ER Polybronze Spring Plate Bushing Help

[NickW21]

Hi folks,

I probably did a dumb thing by going for the polybronze bushings for my mediocre quality 79 911 Targa, but I did it thinking, that I might get into tracking it at some point and it would be a nice feature to have. In any case, I'm installing them now and am having a helluva time. My hunch is that these bushings require the mating areas to be very precise and my torsion tunnels were anything but that. They both looked like someone took a blowtorch to them at some point, with sloppy welding done either by the factory or a repair. I did my best to grind down the high spots as mentioned in the install, but the surface may no longer be level vertically or horizontally. And my guess is that this is causing my issue. So, what is my issue? Here it is:

I've got both of the bushings epoxied into place in the torsion tunnel and spring plate cover as instructed (since they were both a little loose). Spring plate slides in nicely into the torsion tunnel bushing, then the plat cover also slides over nicely. Here's the issue. The holes on the spring plate cover are not lining up with the bolt holes. I've ground down the spring plate holes so that it lines up enough that I can wrench them down. However, when I do that, the spring place can no longer move up/down. I'm assuming that this alignment is not from bushing to spring plate to bushing isn't 100% accurate and thus It's not allowing the plate to move freely.

Any suggestions? Should I order new plates? These are new ones from URO, but I did notice that they didn't really line up without any of the plate or bushings in the mix anyway. They were close, but not perfect. My guess is that the install of these bushings needs more accuracy than my FAR from perfect 911 can accommodate.

Since I've epoxied the bushings into the tunnels, I now also realize that I may have a problem getting them out should I just say F it and go with the rubber bushings.

If anyone has any experience with this same issue and has advice, I would be ever so grateful. Thanks and happy wrenching everyone!

-Nick

[Old H2S]

Do not epoxy the PB bushings in place. You may use some silicone sealant to take up slack if need be, if the poly surface is flopping around inside the torsion bar tube. And they really should be torqued in place and driven then removed again and checked for rubbing marks on the poly and inside the torsion tube as the torque down will cause some squeeze and lock up. You're going to need a slide hammer and heat up the inside bronze side to break the poly side off the torsion bar tube. Can you do it without damaging the bronze surface?
With a job this big and many new parts on a 40 year old frame with poor instructions chances of getting it right the first time on both sides is slim. This is the why of total assembly and a break in and then total inspection for shim adjustments to all the mounting bolts for the side covers. The PB bushings are very accurate little play and with misalignment the spherical type have more leeway and would be easier. Going to stock rubber is fine and easy but misalignments with cause binding and fast wear.

[tseohs]

I recently had a similar experience while installing rebel racing SP bushings where I had to slot the holes slightly in one plate to get the bolts to align. Hope you did not grind down the chassis. The issue was that the bolt hole pattern did not align with the chassis mount holes perfectly combined with the thickness of the RR plates that did not allow the bolts any movement.

Also, the RR system requires shims behind the plates to allow the SP to move freely up and down. Maybe try some shims, especially now you have the bushings epoxied in. You can find RR install instructions on their website.

Cheers and best of luck.

[gsxrken]

If it'll button up nicely without the torsion bar, but won't with it, you might have a tweaked torsion tube.
If that's the case, a pull on a Celette bench could get you back to square. Or, consider going with coil overs, so that your arm will track nicely up and down without binding on the TB.

[snbush67]

It’s probably not a problem with the plates, it’s likely that you don’t have enough standoff or uneven standoff, the plate has to be mounted perfectly. Use washers to space the cover so that the spring plate will drop under its own weight when the cover bolts are tightened. Each mount/post may require a different amount of washers to get the spacing and alignment perfect (3 or 4 is probably normal). The bolts have to be carefully tightened and aligned. Thread each bolt in just a couple of threads and then tighten each one a small amount at a time, as you tighten, check frequently that the spring plate drops under its own weight, if the spring plate binds then it means you aren’t tightening evenly or have to add washers.

Also it’s good practice to tap the threads to make sure they aren’t goobered up.

[nickelplated5s]

All of the above and perhaps PeteK will chime in. With the epxoy you're stuck. ER sells install and removal tools which funnily enough I have here.

I just had this done by a shop as the motor was coming out anyway. Best time for the trailing arm bushings. What Al at A&P in Portland (he allows me to use the name) wanted was the ER plates with everything else. It was sort of a wash cost wise over having my SwayAway's recoated so , OK. I think my shop time bill was only about 5 hours for both sides. In other words my advice is go with ER plates and their rubber. Of course corner balancing will be next.

[AlBackus36]

snbush does a good job of describing how to shim this out. The plate can move freely throughout it's range of motion when it is shimmed correctly.

My extra advice is to get TWO different thickness of washers to use as shims. Get a 'thick' and a 'thin' washer. You may need a combination of two different thicknesses to get this really right. You'll get close with one thickness, but you can get it better

For future readers: The bushings shouldn't be glued at all until after you get the shims PERFECT. Then tigthen it all up together so the plate can press evenly against the bushing while it cures.

Keep going. I'm in the camp that feels this is the design (solid bushing at SP/TB) porsche should've gone with originally.

[NickW21]

Thanks for the feedback gents. Epoxy might be the wrong term. I used a urethane based adhesive per the instructions from ER. In any event, I will try to get the washers shimmed in a manner that would prevent the binding. I'm fairly certain the issue is either that the plate cover holes are not lining up well enough to allow it to go on straight and prevent the friction that is being applied from that. OR the bushing on the torsion tube side is not straight/level and the plate is going on straight and is causing the same binding. I'll continue trying to make space on the plate cover holes so that they align perfect and see if that solves it. If that doesn't, then I likely will need to get a bunch of different sized washers to see if I can get the proper spacing/shape of the plate cover to go on that matches the angle of the bushing.

[AlBackus36]

Epoxy is typically a 2-part catalyzed resin which has pretty good mechanical properties for what it is. The urethane sounds like a better fit. It shouldn't be doing much except keeping the bushing in and keeping it from rotating.

A torch will help you reset if you need to start over.

You've got this, OP!

[Old H2S]

The epoxy goes on the inside, steel slip liners to spring plates..A 1.5mm gap is required between the the 2 slip plates so extra shimming instead of trying to make everything tight together, this will aid in setting rear toe and camber which makes the car feel much more stable.
Every body is out of alignment, the torsion bar tube is the first part the bottom chassis is attached to. Hans and Franz get a beer break at 10 am, and a +/- 17mm fitting is the factory norm and the fights here about the spacing problems are epic.
Shane said it best about the shimming. I did over kill and took everything apart for inspection and looked for rubbing, the main achievement is getting rid of any binding. I can't really say the car got worse NVH because the extra smoothness really counteracts it.

[NickW21]

Really appreciate all the feedback gents!! A trip to the hardware store with some variable thickness washers and I'm getting much closer. One side is moving smooth as butter now. The other one is proving to be a tad trickier, but It'll come. I love this forum and how helpful it is to us non-mechanics.

People think I'm crazy for doing this myself, but I told them if I just wanted to pay someone a lot of money to make the car the way I want it, I woulda bought one in better condition! lol