Yet Another Cycling Forum
General Category => The Knowledge => Topic started by: greenmeansgo on 05 June, 2011, 11:07:41 pm
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I noticed recently that the rear hub on the fixie isn't very smooth, despite doing exactly the same mileage as the front hub.
1. Does anyone know what / where I should be looking for replacement bearing units?
2. Why should the front be fine but the rear not? Simply weight borne by the respective hubs?
Cheers
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Your rear hub takes all the grunt from your drive. If you can get the bearings out measure them accurately (internal dia, external dia, and width) and you'll probably find a commercially available bearing available. If not Wheels Manufacturing should have them.
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2. Why should the front be fine but the rear not? Simply weight borne by the respective hubs?
one thing that destroys rear fixed hubs is having the chain a bit tight, so it binds. It should be tight enough that there's no real play but not so tight it binds. Which is fine if everything is lined up & round & concentric, not so easy with cheap/worn components
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:) sounds about right. I have a tendency to run the chain fairly tight.
Thanks for the Wheels Manufacturing link. They have a nice pdf for identifying which bearing you need. Doesn't look like I'll have to measure that accurately either (just to the nearest mm)!
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Think they are 6001 rs whne you remove them the number are written on.
Any bearing supplier can do the bearings without fail.
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Great, thanks.
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Get a '2RS' as a replacement - that means it's double sealed (moisture can still get in from the inside) and should last a good deal longer.... if your chain isn't too tight ;D
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More friction though! and moisture is sucked into the hub as the air in the body contracts, think nice warm day, heavy downpour cooling contraction,
I'm not sure whether having no seals on the inside makes this better or worse - One seal may allow any drops of water to disperse into the larger centre volume rather than being trapped between the two seals.
Schmidt hubs - with a lot of volume have a tiny breather hole in the centre of the (hollow) axle to avoid this problem.
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I have to confess that I've not given any of my track hubs enough use to compare bearings but the single sealed variety only lasted a friend of mine one winter of commuting (30 miles a day admittedly) before being totally destroyed whilst the 2RS (and admittedly higher quality anyway regardless of sealing!) replacements have since given a good deal longer service.
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Thread resurrection! I've only just got round to starting this :-[
Once I have the old bearings out, what is the best way to install the new ones? I've read a few things about finding a big washer/using the old bearing to press the new bearings in by tightening the track nut onto it, which seems like a good idea. Other techniques just tap the new one in carefully with a hammer.
I understand that the important bit is to not push the bearing in using the inner part as this might ruin the bearings, but to keep the force on the casing.
Have I missed anything?
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Thread resurrection! I've only just got round to starting this :-[
Once I have the old bearings out, what is the best way to install the new ones? I've read a few things about finding a big washer/using the old bearing to press the new bearings in by tightening the track nut onto it, which seems like a good idea. Other techniques just tap the new one in carefully with a hammer.
I understand that the important bit is to not push the bearing in using the inner part as this might ruin the bearings, but to keep the force on the casing.
Have I missed anything?
That sounds right to me. A length of threaded rod, some heavy washers, and nuts will do the job. Putting the bearings in the freezer and the hub in the oven will make the fit looser, provided you work quickly enough.
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I use a socket (as in from a socket set) the same diameter as the outer housing. Then I twat it... OK, tap gently.
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Great, thanks. A job for the weekend!
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For future reference for anyone else needing this info, the bearings are 6000, not 6001. 10x26x8 mm. I've now ordered the correct part, having removed the old ones!
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That's saved me extracting the old bearings on mine to check, thanks. Looks like I've kept the chain on my fixed a bit taut, and the bearings have suffered.
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Glad it was useful to someone else, rather than just being a reference for me, for next time!
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Would you happen to know the cone size as well? Looks as though it might be 17mm, and the nut underneath the same. I've had 13/14 and 15/16mm Campag cone spanners for three decades, but I don't think I have anything to fit these, so I can't easily measure them.
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I've a feeling it's a 15mm cone, and 17mm nut, but I'll check this evening.
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Thanks, I appreciate that. Don't think the cone was 15mm because my Campag spanner didn't fit.
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How old are your hubs? My 15mm Park cone spanner fits the cones (well it's a little bit loose, but it's not 14mm), and a 17mm spanner fits the nuts.
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Couple of years old, maybe. Pretty sure my Campag cone spanner wouldn't fit. I've ordered some Park ones. I'll report back.
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In what way didn't the campag tool fit? The jaws too thick to fit between the cone and the adjacent nut, or just like it was the wrong size spanner for the cone?
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No, wrong size. It's a cone spanner :D
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For future reference for anyone else needing this info, the bearings are 6000, not 6001. 10x26x8 mm. I've now ordered the correct part, having removed the old ones!
Good to find this. I'm a bit too lazy to pull the bearings before ordering replacements. It is also helpful to keep the commuter on the road continuously.
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I replaced the bearings on a similar hub when it was out of the wheel. I don't recommend this - it makes it much harder as the fit is tighter. The tension of the spokes actually stretches the hub radially. Likewise, if you adjust cup and cone bearings in a nutted hub perfectly, then build it into a wheel, you'll find there is a load of free play that wasn't there before. 36 spokes all pulling outwards with over 70kgf is a lot of stretch!
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Wow, thread necromancy squared! Rather apposite, in fact, as I've just, eight years on, replaced the bearings again, with the spare set that I bought last time round. For some reason, and remembering that (obviously) I had done it before, it was one of those really frustrating jobs where only Park Tools really benefit.
Everything went wrong. The old bearings wouldn't shift, and I over-hit the axle-end, with a track nut on it to spread the load. So the threads took a little damage. Then the new bearings wouldn't seat. I was using the old bearings and the track nuts in a make-shift press, and ended up with one track nut locked onto the axle. The usual trick of locking up two nuts on the other end wouldn't work, and I had to buy a Park Tools axle vice to free the nut up. That was just the last in a series of locked-up nuts that I did manage to free. I also bought a nylon support bush for the hub, to spread the load when tapping bearings in. I'm still not that happy with the result, the new bearings run a bit rough, and one cartridge (remembering that they're identical from the same purchase) seems to sit a bit proud compared to its predecessor. Took hours for a dud result, but it's a winter fixed so it will have to do >:(
I replaced them in part because I'd creaked my way round one ACME event, and I knew that they were due for replacement, as was the BB cartridge. But, even after all that, I still creaked my way round the next >:( >:( I think it was actually the cranks and chainring moving - even though they were no longer even on the same BB >:(
Some jobs just seem doomed :-[
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IME there are plenty of hubs out there where the bearings are a fit that is too tight by far. I have even taken to grinding the bearings down before they are fitted in some cases, else they have way too much preload on them when installed.
In theory you can buy bearings that are correct tolerance for the exact fit of the hub, but identifying that is not easy and sourcing the bearings ain't easy either.
If correctly specified and installed, with lots of good lube, such bearings ought to last for tens of thousands of miles. That they don't is for exactly the same reasons as cup and cone bearings can clap out too; they were never set up right and/or lubricated properly, and/or the water got in.
cheers
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checked my bearings (of similar hubs) today and in the rear hub they are not entirely smooth, will replace them in a couple of months. the wheels will have covered 7000km, mostly in damp winter weather.
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IME there are plenty of hubs out there where the bearings are a fit that is too tight by far.
Although the odd thing is that I bought several sets, and this was the second of those that I had fitted in the same hub. The first set went in fine.
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IME there are plenty of hubs out there where the bearings are a fit that is too tight by far.
Although the odd thing is that I bought several sets, and this was the second of those that I had fitted in the same hub. The first set went in fine.
That is a bit odd. Mind you temperature makes a difference (might be worth trying a kettle full of boiling water) during installation, even if it doesn't affect things in quite the same way once everything has cooled down. Also the bearing seats can get marred/corroded.
Another thing which can happen is that the spacing of the bearing outers does not match the bearing inners exactly; eg if the axle has shoulders on and the bearings cannot be driven quite far enough into the hubshell there will be an axial preload. Some hubs are designed to be adjustable like this, but if you want to you can pack the shoulders on the axle with thin shims and that way the hub won't be adjustable any more. The other way is to grind a little off one of the bearing outers. Often a tap on the axle with a soft hammer, both ends, causes the bearings to 'settle' and be less bindy.
A problem with keeping the bearings adjustable is that the inner isn't trapped any more and if it starts to spin (eg if the bearing starts to nip up with even the slightest corrosion) then it soon wears the axle.
Often when cartridge bearings are brand new they are smooth enough that a monster preload is not readily apparent; however the slightest roughness on the bearing surfaces can cause the bearing to feel terrible. Often when such bearings are removed, they mysteriously feel nice and smooth again.
Normally you can quickly/easily bosh a new set of bearings and it'll last a year or two. But if you want the fitment to be perfect and long lasting, with the right grease and the correct preload on the bearings and so forth, cheap cartridge bearing hubs are usually more trouble to set up than cup and cone hubs. I can quite easily set up cup and cone hubs to ten microns or better, but with cheap cartridge bearing hubs that is just a dream.
cheers