Technical advice for getting Bilsteins revalved

[JGood]

I have a set of GE coilovers (450f/650r). Front struts are shortened 1", using 325ix Bilstein HD's. Rears are normal e30 Bilstein Sports.

The car is way under damped in the front, it's bouncy and feels like I'm just running coil springs with no shocks at all. So I picked up a blown set of 325ix HD's to send to Bilstein to have rebuilt and revalved.

Here is the Bilstein data I have for a 325i Sport Shock and a 325ix HD Shock:

BMW 325I SPORT FRONT
COLL/EXT: 515.0/597.5
REB/COM: 2330/755

BMW 325IX 4WD F
COLL/EXT: 438.5/511.0
REB/COM: 1365/465

Looks like the IX rebound and compression numbers are about half of what the Sports are, which are probably slightly soft for a 450/650 setup. I'm thinking maybe 2500/900 or so? This is just a street car, will never see a track, but I need it to be able to handle some bumps under aggressive driving. The car weight is 2680lbs, probably 53f/47r or so.

Anyone have any thoughts, suggestions, or experience?



Here is the order form for the rebuild:

http://www.bilsteinus.com/uploads/tx_templavoila/Repair_Order_Instruction_Sheet_04-2011.pdf

It sort of leaves it up to the user to specify the rates... are the above listed numbers what they are looking for? From what I understand, those numbers are Newtons of force required at 52 cm/sec. Is that what Bilstein uses to universally measure and valve shocks?

Anyone have a number for a contact at Bilstein that I could discuss all of this with?

[jlevie]

There's a very good chance that Bilstein will have a good idea as to rates if you tell them the car & spring rates. Call them and see.

[nando]

I just gave them my spring rates and they were supposed to match it to that. But they came back STIFF. I'm not sure about specifying the rebound/compression numbers instead - you might end up with something more comfortable that way.

I've got the number for them somewhere, I think you just call the California HQ and ask for Raul, but I can't remember if that's his name exactly.

are you sure about the stock ix valving?

[JGood]

Thanks guys.

Nando, I think it's correct, someone pulled it from a Bilstein PDF doc which is NLA. Can't confirm. It feels right though, at least on low speed compression. I had a set of brand new 325i sports and 325ix HD's in my hands next to each other. The iX insert took no effort at all to compress, the 325i sport took all of my weight, and still slowly compressed. Terrible test, I know.

I just contacted Ground Control though, and they said Koni 8641-1198SPORT will handle the 450lb springs well. And it looks like it will be cheaper to buy then what it will cost to revalve the Bilsteins. I think I'm gonna go that route. Koni is having some crazy sales right now. Normally $182 for that shock, $138 right now, from tirerack.com

[ak-]

Is that Koni part # for the iX inserts?

[JGood]

Nope, Corrado

[ak-]

Nope, Corrado

Yeah nvm Sorry. I researched it.
Anyways, isn't the 8641-1198SPORT the shock GC uses and modifies to pair whatever rates you're choosing?
They are telling you in "stock" form, the 8641-1198SPORT will handle up to 450lbs well?

[JGood]

Yeah nvm Sorry. I researched it.
Anyways, isn't the 8641-1198SPORT the shock GC uses and modifies to pair whatever rates you're choosing?
They are telling you in "stock" form, the 8641-1198SPORT will handle up to 450lbs well?

Yep, that's how I understand it from some additional reading.

And yes, Mark said it would. His words were "handle 450# springs with ease" actually.

[JGood]

Well, now this thread has me confused....

http://www.r3vlimited.com/board/showthread.php?t=90481

[nando]

if you want a shorter insert that will otherwise drop right in the ix Koni SA's will definitely handle 450# springs.

[JGood]

if you want a shorter insert that will otherwise drop right in the ix Koni SA's will definitely handle 450# springs.

Hmm, I didn't really think about that. Why would people use Corrado inserts, including GC using them as a base for their spec stuff, if the iX part fits?

[nando]

dunno. maybe it's cheaper and the Corrado inserts can handle higher rates. I ran mine with 600# springs for a long time though, 450# should be no sweat.

you have to shorten the housings of course but I think that is the point.

dimensionally they are the same other than length, no issues with different gland nut sizes etc. I ended up with some VW konis for a while and I had to change my strut bearings for camber plates because the VW inserts used 21mm nuts instead of 19mm and my socket wouldn't fit. I had to add spacers as they weren't the right diameter or length.

[DRTSRFR]

OY...you guys read too much...;)

The 1198sport does have more droop. The shaft of the the 1198 SPGC was exactly the same, it just had droop limiters added.

The only thing 1198sports and 1198SPGC had in common was the body of the damper and the shaft itself. Sports are made in Kentucky, SPGCs are made in Holland.

The 1198SPGCs were discontinued, and the 1547SPGC was introduced with some refinements, to eliminate confusion between the two.

[Wh33lhop]

I am running G60 Yellows at the moment and they seem to handle my 450# ERS okay, though the compression damping feels a bit soft. I have the rebound cranked to 2/2.5 turns to handle the stiff(ish) springs. The G60 inserts are very short--like 4" shorter than stock inserts--and do not have the same amount of stroke. You are going to need a spacer to put underneath them if you want to run them. My housings are shortened by 1-2" and I have spacers under the inserts. I do not have much droop travel, it's very evident when the car is on a lift. But if you don't have helper springs that can be a good thing.

OTS Yellows will "work fine" for damping a 450# spring, but you may run into some headaches when implementing a frankensteined suspension together. For instance, I found out that when running 225/50r15 R888s, my tires hit the frame seam at the top of the wheel well before the bump stops bottom out. Ah, fun times. :p

[JGood]

Just got off the phone with Bilstein.

325iX HD, part # 34-002513
136/47 comp/reb

325i Sport, part # 34-003350
223/75 comp/reb

He didn't want to give those numbers out, apparently they aren't supposed to, so I didn't bother prying into what the units / scale of the numbers are. But he did say that the iX HD's were considerably softer then the normal Sports, which confirms the info I posted earlier and what they feel like by hand.

(EDIT: Those numbers are the same as the ones I posted earlier, just divided by ten... weird)


I'm now on the hunt for Koni numbers. I want a confirmation that the iX Koni's will be valved about the same as the RWD e30 Koni's, in which case they are the obvious choice for a drop-in solution with shortened housings, and not having to deal with changing camber plate bearings, etc... like with the Corrado shocks.