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Chris1981 wrote: ↑Wed Dec 13, 2017 1:32 pm

ionofchios wrote: ↑Wed Dec 13, 2017 11:16 am

ph001 wrote: ↑Wed Dec 13, 2017 11:01 am Does the shock really make a big difference to the ‘hardness’ of the suspension anyway? Obviously it controls compression and rebound dsmping but I would have though the hardness is primarily down to the stiffness of the spring.

I guess the more it damps, the more it stops the spring compressing as fast as it otherwise would, so it will be 'harder'.

When i went from OEM to B8's the ride firmed up significantly... although my OEMs were 90k miles old and completely shot!

I believe you've come to this conclusion yourself already but if you have M Sport you need the B8's, image below is front B6 and OEM M Sport, I made the mistake of ordering B6s as I read they are fine to replace M Sport and cheaper than the B8's while offering the same damping rate... but I didn't feel comfortable fitting something so different and the supplier was kind enough to do a straight swap to the B8s!

IMG_0953.JPG

Good pic!

Right, so now I am going to let you all know how dumb I really am How can it be that the strut designed for lowered springs (the OEM M Sport in the pic) has a longer body than the strut designed for standard sprin (the B6 in the pic)? Wouldn't that mean that the strut does affect ride height? If the flange on the strut the spring sits on is further away from the wheel on the B8/ OEM M Sport strut, doesn't that negate the effect of the shorter springs - so you are lowering the car with the springs, but raising it with the longer strut body, in effect?

Until now, I had been imagining that all struts bodies - B4, B6, B8, OEM M Sport, OEM standard, whatever - were the same length, it is just that some are designed for the shorter piston travel of shorter springs and some not.

Chris1981 wrote: ↑Wed Dec 13, 2017 1:32 pm

ionofchios wrote: ↑Wed Dec 13, 2017 11:16 am

ph001 wrote: ↑Wed Dec 13, 2017 11:01 am Does the shock really make a big difference to the ‘hardness’ of the suspension anyway? Obviously it controls compression and rebound dsmping but I would have though the hardness is primarily down to the stiffness of the spring.

I guess the more it damps, the more it stops the spring compressing as fast as it otherwise would, so it will be 'harder'.

When i went from OEM to B8's the ride firmed up significantly... although my OEMs were 90k miles old and completely shot!

I believe you've come to this conclusion yourself already but if you have M Sport you need the B8's, image below is front B6 and OEM M Sport, I made the mistake of ordering B6s as I read they are fine to replace M Sport and cheaper than the B8's while offering the same damping rate... but I didn't feel comfortable fitting something so different and the supplier was kind enough to do a straight swap to the B8s!

IMG_0953.JPG

Interesting that the B8s firmed up the ride alot over knackered old 90k suspension. Your experience confirms what others have said in previous threads and that they're supposed to be uprate anything from 10 to 30%. It's the main reason I have held off fitting them to mine. I may go down the B4 route instead now.

B4s and Suplex MSport replacement springs here, and the ride is like a different car to the old factory parts. Much easier over bumps, but also much more planted and sure footed than the MSport shocks.

Consider however that replacing old shocks, they're going to be pretty worn out by now if they're factory parts.

ionofchios wrote: ↑Wed Dec 13, 2017 7:02 pm

Chris1981 wrote: ↑Wed Dec 13, 2017 1:32 pm

ionofchios wrote: ↑Wed Dec 13, 2017 11:16 am

I guess the more it damps, the more it stops the spring compressing as fast as it otherwise would, so it will be 'harder'.

When i went from OEM to B8's the ride firmed up significantly... although my OEMs were 90k miles old and completely shot!

I believe you've come to this conclusion yourself already but if you have M Sport you need the B8's, image below is front B6 and OEM M Sport, I made the mistake of ordering B6s as I read they are fine to replace M Sport and cheaper than the B8's while offering the same damping rate... but I didn't feel comfortable fitting something so different and the supplier was kind enough to do a straight swap to the B8s!

IMG_0953.JPG

Good pic!

Right, so now I am going to let you all know how dumb I really am How can it be that the strut designed for lowered springs (the OEM M Sport in the pic) has a longer body than the strut designed for standard sprin (the B6 in the pic)? Wouldn't that mean that the strut does affect ride height? If the flange on the strut the spring sits on is further away from the wheel on the B8/ OEM M Sport strut, doesn't that negate the effect of the shorter springs - so you are lowering the car with the springs, but raising it with the longer strut body, in effect?

Until now, I had been imagining that all struts bodies - B4, B6, B8, OEM M Sport, OEM standard, whatever - were the same length, it is just that some are designed for the shorter piston travel of shorter springs and some not.

Sorry, the photo is a bit deceptive... the tapered part at the bottom of the OEM extrudes below the front Hub and the Bilstein doesn't. That brings the spring pads inline when fitted on vehicle but makes the height difference even greater.

Bilstein OEM

I'm running B4s along with the Suplex equivalents to the M Sport springs. I'm happy.

NickDE wrote: ↑Sun Dec 17, 2017 11:36 pm I'm running B4s along with the Suplex equivalents to the M Sport springs. I'm happy.

Same here. On bumpy british roads, a better choice than B12 kit.

I now have all the bits to rebuild the front suspension on my e86 with M Sport suspension: Bilstein B8s (35-124122, 35-124115) and Suplex springs (06248). The instructions that came with the Bilsteins don't show any rubber spring pads at the top and bottom of the springs (RealOEM parts 8, 11 in the diagram), nor any dust protection collar (RealOEM part 5 in the diagram).

So, do I need these parts? I guess the collar is a good idea, as it might keep some crap out of the bearing in the strut mount, but what about the pads?

RealOEM diagram:
http://www.realoem.com/bmw/enUS/showpar ... Id=31_0648

Bilstein instructions attached.

Pretty sure you re-use the oem spring pads etc. hence the diagram showing them with OE arrows pointing to them. No external bump stop needed on the fronts though as the B8s have internal ones.
Not sure if the same is true for rears.

Edit: effectively against the RealOEM drawing, you re-use 1-2, 4-8 and 11 from what I see. The new struts will have a new locking nut to replace 3 and a dust boot to replace 10, 9 is not needed with B8s.

mjennings23 wrote: ↑Mon Jan 15, 2018 9:50 pmPretty sure you re-use the oem spring pads etc. hence the diagram showing them with OE arrows pointing to them. No external bump stop needed on the fronts though as the B8s have internal ones.
Not sure if the same is true for rears.

Edit: effectively against the RealOEM drawing, you re-use 1-2, 4-8 and 11 from what I see. The new struts will have a new locking nut to replace 3 and a dust boot to replace 10, 9 is not needed with B8s.

Cheers!

The only OE-labled parts in the Bilstein diagram are the top spring plate, the washer and the strut mount - I can't see any lower or upper spring pad.

But, regards re-using the parts you list from RealOEM, I reckon you're probably right.

ionofchios wrote: ↑Tue Jan 16, 2018 7:28 pm

mjennings23 wrote: ↑Mon Jan 15, 2018 9:50 pmPretty sure you re-use the oem spring pads etc. hence the diagram showing them with OE arrows pointing to them. No external bump stop needed on the fronts though as the B8s have internal ones.
Not sure if the same is true for rears.

Edit: effectively against the RealOEM drawing, you re-use 1-2, 4-8 and 11 from what I see. The new struts will have a new locking nut to replace 3 and a dust boot to replace 10, 9 is not needed with B8s.

Cheers!

The only OE-labled parts in the Bilstein diagram are the top spring plate, the washer and the strut mount - I can't see any lower or upper spring pad.

But, regards re-using the parts you list from RealOEM, I reckon you're probably right.

That was the case when I installed my B4 kit, albeit I also used OEM bump stop and dust boot.

Got an email reply from Bilstein, and, yes, you are supposed to re-use spring pads and dust collar, and no bump stop, as was mentioned before. Makes sense.

Anyways, I fitted this lot on the weekend and results are good. It sits a bit higher than it did with old suspension, even after a few drives, but that means it is now level with the back - I think there might have been lowering springs on ont he front originally, since there always used to be more clearance in the rear arches than the front.

Feels good - smoother than before, and has made further reduced twitchy, tram-liny steering issue I have been trying to correct. Old struts were not in good shape. Also replaced the dog-bones with Meyle HD at same time, so maybe that is responsible for improving steering.

Now all I need to do is work out why it pulls left under heavy acceleration. Also gonna try https://z4-forum.com/forum/viewtopic.php?f=3&t=100725 to see if it improves steering further.

Some pics.

You mention pulling left, but I see no mention of having a full alignment done? Will absolutely be needed after new struts, guarantee your camber is going to be out at least.

Get it done at a good alignment place and it transforms the car. I couldn't believe the difference in mine.

mjennings23 wrote: ↑Wed Jan 24, 2018 8:46 pmYou mention pulling left, but I see no mention of having a full alignment done? Will absolutely be needed after new struts, guarantee your camber is going to be out at least.

Get it done at a good alignment place and it transforms the car. I couldn't believe the difference in mine.

Thanks! Yes, am planning to do that. It pulled left before I touched anything, and I think it still does it, but it is hard to tell, since weather is really bad here at the moment (snow and ice). Am also thinking about changing rear struts as well, so might do that first.