RTAB bushing that won't stay put

#41

[quote=“Ranger” post=59462]Re. Welding the eccentric. I’d do this except I’m worried that I’d check it 10X to make sure it was perfect, tack the eccentric in place, and then my alignment would be a little wrong and I’m be stuck in this quandry of whether or not it was enough wrong to go thru the monumental hassle of removing the rear subframe and redoing it.

Removing the subframe wouldn’t be such a hassle if I cut holes in the bottom of the trunk and put studs into the diff. I don’t remember who’s idea that was, but I like it.[/quote]
That would be the hard way to remove the subframe. It is easier to drop the subframe with the differential still mounted. Remove the rear portion of the exhaust, disconnect the brake and e-brake lines and drive shaft, remove the shocks and sway links, knock the subframe bolts up and out of the bushings, and lower the subframe. However, if the welds are on the rear of the eccentrics, you can get enough room to cut those with a dremel by just lowering the subframe a couple of inches. In which case the exhaust does not need to be removed nor does drive shaft or brakes need to be disconnected. I release the muffler from it’s hangers and let it sit on a jack stand, remove the shocks and sway links, knock the bolts up and lower the subframe.

#42

[quote=“jlevie” post=59465][quote=“Ranger” post=59462]Re. Welding the eccentric. I’d do this except I’m worried that I’d check it 10X to make sure it was perfect, tack the eccentric in place, and then my alignment would be a little wrong and I’m be stuck in this quandry of whether or not it was enough wrong to go thru the monumental hassle of removing the rear subframe and redoing it.

Removing the subframe wouldn’t be such a hassle if I cut holes in the bottom of the trunk and put studs into the diff. I don’t remember who’s idea that was, but I like it.[/quote]
That would be the hard way to remove the subframe. It is easier to drop the subframe with the differential still mounted. Remove the rear portion of the exhaust, disconnect the brake and e-brake lines and drive shaft, remove the shocks and sway links, knock the subframe bolts up and out of the bushings, and lower the subframe. However, if the welds are on the rear of the eccentrics, you can get enough room to cut those with a dremel by just lowering the subframe a couple of inches. In which case the exhaust does not need to be removed nor does drive shaft or brakes need to be disconnected. I release the muffler from it’s hangers and let it sit on a jack stand, remove the shocks and sway links, knock the bolts up and lower the subframe.[/quote]
I agree, that would be the way to do it.

Consider this…I did some testing re. toe and trailing arm deflection. That is to say…does toe change when the suspension is compressed. And the answer, as near as I could tell was somewhere between no change and maybe just ever so slightly toe in.

Because I shoot a laser forward from the wheel to measure toe, I can get it very precise. The laser amplifies toe changes by 6 so even a half of a mm of toe change creates a very visible 3mm of change when I’m measuring. So if there’d been enough toe change to note, I’d a seen it.

My point is this. A person could pull their rear subframe off with diff attached, pull their springs out and replicate approx the right location for trailing arm deflection, and then weld their toe eccentrics while still be able to measure toe. That way they’d know it was right even before they put the subframe back on because if they got the trailing arm deflection a little wrong they’d take comfort in the knowledge that toe doesn’t change with suspension compression.

Obviously this would not work with camber.

#43

My bushings have steel sleaves.

Yes the toe does change but it goes out in out as you move the suspension unlike the camber which goes negative as the arm goes up and pos as it goes down

#44

seems to me welding them into position sort of defeats the purpose of having them adjustable in the first place. the way i see it, you either mostly ignore the variance (or hope they don’t vary too much) and adjust your driving to suit or don’t bother with them at all and keep it stock. i’ve seen at least one car up here in the NE with holes cut in the rear seat deck to allow for easy adjustment.

#45

I believe there are hard brake lines in the way or i would have cut holes in mine

#46

should be able to re-locate them. i’ve not looked into it.

#47

[quote=“turbo329is” post=59473]My bushings have steel sleaves.

Yes the toe does change but it goes out in out as you move the suspension unlike the camber which goes negative as the arm goes up and pos as it goes down[/quote]

I hear you, but my testing shows otherwise.

There’s some guy out there that published some diagrams of trailing arm geometry and alignment changes to due to suspension compression. IIRC correctly he says that the geometry indicates that toe in will occur during compression. The flaw in his analyis tho was that he was talking about suspension angle changes significantly beyond what occurs in a SpecE30.

#48

Would having only one adjuster on the rear trailing arm have a lesser chance of loosening up?

I have the subframe bushings with spacers and can adjust my camber by swapping the spacer thickness.

#49

I never closed the loop and posted specifics on what I did to get the rtab toe adjuster to stay put.

I dreamed up and discarded a bunch of ideas, but ultimately I removed the eccentric, drilled out the threads of a 6mm nut, and welded the nut to the top of the eccentric. Then I fabbed a piece of steel in the logical place on the eccentric’s push plate such that I could run a 5mm bolt thru the 6mm nut on the eccentric and hold it in place.

A charm of this design is that toe remains adjustable. I can loosen or tighten the 5mm bolt so the eccentric can move. The reason I used a 6mm bolt and then drilled out the threads is that the bolt has to be able to handle different angles if I choose to adjust it by tightening or loosening the bolt.

Whereas the toe eccentric used to shift after only a couple laps, it’s now made it thru several events without the setting changing on me. It’s kind of a kludge, but it’s nice to see a solution work for a change.
[attachment=1613]ToeRestrainer.jpg[/attachment]