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Old 03-28-2019, 05:25 AM   #1
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Experiment: Installing 986 Coilovers on a 987

I've got a set of 986 PSS9 installed on my Boxster, and now I need some suspension for my 2009 Cayman as I transition the Boxster back to stock format to sell it. (Ha, I am probably going to end up keeping both of them)

My plan was to remove and sell the PSS9 to a spec boxster person (as I didn't realize there was a shortage of PSS9) and use that money to fund some coilovers for the Cayman, but now that a new coilover is approved for spec boxster, I figure folks are going to want to move to that:

PCA Announces New Spec Boxster Shock Package

So, I need to find some coilovers for the Cayman. I have liked the PSS9 on the Boxster, and have shaved time on every track I have been to with them, and I have been thinking about moving them over to the Cayman.

There are a few issues to work out:
  • Struts tops - these are the same across 986/987
  • Strut bottoms - these are bigger on the 987
  • Height/positioning - in addition to the strut bottom being bigger, are there any other differences in height or mounting?

Strut tops

The strut top mounts are the same between 986/987 so no issue there. I have Tarett camber plates on the front and a stock rear strut top mount retrofitted with a monoball cartridge from Elephant racing so I am covered there.

Strut bottoms

I understand that the strut bottom diameter is larger on the 987 than the 986. I have heard that the backs are the same, and I have also heard that the backs are also larger on the 987.

Several vendors sell the same sku for 986/987 and include adapter sleeves so that the same kit can be used for either car, with the adapter sleeves not being used when installing into a 986. Ohlin's Road & Track is one. I reached out to them and they would sell the sleeves to me at $90 each, yikes

I reached out to several other vendors and MCS has the sleeves for $50 each and was able to set me up with a set. In the process of doing this, I learned more about their company and talked with some folks and I came away pretty impressed with their company and offerings. It is some serious $$$ though (relatively speaking )



Height/positioning

Here's where I have some unknowns. I am hoping that the 986/987 struts are about the same between the 986/987 versions of the PSS9 (and between 986/987 struts in general, but this is unknown to me right now until I get a chance to take some measurements), this is the tricky one. Since the PSS9 does not have an independent height adjustment, the trick is getting the car to sit at the right height while keeping the piston in the sweet spot so that it has a good range of travel and doesn't bottom or top out too early.

Since the only set of 987 struts I have access to are installed in the Cayman, I don't have easy access to make those measurements. When I get a chance I am going to put it on jack stands and take the wheels off and see if I can get some measurements that way.

I am not too worried about the fronts, as the allowable range for the spring collars, as measured from the sway bar upper pinch bolt, has overlap between the 986/987 front PSS9 strut. Fro looking at pictures I can see that the fronts are very similar so I'm not too worried here.



In the backs, that range does not overlap between the 986/987:



I am hoping this is because the 987 rear PSS9 spring is a single larger progressive spring, vs the liner spring/helper spring combo in the front of the 987, and on both front and back for the 986.



I am hoping that the rear wheel carrier is substantially the same between the 986/987, with regard to the relation of the sway bar pinch bolt and the travel of the shaft, and I should be OK.

Stiffer springs

At the same time as I do this, I am thinking about going to some stiffer springs. Tarett sells the spec boxster springs which fall within the damping range that the stock PSS9 damper can handle. Right now my understanding is that the stock PSS9 springs for 986 are:

260 lbs/in front, 41.8% front (ratio front to back spring rate)
362 lbs/in back, 58.2% back

spec boxster is
447 in/lb front, 47.1%
503 in/lb back, 52.9%

That's a fairly big jump in rates and a moderate change in front/back ratio (unsure how important that ratio is, I just know I don't want to deviate too much from these "tested" ratios.

If I go spec boxster springs and don't like it, I figure I can easily resell them to someone doing a fresh SPB build.

Another choice would be to move that 362 spring to the front (they are the same size) and get the front SPB spring (447 in/lb) and put it on the back, giving me:

362 lb/in front, 44.7%
448 lb/in back, 55.3%

That wouldn't be as big of a jump in spring rate all at once, and has a ratio that splits the difference between spec box and stock PSS9.

If I were to do this but put the SPB 503 lb/in spring in the back, that gets me:

362 lb/in front, 41.8%
503 lb/in back, 58.2%

Which is exactly the same ratio as the original PSS9 rates.

I have noticed on the PSS9 stock rates that I can run my Tarett bars in the front, 2nd hole to softest, and rear bar 2nd hole from softest, and the car feels great. (Previously I had the front bar set to the middle hole with the M030 springs, too much understeer and when I moved the back bar up one hole in hardness, I didn't like the way it felt)

This is the area that scares me the most, playing with these spring rates, I feel like I could easily get into a bad situation, and while the fronts are pretty easy to get to, the backs are a big hassle. If I have to tweak I would rather do it by swapping front springs.

That's where I am right now. I am probably a weekend or two away from being able to actually get started on this work, but if anyone has been down this road before I would love to hear your feedback

Last edited by steved0x; 03-28-2019 at 05:29 AM.
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Old 04-11-2019, 05:17 PM   #2
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This thread was a dud, after doing more thinking about it (and while putting my Boxster back to stock and swearing this was the last time i was doing suspension) I decided to get the Ohlins Road & Track for my Cayman... If i put that pss9 on the Cayman and couldn't set a good ride height without topping or bottoming out the strut due to height differences i think i would cry...

Last edited by steved0x; 04-11-2019 at 05:27 PM.
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Old 04-11-2019, 08:34 PM   #3
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... I decided to get the Ohlins Road & Track for my Cayman...
I think that was the right decision.
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Old 04-11-2019, 09:06 PM   #4
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I think that was the right decision.
Yeah... agreed. Cobbling suspension just gets to be brain damage. And I am with you on the swearing off suspension work... jeez, my Jeep handed it to me this last weekend! Ugh!
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Old 04-12-2019, 05:36 AM   #5
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No further parts available or rebuild services for PSS9s? Wow! Should have gone JRZ
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Old 04-12-2019, 07:44 AM   #6
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Originally Posted by jaykay View Post
No further parts available or rebuild services for PSS9s? Wow! Should have gone JRZ
I think there are some 3rd party folks that can rebuild the PSS9 if Bilstein isn't doing it, such as Fat Cat Motorports ($$$ but with additional features added), Feal (although their website has changed and all non-store content seems to be gone), and I am sure (hope?) plenty of others. Here might be one:

https://deltavee.net/shop/services/bilstein-adjustable-strut-ex-pss9-rebuild-service/

Edit: I emailed Delta Vee and they say they can do it, but they are pretty backed up with strut rebuilds so they say it may take a while...

Bilstein still lists the PSS9 rebuild as one of their services:

https://www.bilstein.com/us/en/technology-and-knowledge/service/

But that PCA announcement did seem to say it was NLA. I did just see a set of freshly rebuilt PSS9 for sale on one of the FB Spec Box groups so it must be able to be done somewhere.

I wonder why they would stop support for such a wide installed base, maybe they are making too much money on Toyota Camry shocks and losing support for their "niche" markets?

Last edited by steved0x; 04-12-2019 at 11:23 AM.
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Old 04-13-2019, 07:26 AM   #7
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I have done the opposite and put 987 suspension on my 986.

To make it work was a bit of a process, but finally worthwhile.

My reasoning for doing it was I wanted to use the 987 carriers with the larger wheel bearings and lighter construction for my racecar.

Rears were very easy. Just a straight swap of the carrier and the shocks bolted right up.

Fronts bolted up fine, but the front sat about an inch higher than it should. Even using shorter springs I couldn't get the ride height I wanted.

First of all I tried using rear carriers on the front - on the 986 the front and rear carriers are the same, but on the 987s they are different. This solved the ride height problem, but the front discs fouled on the carrier. The brake ducts also fouled on the carrier, so this solution was abandoned.

So I went back to the 987 front carriers and compared them to the 986. The overall distance between the bottom ball joint and the shock mounting hole was the same, but the distance from the top of the carrier to the shock mounting hole was larger by just under an inch on the 987. This locates the shock higher overall in the carrier.

So I machined an inch off the top of the carrier to bring the overall height down to that of the 986. This solution seems to work perfectly.

Ride height is great, no issues with any fouling and the carriers seem to be holding up fine with the material removed.

One potential issue from this swap is that the ABS sensors are different. I got rid of the Porsche ABS controller and am using a Teves MK60, so I don't know if they would work with the original Porsche controller on the 986.
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Old 04-13-2019, 09:32 AM   #8
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Steve,

Thanks man you are A1 King of Information and enthusiasm!



Quote:
Originally Posted by steved0x View Post
I think there are some 3rd party folks that can rebuild the PSS9 if Bilstein isn't doing it, such as Fat Cat Motorports ($$$ but with additional features added), Feal (although their website has changed and all non-store content seems to be gone), and I am sure (hope?) plenty of others. Here might be one:

https://deltavee.net/shop/services/bilstein-adjustable-strut-ex-pss9-rebuild-service/

Edit: I emailed Delta Vee and they say they can do it, but they are pretty backed up with strut rebuilds so they say it may take a while...

Bilstein still lists the PSS9 rebuild as one of their services:

https://www.bilstein.com/us/en/technology-and-knowledge/service/

But that PCA announcement did seem to say it was NLA. I did just see a set of freshly rebuilt PSS9 for sale on one of the FB Spec Box groups so it must be able to be done somewhere.

I wonder why they would stop support for such a wide installed base, maybe they are making too much money on Toyota Camry shocks and losing support for their "niche" markets?
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Old 04-13-2019, 05:16 PM   #9
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Steve,

Thanks man you are A1 King of Information and enthusiasm!
Well, maybe enthusiasm, thank.you!
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Old 04-13-2019, 05:24 PM   #10
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This is very interesting, thank.you for sharing. Now that I am getting the Ohlins, which is the same sku for 986 and 987, i was reading the install instructions, and the 986 uses 13mm more of spring preload on the main spring, and a different starting point for the lower height adjustment, I don't have the numbers handy. So I guess that is how they account for those differences. With the PSS9 not have independent ride height adjustment I probably would have had trouble...

Quote:
Originally Posted by specboxCO View Post
I have done the opposite and put 987 suspension on my 986.

To make it work was a bit of a process, but finally worthwhile.

My reasoning for doing it was I wanted to use the 987 carriers with the larger wheel bearings and lighter construction for my racecar.

Rears were very easy. Just a straight swap of the carrier and the shocks bolted right up.

Fronts bolted up fine, but the front sat about an inch higher than it should. Even using shorter springs I couldn't get the ride height I wanted.

First of all I tried using rear carriers on the front - on the 986 the front and rear carriers are the same, but on the 987s they are different. This solved the ride height problem, but the front discs fouled on the carrier. The brake ducts also fouled on the carrier, so this solution was abandoned.

So I went back to the 987 front carriers and compared them to the 986. The overall distance between the bottom ball joint and the shock mounting hole was the same, but the distance from the top of the carrier to the shock mounting hole was larger by just under an inch on the 987. This locates the shock higher overall in the carrier.

So I machined an inch off the top of the carrier to bring the overall height down to that of the 986. This solution seems to work perfectly.

Ride height is great, no issues with any fouling and the carriers seem to be holding up fine with the material removed.

One potential issue from this swap is that the ABS sensors are different. I got rid of the Porsche ABS controller and am using a Teves MK60, so I don't know if they would work with the original Porsche controller on the 986.
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Old 05-31-2019, 01:03 PM   #11
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I was looking at this on another thread, so am including the info here. If you download the install manual for Ohlins Road & Track, which has independent height adjustment and spring load, and which can be used on ether 986 or 987, you can see the differences in the heights by looking at the spring load setting and height adjustment differences between 986/987
  • 986 front - 15 mm of spring load and 80 mm between lower spring collar and height adjustment collar
  • 987 front - 2 mm of spring load and 59 mm between lower spring collar and height adjustment collar
  • 986 rear - 15 mm of spring load and 130 mm between lower spring collar and height adjustment collar
  • 987 rear - 2 mm of spring load and 105 mm between lower spring collar and height adjustment collar
The PSS9 doesn't have the lower independent height adjuster and so all the height has to be done by moving the lower spring collar and it might take the strut piston out of the sweet spot in the middle and to where it is topping or bottoming out.

If that can be solved, MCS will sell the sleeves to adapt the strut bottoms.

Last edited by steved0x; 06-01-2019 at 04:50 PM.
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Old 05-31-2019, 01:05 PM   #12
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And here are some gratuitous pictures of the Cayman with the Ohlins Road & Track installed:




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Old 06-01-2019, 02:22 PM   #13
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And here are some gratuitous pictures of the Cayman with the Ohlins Road & Track installed:
Steve, I love the stance of your car, it looks awesome! And those wheels look great as well, congratulations :-)
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Old 06-01-2019, 04:49 PM   #14
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Steve, I love the stance of your car, it looks awesome! And those wheels look great as well, congratulations :-)
Thanks! I liked tbe lobster claws, but i really like these
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