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Old 08-01-2012, 05:48 AM
dkindig dkindig is offline
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Location: Murphy, NC
 
Join Date: Nov 2009
Posts: 313
Mein Auto: '01 Z3 3.0i Roadster
Quote:
Originally Posted by BStanton View Post
I have a 1998 Z3 2.8 that is experiencing tramlining and at times pretty serious. Sometimes it feels like there is a huge magnet pulling the car. I took the Z in to be checked out and it was determined that rear subframe mounts are worn out as well as the front bushings. Both of which I will have fixed. The place that will do the work recommends that I consider an adjustable rear trailing arm.

Any thoughts on having an adjustable rear trailing arm?

Thanks in advance.
Bushings are a common wear point on these cars and will definitely help with getting rid of some of the tramlining. As pointed out, these cars are sensitive to tire choices and often a lot of the tendency to tramline will be dependent on that.

I'm not sure how you feel about NVH (noise, vibration, harshness), but there are a few choices along the continuum for bushings. You can go with stock or you can make incremental upgrades.

Polyurethane bushings will give you the most precise handling and performance but the trade-off is increased NVH and having to pull them apart once a year or so and grease them again so they don't squeak and creak.

OEM bushings are the most comfortable and lowest maintenance but also have the most "give", so your handling won't be as precise as with poly.

An alternative OEM bushing for the front control-arm-bushings (FCAB's) is to go with the M bushings. These are rubber but are solid instead of having the gaps in the rubber like the non-M bushings and they have less give. That's what I used for my FCAB's.

For the rear subframe bushings, poly is definitely the way to go. You can get those in several different hardness ratings with the softer ones (approx. 80A durometer rating) being appropriate for the street. Ireland Engineering green or Powerflex purple are two of the most common choices for those. These bushings aren't in a rotating assembly so the issue of squeaking and creaking isn't a consideration in this application.

The general train of thought on the rear suspension bushings is poly for the subframe bushings, OEM rubber for the trailing arm bushings and the standard non-M differential bushing for the diff housing. This locates the suspension solidly yet allows for some give where the diff attaches to the body. The logic for this is that it reduces the potential for placing stress on the trunk floor and popping spot welds back there.

I would definitely go with the adjuster tabs (Ireland Engineering weld-in tabs) on the trailing arms. It's not that much more labor, especially when you already have the rear suspension apart for other things. You will be able to dial in the camber and toe-in on the rear tires to fit your driving style and it will save you money on tires and mounting. I generally have my rear tires dismounted and swap sides about halfway through their service life because of the excessive wear on the inner edges due to the aggressive camber, just to get the most wear out of them.

The other advantage to having adjustments in the rear is if you ever go with an aftermarket suspension that lowers the car, you can use the adjustments to compensate for the increased camber and get your camber and toe-in back to specs.

Just my $0.02. Hope this helps...

Last edited by dkindig; 08-01-2012 at 05:52 AM.
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