CAB: Rubber, Urethane or THR?

[MarkH]

I am planning a rebuild of my front suspension, and have a question for everyone. Which CAB do other recommend, Rubber, Urethane or the Treehouse Racing?

I will be replacing the Control Arms, CABs, Sway Bar Bushings, Sway Bar Links, and Tie Rods. I have decided to go with the offset M3 style bushings. I use my 325i mostly as a daily driver.

[nando]

I say stick to M3 offset (rubber or urethane). all the boy racers will tell you THR, but they'll also bitch about the popping noises and in a year or two they'll be bitching about their trashed ball joints too. the difference between the THR solid mounts and urethane M3 offset isn't going to be enough to make you "faster" either..

[MarkH]

That was the direction I was leaning. So the follow on question is rubber or urethane? I have heard a lot of negative comments regarding urethane, from ride harshness, to noise, to reliability. I would be interested in the experiences of others who installed urethane bushings in their cars.

[JRowe]

I've got urethane offset CAB's from www.suspension.com I've run them for a year and half with not problems or complaints. I have no problem recommending them.

[nando]

well I went with rubber since my car sees 90% street duty. but urethane should work well too. just make sure the heat shield for the exhaust on the passenger side is in place (right next to the CAB) or it will fry the bushing.

[Skafrog]

hey nando, just FYI: The popping noise has been taken care of, and I have been running the bushings for more than 2 years without a broken ball joint. The race car has them for 3 years, and no trashed control arm. Customers cars have had them on for 2 years with no trashed ball joints. The list goes on and on. Dont talk out of your ass.

[nando]

you can't deny that they will be harder on the ball joints. those forces have to go somewhere if they aren't going into the bushing..

so what ended up being the problem with the popping noise?

[Digitalwave]

I have been running urethane M3 offset CABs (from www.bmwbushings.com) for a year now and I didn't notice any more noise or harshness. You can feel the difference in stiffness and response coming from torn up stock CABs.

[Jand3rson]

so what ended up being the problem with the popping noise?

The cause of the popping noise was the urethane bushing in the CAB binding up on the paint on the end of the control arm, where the CAB mounted to. The easy fix that no one ever seemed to notice, even though it was posted in several threads about the Treehouse CAB's, was to sand all of the paint off of the mounting area at the end of the arm. The popping noise would then go away. I'm not sure what was changed on the CAB's to eliminate the noise, though.

[nando]

IMO sanding the paint (isn't it powdercoat?) off the control arms is a pretty ghetto solution. :P

[m42technic]

IMO sanding the paint (isn't it powdercoat?) off the control arms is a pretty ghetto solution. :P

My brand new control arms came without paint on the end that the bushing mounts on. I just sanded down the bare metal a bit.

[KenC]

IMO sanding the paint (isn't it powdercoat?) off the control arms is a pretty ghetto solution. :P

My brand new control arms came without paint on the end that the bushing mounts on. I just sanded down the bare metal a bit.

Word. There shouldn't be any paint on that surface in the first place.

[nando]

all the control arms I've seen have a finish on that end, including my two originals and the set I ordered for a 318is. what brand did you guys get?

[m42technic]

all the control arms I've seen have a finish on that end, including my two originals and the set I ordered for a 318is. what brand did you guys get?

OEM BMW

[royalflush313]

to shed a piece of anecdote, I have experience with stock, THR and M3 offset bushings, and from the driving that I do (street driving), I am the happiest with the M3 bushings.

THR were harsh, and even going over painted lines on the streets felt a lil harsh. I also experienced annoying popping noise from the THRs, which after taking it on and off etc faded to pretty much nothing.
No-one seems to know what caused the noise (afaik). I don't think it would be mis-installation, as CAB install is pretty straightforward...

M3 CABs are huge improvement from stock, it gives a nice tight feeling without the harshness.

Just my opinion.