock that was just about perfect. The free-length is a bit long, so I had to pick up some internal spacers to shorten them up. They still offer almost 5" of travel after being shortened though. They are fully rebuildable 46mm inverted monotubes and the standard valving puts the rear at roughly 60% of critical damping. It is a linear valve so I may have to revalve it on my own in the future to add a digressive piston to match up better with the front.



Ground-Control top mounts, Ireland Engineering toe and camber kits and RTA bushings, and AGK subframe bushings finish off the back. Here is where the back sits with the Bilsteins and spring setup on the maximum low setting with the 5" spring. The fronts are still stock in these photos.





Full Droop


I'm running 680/950 lb/in springs Front/Rear so I'm going to try the car out without a front or rear sway bar to see how it goes. This is for auto-x in SM. I was able to do the entire suspension with control arms and bushings for about the cost of the PSS9 coilovers alone.

[spidertri]

Very cool, thanks for posting up. Do the 3000GT bilstein inserts come with the digressive valving? Or is that something you do separately?

[03whitegsr]

They come that way, so I was told by Bilstein anyway. There are dyno charts floating around on them but they only go up to 5in/sec and the knee is supposedly around the same speed.

Contrary to everything I've read, the after market support tech at bilstein also told me that for all out grip, a linear curve is faster. I could see that on a glass smooth road course (which is what the closest road course to me is) but for rough surfaces it seems like a digressive piston would be better based on all the engineering data I've read.

[raamaudio]

Very impressive research and work, to say the least! I have done hundreds of things, can do most, never touched real machining work and always wanted to.

PM sent

[03whitegsr]

Thanks

Unfortunately, the camber plates I picked up have some non-standard caster offset. It's not the '95 M3 offset and it's not the standard centered caster. I picked up the Bimmerworld TrackCAB control arm mounts for the front to add caster and thought the camber plates I have were the correct M3 offset to work with them. Unfortunately, the non-standard offset is not moving the wheel back far enough to work out right. The car is also about 1/2" lower then I was thinking it would be.

Here is full droop in the front


This is about where I expect ride height to be with the spring rate and weight of my car.


As you can see, the tire is sitting too far forward due to the camber plate not having the M3 offset. To correct this and the height issue, I am likely to add a 1/2" spacer between the camber plate and the car body that adds additional caster. The added benefit, when I go lower (roll center and bump steer adjustable uprights are next for this car), I can add a helper spring to a shorter spring and put the strut further into it's travel range at ride height. Right now, I have more compression travel then I can use and trading some compression travel for some droop would likely be a good thing.

Last item I had to address was the wheel clearance. I had to add a 15mm spacer to clear the coil-over spring with the 17x8.5 ET42 wheels. I picked up some RS Technik spacers that seem pretty nice. They are definitely hogged out and light so I hope they don't crack or warp on me.

[raamaudio]

Really pushed forward!

I love a lot of castor and like a longer wheelbase but you have to be able to turn the wheels without the tires rubbing as they would in this case I am sure.

The droop travel is indeed quite short, tender springs will help a great deal there.

Keep up the great work and great posts

Rick

[03whitegsr]

Yeah, I've got a solution I'm working on that will correct the castor and bring the ride height up to where I was orignally planning. After I modify some hubs, I'll go over to a 6" spring and tender to get down to the final ride height. I just don't want the car to be that low until I can correct any roll center and bumpsteer issues.

Here is the finished front strut assembled and ready to be installed.


I had to cut down the rear spring adjusters as well to get some additional travel out of them.




Cutting EBAY tubes to final length

[raamaudio]

Most fun, I need a lathe someday

The height adjusters were really long!

I like the pivoting bottom mounts made my GC for using inboard springs but true coilovers in the rear are the way to go!
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I sold a bunch of parts recently that would of been sweet on your car, tubular front control arms, monoball lollypops, bump steer/roll center correcting and steering quickening setup and CG race sway bar....

I had tubular upper and lower control arms in the rear so no mounts for sway bar, was not going to run one, on the M3 I was building.
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[03whitegsr]

The Ground Control weight jackers won't work on the ti or I would have bought them. I had my own design to work with the E30 trailing arm but the cost to have them machined as a single set was too high. If I wanted to run 10 or so sets I could have gotten the set cost down to a reasonable level. Last I talked to GC, they were working on a kit for the E30 but it sounds like it would require you to cut off the stock spring mounts and weld the kit into the trailing arm. Not really a problem, but they aren't available as far as I know.

The stock shock mounts seem pretty weak on the unibody and trailing arm. If you had a cage tying into the upper shock mounts and beef things up on the trailing arm, I'd agree coil overs make sense. However, you will have more wheel/tire clearance sticking with the separate shock and spring setup and there really isn't any down side to the separate spring setup. A true coil over is a tough sell for me on the ti other then you could then use some hydraulic perches and the spring is no longer being bent. Although, the amount of bending that actually takes place over the limited range of travel that should take place with 950 pound springs probably has very little impact on spring rate and it's probably a very minor issue. If the suspension was more sophisticated, it might be worth worrying about, but this semi-trailing arm suspension is miles from ideal to begin with and some non-linear spring rate issues probably aren't going to make much of a difference.

[raamaudio]

I was just looking over the quote from GC and it does not include their weight jackers, I just assumed it would but I realize now, thanks to you, not included, not made, etc......

I have no problem welding on mounts to the control arm if I had to as it would be great to have the adjustment for corner balancing and height tweaking.

I was going to run coilovers, no cage but would of beefed up the shock upper and lower mounts and made a STB/xbrace, as well, saves a lot of fab time sticking with stock spring locations.

I know the design of the rear is not optimum, by a long ways, but it is also a bit of what makes the car more fun to drive according to my diff builder, he races one, tail likes to come out but very linear and easy to control

I drove highly modified 510 Datsuns for 10+ years which was very similar in design and I loved them, these are the only cars I find as fun

For my dual purpose car, street with 200 lbs of dogs in the back seat and hauling groceries, track car, etc....they recommended 700 lb rear springs. The car will see some inclement weather at times as well, rain, cold, even a bit of snow on occasion is possible so do not want it too stiff.

I will be on Conti Extreme all season tires for street and R comps for track and autocross.

Thanks
Rick

[raamaudio]

I am looking into PSS9's, I do like Bilstiens, ran them on many vehicles and all but one of my trucks as not yet made for the 2012 Duramax dually.

BUT, I have a ton of work to do so not a big rush for suspension. I am not going full time RV this fall as hoped, next spring instead, keep us posted, I am very much interested in your setup

Rick

[03whitegsr]

I get you on there being something more enjoyable about how simple the rear is in these cars. Long term, I'm considering building some custom trailing arms with a new rear subframe to reduce the trailing arm pivot angle to help cut down on some of the camber/toe change with travel. The Grp.B E30s suypposedly ran around 12 degrees where the standard angle is 15 degrees. I'm thinking 10-12 degrees and then add a quick change rear diff into the mix to go with my engine swap plans. I gotta get my EVO back together before any of that though.

As for the PSS9...
http://farnorthracing.com/autocross_secrets18.html

It's worth reading his site in general, but here is what he had to say about the PSS9 adjuster.

"There is only one small problem with Bilsteins: no knobs.

Bilstein does not really make adjustable shocks. They have a rebound adjuster (and they use it on the PSS9 series shocks) but it is really crappy and hard to tune - to the point of worthlessness. It's an on-off switch for the most part. That turns out to not really be a problem for those inclined to tune shocks by revalving, but the average customer wants a knob to fiddle with and so Bilsteins wound up being a hard sell. Those that bought them were universally ecstatic with their performance, but it was tough work getting anyone to buy them when they could buy a shiny quadruple-adjustable from some no-name brand.

And those people were invariably unhappy....

NEW Jan 01 2011 It looks like Bilstein finally decided to release a proper adjustable bleed shaft, as they were being shown at PRI 2010. See this press release for more details. I can't tell from the photos how the mechanism works, but I can tell that the upper seal and piston will fit the "standard" Bilstein tube so there is no reason why this shaft couldn't be used in any standard Bilstein. I can also say that - assuming that it hasn't been smoothed and fudged all to hell by the marketing department - that the dyno plot used as an example is NOT the ****ty PSS9 "cheesewedge" bleed adjuster that has been the only way to get a bleed on a Bilstein to this point."

Their motorsports 10 way shaft is also supposed to be awesome. This would be on the PSS10 though, which isn't available for the 318ti and they are about 3X the price of the PSS coilovers on fitments they do make.

[raamaudio]

VERY much appreciated info buddy

I guess PSS9's are out unless they fixed that issue, no wonder the ones on my 95 M3 where not even adjustable any longer when I bought it, driven in one winder, one broke while trying to turn it, I just pulled them off and sold them cheap and moved on.

I have a very good price quote from GC, holding off until I see how this all goes with what you are doing though

[03whitegsr]

Something that is pretty interesting though is that Bilstein has a Group N strut listed in their new catalog for the M3 that wasn't in their old catalog.

K4-VE3-64175M0 (Right)
K4-VE3-64173M0 (Left)

I might have to see if I can get some more info on these. They look like they might be the PSS struts. If so, then I'm not too disappointed with the way I went as I'll have far more travel at low ride heights. If they are the PSS10 or clubsport struts though, I'm pissed!
http://cart.bilsteinus.com/product/K4-VE3-64175M0#

[M-technik-3]

How did you keep the inserts in the strut housings? Did you weld on E30 Type gland nut threading? Or did these have the bottom type threading like the Koni's do for the e36 M3?