LM501311 Conversion race - problem

Nikmill....this sounds like one for you...

This is my second front disc brake conversion I'm doing...the first was on my 68' Jeepster and it went over easy peasy.....now I'm doing my 55' CJ5 and I've already ran into a headache.

In both cases, I've used the LM501311 conversion race for the rear of the hub, to space the hub/rotor out properly. I've read that there's differences between the "early" model hubs on the D25's....vs a "later" hub (like my Jeepster would have had) on the D27. For instance, on the Jeepster hub, we had to machine the back side of the hub pretty significantly to make it true, plus we had to remove material from the back snout of the hub on the flywheel lathe just to get the rotor eccentric to lay flat against the hub snout and face. No biggies...took very little time and everything worked great. On the 55' CJ5 hub, the backside was already true as it was, and sandblasting the hub prior had it nice and clean....plus the snout on the backside of the hub is much narrower and no material needed to be removed...in fact...the eccentric on the rotor is actually too big...but that doesn't matter as the studs line everything up.

So...here's the problem...my machine shop guy calls me and says we have a problem...the 501311 race is actually .016 larger outer diameter than the 18520 original race (also a Timken number). He measured the hub I.D. and confirmed, saying anything over .003-.004 press fit is going to be problem, break the race, damage the hub, etc. We were puzzled as to how the Jeepster hub worked fine and this one doesn't...so I took to the paper catalogs and went to a local bearing shop to help me out...turns out the 501311 race is bigger....The 18520 race is 2.875 outside diameter....the LM501311 race is 2.8910. I told my machine shop guy not to proceed yet. I suppose I can rout out the inside diameter of the hub just a tad, freeze the race and heat the hub...but why in the world isn't this going to work? Has anyone else encountered this? I'm only assuming that maybe the press-fit on the Jeepster D27 hub is either much looser, or has a different stock race in it than the D25?...but I haven't confirmed that yet.

Anyone else have any experience with this? I really don't want to take a die-grinder to the inside of the hub or pay the machine shop a crap-ton of money to bore the back of the hub.

 

I had the exact same thing happen. You have to use a later hub.

 

The problem is the early hub. The conversion race won't work with it anyway as it only works to replace the LM50310 race, and it's just enough wider to center the rotor and hub to the caliper.

The earlier hub uses a narrow inner bearing and race just like the outer and the step in the hub that the race seats again is in a different spot to accommodate this. The later hub uses wider/heavier duty bearings so the location of the step in the hub works.

I've heard some people have used the early hub with stock bearings and races and had everything line up ok, but I've never done it as I've always wanted the heavier bearings, so I always use the later hubs.

 

You need the later hubs that will accept the larger bearings (and wheel seal)
When doing the drum to disc conversion on the Jeepster, you happened to have the correct hub so you could swap the races.
On the early hubs, no-no.
That would be my take of your problem.

 

Ugh. I'm going to slap the races back in and see if everything will line up. At least it'll be documented here for future peoples to try. Ugh...I wish I would have known this...my fault for not reading enough I guess. Another idea we had was to press a large, hardened seat into the back of the hub first (approx 0.20) and then put the race back in...that should space everything out if needed....or possibly use a washer/spacer on the backside of the bearing maybe...inbetween the bearing and the seal?? I'll see what happens...I've already got new studs pressed into this freakin thing. UGH!

 

I feel your pain, main ... I gotta press a bunch of studs out for the exact same reason ... just haven't done it yet. In fact, I am going to make a stud pressing jig, because I got real tired of lining up sockets under a heavy rotor/hub combo. Sucks to have to learn the hard way ...