right rear is getting bouncy, what are my options?

[Dekdo]

Eventually I want to do Bilstein B8 and BMW performance springs all around, but I am wondering what I can get away with before i do a full suspension refresh.

[gjm120]

Originally Posted by Dekdo

Eventually I want to do Bilstein B6 and BMW performance springs all around, but I am wondering what I can get away with before i do a full suspension refresh.

It depends on how much you want to spend as an interim fix and how long until you do the whole refresh. Also depends if your current springs have no problems such as a break.

Probably least expensive stop gap fix would be Bilstein B4. B6's will work, but they aren't cheap and I think you'd have sub-optimal dampers if and when you installed BMWP springs. General concensus is B8's pair better with the BMWP springs. However, there isn't a clear answer on what Bilsteins are best for BMWP springs. If you don't mind a bit more drop than the BMWP springs, a good setup is the Bilstein B12 kit. See the thread just above for a recent discussion.

[Dekdo]

Originally Posted by gjm120

It depends on how much you want to spend as an interim fix and how long until you do the whole refresh. Also depends if your current springs have no problems such as a break.

Probably least expensive stop gap fix would be Bilstein B4. B6's will work, but they aren't cheap and I think you'd have sub-optimal dampers if and when you installed BMWP springs. General concensus is B8's pair better with the BMWP springs. However, there isn't a clear answer on what Bilsteins are best for BMWP springs. If you don't mind a bit more drop than the BMWP springs, a good setup is the Bilstein B12 kit. See the thread just above for a recent discussion.

Might do the B4 rear shock as a short term fix, maybe til next summer for the full suspension refresh.

I see so maybe I’ll do the B8’s with the BMWP springs then since I don’t want to lower it too much.

[gjm120]

Originally Posted by Dekdo

Might do the B4 rear shock as a short term fix, maybe til next summer for the full suspension refresh.

I see so maybe I’ll do the B8’s with the BMWP springs then since I don’t want to lower it too much.

Just make sure you get the right B4. There is a variant for a 128i standard suspension and a 128i Sport / 135i.

And you may know this - BMW springs, whether sport or Performance, have 3 or 4 'grades' with a certain one being suitable for your car based on model and options (effectively weight).

[Dekdo]

Originally Posted by gjm120

Just make sure you get the right B4. There is a variant for a 128i standard suspension and a 128i Sport / 135i.

And you may know this - BMW springs, whether sport or Performance, have 3 or 4 'grades' with a certain one being suitable for your car based on model and options (effectively weight).

I believe I found the 135i m sport option on FCP. What other things would be needed?
Shock mount lower
Shock mount upper
Shock bump stop

Anything else?

[gjm120]

Originally Posted by Dekdo

I believe I found the 135i m sport option on FCP. What other things would be needed?
Shock mount lower
Shock mount upper
Shock bump stop

Anything else?

- the metal supporting cup
- the rubber sealing grommet.
Neither are expensive and you should be ok to reuse them when you get your BMWP springs.

- the bolts for the lower shock mounting (2 per side and kind of pricey for a torx bolt)

For the upper mounts, Monroe makes a hard rubber product that is inexpensive and a bit of an upgrade from the foam-like OE ones. (I'm assuming you're are NOT on runflats).

I don't know if the B4 has internal bumpstops. If not, you will almost certainly need new bumpstops unless they were replaced recently. They tend to degrade to the point of crumbling.

[Dekdo]

What springs go well with the B4?

[///Makis]

Look into rsfb while you're at it