Size of ball bearings in Shimano hubs

[Lightning Phil]

I’ve got two Shimano hubs , one appears to use what look like the standard (ish) size bearings I’d expect to see. The Dynamo hub uses smaller bearings than I’d expect.

I’ve had a look but can’t find the Shimano technical diagrams that would state the ball bearing sizes.  Do such documents exist and any clues as to how search and find the right ones?

[rogerzilla]

There are so few potential sizes that you can just measure one ball with calipers.  They will be 1/8", 5/32", 3/16" or 1/4".  I don't think Shimano ever used 7/32", but Campag and Sachs did.

[sojournermike]

Front and rear are typically different. DA9000 are 5/32 and 3/16 iirc. Not sure about the Dynamo hubs.

As Roger says, easy enough to measure but SJS sell replacement kits that tell you the size - you can of course buy the bearings cheaper if they’re not labelled shimano.

[rogerzilla]

The only Shimano dynamo hub I've overhauled was the (easy to do) DH-F703-B Brompton one.  That has 3/16" bearings like most front hubs.

[FifeingEejit]

What's the hub model number?
Critical information if checking your google/Tech Doc Fu is failing you.

[Lightning Phil]

What's the hub model number?
Critical information if checking your google/Tech Doc Fu is failing you.

Rear is SHIMANO XT HB-M756-A I think.  The front is SHIMANO XT T785 Dynamo Hub. I look forward to seeing the results of your superior Google Fu

[Lightning Phil]

Damn just found size for rear which are 3/16”. Why didn’t I find that tech doc before?

[Lightning Phil]

Now also found tech doc for front which claims they are also 3/16” but pretty sure they are not. Sure I’d done those searches before but the user and dealer manuals were what was coming up.

[FifeingEejit]

So your google fu was failing you, but it then redeemed itself before anyone else could use the model numbers to have a bash at it.

 

[Lightning Phil]

So your google fu was failing you, but it then redeemed itself before anyone else could use the model numbers to have a bash at it.

 

I don’t use Google for search which maybe is the problem.

[FifeingEejit]

Google is a generic term even if they don't like it...

I was actually thinking you were digging around the Shimano tech docs system in this case.
I've plugged numbers in before and got nothing, then 5 mins later i type it in again and it works... typos possible in that case.

[Lightning Phil]

Google is a generic term even if they don't like it...

I was actually thinking you were digging around the Shimano tech docs system in this case.
I've plugged numbers in before and got nothing, then 5 mins later i type it in again and it works... typos possible in that case.

I was indeed in the tech docs section (and sometimes search engine) but their search is hit and miss.  Plus naming of documents not the most intuitive outside of Shimano dark basement world!

[BFC]

In the shimano technical documents the usefull documents for this are "EV" (exploded view?) which list serviced parts (and inter series compatabilities when apppropriate).
In EV documents under General category there are 5 pages (of 25) items for Dynamo Hub sub category.
A quick look at a few says they are 3/16" balls.

[D.A.L.E.]

Rear is SHIMANO XT HB-M756-A I think.

Definitely 1/4" then. HB is a front hub, FH is rear.

https://si.shimano.com/api/publish/storage/pdf/en/ev/FH-M756-A/EV-FH-M756-A-3295.pdf

https://si.shimano.com/api/publish/storage/pdf/en/ev/HB-M756/EV-HB-M756-2098A.pdf

[Lightning Phil]

Thanks for that. I know front are smaller than rear. That’ll help when I order some ball bearings.