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Feedback on 3.2 rear suspension setup?

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Seeking feedback on where to go next; I recently replaced shocks all round with Koni yellow sports on the front and reds on the rear (same setup I previously had and very happy with).

I also fitted 4 new tyres (RE003's) and when I got the car back tyres on the rear were rubbing on the guard.

To stop wheel rub, I was told spring plates were at their max and needed to come out and get re-positioned so that height could come up a bit which seams to have fixed the wheel rub issue, still only about one finger diameter clearance so happy with the look.

My issue after several spirited drives is the rear feels bouncy and it's more of a handful when taking corners at speed due to a bit more roll.  Prior to getting told the rear shocks were gone, the car felt solid and evenly planted when driving hard, even on shocks that were apparently stuffed.

I've taken the car back again and told shocks have been adjusted as firm as should be expected, bump stops were cut I think in half and if I want the firm ride I had previously I should consider new torsion bars, I believe from a 930 that are bigger.  I've read up on torsion bars and don't find much info to say they deteriorate, if they aren't cracked, broken or rusted, just clean them up and reinstall.

Any feedback before I consider the torsion bar replacement would be well received.

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Hiya @Stepo you mention that the bump stops were cut to be shortened. Is there any chance that the car was riding on the bump stops prior?

I went the big bang and did everything at once, shocks, trailing arm + spring plate bushes plus turbo torsion bars along with sway bar drop links and rubbers.

You are correct that the torsion bars do not deteriorate. If you are going to do the bars, I would suggest the spring plate bushes also as ....you know....it's going to be out anyway.....:EvilSmile:

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As the old shocks had been in the car since I purchased it, I was wondering the same thing @P-Kay.  I suppose riding on them would give a flat ride where the shocks basically don't provide any dampening, solid as a rock but no wonder my shocks were worn out, maybe lucky there wasn't other damage where the shocks are bolted.  Given everything replaced was similar, I couldn't think of what had changed, unfortunately I don't have the original shock bump stops to compare with :unsure:.

Looks like bigger torsion bars might be the way to go and yes I'll have a look into the spring plate bushes whilst I'm there, thanks for the tip and comments.

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How low is that rear ride height?  Suspensions need some travel to work.

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I have some spacers on the rear wheels @Merv and maybe 20mm gap between the tyre and the inner wheel arch. Ive seen plenty of cars lower and prior to replacing the shocks and moving the spring plate location never had any issues.

Preference is to keep the stance as it is as long as I can work out what needs doing to get rid of the bounce.

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Are you sure the new shocks aren't faulty or installed incorrectly, were they pre primed or pumped before installation, been adjusted incorrectly ie to full soft ?

Maybe full hard is too hard, have you tried a softer setting?

Probably dumb questions 🤭

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No dumb questions here Oz, I’ll take all the feedback I can to get my baby back to how she was.

I believe the shocks are installed properly, Porsche only mechanic and I’ve had the car back twice for checking, told I need turbo torsion bars to solve the problem but why isn’t every Fucher that replaces their shocks having to install bigger bars 🤔

I’m building a list of questions to ask the mechanic when I next drop in.

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Brian is right on the full soft suggestion.  I have seen many where the shocks were adjusted so hard that an otherwise normal suspension was almost, locked and could not work. The spacers could contribute to potential for wheel rubbing on the arch, Peter. However reindexing/increasing the spring plate angle a little may help.  It is not a difficult task. 

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My car is currently in for its third check and adjustment, shocks were on the middle setting and there was room to firm them up more, apparently it's riding a lot better so will collect tonight and try and test it over the weekend.

Mechanic tells me the torsion bars are probably original (1985 car) and they can soften over time?  Suggesting upgrading to turbo torsion bars that will apparently make it ride perfect, but I'm still a little unsure that path is correct, will probably go there if I'm not happy with it.......TBA

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It sounds a bit like guesswork.

If you want it to really handle well, give it to a specialist and have it set up and corner balanced.

My '84 is running the original bars, which were quite small, with adjustable Koni's and slightly larger sway bars. I've done a few track days and can't see why I'd need to go stiffer.

The height, corner balance, & damper adjustments need to be set right (in that order).

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Sounds as though you are on the right path Peter.  Softening the rear shocks is a good move. I would start with 1 over soft and see how that feels. Torsion bars are pretty bullet proof IMO. I am not sure of the history of your car however in terms of its previous use. Mine are original and it rides and handles really well. I re-indexed the front and rear TBs (necessary if the minor adjustment on the rear spring plate is exhausted) to get the height and stance I was happy with.  I also spend a good deal of time getting the right engine and transmission mounts as well and fitting turbo tie rod ends at the front (major difference). Finally an 'old school' alignment.

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Hey Pete, how did you go? It sounds to me like the shocks need to be set a bit stiffer. Lowered cars pretty much ride on the bump stops. The Koni bump stops are massive. I cut 20mm off mine and at rest there’s 10mm of travel before they start being compressed. There is a lot of compression in them but consider that your bump stops are doing a lot of the work the torsion bars are supposed to be doing. When you go over big bumps, the car bounces off the bump stops so the shocks need to be set stiff enough to control that bounce, other wise it will feel like a pogo. Learn how to adjust them yourself so you don’t have to keep going back to the mechanic. They’re easy to adjust and access isn’t too bad. You might have to remove the Airbox cover to get to the right side.

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You certainly don't want your car riding on the bump stops often. They are there as a back up.  Frequent riding on the bumps stops suggests dampers, and springs/torsion bars that don't work correctly and a suspension that is not well set up, for the conditions in which it is driven. The general rule of thumb is to start with a softer setting and then progressively move up the stiffness as the car is tested in road conditions. Keeping in mind that some body roll is not a bad thing if it allows the suspension to work as designed and retain tyre grip and not replace the odd bump experience with sideways skitter and traction loss in everyday driving. 

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So to update where I'm at, the car has been at a Porsche specialist @sus911 where suspension was adjusted in a methodical manner. Along with new tyres fitted, cambers were originally way out (needed Mike Tyson strength to perform a U turn which I'd just gotten used to) and after corrections the front end felt like it had power steering fitted.  That change in the front end probably hasn't helped me when questioning the rear end bounce as I've gone from totally worn front and rear to a car that is actually responding more confidently (a big change to get used to when you don't know the wiser).

The rear end bounce (definitely that pogo stick feeling @Simonk) has been my major concern, and happy to say it feels much better after getting the car back late last week and getting out on one spirited drive.  It's feeling more solid on the road and handling corners much better after the last tweak which involved winding up the firmness on the rear shocks, cutting a little more off the bump stops and adding a little more clearance between the tyre and the wheel arch (see pics). There is some sacrifice in comfort to achieve the firmer ride but that's how I like it, the car feels more planted, can take corners harder but without the unwanted bounce and roll.  I can still feel the rear shocks working without over-travelling and in my mind the balance is much better.

Will test again on the next SMT and consider bigger torsion bars if I find the suspension settling too much.

Thanks for your feedback guys.

 

This is where it was riding previously, pretty low but no bounce or roll, probably no suspension either, bump stops all the way 😆

5CxR5Li.jpg

 

Here are a few pics of the current clearance, I'd say at least 25mm higher than before.

4kzCJOH.jpg

That pic above looks like scratches all around the arch but just reflections from my picket fence and dirt from a good thrashing 😁

 

wwQ2Zu8.jpg

 

nBgkwdr.jpg

 

 

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Looks much better. Very nice indeed.  I found fitting the Turbo tie-rods made a big difference to the steering feel and directness.  Have you tried those?

IMG_20200601_162828.jpg

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Nice pic Merv, she's a beauty, looks like you still have a bit more clearance in the arches than my new height.

The piggy bank is feeling a little bruised of late, steering is the best it's been so will just suck it up for a while and see how it goes over the next few months, will keep the turbo tie rods in mind.

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I have a little more clearance at the front in that pic., but have since changed those front shocks.  The tie rods are not costly and really easy to fit yourself. It does need toe-in etc to be re checked afterwards, however. 

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Here's mi911ne.

Turbo tie rod ends, upgraded sway bars, adjustable Koni's, strut brace, lowered to sensible height & corner balanced.

Car feels great on the track & road.

IMG_1862.JPG

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