So I posted a similar post over in the 2015+ General forum but I think this forum is perhaps more applicable. This week while installing my Bilstein 4600/5100 (I ordered both as I was curious if I could discern which one compressed easier by hand and I found out that the 5100 feels a bit harder to compress), I made the following observations:

1. Both the 4600 and 5100 and factory 4WD strut have 100% identical snap ring OD's and strut body OD's. That is to say, the snap rings protrude from the strut body by the exact same amount.

2. The factory 4WD strut does not use a collar of any kind. The lower spring perch rests directly on the snap ring.

3. Both the Bilstein 4600 and 5100 have the lowest snap ring groove 3/4" lower than a factory 4WD strut. And before anyone says anything, yes the Bilsteins are in fact 4WD struts. Part numbers etched on strut bodies and they are basically the same length as a factory 4WD strut.

4. The Bilsteins (both 4600 and 5100) come with a "collar" that is meant to slide over the strut shaft and rest on the snap ring. When you do this, the lower spring perch sits 1/4" HIGHER than it does on a factory 4WD strut.

5. If you omit the collar on the Bilsteins (and simply mockup the lower spring perch on the strut on the bench), the spring perch sits exactly 3/4" LOWER than it does on a factory 4WD strut.

So my question is, has anyone experimented with omitting the Bilstein strut collar to achieve 3/4" of drop?

I previously had 2WD Ford struts on my F150 but I found it lowered the front end TOO MUCH (1.5"). I had to install 2" rear shackles (and remove 4x4 block) and still the rear was 1.25" higher than the front and the truck had a weird rake and I had to use a bunch of shims to correct pinion angle.

My hope is that I can install the Bilstein 4600 without the collar (3/4" drop compared to 4WD strut) and then go back to a Ford Racing 1.5" rear shackle (which actually is prove to only lower these trucks 3/4" since you need to use a pinion angle shim).

 

As a follow up. Installed the Bilstein 4600s both with and without collar last night. WITH collar raised the truck over 1/2” higher than stock!!!! Unacceptable.

Without Collar lowered 3/8” lower than stock (both measurements confirmed after 10 mile test drives and repeated aggressive stops to compress suspension).

 

https://www.f150forum.com/f118/bilst...3/#post6581156

 

Now I understand why after removing the rear block and installing 2wd 5100s on my 4wd I effectively put a 1/2 inch level on a 2wd truck. Not what I intended, but things could be worse. I am a little annoyed at Bilstein.

Excellent write up OP-

 

2WD Bilsteins will lower a 4WD by 1”, however a factory 2wd strut will lower a 4WD by a full 1.5”

A 4WD 4600 or 5100 will raise a 4WD by 1/2” if the strut is assembled with the collar at the lowest setting.

 

Wish I knew this two weeks and an alignment ago! I would have at least gone with the 4600s...I bought the 5100s in case I decided to add a bit of level. Now that Bilstein has taken the decision away I will always wonder if the ride could have been better with the 4600s.

 

Im not sure I follow? If you installed your 5100s at the lowest snap ring groove then that means you have three more snap rings to go up on.

Also 5100s when compressed by hand are stiffer than 4600s but with the weight of the truck on the ground (and most importantly when the 5100s are installed on the lowest snap ring groove), the difference in ride firmness is negligible.

 

Correct; I thought I would have achieved exactly the 2wd height when I installed them on the lowest groove and might have wanted to go up one groove after seeing it. Because the 5100s didn't lower the truck down to 2wd height I am effectively already 'up one groove' from where I thought I would be. The truck looks good; glad to hear about the ride quality...I'll try to forget about it!

 

Take the shock to a quality machine shop and have them cut an additional ring land where you want it. Before I put the 5100s on my RCSB I had two additional lowering lands cut in case I wanted to go lower. It cost me about $80.00 for both. I would have done it myself but all my machine shop access is in SoCal and I live in ETN now.
Bottom line is if you are trying to do something custom then get your wallet out. Don’t complain that you can’t get your desired result with off the shelf pieces.

 

Yes that’s a viable option or you can also have the Bilstein-supplied spring perch collar machined down some as well, or use the 4wd Bilstein spring collar on the Bilstein 2wd strut. Doing either of those will yield a 1/4” additional drop. But remember that every additional drop will slightly lower the spring rate below stock, since the length which the spring is compressed into is increased. I’d love to knock a few in/lbs off my front springs so after I see what the ride height looks like with the additional 80lbs of the Whipple on it, I’ll explorer grooving the Bilsteins.