Rear suspension

#1

I know this issue has been covered before, but I still have a few outstanding questions. I have a 1989 325i with Spec E30 suspension except for Treehouse Racing Control Arm Bushings. I installed AKG subframe bushings a few years ago. The RTAB are the originals…can’t really see them well enough to tell the condition. I had the car aligned a few years ago and everything looked normal in the rear, but the car has always been a little twitchy and tends to oversteer.

I recently put the car on an alignment rack and the rear suspension is different between the left and right sides and I have too much toe on one side. Unfortunately, I don’t have the alignment printout with the specs. I know that the stock rear suspension isn’t adjustable, so how do I know if the problem is from worn out bushings or a bent trailing arm. The car hasn’t been in any accidents, but has been in a few minor off track excursions since the fist alignment. I’d like to fix the problem and am thinking about having the RTAB’s replaced, but don’t want to do this twice if it turns out that the trailing arms are out of spec.

How do I tell if the Trailing Arms are bent?
If they are bent, can they be straightened or do I need to replace them?
Does the Subframe need to come out to install RTAB’s?
About how long will it take and how much should I expect to pay?
Should I get adjustable bushings?
What do people recommend getting?

Thanks. I know I’m asking a lot.

#2

If the alignment error is gross, a trailing arm is bent. If the error is small it could be a bent trailing arm, or simply bad RTABS. Gross problems with the trailing arms are usually evident from inspection, but for small errors all you can do is to replace the bushings and see if that fixes the alignment problems.

The subframe need not be removed to replace the RTABS. You could use eccentric bushings, but those are a pain to adjust and tend to drift out of alignment. The weld-in adjusters are a better solution, but installing then requires removal of the subframe.

#3

Thanks. I don’t think the alignment is that bad, but I’m a newbie, so it could be the trailing arm or just the bushing. Guess I’ll have to just try the bushings to see if that fixes the problem.

I’m leaning towards the weld in, but was afraid that would involve dropping the subframe…seems labor intensive and expensive if you have it done.

Any idea on how much time it should take and/or the cost? Any recommendations on which weld in kit to get? Thanks.

#4

ireland kit but yes it involves dropping rear sub-frame. could be a $500 minimum job at an independent or more depending where you live. You could try and DIY it. Not hard, just painful :slight_smile:

#5

kishg wrote:

Rackeu (Al K) just did this. It was one of the first major DIY jobs he’s done. Send him an email and ask for links to some of the articles he downloaded for guidance.

#6

Ranger wrote:

[quote]kishg wrote:

Rackeu (Al K) just did this. It was one of the first major DIY jobs he’s done. Send him an email and ask for links to some of the articles he downloaded for guidance.[/quote]

Thanks. I’ll contact him, but I suspect this project will be more than I can tackle…I don’t have a garage and don’t know how to weld. Just want to confirm that I should get both the Ireland Adjustable Camber Kit (part #e30adjsf) and the Ireland Adjustable Toe Kit (Part #02adjrt)? Do I just get the stock bushings or should I go with something else?

BTW, I live in Northern Virginia, so labor is expensive.

#7

You wouldn’t be doing the welding, you’d be taking it to someone for that part. Find someone that has done this before. There’s a number of shops up there that have race prepped E30’s. Ask the Mid-Atl guys for some recommendations.

Re. bushings. There’s some dispute about this. Some folks say that the compliance of OEM bushings is needed when you weld in solid toe/camber adjusters. Others disagree. Chuck Baader is doing a subframe for me and I’m just going to go with his recommendation on bushings.

#8

When I did mine I tried Powerflex RTABS, but felt a lot of resistance when I had the rear suspension aligned the way I wanted it. I switched to OE RTABS and the resistance from the misalignment of the bushings was better. There isn’t all that much difference in the stiffness of urethane vs OE bushings so I doubt that it makes much difference which you use.

#9

I am tackling the weld-in kit my self right now actually.

Car had eccentric bushings and always has too much toe-out for my liking making it twitchy and killing my rear tires. Was never able to get enough adjustment out them to corrrect it.

I dropped the sub-frame with wheels and all still attached, pretty easy. Mine simply fell out with gravity’s help.

I removed the eccentric bushings and went with OEM bushings mostly because they are cheaper.

I’m going to do the grinding on the stock mounts this week and check the alignment my self before I get it all welded up. I have a freind who welds so this install is pretty much free. I can’t see anyone charging you alot to weld the tabs if you simply take the sub frame to them.

Not a hard DIY, just give yourself pleny of time to complete it and use some good jack stands and get the car as high as you can.

#10

I’ll probably go to Piper Motorsports for the welding. I’ve had them do some welding for me the past. Work is fantastic and they’re very easy to work with. Not sure if I’ll be able to DIY this one. I live in a townhouse without a garage, so even if it isn’t hard, it looks very time consuming…I probably won’t want to have the car disassembled in my parents driveway for that long.

#11

jlevie wrote:

[quote]If the alignment error is gross, a trailing arm is bent. If the error is small it could be a bent trailing arm, or simply bad RTABS. Gross problems with the trailing arms are usually evident from inspection, but for small errors all you can do is to replace the bushings and see if that fixes the alignment problems.

The subframe need not be removed to replace the RTABS. You could use eccentric bushings, but those are a pain to adjust and tend to drift out of alignment. The weld-in adjusters are a better solution, but installing then requires removal of the subframe.[/quote]

I just found the alignment printout. Based on the below numbers, does it look like anything is bent in the rear? Will a weld in camber/toe kit solve the problem in the rear or are the numbers too far off? Any other recommendations? Thanks.

Front

Caster
Left 11.0
Right 11.3

Camber
Left -2.0
Right -2.2

Toe
Left 0.05
Right 0.05

Rear

Camber
Left -3.4
Right -2.7

Toe
Left 0.45
Right 0.0

Thrust Angle 0.2

#12

I finally got my rear end dropped and am doing the welding myself. How exactly are slotted pieces located in relation to the original holes. Pics please.

#13

swooper wrote:

That error could be from bad RTAB’s or it could be from a slightly bent trailing are. But I think the error is within range of what weld-in adjusters can handle.

#14

turbo329is wrote:

Center the slots on the original holes with the outer slots horizontal for toe adjustment and the inner slots vertical for camber adjustment. After welding in the tabs, use a die grinder to open up the OE holes to match the slots.

#15

jlevie wrote:

[quote]swooper wrote:

That error could be from bad RTAB’s or it could be from a slightly bent trailing are. But I think the error is within range of what weld-in adjusters can handle.[/quote]

Thanks. I guess I’ll install the adjusters and see if I’m able to fix it.

#16

Swooper, re. Rear Toe alignment specs. That’s 0.05 inches? If so, that’s close enough to zero that it’s in the noise zone. If you were 1/4" toe at one rear wheel and -1/4" in the other, that’d be a problem.

I don’t see a problem in your rear alignment that justifies much bother.

#17

Ranger wrote:

[quote]Swooper, re. Rear Toe alignment specs. That’s 0.05 inches? If so, that’s close enough to zero that it’s in the noise zone. If you were 1/4" toe at one rear wheel and -1/4" in the other, that’d be a problem.

I don’t see a problem in your rear alignment that justifies much bother.[/quote]

Ranger

Sorry, I should have been more clear, but wasn’t sure how to add the degree symbol on my mac. Left rear toe is .45 degrees and right rear toe is 0.

#18

Dropped the car off tonight for the adjusters, wheel bearings, and alignment. I know that it will vary from driver to driver, but does anyone have any recommendations for alignment specs. I know this has been covered numerous times, but I’m a newbie and I haven’t seen a lot of recommendations on the rear since the rule change allowing rear weld-in kits. FYI, the car is a little tail happy if that matters.

#19

I like the fronts at 3.5deg camber and zero toe and the rears at 2.5deg camber and 1/16" total toe.

#20

jlevie wrote:

Thanks. I’ve seen others recommend these specs. That’s what I’ll ask for.