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View Full Version : Replacing Freehub body on Shimano M756 hub - not quite matching replacement body?



brendan
04-28-2014, 10:53 AM
Hi folks.

I'm replacing the freehub on the M756 on the 2010 big dummy, but ran into an issue.

I ordered this part: http://www.amazon.com/Shimano-M756-M570-M555-freehub/dp/B0012K7M44

It appears to be the right size freehub, but in addition to having loud pawls (the existing pawls have always been silent, so I'm perplexed) it includes a pressed-in and non-removable metal dustcap/ring. The existing freehub uses a rubber seal and a retaining cap for the same purpose.

The metal dustcap makes it extremely difficult to get the drive-side cone properly placed when the axle is installed because the adjustment surface is recessed below the dustcap when it sits correctly on the bearings. I suppose I could try to get it into place by sight/measurement with the axel removed, then insert it into place...but that's going to be a lot of repeated trying, failing, disassembling, reassembling.

So, I have questions related both to learning as well as solving the problem...

Do more recent M756 hubs come with a different stack of axial parts? Do the other hubs that share the same freehub body use a taller cone unit and less spacers/seals beyond it?

Did I order the wrong part? If not, do I need to order a replacement set of axel/cone/bits to make it work?

Should I just have ordered a replacement hub and transferred the axial parts, the freehub spacer and the freehub to the old hub?

So many questions... :)

Thanks,
Brendan

PS - I also plan to build up new wheels this summer to have a set to replace the Salsa Gordos when they fail. Any suggestions for a similar set of 26" heavily reinforced rims?

cyclingfool
04-28-2014, 11:14 AM
I'm afraid I probably can't be much help on the freehub questions... I just did my first hub bearings overhaul this weekend, but have never touched a freehub replacement, though I would give it a go if I had to.

That said, I wanted to chime in with a rim recommendation... I have been VERY happy with my Sun Rhyno Lite rims (26" 36h). They're double walled w/ hole eyelets. I built up a wheelset with them last spring/summer. Suffice it to say I am a heavier rider, and almost all my riding includes a loaded set of panniers on the rear or a Burley trailer hooked up behind to tow my son, and I only have to do a little truing on the rear once after about 1,000 miles of riding. Otherwise, they've been bulletproof. (Knock on wood.) No broken spokes and nice and true.

I don't know if they're heavily reinforced enough for your purposes, but they're solid rims and quite affordable.

paulg
04-28-2014, 12:01 PM
I think I know what you are trying to do. Before inserting axle into hub you lock the cone and the locking nut on to the axle on the drive side, then put in the new wheel bearings into grease in the freehub to stop them falling out, you can then insert the axle from the freehub side to sit the cone against the bearings. Now you thread the cone and locking nut to the axle that protrudes on the NON drive side (after putting in new bearings in grease) and do all you axle adjustments on the NON drive side where you should be able to access, with cone wrenches, both the cone and locking nut.

This article is great for cone adjustments.

http://sheldonbrown.com/cone-adjustment.html

Hope that helps.

Harry Meatmotor
04-30-2014, 09:07 AM
I think I know what you are trying to do. Before inserting axle into hub you lock the cone and the locking nut on to the axle on the drive side, then put in the new wheel bearings into grease in the freehub to stop them falling out, you can then insert the axle from the freehub side to sit the cone against the bearings. Now you thread the cone and locking nut to the axle that protrudes on the NON drive side (after putting in new bearings in grease) and do all you axle adjustments on the NON drive side where you should be able to access, with cone wrenches, both the cone and locking nut.

This article is great for cone adjustments.

http://sheldonbrown.com/cone-adjustment.html

Hope that helps.

This is exactly right - another reason to only touch the non-drive side lock nut and cone is so you don't affect the drive-side outer lock nut to drive-side hub flange spacing. If you add or take away spacing from this side of the axle, you're shifting will be off as you've effectively moved the hubshell either towards or away from the dropout in the frame. Also, the metal dust cover is, in fact, removable, but you'll likely need a blind bearing pull to remove it without damaging it. Another tool that's indispensable when working on cup and cone hubs is a decent axle vise. Hozan makes a nice axle vise (http://www.amazon.com/HOZAN-YD-1027-axle-holder-C-354/dp/B000BSBSKW/ref=sr_1_fkmr1_1?ie=UTF8&qid=1398866570&sr=8-1-fkmr1&keywords=hozan+axle+vise) but the Park Heavy Duty axle vise (http://www.amazon.com/Park-Tool-AV-4-Heavy-Pedal/dp/B000C14PDU/) works just about as well.