M Roadster Suspension Swap (front and rear subframes, brakes, etc) questions
 

Hey all, I'm mostly a lurker on these boards but I wanted to tap into the expertise here so I'm prepped for my suspension upgrade. I bought a salvage titled M Roadster almost entirely to snag the rear dropout out of the car. Here's where my questions come in.



Rear Suspension
Bushings
What bushings are recommended for a mostly street and occasional HPDE car? I've read that using poly or urethane subframe bushings coupled with OEM rubber trailing arm/diff bushings are the best compromise, but I'd like to hear some opinions. I want the car to be planted but not overly harsh and I don't want to deal with squeaking.

Parking Brake Cables
I read that the coupe/roadster parking brake cables are too short. Do the 318ti's brake cables connect directly to the parking brake assembly?

Offsets
I've read on r3vlimited that, from hub to hub, the M Roadster rear suspension is 18 mm thinner on each side. Is this true? Would you be able to run a lower offset tire with the M Roadster suspension compared to the 318ti?





Front Suspension
Subframe
Does the M3 front subframe and motor mounts fit the M44? I wanted to refresh the control arms and motor mounts before going through with my swap.

Z3 Steering Rack
Swap the high and low pressure lines and go? Or is there more to this?


I know there are a lot of questions here but I appreciate the help! The resources here already answered a ton of my questions.

Roadster parts on a ti
 

I will share what I did on my swap.
I have an M roadster rear subframe on my 96ti. I opted for the stock bushings because I wanted a planted but not an overly harsh ride. The M bushings are pretty stiff already. Urethane subframe bushings will transfer the diff noise more than anything. I did use a urethane diff mount. I do get some of that noise through, but it's not so bad.
I used the ti parking brake cables. The roadster cables were too short.
I am running stock E36 M3 wheels. 8.5 X 17 with 41 offset. Perfect fit. I used the same wheels on the same car before the swap. I did not measure but I also do not recall any difference either. I should have taken pictures "before."

I can't help you with the front. I swapped the S52 with the M3 subframe so I don't know about the M44. My question would be: Why? Swap it when you swap the motor.

Best of luck.

I wanted to swap the subframe when I do the suspension refresh. The car needs control arms/bushings and rotors anyway, so I wanted to bang this all out at once. My plan is to upgrade the full suspension first and get my impressions of it, then do the motor swap a few months later.

Not a good idea
 

If you are swapping a six, you will need the six suspension. If you use M3 suspension components with an M44, you will not get a fair assessment of how it will feel with a 6 because of the weight difference.

Weight difference won't matter for right now. I have Bilstein PSS9s right now for the 318ti. I'm not talking about corner balancing the car with the M44 in it, just swapping over a larger braking system and the stronger subframes. I wanted to test the bushing setup for a bit to make sure I like it for the street and HPDEs and then I can do any final tweaks when the car is being swapped.

Regardless, I'm sure this has been done before when people want to keep their cars in a certain track class that are Power/weight or original-engine restricted.

Bump, anyone?

I had full urethane bushings in my last E30, FCABs, and everything in the rear including the diff and it had a bit more vibration but honestly not that bad. It was a DD and was at an HPDE at least once a month all over the southeast. I put about 20k miles a year on that setup and even cruising on the highway was fine. I did notice a bit more buzz at certain speeds from the diff but I had a nice radio and with it even at normal levels I couldn't hear anything. I thought it would be much worse than it really was with everything urethane.

What bushings did you use? I'm most concerned about the polyurethane RTABs...I heard without proper lubrication or self-lubricating bushings they can get very annoying.