Shimano Deore XT HB-M785 retainer vs loose bearings



ThingBlob

New Member
Dec 25, 2013
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My question has to do with the way loose bearings look in an HB-M785 hub. That's the 2012* Deore XT front hub with the plastic bearing retainer (w/11 bearings) and a 14mm** hallow axle. The lock nuts are a nut/adapter (reducer) combo with a 5mm socket head.
I can almost fit 13 - 3/16 bearings in there, but they bind. If I put 12 in there (all new by the way), without the seal, and manually turn the axle, I can sometimes see a gap of almost one bearing diameter (minus the difference caused by the compound angle) in group***.

Is that ok, or, should I put the retainer back in?

The reason I ask is because the reducer part of the lock nuts no NOT seem centered. I recently sized up the loose balls and it seems that the original Shimano bearings are a tiny bit bigger. Perhaps that's the lot they came from?

Am I just being paranoid?

*I think it's 2012.
**I read somewhere that it's 14mm.
***I'm pretty sure I have the cones properly adjusted - a little drag with no rattling.

PS: I originally posted this in a not so appropriate place. When I copied it here, I removed one thing and added another.
 

alfeng

Well-Known Member
Jul 23, 2005
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IF the "plastic bearing retainer" to which you are referring is simply a carrier ring which holds the 11 bearings, then it is merely a convenience which was introduced to facilitate assembly ...

carriers are typically not used for hubs, but I haven't dis-assembled a Shimano through axle hub ...

but, why not use carriers for hub assemblies?!?

FYI. The carrier rings are not found on bikes before ~1980 +/- ...

again, it is a convenience for assembly and/or dis-assembly ...

but, if the "plastic bearing retainer" is some type of shroud to keep water/mud/dirt out, then you need it.

So, you should be "okay" with the 12 loose bearings sans "retainer."
 

CAMPYBOB

Well-Known Member
Sep 12, 2005
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As Alf stated, 12 loose balls should be good to go. Make sure you are not just adding one more ball from a different/new bag of bearings. Add twelve new balls all from the same production bag or container.
 

ThingBlob

New Member
Dec 25, 2013
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Thank you for your input.

This is the first time I've seen this kind of configuration. This is also first set of hubs I've ever seen with 3/16 bearings in the rear hub too. And they appear to both have the same diameter hollow axle.

I probably shouldn't be so paranoid, since the cones are quite large, and are not likely to fall into a gap with 12 bearings.

Thanks again.
 

ThingBlob

New Member
Dec 25, 2013
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Thank you for you input.

And yes I did. So ALL of the new bearings are about 5 10,000ths of an inch smaller than the original Shimano.

Thanks again.
 

CAMPYBOB

Well-Known Member
Sep 12, 2005
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5 tenths makes a difference! I take it that you own and know how to use a micrometer...uncommon trait these days. 99.9% of the people on the planet could not figure out that half a thou in a bearing is big enough to park a semi in! Hat's off to you, OP! Good call.