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Suspension rebuild 1990 S2 Cab, looking for advice

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Old 05-08-2020, 11:12 AM
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59gene
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Default Suspension rebuild 1990 S2 Cab, looking for advice

Hi everyone,

I am going to bite the bullet and overhaul the front and rear suspension on my 1990 S2 Cab. The car has ~ 120K miles and has a random shake at 60 MPH. Rims have been checked and refinished, new tires and a 4-wheel alignment. I have had the car on the lift and nothing is drastically worn but I think it is time for a refresh. Here are my plans, looking for anything that I may be missing.

Front:

Ball joints (the arms are rebuildable)

Front A-arm bushing in rubber from Paragon

Updated 968 caster blocks

Replacement Koni strut inserts, bump stops, dust deals and pray the upper strut mounts are in great shape.

Tie rod assemblies, rack boots

All rack and sway bar bushings

Will likely address the seeping oil pan gasket and worn motor mounts while I have the front end this far apart.

Rear:

Here is where I could use some advice.

So far the plan is to drop the torsion tube and check the mounts and vibration dampers and replace as necessary. Not sure about the spring plates?

Koni Shocks

I have read every thread I could find on this forum about front and read suspension upgrades/fixes and I think I have a comprehensive list. This car is a driver and I want to have the best ride, so I want to stay away from race style setups. I would prefer to go with factory struts and shocks to maintain the factory ride. But the cost of what I am proposing is already in the $2K range (assuming worst case on the rear).

Thanks in advance!
Gene
Old 05-08-2020, 10:03 PM
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MAGK944
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Your list looks well researched except imo by keeping it factory you will be missing a huge opportunity to vastly improve the ride quality while still maintaining a very driveable car.

If I were doing this, which I have just not on an S2, I would look at replacing any rubber with a slightly harder version such as that made by Elephant Racing. I would replace the rubber spring plate bushings with a bearing type again by ER. The spring plate bushings are the ones which wear badly in that assembly, in fact I am betting yours are oval-shaped by now. I have never seen a worn out rubber bush on the main carrier to body mount and I'd put money they would survive a nuclear explosion. The only other bushes back there which I would change are on the trailing arms, again a harder rubber. Oh and wyit do the urethane mod on your trans mount.

At the front I would fit the Bilstein inserts in preference to the Koni's, I find the Koni insert valving quite a big change (more aggressive) than stock, while the Bilsteins maintain a more compliant ride yet they still perform as good as the Koni's or even better, when pushed. I would also up the spring on the front to 200lb/1in lower and lower the rear on the eccentric to its lowest setting (iirc about 3/4in). Weltmeister used to make just such a front spring but I'm not sure now.

Anyway all that will provide a great driver, put a smile on your face and a hole in your wallet. Hope that helps
Old 05-09-2020, 09:54 AM
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59gene
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Thanks Mike,

I did see some articles about the rear spring plate bushings but was not sure how worn mine would be. Sounds like I should just plan on those too. Appreciate the insight on the shocks and struts. I did not realize bilstine offered a strut insert for this car. I will definitely look in to that as well. I had see the harder bushings but was really thinking that would give me a more rigid ride. I will start pricing the elephant racing bushings. Thank you again for the advice, I will ponder this a bit more with your input.

Does anyone have experience with the aftermarket upper strut mounts? At 120K miles I am sure mine will need replacing. There are some cool race style adjustable plates available but think that is a bit overkill for what I am trying to do.
Old 05-09-2020, 11:51 AM
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harveyf
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No offense to MAGK944 but based on your goals, I would lean towards OEM rubber bushings versus urethane. Being a cab, I doubt that you are going to be taking your car to the limit, only really possible at track events. So you'll probably never reach the potential in handling that urethane might offer. That said, you'll feel the additional stiffness at every joint in the pavement. Porsche put a lot of engineering into the development of the rubber bushings to obtain an optimum balance of handling versus ride. Why mess with success!

Agree with MAGK944 that you need to bite the bullet and replace the spring plate bushings. Not a pleasant job but nceesary in the great scheme of things. As long as you're in this deep, I would consider doing all the wheel bearings. And put fresh rubber seals in the brake calipers. I would say do the CV joints while you're in there but they can be done later quite simply if they start to give you trouble.

When you talk to Jason at Paragon, make sure that you are getting OEM rubbler bushings, not aftermarket. All rubber bushings can tend to look the same but the engineering behind the "durometer" stiffness of each bushing is quite important and worth paying for.

I've got quite a few articles on my website that may help. Search on "suspension". Here is one where I did the spring plate bushing. As discussed in the article, I went with Racers Edge delrin bushings which presented some problems with fitment. The rubber bushings will not give you those problems. The delrin was worth it for my track car but I think not so much for your application.
https://newhillgarage.com/2013/06/13...sion-bushings/

Good luck!
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Old 05-09-2020, 12:03 PM
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mj951
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I went with Racers Edge camber plates when my upper strut mounts needed replacing. They cost about the same as OEM replacement bushings and my car is dual purpose so why not.
Not sure how much those alone changed the ride stiffness because I made a number of changes to the suspension at that time but I doubt they alone would effect the ride significantly. If you're tooling around town on bumpy roads probably not worth it but if more of a sprinted driver then no reason not to upgrade in my opinion. Many folks also go with Delrin bushings on the center two front sway bar bushings both for stiffness and to resist the oil swelling common on these cars from the leaks above. Keep the outer bushings at the control arms rubber. Also a good time to add the KLA sway bar brace for the center mounts...link below.

https://www.paragon-products.com/KLA..._swaybrace.htm


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Old 05-09-2020, 03:01 PM
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MAGK944
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Originally Posted by harveyf
No offense to MAGK944 but based on your goals, I would lean towards OEM rubber bushings versus urethane....
@harveyf no offense taken however I never and would never recommend urethane bushings. I recommend harder durometer rubber bushings

@op ...just something worth thinking about if you are considering camber plates and not knowing your tolerance for such things, apart from a solid trans mount, the next best thing you can do to increase nhv is fit camber plates.
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Old 05-09-2020, 04:57 PM
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59gene
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Thanks to all for the feedback. Sounds like we all agree that rubber bushings are the way go in the front to maintain a nice ride. I will definitely reach out to Paragon. Mj951 I will check out the delrin for the center sway bar as mine are showing some swelling as you pointed out.

I did find some good information on the trans mount that I was not aware of. Thanks for pointing that out.

I have already done the front wheel bearings and all 4 calipers. I did one axel boot and the rest looked in good shape but I will check them when I pull everything apart. I will add rear bearings to the list, why not.

I will plan on the spring plate bushings in the rear, there are a few options that I will read up on. Last thing is to nail down the upper strut mounts then throw the AMEX at it and get started.

thanks again to all for the responses and if you think of anything else I would appreciate hearing about it.
Old 05-29-2020, 07:56 AM
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Originally Posted by MAGK944
At the front I would fit the Bilstein inserts in preference to the Koni's...
Does using the Bilstein inserts require modification of the original strut? For that matter, does using the Konis require any mods?
Old 05-29-2020, 08:25 AM
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beamishnz
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I run Bilstein and Koni on a number of different 944's and from what you are looking to achieve I think the Bilsteins would be a great option. Here is a link to 'How to' for the conversion of the existing Sachs shocks to Bilstein. Good DIY project. Bilstien Conversion Article
Old 06-02-2020, 11:56 AM
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59gene
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Hey beamishnz, thanks for the info in the Bilstein inserts. I had seen the video on this mod. I have not been able to find information on the modified collar and a list of inserts that will work with this mod.

Anyone have a source for the collar or a drawing for me to send to my machine shop? Would also like a list of inserts by part number if that is available.

Thanks in advance!
Old 06-02-2020, 05:48 PM
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beamishnz
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Originally Posted by 59gene
Hey beamishnz, thanks for the info in the Bilstein inserts. I had seen the video on this mod. I have not been able to find information on the modified collar and a list of inserts that will work with this mod.

Anyone have a source for the collar or a drawing for me to send to my machine shop? Would also like a list of inserts by part number if that is available.

Thanks in advance!
Hi. I have made a few inserts up for the community. They are a little different to the ones shown in the German video. They are machined to locate with an internal lip inside the strut which allows the insert to set to the correct height. I have also printed a cutting guide which facilitates making the cut in exactly the correct spot. If you check through the installation link I provided in a previous post you will note that the installation is somewhat easier than the German video. I have developed a procedure that removes the need of prising off the original stock cap. I have done quite a few of these conversions and supplied a good number of inserts to other enthusiasts. Great feedback so far.

The inserts are $49USD each ($98/pair) and global shipping is $25USD.






Old 06-02-2020, 07:57 PM
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59gene
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PM sent!
Old 06-06-2020, 05:48 PM
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beamishnz
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A few folk have asked me about the differences between the strut insert options offered by Bilstein. The options are 34-000403 and 34-001042. Dimensionally these units are identical but the 43-001042 has higher rated rebound better suited to uprated springs. So if you are running std strings
i recommend 34-000403 and if you have moved up to 250lb aftermarket springs (std are around 170lb) then 34-001042 would be the way to go.



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Old 06-06-2020, 06:08 PM
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Jfrahm
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At 120K if you are taking the pan off it'd be easy to do the rod bearings. At 150K or so in my 968 they were worn enough to cause low (but in spec) oil pressure and at 162K or so when I removed them I found the bearings to be at the wear limit.
New nuts and Gylco bearings and my oil pressure is back.

Consider also the oil pressure sensor, these seem to fail. The small PS hoses could be replaced as these leak and eat the bushings on the RH side.
Old 06-07-2020, 08:09 PM
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59gene
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Thanks beamishnz,
That is the info I was looking for. I will PM you about collars soon. Appreciate the support.


Thanks Joel,
I was debating pulling a rod cap as the oil pressure is spot on but at 120K I think it might be a good time to take a look. In for a penny in for a pound!


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