I was thinking last night about the extra X5M bump stops I bought when I was collecting parts for my recent suspension work. I wound up not using them because the opportunity to use a lift came up quickly and honestly forgot why I bought them. I remembered last night. On the non-M E70 the strut / rear shock isolator foam donuts are compressed by the lower dust cover and the upper washer as you torque the nut on the shock piston. The lower dust cover is made by moulding the plastic dust cover to a washer like the top washer.
The M version front upper strut mount doesn't use the foam isolators and relies on rubber isolation in the upper mount, only. Because of this there are no washers in the assembly, so the X5M uses the secondary shock absorber (bump stop) to hold the dust cover.
If I was to do it over again I would remove the non-M dust cover and replace it with a washer like on the top of the assembly, then use the X5M bump stops with integrated dust cover. I have the X5M bump stop w/covers if anybody wants to buy. Brand new. The X5M bump stops are softer at the tip so they allow more undamped movement before the solid portion kicks in, which will be more abrupt and sporty. The non-M bump stops will be more progressive because they are more uniform. At least this is my take on it.
I would do the above with the poly donut isolators. Somebody should check to see if the poly donut isolators can be adapted to the non-M rear shocks. They need to slide on the aluminum sleeve or at least engage the sleeve properly (with care) when the piston nut is torqued.
The poly donuts with the non-M upper mounts would probably put NVH between the regular E70 and X5M.
When you install the upper mount to the front strut, mind the proper orientation of the rubber mount in the upper mount. You rotate it depending on the side of the car - seems to aid installation. I don't see how a different rotation of the spring around the central axis of the strut would affect anything once installed. Best to follow instructions though.
A lot of parts are interchangeable with some analysis. X5M springs are probably shorter, but would need to check.
The Bilstein B12 kit is pretty attractive if you want a X5M type stance; B12 kit (with correct rear upper mount), poly donuts, B8's have integrated bump stops, then X5M rear bump stops or use the bump stop in the kit. Initially was going to get the B12 but it was on pandemic back-order and I switched to a sport/comfort concept due to that and uncertainty how the air springs would perform at the pressure needed to lower the rear because I do like the air suspension. I bought the rear spring perches just in case I ever need them.
Pics below are the X5M (Forget the date), like 2012. The others are around a 2012 35d. Hope this helps.
