RTAB bushing that won't stay put

#1

One of my 4 rtabs won’t stay put. The reason I installed the weld-on kit was because my eccentric rtabs weren’t staying put so it’s a little frustrating that the same problem is still kicking my ass. I think that the cause of the problem is that rtab bushing isn’t rotating freely around the aluminum shaft inside of it. My choices to fix this were 1) remove a little material from the outside dia. of those aluminum shafts and maybe put some grease in there too, or 2) figure out how to help hold the rtab eccentric in place. I figured that if I could hold the eccentric in place for an event or two, the action of rtab bushing rotating about the aluminum shaft would abrade a little material off of the inside of the rtab and that would make the rtab bushing more willing to rotate around the aluminum shaft.

The problem with idea 1) is that it would require that I drop the subframe and I was hoping to avoid that.

So I spent some time imagineering idea 2)…how might I lock that eccentric in place. One idea was to just tack weld the eccentric to one of the rtab ears. I figure that would work, but it’d be a real problem when the day came that I wanted to change it. I’d be right back to dropping the subframe in order to get in there and grind out the weld.

The perfect solution, so my imagineering went, was to come up with an “adjuster”, that would allow me to move the eccentric a bit, yet hold it in place. After working thru some ideas, that’s what I did. It uses a 5mm bolt that is fastened to both eccentric and rtab ear.

In the pic of the toe adjuster, everything in red is the mod and the black vertical lines are part of the weld-on kit. For those that have not played with the weld-on rtab kit, the big circle is the eccentric and the small circle is the bolt that goes thru the rtab. Turn the bolt and the eccentric turns. The eccentric shoves against one of the black vertical plates and that pushes the bolt forwards or back. The camber adjuster is the same except it’s diagram would show black horizontal plates.

[attachment=1562]RTABEccentricFastener_2011-07-14-2.jpg[/attachment]

The mod consists of 3 pieces, the 5mm bolt and nut, the 6mm nut welded to the eccentric, and the little piece of steel shown as the vertical red line.

I can move the eccentric by tightening or loosening the 5mm bolt. It doesn’t give me a helova lot of range of motion, but I don’t need a lot because the eccentric is already in the right place. A 6mm nut, with it’s threads drilled out, is welded to the eccentric and the bolt goes thru it with room to spare. That’s necessary because any tightening or loosening of the bolt is going to change the angle that it goes thru the 6mm nut so there needs to be room to accomodate that.

Hopefully this will hold the eccentric in place long enough for the rtab bushing to “work itself in” and acquire enough looseness to rotate freely on the aluminum shaft. If it doesn’t work, I’ll have to remove the subframe and weld the goddamned toe eccentric in place.

Final notes:

1)If you put on the weld-on kit, take care that the rtab bushings are able to rotate freely on the subframe before you install the subframe. I had problems with my bushings from the get-go because I had to drill out the aluminum shafts because my bolts were a little too big. Drilling them out with a hand drill created some problems that aren’t worth going into.

  1. Toe does not seem to change on our car with suspension movement, therefore you can assemble your trailing arms to your rear subframe and set your toe with the whole assembly sitting on your garage floor. I did some experiments a couple months ago and no matter what the trailing arm angle was, I couldn’t find a change in toe large enough that I was sure it wasn’t just measurement noise. So with your subframe and trailing arms assembled on the floor of your garage, I would attempt to put the trailing arms at the right angle, and then go ahead and set your toe while it’s still nice and easy to get to your adjusters.
#2

We really need spherical bushings.

Every 1-2 races, OPM adjusts the rear alignment on my car. Then they drop the subframe enough to really crank the bolts down tight, then reinstall.

What a pain.

#3

[quote=“Steve D” post=58382]We really need spherical bushings.

Every 1-2 races, OPM adjusts the rear alignment on my car. Then they drop the subframe enough to really crank the bolts down tight, then reinstall.

What a pain.[/quote]
Holy shit, what a nightmare.

Well, if we were clever about it we might be able to swing a rule change for spherical rtab bushings. Here’s how it might be done…

  1. We have to make it easy to do. So we put together a clearly identified package of stuff, and be prepared to write up guidance on how to do it. Potentially we also constrain folks to use that specific package in order to maintain control of the idea vs. having to fight over every “what if” interpretations that malcontents like that DeVinney guy can come up with.

  2. We carefully coach the idea as a reliability and $$ saver issue vs. a performance issue. It would seem to me that there’s a helova lot of merit in everyone being able to trust their alignment settings and a set and forget system ought to be a nice cost savings over the status quo where we’re forced to dick around endlessly with crappy alternatives.

We would have to keep control of the issue. The folks that start dreaming up performance advantages will kill an idea awful quick. They seem slow to understand that the word “performance” puts a bullet into any rule change idea.

  1. We need to talk to smart people about this. There’s sure to be different ways to do it, different kinds of spherical bearings one could use, and possible problems that need to be avoided. I don’t know enough about the idea of spherical rtab bushings to know what we might be getting into. There’s been some posts at Bf.c on the issue over the years, I’ll go look them up.
#4

[quote=“Steve D” post=58382]We really need spherical bushings.

Every 1-2 races, OPM adjusts the rear alignment on my car. Then they drop the subframe enough to really crank the bolts down tight, then reinstall.

What a pain.[/quote]

you gotta be jonesing me. my subframe has never been removed since i’ve owned the car, as my alignment numbers can attest. you mentioned that you’ve taken enough ribbing about your motor this year so i’m gonna lay off that for a while and instead mock your suspension and prep for a little while just to break up the monotony.

#5

[quote=“jtower” post=58390][quote=“Steve D” post=58382]We really need spherical bushings.

Every 1-2 races, OPM adjusts the rear alignment on my car. Then they drop the subframe enough to really crank the bolts down tight, then reinstall.

What a pain.[/quote]

you gotta be jonesing me.[/quote]Nope. And every time I turn around they are having to top off my blinker fluid. Is it legal to attach a catch can? I’m going broke over here.

#6

it’s gonna take more than a little blinker fluid to make me believe that statement. it’s not like you have to replace your muffler bearings every weekend like i do.

#7

Steve and Scott aren’t the only ones having problems with the weld-in kits not holding their alignment settings. I’ve had the same problem. And this past weekend I had the left toe adjuster bolt strip. On my car at least the torque required to have the alignment hold through a weekend is perilously close to what will strip the threads on a Grade 8 eccentric bolt.

At the same event, Adam Nitti’s E30 GTS-2 car had a toe adjuster nut loosen or strip, we don’t know which, and the bolt came out.

#8

What aluminum shaft? What are your bushings made of? Who makes the weld on kit you have.

I suspect that you bought an inferior product because you were blinded by your unreasonable hatred for Ireland Engineering.

#9

[quote=“turbo329is” post=58397]What aluminum shaft? What are your bushings made of? Who makes the weld on kit you have.

I suspect that you bought an inferior product because you were blinded by your unreasonable hatred for Ireland Engineering.[/quote]
The bushings came from AKG. They’re some kind of hard plastic looking stuff.

I hate IE? In the couple of times over the last several years that I’ve called IE they’ve been very helpful.

#10

that’s hard to believe, i thought you were a microsoft fanboy

#11

I love Internet Explorer, but he is probably talking about me. I made the statement I won’t buy an IE product.

#12

I know I’ve made this statement before but I really do wish this rule change would have never been allowed!! Look at all the headaches it has caused. I’m certainly happy that I haven’t gone this route with my rear suspension. I’ve been running kmac eccentric rtabs since I built my car. I really have not had a problem with them slipping at all. Of course I don’t get an alignment after every race but my handling has never suffered!! 3 years ago the rule of thumb around here was risk the eccentric rtabs or run normal rtabs. I don’t think this new weld on camber/toe kit has made the racing any more exciting!!

I’m not afraid to drop the rear subframe to do work on my car, I actually think working on the rear suspension is just as easy or easier than the front, but If I do need to pull the rear apart I’m with Steve Spherical bushings!! If that doesn’t happen I’ll stick with what I’ve got. At the end of the race your driving puts you on the top step of the podium, not your alignment numbers or freshly built engine. That is why we love this class so much!!

K.I.S.S.

Greg

#13

Ranger

Are your weld on tabs bent or machined? While bending the tabs is much less expensive (and thus cheaper to the customer) bent metal brackets simply do not offer the tighter tolerances that machined brackets can.

An interesting history lesson. Jeff/Jeremy @ IE used to do a lot of performance service work back in the day and used the Dinan rear weld in kits (bent brackets) but they had some brackets that were too tight (bolt wouldn’t fit!) others too loose, that is why they started with the machined brackets, to keep the consistency and tolerances acceptable.

#14

I started threads at both Bf.c and e30tech.

http://forums.bimmerforums.com/forum/showthread.php?t=1683367

http://www.e30tech.com/forum/showthread.php?p=1230209#post1230209

MassiveLee@e30tech says that when our rear spring binds up because it runs out of travel, which it certainly does, significant force is placed on the rtabs. The force is significant enough to break spherical rtabs and move eccentrics. He feels that this is the root of the problem we have keeping an alignment.

That’s an interesting theory because it means that a bit of compliance in the rtab bushings could be a good thing. What if softer rtab bushings allowed enough flex that when the spring bottomed out the eccentric was less likely to change. I’d just as soon toe didn’t change when the wheel was under a load so high that the spring bottomed out, but maybe putting a hard bushing at the toe pivot and a softer bushing at the camber pivot would work.

Lee’s recommendation is rear coil-overs, but that will never fly.

It seems to me that, between coaxial bushings, eccentric bushings, the weld-on kit, and playing with different hardnesses for bushings, we have a lot of ways to do this. But if the theory re. our springs binding is correct, then none of the ideas are all that terrific.

Anyone know why our rear springs are such that most of the coils are bound with the car just sitting still?

My rtabs ears are bent, not machined.

#15

[quote=“Ranger” post=58399][quote=“turbo329is” post=58397]
I suspect that you bought an inferior product because you were blinded by your unreasonable hatred for Ireland Engineering.[/quote]
I hate IE?[/quote]
In the several times over the past couple yrs that I’ve called IE, they’ve been very helpful.

#16

[quote=“Ranger” post=58408]MassiveLee@e30tech says that when our rear spring binds up because it runs out of travel, which it certainly does, significant force is placed on the rtabs. The force is significant enough to break spherical rtabs and move eccentrics.[/quote]Does the rear spring compress fully before we hit bump stops?

I find it hard to believe that this bottoming puts any more stress on RTABs than forces experienced under braking and cornering. The RTAB, being on the long end of a lever, has a lot of leverage against the wheel (the short end of the lever).

Show me some broken sphericals and I’ll become a believer.

I wish Elephant Racing could fab something for us like they have for the old 911 trailing arms, but those are a single bushing on each arm. Dunno if our twin-bushing setup still works with their kind of solution.

#17

[quote=“87isMan” post=58403]At the end of the race your driving puts you on the top step of the podium, not your alignment numbers…[/quote]True, but when one side of your trailing arm goes completely floppy, the resulting “dynamic camber and toe” can be quite an adventure to drive around.

Walsh DNS’d at Road Atlanta when that happened to him. I had a race last year where I lost an eccentric nut (not to be confused with Ranger, our resident eccentric nut) and had to really fight the last three laps not to go backwards too fast.

#18

Ireland is apparently coming out with a new design for the weld on kit soon. I’ll have to see it before I really understand how it works, but apparently it should keep the rtab pivot point in place without depending on only the clamping force of the rtab bolt.

#19

Hey guys. I posted some info in Rangers thread over on Bimmerforums. I have been all over this issue for about a year. The problem can easily be resolved by allowing two of the four bushings to be “Free”. Spherical bearings in place of two of the bushings will fix this problem. Keep your adjusters, nothing will change except for the fact that your bushings will not be binding anymore.

I have no dog in this fight, I don’t own/race se30, I don’t supply parts for se30, but I do work on them, I would be VERY thankful for someone submitting a rule change for this.

Regards, Nate.

#20

Perhaps aluminum subframe bushings do not provide enough give. I use the purple street polyurethane subframe bushings and rarely have a problem with my alignment changing in the rear even after offroad excursions.