Kingpin Replacement

[BOTIGER1970]

Hi all,
I started the rebuilt of my front suspension for my 1970 280SL.  I have taken everything apart and cleaned all parts.  I have also powder coated the appropriated parts.  I'm now in the process of putting all required parts for my Kingpins together, but am having problems with the shims and getting the spindles to move back and forth correctly (smoothly).  I have tried using the smallest shim on each side, but the spindles tighten up before I get to the proper torque setting (64ft lbs).  Has anyone else experience this issue and how did you resolve the problem.  I appreciate any advice on what I might be missing in my reassembling process.  FYI, I have replaced the Kingpin bushings, washers and nuts. 
Thanks,
Mark

[Duncan200]

Hi Mark,

If you are doing them up without the spring load on them, then I suspect that may be the reason you can’t get to the torque.

At least that was my issue.

Doug

[BOTIGER1970]

Doug,
Thank you for your response, and yes that is exactly what I was trying to do.  I saw a You Tube video and the gentlemen was doing it without the springs installed, so that was how I was doing the procedure,
Mark

[ja17]

First of all, make absolutely certain that upper notched spacer has remained keyed in place around the index pin. If it has shifted during assembly, it will cause the kingpin to bind. Next is not uncommon to find that even the thinnest shim is too thick, If so no matter what you do, the assembly will bind during final torque. I have run into this issue many times. To resolve the problem, temporarily assemble the unit without the lower shim. Measure the up and down movement of the king pin and check it against specs. Some movement up and down is normal and the specification is given in the factory procedure. The king pin should now turn easily. Calculate the excessive up and down clearance of the assembly without the lower shim installed.  A  machine shop can precisely grind one of the shims thinner, to provide the specified clearance. Install your new thinner shim to finish. Since the connection of the kingpin is tapered, allow for a little additional compression of the parts, during final torque so things don't get too tight again.

[BOTIGER1970]

Joe,
First let me offer my condolences to you and your family on the lost of your wife.  I appreciate you taking time to respond to my issue, thank you. 

I'm very new to the king pin process and want to make sure about when I do the process you described; is that with the springs in or out?  Since I have the suspension out of the car,  I will have to use a spring compressor to take the springs in and out.  On the one side I did the process as you describe (no springs) and still had tightness on the spindle before I go to the proper torque setting.  I have checked the thrust washers and everything seems to be in place.

Mark

[ja17]

Thanks Mark,  it should not make any significant difference with the springs in or out. It is a tough dirty job for even the experienced.

[BOTIGER1970]

Thanks Joe.

[ja17]

McMaster Carr, sells metric shims from .1mm thickness to 2mm thickness. Looks like the 20mm inner diameter by 28mm outer diameter should work. https://www.mcmaster.com/products/metric-shims/

[BOTIGER1970]

Joe,
Thanks for the information.  I've worked on one side and got it to work well without a shim and torqued to 64 FT LBS.  However it only has an up and down motion of approximately .5mm, which is what the book calls for with a shim.  Feel like I'm missing something.  What is the thinnest shim you've ever heard being used?  has there ever been a time a shim wasn't used?
Thanks again,
Mark

[ja17]

When the suspension is loaded with the weight of the car, there is not much load on the lower king pin assembly. Some clearance is required to enable the steering to operate freely, as you know. The excessive clearance specification in mainly to prevent noise and pre-mature wear from the loose fit when traveling over bumpy roads. In this respect the main purpose of the lower shims is just to adjust the spacing and is not critical as long as you are with-in the factory spec. Since you are near the outside of the specification with .5mm you might consider adding a .2mm or .3mm shim. As you know the clearance gets tighter and tighter until the final torque is achieved so don't use a shim which is too thick! Grease the front suspension at least once a year and you should never have to go through this again!

[BOTIGER1970]

Thanks Joe, I'll let you know how it turns out.  I'm happy to be learning new things about the car.  Much appreciated.