Knuckle Centering Issue - Real time help needed

[74HogGuy]

I'm working on centering my knuckles right now using the SST.

I'm getting:

A: 167.68mm
B: 165.18mm
C: 2.5mm
D: 5.7mm
E:2.7mm
F: -0.2mm

Overall it seems that the total shim thickness seems correct around 2.5mm, but the FSM says that if theres considerable difference between E & F then to remeasure.

Is it ok to have have ~2.5mm shim on the bottom and 0 shims on the top?

Thanks,
Justin

 

[Rigger]

Mine is a relatively uninformed opinion but isn't it normal to have more shim thickness on bottom?

 

[74HogGuy]

Based on the shimming on my drum brake knuckles I'd say yet. There wasn't a single shim on top. Just trying to make sure the 2.5mm of shims seems normal in total. Both sides were right at this with the bulk of the shimming on bottom.

 

[Bluegrass40]

Here were my drivers side measurements:
167.3098
165.0873
2.2225
4.2037
1.203706
1.018794

Pass side
167.2336
165.1
2.1336
3.3274
0.327406
1.806194

My knuckles were leaking (which prompted the rebuild) and the shims that were in there were significantly off. I'm assuming that the knuckle job had been done in the past without much attention to the shims. The shims that were in there were exactly the same on the drivers side as they were in the pass side. When I saw this turning dissassembly, I knew something was up!

I also measured each side 2-3x.

Good luck.

 

[Bluegrass40]

Mine is a relatively uninformed opinion but isn't it normal to have more shim thickness on bottom?

Why would that be the case?

 

[74HogGuy]

@Bluegrass40 - your measurements make me feel better. I was worried that 2.5mm of shimming per side was way out of whack. I too took the measurements 3 times per side to make sure I wasn't crazy. Sliding off the lower bearing without erasing my lines was a chore.

 

[Rigger]

Why would that be the case?

I don't actually know. I do seem to recall a thread where it was pointed out that most all knuckles have more shim on bottom than on top.

I'll dig into it a bit and post more if I can find it.