Bilstein shocks- weird differences

[genphreak]

I'm still trying to fix this damned bent rear Bilstein Sport off a 540i, so I took it to the nearest qualified Doc- the Australian Bilstein distributor. They rebuild and make custom race suspensions too so can replace the tube of my old shock. However they'd charge more than a new one to do it so there's not much point... they also said "there's more than 300lb of pressure behind the tube" should I go opening it up... so I guess my ideas about changing the casing over with a good one (I'm still trying to find one) are all but gone.

In the meanwhil though, I noticed interestingly, (pics courtesy of BavAuto's website) that Bilstien's B46-1247 (the version for 525/535/530) has three diffrenent height settings for the spring (see the pic below) whereas the 540 one (B46-1486) has only one position (pictured below that)

They say these (sport) shocks are only for lowered springs, so (I'm guessing here) perhaps each model (535/530/535) uses a different position on a 1247 tube- for all I know there may also be a specific bump-stop kit to allow for different spring positions. This would suggest there are different springs for each car model (and there are already about 8 different rear spring part numbers listed in the ETK for the 535 alone)...

Anyone know about differences with the 540 shock? Anyone care to suggest why it is different to a 525/530/535 shock? I'm trying to work out whether I should buy a new pair of 540 ones or the 535 type... I have the M-technic springs from the 540 and am thinking of using them instead of my older 535 springs (again) when it all comes out (soon). At present I'm tempted to buy 540 type shocks in order to stick with the correct rated shock for the new springs.

Any opinions out there would be appreciated before I go forking out for a new pair... (if only those Sashs Sports were available for the rear!)

[jjw]

The 540i is heavier then 535i by about 400 pounds. I would not put anything from 540 to other e34. Anything from 540 will raise the car and the springs will feel really soft, different weight ratings. As far as shocks go, they will never match the springs exactly, but different ride height is interesting, wish they have that option for the 540i.

[genphreak]

The 540i is heavier then 535i by about 400 pounds. I would not put anything from 540 to other e34. Anything from 540 will raise the car and the springs will feel really soft, different weight ratings. As far as shocks go, they will never match the springs exactly, but different ride height is interesting, wish they have that option for the 540i.

Indeed. I wasn't aware of a major weight difference.

I was thinking the alloy V8 - Steel L6 motor would have made up for it, however as I have now found out the motors weigh a similar amount but the driveline is a lot heavier. Crumbs.

Am thinking these 540 shocks and springs are gonna be hard as nails on my 535... but you say it will raise the car and make it soft. I get the raise side, (although this will countered by these sports springs which should still lower the car a little (but I don't care, I find the height keeps me out of trouble on country roads) but I would have thought it'd be harsher ride as the springs and shocks are beefier... am I wrong on this? Maybe it will mostly cancel out.. then again, maybe it'll ride an inch too high and the shocks won't dampen properly...

[emw525E34]

Bilsteins has INTERNAL bumpstops so you don't need any external ones. You can always weld a higher perch for the lower spring support just to compensate for the lowering if you desire less lowering or zero lowering at all.

If your springs are the 540 ones, it should be ok. I think the rebound rate for Bilstein sports are 20% faster than stock, you you do get a thump over a decent sized speed bump. This is the only negative thing about Bilstein I disklike. On normal roads they are superb!.

[jjw]

Only the front has internal bumpstop. Rear is the same as other shocks. From past experience, I had put 540i spring and shocks into a 525i, the whole car is higher and ride was very soft. I would think it is about the springs not in the proper load range, wrong spring rate, at all times and initial input is to get to the right load range, softer, and then it will respond like it suppost to.

[genphreak]

Only the front has internal bumpstops. Rear is the same as other shocks. From past experience, I had put 540i spring and shocks into a 525i, the whole car is higher and ride was very soft. I would think it is about the springs not in the proper load range, wrong spring rate, at all times and initial input is to get to the right load range, softer, and then it will respond like it suppost to.

Thanks JJW, it makes sense. Im going to put them on and see. Thing is I have M-tech springs and sways so I think they will want to sit lower, though due to the weight it may cancel out.

It might be interesting- it looks like accordingly I can expect the ride on-road to be 'gooeyer' than my stock setup, but through corners it should stiffen considerably. The sways will have to make a big improvement in this department.

Hopefully the extra weight of the 535 (over your 525) will give keep things in check. Still 400lbs is a heck of a lot- I never imagiend so much difference would exist.

Does anyone know where the exact weight specs of the e34 525/35/40 out of interest? Nick

[jjw]

Only way to find out is put it on and see. It is hard to get the exact weight of the cars. My 540i spec is about 3880 pounds and touring is 3800 pounds. But when weighted, 540 came out at about 4150 pounds and touring about 4000 pounds, I would guess 535 will be around 3800 weighted and spec. about 3400 to 3600? 525i is little lighter, not much. Heaviest have to be the 540i and the M5. Or the 540i touring. Good luck on the project, hope it come out good.

[genphreak]

Hey JJW, thanks. From the best I can work out, the tranny and brakes are heavier- front shocks but not much else. The engine and bay componentry might have some more weight, but I can't imagine much-

My figures so far are;

m30/m60 Engine- about the same (maybe 20lb more)
bay componentry- plus say 20lb (guessing)
body- plus 20lb (electric seats)
tranny- plus say 100lb (comparing autos, a guess)

Brakes and front shocks- plus 50lb (bigger shafts, calipers and rotors)*

* All unsprung weight.

That only makes 150lb sprung and 50lb unsprung difference. Perhaps there is more I'm not thinking about... still we'll see soon enough- I'll post some pics when done