Not bearing up

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MartinF
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Not bearing up

Post by MartinF » Thu Nov 04, 2004 14:07

After last Sunday's ride at Brockley Combe, my bike's wheel bearings sounded less than totally healthy. Took it to the local shop for a 2nd opinion, which they unfortunately confirmed. :'-(

WHilst I'm sure I could manage to dismantle, degrease, regrease & reassemble the front hub bearings, the rear one sounds somewhat more complex, involving the removal of the gear cassette, which itself requires special tools :'-(

Can anyone throw any light (or any dark, for that matter) on the subject?

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Ian Long
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Post by Ian Long » Fri Nov 05, 2004 17:23

Your rear cassette is held onto splines on your freehub (the bit that allows the chain to stay still while the wheel rotates when your not pedalling). It is held in place by the smallest sprocket which screws onto the freehub, locking the other sprockets into place.

The freehub itself has bearings which are also known to fail (as mine did while Neroli and I were riding round the Lake District - I eventually had to replace the entire hub and get the wheel rebuilt :-( When this happens it a.) makes a horrible noise and b.) the bike won't stay in gear because the cassette is wobbling too much - one of the many reasons I have found for my bike not staying in gear)

To remove the locking sprocket you need the tool appropriate for the type of rear cassette you have. The tool looks like a large socket and (ideally but not always) slides over the axle and engages splines on the inside of your rear cassette.You have to remove the quick release spindle and occassionally the outer cone to push the tool far enough in to engage the splines properly.

It is then a matter of holding the sprockets still while you unscrew the lock ring. A "chain whip" is the ideal tool for that, something that looks like a car oil filter remover but has a fixed and floating length of bike chain that wrap round your sprockets to hold them still while you turn. If you don't have one, I have got by in the past by putting soft wood either side of my sprocket and tightening it in a vice. The teeth dig into the wood to protect themselves and "should" live happily ever after.

After that the chain rings and spacers slide off the freehub. Usually the smaller chain rings are separate entities with spacers and the remainder are all one unit. (Note when you reassemble, one of the splines is wider than the rest to act as a key and ensure the sprockets go on in the correct orientation.)

With the cassette off it should be straight forward to access the wheel bearings and associated surfaces.

Trying to access the bearings for the freehub appears to be a significantly more involved process, also requiring specialist tools.....
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steve powell
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Post by steve powell » Sat Nov 06, 2004 09:21

We have several bits and bobs that may fit for this job. Will bring them along tomorrow.

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hubs & bearings - the continuing sago

Post by MartinF » Mon Nov 08, 2004 17:02

As I mentioned yesterday, I had my wheel bearings serviced (new ball bearings & regreased) at the new Chain Life shop in Thornbury last week.

Cleaning down my bike after yesterday's great outing to Cwmcarn, I noticed my front disk rotor was slightly buckled. I'd also noticed yesterday that braking eficiency seemed less than should have been - that was grease they'd managed to get on the rear rotor!

Anyhow, my front wheel wasn't spinning quite as free as I thought it should be. Then I noticed the bearing nuts weren't tight.

Cut a long story short - they'd only cleaned/repacked one side of the hub. The other side was still dirty, but worse still - they managed to drop one of the ball bearings down inside the hub (where it's effectiveness is highly questionable) leaving a deficit of one in the bearing department. Interestingly, another of the ball bearings is very discoloured - burnt, even.

Don't think I'll be using that shop again for servicing.

Rear hub not yet dismantled, but still noisy/graunchy. So I guess I'm going to have to bite the bullet, buy the ness. tools & get on with it. Nothing like diy! :wink:

BTW: The bearings themselves, seem to be about the most basic I've seen: Simply a backplate pressed into the hub, upon which the ball bearings sit. There's then a bearing nut on the spindle which tightens down on the balls, an outer lock nut, and a rubber "cone" to cover it up (pretty poorly). (I'll post some photos tomorrow.) Is this normal for a bike hub/bearing?

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Re: hubs & bearings - the continuing sago

Post by MartinF » Tue Nov 09, 2004 23:32

MartinF wrote:Is this normal for a bike hub/bearing?
To answer my own question - "yes, it is". At least on the cheaper end of the market. Reasonable sealed bearing hubs seem to start at around £40. The former is fiddly, but possible to maintain, the latter shouldn't require maintenance, but when it does, can be a dog to remove the bearings.

To add to the sago: The front hub is shot. No question. There's a high spot on the inner ball race race.

Q: Do I replace the hub (~ £17 for a new hub), which necessitates new spokes also, wheel rebuild, spoke tensioning, wheel truing and aligning (~£35 + hub), or do I go for a new wheel?

A: I've plumped for a new hand built wheel - still very much at the cheap end of the market: Shimano Deore hub, Swiss DT spokes, Mavic 717 rim; all built, including postage, for £50. And keep my old wheel for emergencies.

Hopefully should arrive in time for this weekend's Afan trail bash.

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Post by MartinF » Wed Nov 10, 2004 21:44

Rename this thread "MF and the art of mountain bike maintenance" :wink:

The bearings on my original front wheel are now rebuilt & much happier. I took to the bearing surface with 400grit wet & dry paper, repacked with grease on both sides & got exactly 12 * 3/16" ball bearings on each side (better than having only 11 on one side!). It's not entirely noise-free, but has no play at all now & is certainly much better than before the Cwmcarn ride last weekend. If my new wheel doesn't arrive in time, my old one will do fine for the proposed Afan Forest ride this next weekend.

Better still, the wheel now sits further over to one side than before, meaning the disc rotor is now further away from the fork. It previously had so little clearance, it had been wearing the paint off the fork.

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Post by MartinF » Thu Nov 11, 2004 17:06

Respect to Chain Reaction in Northern Ireland. My new wheel arrived today!! Fantastic service.

BUT!!! The disc rotor is once again only about 1.5mm clear of the fork.

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