BMW 135is CONVERTIBLE Suspension Refresh Upgrade

[TridenTBoy]

I saw this thread https://www.1addicts.com/forums/show....php?t=1567496 and this thread https://www.1addicts.com/forums/show....php?t=1203243 and this thread https://www.1addicts.com/forums/show....php?t=1147857

but I noticed all these threads are for the coupe. I'd think the only real difference is shock and springs. Now, my real struggle is when going out and sourcing parts... trying to find the parts for the convertible is hard. Bilstein, Ohlins, Koni, Eibach, etc. all really don't list accurate descriptions for parts out there. There's *no way* the shocks for a 128i and a 135i should be the same on a convertible and yet some manufacturers suggest the same shocks. You look at coupe shocks and they break it down by 128 and 135. They do this for springs too - which to me screams it even more insane.

Originally, I had this idea of redoing my whole suspension setup, getting some kinda wacky square setup, and yadda yadda... but I've given up on that. I just need something that is slightly better than OEM and I'm gonna replace some inserts and whatnot. (rear subframe, transmission, whatever else is recommended)

Any suggestions? It would be nice if there was someone with a 135i convertible that could chime in with what they did and if it works great. I'm looking for stock ride height and all that because I need as much suspension travel as I can get with the roads in the bay.

[tracer bullet]

It might be obvious, but differences are usually due to weight of the car at either corner, and whatever ride characteristics they wanted baked in. It's almost certain parts will physically swap but there's a chance ride height might be a little higher or lower (or stiffer or softer) than whatever was the intended application. Not too surprised the shocks are the same if the spring rates were actually similar.

Not the answer tot he question but maybe something to think about if you are considering parts from another application.

[135ivert]

ST Suspensions lists different part numbers for the coupe and convertible coilovers. I'd assume it's because the rear parts are different. You can reach out to them to see what the differences are.

[friedymeister]

Any update on this?

[Wazowski]

When I finally realized after 10 years (150k miles) my 135 e88 suspension needed help 6 years ago, I went with Koni Yellows (adjustable front). Kept the factory sport springs, and added Whiteline RSFB inserts. That was a great day! Transformed the car, and 45k miles later it is still sweet. It is a DD for spirited driving (modest needs). It also has a Dinan stage 1 tune from around the same time.

[TridenTBoy]

I'll add a small update. Added Koni Yellow Sport + M3 Control Arm. I did do several other things at this time but nothing else suspension related. Mind you, I only had many 100-200 miles on the car of driving before I had to go back to NYC. In terms of feel, I'd say the car feels a lot better. Before, I'd go into turns and the car would jostle around and take a long time to get set into a turn. The most minor of bumps or steering adjustment would upset the car and make it very challenging to control through a turn. Now, I understand what people mean by "on rails" when referring to taking a car through turns. It's incredibly stable, easy to adjust mid-turn, and doesn't get upset by any minor jostles or deviations in the road. It just holds grip. I cannot say whether or not I am *faster* in turns right now. It is far less "lively" and less scary - which does take some of the fun out of it. I'll admit, I'm a bit weird and I like things that can be hard to control or some uncertainty. Now, it is comical how easy it is to drive in these turns. It feels like it requires no skill or fine motor control.

In terms of daily driving and going over the usual bumps and whatnot - I cannot say I notice a huge difference. It is not magically more compliant over roughness in the road and so forth. It's mostly that the car performs better at the limits now and I think 99% of that has to do with worn suspension components that I was replacing. I have left all the components in their softest setting to the best of my knowledge, btw. I might consider putting them in a firmer setting later but I am not sure when.

My alignment:
Camber:
LF: -0.9*
RF: -1.4*
LR: -2.0*
RR: -2.1*

My guess is that the car will add about -0.5* of camber to the LF when I am sitting in the car.

I did the whole Koni Yellow Sport suspension change. These are the parts I used:

Rear shocks (82401236SPORT):
https://www.ecstuning.com/b-koni-par...82401236sport/

Front left (87411484LSPORT):
https://www.ecstuning.com/b-koni-par...7411484lsport/

Front right (87411484RSPORT):
https://www.ecstuning.com/b-koni-par...7411484rsport/

I used the cup kit/coilover kit from ECS as well. https://www.ecstuning.com/b-assemble...1306775098kt1/ I do not recommend it though because it includes parts you don't need and doesn't include that you *do* need.

You will need new bump stops and whatnot.

I got the rear bump stops from FCPEuro (Vaico 33536783101): https://www.fcpeuro.com/products/vai...x1-33536783101

I got the front from FCPEuro as well.
Bump stop (31336783090): https://www.fcpeuro.com/products/bmw...nt-31336783090
Dust sleeve (31331094749): https://www.fcpeuro.com/products/bmw...nt-31331094749

At this same time, I did the M3 front control arms upgrade. You will need several new bolts to do this. I'd google those but the main parts I used are:

TRW JTC1424
TRW JTC1423
TRW JTC1426
TRW JTC1427
37142283867
https://www.ecstuning.com/b-trw-part...102283575~trw/
https://www.ecstuning.com/b-trw-part...102283576~trw/
https://www.ecstuning.com/b-trw-part...102283577~trw/
https://www.ecstuning.com/b-trw-part...102283578~trw/
https://www.ecstuning.com/b-genuine-...d/37142283867/

I'd shop around for all these parts. Sometimes Amazon has them for cheaper. Sometimes FCPEuro. Sometimes some random website.