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Existentialism-- Just a bloody good excuse to go riding...

Sunday, January 19, 2014

XT M765 rear hub overhaul

All the mud and slush this monsoon has been pure fattie delights right up till last week's Green Corridor ride. Time to lift my procrastinating ass and pay the maintenance due now....

Needed sizes of cone wrench, 15 and 17mm

Of all places, finally found my cone wrenches needed to open up the XT hub at Daiso!
And that's where I got my magnetic trays awhile back plus a few other bike workshop bits. See...cheapo shopping at $2 Bucks Store does have its merit.

2 pieces included every size except a 15mm slot... but at least it wasn't hard to file down by sacrificing the 14mm from the smaller one.

Not sure how many ball bearings are on each side after taking out? Its 9 a piece and if yours are crushed are pitted-- get them at hardware shops. Size = 1/4" diameter.

Having been on mostly sealed cartridge bearing hubs for the better of the last 10 years, it took a bit of digging at the neural archive on how these hubs work... but exploded diagrams from the web is never more than a few keystrokes away. So fret not.

My rule of thumb? - Place everything in sequence. Last in first out and face-up each small bit in the direction they are removed. That way each piece that goes back in, the inner surface is always the way you set it down. Seems trivial until you pick up a piece look away and then back at it only to wonder if a recessed surface should be facing in or out.....

Remove bearings, axle + bits and clean everything out. For ease of  assembly afterwards and the unwinding for the next round of maintenance- degrease the axle to totally remove all grit.

Most freebody removal of sealed bearing hubs is simply a matter of pulling it off and catching any pawls and springs along the way. Takes a 10mm hex for Shimano hubs. Pawls and spring are further sealed away. Mostly clean and no gritty feel... not stripping freebody further.

Doubt this hub ever gotten open up before and the grease within looks kinda sparse. No problem just repack but not gonna reveal my super secret frictionless goo in use ;p

Same was done for the non drive side bearings

For the less adventurous, the method is only to remove the axle bits from the non drive-side (NDS). That ensures the drive-side end that goes into the dropout remains fixed and all you have to do is put everything back on the NDS and the axle alignment should not be off.

Still others advocate measuring the ends that stick out before removal so that you know where the end bolt should be on the axle on re-installing.

I thought about it-- what if  I just want to have everything out to be cleaned but don't have a Vernier caliper. Well I do but...
Use your frame dropouts as a guide. For vertical dropouts, turning the bike over would make life easier.

Just out of curiosity, I measured the axle length and also the end-end of the dropouts (which is about 4mm longer at 150mm). But final alignment is still best done with Eyeball-O-Meter as usual.
Screw in drive-side cone, align axle shaft into position within dropout..wind cone until it touches side of dropout. At this point take out the axle and slightly tighten with the 15 and 17mm cone wrenches. It's a little tricky doing it freehand. Clamp the NDS axle end between your knees. These are times when you really feel good having a vice of sort... no matter how dodgy a little thing it may be.

Back to the bike.... lube and put everything back in reverse order. Do not forget the two seals... if you have taken it off the freebody (part no. 11) and the NDS cone-shaped one (part no. 9). There is also the funny shaped washer (part no. 13) between the hub and freebody.

Yes it was Fix and Bake day...almost forgot. Tuna Puffs in the oven...

and while munching, giving it a good spin to see everything's revolving as they should be...

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