Rear Spring Perch Initial Setting? Options

[bkrantz]

Can anyone offer a suggestion for the initial setting for my new rear springs? I know I will likely adjust to fit, but I would like to get it close to start.

These are new Bilstein sport shocks and 914 Rubber 100 lb springs. The car will be a near stock 4 cylinder.

[horizontally-opposed]

You're not alone on this one, as this just came up here:

http://ftp.914world.com/bbs2/index.php?showtopic=350758

The 100lb springs are going to be a variable, as will the lighter engine, but maybe the pics get you into the ballpark? I might try one perch "higher" with 100lb springs vs 140s, but not sure what you are after for ride height.

[drem914]

You're not alone on this one, as this just came up here:

http://ftp.914world.com/bbs2/index.php?showtopic=350758

The 100lb springs are going to be a variable, as will the lighter engine, but maybe the pics get you into the ballpark? I might try one perch "higher" with 100lb springs vs 140s, but not sure what you are after for ride height.

(IMG:style_emoticons/default/agree.gif)
It all depends on if your looking for a "stock" or more "aggressive" ride height, what your wheel and tire combination is and where you plan on setting the front ride height.

[Cairo94507]

My car has the Bilstein spring perch on the 4th ring from the bottom of the shock and it sits perfectly in my humble opinion. I also have 140 pound rear springs and 195X55X15 tires. (IMG:style_emoticons/default/beerchug.gif)

[914Sixer]

2nd slot from bottom

[cary]

I used #4 on the Matt Carey barn find.

[DRPHIL914]

i have the exact same set up , stock 2.0 motor, and bilistein Sport shock, 100# springs, and i am on the second down from the top. when on the top one it was too bouncy, and too little negative camber, as you lower you will add about .25-.5 degrees negative camber, you may have to play with training arm shims to get this balanced, but right now for me, i have no shims, and i am on the second down slot and i have 1/2degree negative camber. I may go down one more slot and add a bit more negative camber or A/X but then i will have to drop the front slightly as well, i like the current stance and ride quality though.

good luck, but id would start at #2 and see how it sits.

@bkrantz


Phil

[DRPHIL914]

2nd slot from bottom

that was way too low on my car added too much negative camber, ride was not comfortable

[drem914]

My car has the Bilstein spring perch on the 4th ring from the bottom of the shock and it sits perfectly in my humble opinion. I also have 140 pound rear springs and 195X55X15 tires. (IMG:style_emoticons/default/beerchug.gif)

(IMG:style_emoticons/default/agree.gif) only difference is I have 205/50/16 tires

[Mark Henry]

There's 2 kinds of Bilstein perches and the shocks are cut differently for the two styles, early it's it's 4th (ballpark) from the bottom perch and the latest style perch it's 2nd from the bottom.
That's why you're getting two different answers to the question.

[Cairo94507]

I did not know that. My Bilsteins were bought in 2016-ish from PMB.

[Mark Henry]

I did not know that. My Bilsteins were bought in 2016-ish from PMB.

I do think the earlier style would be more up to mid 2000. They do have a much more substantial perch, where as the newer rears just have a pressed steel plate.

Personally I like the newer style as you can drill and ziptie both the top and bottom perch to the spring, where the old style you could only do the top perch. The new style perch will ride up the shock when you lift the car.
The ziptie trick keeps the spring clocked in the correct spot of the perch.

[Mark Henry]

This is the current style, this is at 4th 5th from bottom grove with the shorter "progressive" style 160lb spring, and a /6 engine. Measuring from center up I have about 2-1/4" from fender to rim lips. I personally really like this on a 15" rim, aboot as low as you can go before hitting into bad bump steer.

Note: You can see I have the perch zip-tied to the spring, there's a 3rd zip-tie, I've been meaning to replace with a heavier zip-ties.
The progressive spring is shorter than the travel of the perches, this isn't an issue with stock style/length springs

[Mark Henry]

Here is the earlier style perch, it will not slide on the shock body, so you can only zip-tie the top perch.
This is sitting on the 5th perch, but has the longer stock style 100 lb spring and is a /4. the center to top fender to 15" rim lips is more like 3-1/4"

[bkrantz]

Thanks, everyone.

And thanks, Mark for the reminder about tying the springs to the perches. I will drill holes before I assemble the springs and shocks.

[Cairo94507]

OK, now I know I have the current style perch. The next time I put my 6 on the lift I will check to see if the rear springs need to be zip-tied to the perch. I am guessing no, because I am pretty sure I would have heard them drop or move when I have lifted it and cleaned the underside. But, worth check9ing for sure. Thanks @Mark Henry for the great pictures of the two styles.

[Mark Henry]

I can't say for sure if you have to zip tie the newer perches, as mine have been tied top and bottom since new, but with progressive springs I'd still do it.
With the old style perch the springs would always spin, even with the top perch zip-tied to the spring the bottom was rarely seated correctly for long.
YMMV (IMG:style_emoticons/default/beer3.gif)

[Dave_Darling]

Simple answer:

Start it in the middle. Bounce the suspension and roll the car around for a bit to see how it settles. Then look to see if you like the height.

Too low? Raise it up halfway from where it is. Too high? Lower it halfway from there.

Repeat this process (go half the number of notches as last time, but in whatever direction is appropriate) until you feel you're close enough.

In computer science, this is called a "binary search".

--DD

[bkrantz]

Here's the spring in place with the new Bilstein lower perches (with new holes for tie downs if necessary) and the stock upper perch temporarily in place.

[bkrantz]

With the lower perch mounted to the second groove (from the bottom), there is free play for the spring. I might move the perch up one groove for now to eliminate the play.