I'm finally at the fix the severely sagging rear springs project for my car, and am wondering if there's any guidance on where to set the lower spring perch for the new rear Bilstein shocks?

I'm keeping the car as sock as possible, think of me as a James May if you must, so I have a new set of stock ride height springs (85 lb) and the new replacement struts. Comparing the old and the new side by side, it almost seems that I need to move t he circlip all the way to the top on the new shocks... but that seems almost crazy! Since I'm aware that the new springs, at 85 lbs, are heavier than the originals (maybe 70?), would it be better to move the perch down one relative to the old shocks?

Old springs/shock on the left, new on the right


Any advice or recommendations out there?

The stock rear sway bars stay (front and rear), which was also a driving motivation for keeping a lighter weight spring in the back.

Maybe it's time for a project thread... but progress is piecemeal and slow, so it might drag on, and on, and on...

Thanks!
Robert

Start at 2 up from bottom The spring carries the weight not the shock.

I probably shouldn't weigh in on this since I have yet to put any weight on my rebuilt rear struts, but 2 up seems like a good starting place. The stock springs actually run around 52 to 57 ish if you do the math on the info provided in the factory manual. It looks to me like 2 down would most closely match the height of your old perches but with heavier springs, I agree on dropping them down more.

I put mine at the top because I am using my stock springs and the top ring matched the perch height of the Boge shocks I replaced but I may have to fiddle with that once the suspension is fully loaded.

+1 on starting a build thread!

You won't really know till you set it on the ground with the front suspension ballpark adjusted as well. If your front is out of whack, or if the rear spring is not sitting into the perch correctly, you can have a one rear corner high situation. The clip perch makes adjustment almost as easy as the front, but remember front height adjustments affect your front alignment.
I'd always drop a 914 an inch or two over stock ride height.

I just installed a set on my 914, I drilled two holes in the perch and zip tied the spring to the perch, I've also done this to the top perch. Now when I raise my teen the perches stay where there supposed to be.

I have 180lb springs which are, at rest, way shorter than stock. The new style bilstein perches are nice because you can zip tie top and bottom perches and the bottom perch rides up the shock when you jack the rear end. No more clocking the bottom perch as you lower the jack.

Edited post to read 2 up from bottom. Sorry for the confusion.

Pictures tell the story
Stock springs dated '74
Three green paint dabs on each spring
Bottom perch in third groove
Results in pictured rear height.

Based on this, I'll probably have to adjust mine down.

Don't want to hijack, but if you have a pic of the dots on your springs Rory, I'd love to see it. @rgalla9146

I have 160lb springs on a narrow body 3.2 conversion. Clip is on the 4th groove from the bottom. It’s a little too low. I’ll buy some spring compressors and raise it a bit when I have time.
It’s going to be a little different for every car.

I have the same springs as rgalla9146, 2nd from bottom gives me similar ride height to his car. Much fiberglass, battery relocation lighten the rear - 2.2l six in my car - but strengthening panels and roll cage add to the mass. Even altering front height may affect the rear slightly.

In other words: there are many variables at play, basically you should start with "best guess" and be prepared to alter if needed.

- Tony

Tony your last sentence says it all.
I trailered my car to the alignment shop after it was driven maybe one mile.
Driving out of the parking lot I looked over my shoulder and realized
the rear of the car looked too high.
It was sitting on Konis all around. No rear height adjustment possible........
.......back onto the trailer.......change all four corners to Bilsteins and do a
trial fit with the perch set as pictured. I got lucky.
It could have been a few remove/install cycles.
Be prepared.....you might have to do it over.

I'll take pictures as soon as I can.
Yesterday my laptop gave me trouble.
Today I removed my front spoiler to do a minor touch up. I put the spoiler
on a work table outside. A breeze turned my minor touch up into a fiberglass
festival. ....and repaint.
Pictures of rear spring paint dabs to follow.