Disc conversion shim question (1 Viewer)

[cruiser_guy]

I posted in my "Can this birf be clearanced" thread to try to keep all this info in one place but no one noticed so here it is again.
I have clearanced the axle and taken my measurements with the OEM knuckle centering tool. After I've gone through the formulas I end up needing a NEGATIVE number of shims on the bottom and about 2.5mm on the top (total shim requirements on both sides came to less than 3mm)!
Does that make sense? This is a '67 axle with a mini disc conversion

 

[jim45r]

Didi you find the same measurements on both knuckles? That would mean they are both off center by a lot (2.5 mm is a lot in the world of shim adjustment). If other people have successfully done pre-68 axle to mini knuckle swaps without these problems, then I'd suspect an "Oh s***" kind of error, like putting the knuckle on upside down or something. Did you check to see if the fill plugs were pointing up when you did your measurements?

 

[cruiser_guy]

James, have you got to your mini disc front yet? I had approximately the same on both sides 9one was 2.1 and one was 2.65 and I had the knuckles on correctly (fill plug up and oriented to ensure the axle is straight [if it was upside down there would be incredible caster!]).

 

[jim45r]

Yup, but I found a '73 axle, which had birfs, fine spline inners and the seal inside rather than the old bushing in the '66. I still had to remove some material to fit the mini birf, just like they describe in the tech articles. I didn't have the alignment tool, but a buddy who builds TLCs and minis advised me that he typically found from the factory that they use .040" shims top and bottom, so what he does when replacing knuckles is go with the 40s top and bottom, then shim for correct preload, starting with the thinnest shim on the bottom. That's what I did, and it really went pretty quick. I won't know whether it actually works until next summer, when I hope to get the rig running. As I understand it, if you don't have it centered, it will wear the inner seal out.

For it to be out of center in the negative millimeter range, something has to be goofy. Either the older axles are different, the knuckles are odd, or you're measuring or calculating something wrong. I don't know whether the non-US parts are different. Are you following the FSM method for calculating? Are you converting all of your units to either english or metric? Did you use a gasket between the knuckle and the spindle when you made your scribe on the rod gauge? Did you replace all of the knuckle bearings? Use OEM? What a mystery!

 

[too tall]

if there is any question why not assemble while checking the preload as you torque ,if the knuckle goes too tight -too many shims.

 

[cruiser_guy]

Well the mini axle had some 1mm shims in it for sure (not 0.4mm's only). I'm doing all the measurements in mm to avoid conversion screwups. The preload on the first bearing was nearly dead-on. I had to add a 0.1mm shim for the right pre-load (to me that's forgivable when trying to measure the scribed line on the OEM tool). All new knuckle bearings and races (races were thoroughly seated in the recesses and the recesses were cleaned out), though the bearings are not Koyo they are equivalent in that they have the sharp angle to carry the axial load etc. etc. I didn't use any shims in the initial measurements and followed the diagram in my manual for the '60 series because it seems clearer.