Shimano Exage HB RM50 hub

[Sweep]

Anyone got any views on them?

I acquired a 90s Ridgeback hybrid the other day for all of £21 that came with one on the front.

The hub is definitely slim.

Haven't taken it apart yet but first impressions are that it is smooth, despite the grotty state of the rest of the bike.

On the hub it says that it is "sealed", implying cartridge bearings, but a quick google seems to imply that it actually uses loose ball bearings.

[meic]

I think that it has the word sealed on it because the other (possibly earlier) RM50 hubs that I have are certainly not sealed in any way.
Hopefully the ones that you have are improved over mine in that respect.

My RM50 hubs are pretty cheap but solid and serviceable with that one flaw that they let water in very easily. The front ones were soon replaced by some cheap modern ones with seals in, the rears I hang on to because they are Uniglide hubs and I need them for my Uniglide cassettes (which I bought for my Uniglide hubs ). When packed with waterproof grease I can get about a thousand miles (a year on that bike) without worrying about regreasing, unless I get really wet.

[random37]

There are no cartridge bearing hubs in Shimanoland.

Exage hubs are good, middle quality. Original equipment on my Dawes Galaxy in about 1992. There is no reason that it won't work perfectly well as a hub, with a bit of grease.

[Sweep]

Thanks folks, and thanks random for the encouragement. "good middle quality" sounds good to me, as I have the impression that once away from the very bottom Shimano doesn't do anything that is really bad. Dawes Galaxy circa 92 sounds like a thumbs up.

Looking forward to having a look inside them.

Maybe they will last be a good few years yet.

Not sure what the accompanying rear hub is - haven't cleaned all the grot of yet. That also seems to spin well.

[Brucey]

There are no cartridge bearing hubs in Shimanoland.

plenty in bottom brackets, headsets, RD pulleys, etc etc etc ...

Exage hubs are good, middle quality. Original equipment on my Dawes Galaxy in about 1992. There is no reason that it won't work perfectly well as a hub, with a bit of grease.

IIRC the 'sealed' versions of RM50 hubs have the 'ring in a slot' type seals that were first seen in the 1980s. They are not super effective but if you (say) add a grease port and use it, the hubs will give good service. If with water is kept out and they are adjusted and lubricated correctly, they just get smoother the more miles they do.

cheers

[random37]

There are no cartridge bearing hubs in Shimanoland.

plenty in bottom brackets, headsets, RD pulleys, etc etc etc ...

All well and good, but we're talking about hubs.

I used to commute 20 miles a day on my Galaxy. The hubs lasted for quite a few years. Certainly enough to rebuild them onto three new rims.

With most bike parts, if you keep them clean and lubricated they will last a long time.

[Brucey]

IIRC there may have been some (short lived) Dura Ace /XTR models which had cartridge bearings inside the Freehub body.

Here

http://si.shimano.com/pdfs/ev/EV-HB-RM50-0981B.pdf

you can see the HB-RM50 EV techdoc. Items #6 are the seal rings. These commonly stick in the grooves and do little good. This hub will accept cones from a number of other models of shimano front hub. IIRC the hubshell is not anodised, so can be polished to your heart's content.

The matching rear hub FH-RM50

http://si.shimano.com/pdfs/ev/EV-FH-RM50-0982A.pdf

has no seals and its most common form has a UG compatible 6s freehub body. Very commonly the weather gets in the LH side of the freehub body and ruins the bearings, even if you keep on top of the main bearing condition. You can fit HG sprockets to this freehub body, provided you use a UG top sprocket to hold them on and modify the HG spline on each sprocket so that it fits the symmetric UG spline.

You can of course change the freehub body for another one without great difficulty. Briefly shimano made hubs which accepted both UG and HG splined 7s/6s cassettes; one of those would be ideal.

cheers

[Sweep]

The front ones were soon replaced by some cheap modern ones with seals in, the rears I hang on to because they are Uniglide hubs and I need them for my Uniglide cassettes (which I bought for my Uniglide hubs ).

Ah, just noticed the possible significance of this.

There are different standards for the cassette/freehub interface splines? I had imagined all Shimanos were the same.

[Brucey]

There are different standards for the cassette/freehub interface splines? I had imagined all Shimanos were the same.

as explained in my post. Pictures on Sheldon brown.

cheers#

[Sweep]

sorry brucey, scanned too quickly.

In their good sense Ridgeback may not have used this on the rear - I didn't notice the same clear branding. Will clean some muck off it in the near future and check it out. Pretty sure the bike would originally have been 7 speed.

[meic]

Pretty sure the bike would originally have been 7 speed.

The RM50 may have started with 6 speed but the 7 speed fits fine too.
I think that they were still being used on the 7 speed bikes as well as the 6 speed ones.

[NetworkMan]

Pretty sure I had them on the 1992 Horizon which had 7 speed Hyperglide, but neither front nor back had seals. Dawes spec. sheet says front hubs are Exage so they may have been part of the Exage groupset.

[Sweep]

eventually did some fiddling with this when I needed a new front wheel for another bike.

Opened the hub up.

Couldn't see any seal in a slot.

Did note that, as brucey reckons I think with new hubs, there was very little grease in there.

Pretty sure that in 20 years this hub had never been serviced, but on the other hand am fairly sure that it had hardly ever been run.

Now runs very nicely, far nicer than the XT hub wheel which, in my earlier ignorance I had allowed to degrade through lack of care.

The whole wheel (rim is Araya) appears to only be 50g heavier than the old CXP22 XT hubbed wheel.