hokiefyd 

I have a Novatec hub (model D481SBT if that's helpful) with two sealed cartridge bearings (6000-RS2). The disc side bearing has become a little crunchy and, when spinning the axle by hand (as in the photo below), the inner race will sometimes "catch" on something in the bearing and stop, while the axle continues to spin smoothly inside the race. When that happens, the gritty feeling goes away completely and it feels like glass. The non-disc side bearing seems to be smooth, and the inner race on that one always spins with the axle. So it seems to me the disc side bearing is going south. I'd like to replace the bearing before it locks up completely and then the axle starts wearing directly against the locked inner race.

This being my first set of hubs with cartridge bearings, I'd like to learn and replace the bearings myself. After much internet searching, however, there seems to be 1,000,000+1 various ways these are done (meaning different design standards, many proprietary to hub makers like Zipp, DT Swiss, etc.).

Looking at the photo below, how would you reckon I should attack this? Do I simply drive the axle out one side or the other, and then remove the bearing by driving it out from the back side? I'm aware of the potential to inadvertently separate the two races doing it like this, so I appreciate any advice. Because the axle seems to be able to spin freely inside the inner race of the disc side bearing, I presume it could simply slide in or out of this bearing. But the axle seems pretty fixed to the wheel -- I assume it's fixed (pressed?) to the non-disc side bearing, and that's what's retaining it.

If the axle is supposed to just be a tight slip fit to both bearings, I should just be able to drift the axle out and then pull and install the bearings using conventional practice, right? Many thanks.

dsaul

The axle should have a shoulder behind the inner race. You can drive out the bearing by striking the axle with a soft mallet from the other side. You will need a way to press the new bearing in by pressing on the outer race. An appropriately sized socket placed over the bearing can work to press it back in with a bench vise.

Due to manufacturing tolerances, it is usually possible to press the outer race in too far with the socket and cause the bearing to bind. If that happens, I have had some success with lightly tapping the axle from the other side to move the bearing enough to get rid of the binding. Using the appropriate bearing press will press on both inner and outer and prevent you from pressing the bearing in too far.

Unca_Sam

It's good you're replacing it rather than trying a repair to a sealed bearing. Unless you're strapped for cash, why not do both sides? Is there something about the disc side that's causing a premature failure?

hokiefyd 

Thanks -- so if I'm understanding this correctly, the axle will have two shoulders (similar to a classic bottom bracket spindle), and the bearings being properly installed in the hub acts to center and retain the axle? So I can drift the axle in either direction, and it should push either bearing out that way?

You're right about the title. I guess I was thinking "hub repair" or something. It seems like it's just the disc side that's bad but, yes, I'll replace both. Once I know how to get one side out, I'll be able to get both out. I don't think there's anything about that side in particular that caused it to go bad; I think it's just the luck of the draw with this particular sealed bearing.

But something definitely changed in the last hundred miles or so. The hub used to spin so freely, it seemed like the wheel would never stop (and it would come to a very gradual and gentle stop). I noticed yesterday that there was more drag on the wheel now (and checked the disc brake, which was not rubbing), and the wheel, when let spin really slow to a stop, would find a "notch" in which it would stop, like a cup-and-cone bearing with too much preload. So I took the wheel out and found the grittiness in the disc side bearing.

hokiefyd 

How hard should I expect to have to hammer on the axle to drive it out? A small-to-medium sized hammer with a rubber head didn't move it. I have much larger hammers, but I thought I'd check once more before really wailing on it for fear of damaging something. :-)

I know the bearings are pressed-in to the hub shell, but I didn't expect them to be quite this tight of a fit.

dsaul

Try putting a block of wood over the end of the axle and give it a good whack. It helps if the wheel is solidly supported on the other side.

davidad

hokiefyd 

Thanks, all. I did get the axle pushed out of the disc side, which pushed that bearing out. I did confirm it was a bit gritty (though not as bad as I suspected). The non-disc side is smooth. I played with the disc side bearing some, it seemed to smooth out, and I reinstalled it. There seems to be little change. So I'll pop it back out, and the other side as well, and just replace both. This is a front hub so, fortunately, no dealing with the freehub body. That is a nice bearing tool set in those videos, though!

hokiefyd 

This is turning out to be a real pain in the butt! I bought new bearings from Amazon. I paid $10 for a pack of 4, PGN brand (probably Chinese, like most this size). They seem to spin very smoothly. I made a DIY bearing press out of 8-32 threaded rod, which is the largest size that would fit through the axle. That worked until the very end, when the rod snapped. I got the bearings pressed most of the way in. I had to finish one side with a hammer and socket/washer against the outer race.

As reported above, there seems to be a very fine line between too tight (bearings pressed too far in against the axle shoulders, making them really tight), and too loose (where the axle has lateral free play). In fact, it seems like one bearing doesn't sit quite square because I can get it nearly all the way in, with a slight bit of free play still, but there's still a slight bind when spinning the axle.

I may give the whole lot to the bike shop to see if they can get it right.

This makes me yearn for a set of cups and cones -- I don't s'pose there's any way to convert a cartridge bearing hub to loose balls, huh?

hokiefyd 

Dang -- I tapped the bearings out again, and it looks like there's a slight ridge now in the aluminum shell where one bearing was not quite straight. Is this hub likely trash now, or do you think it could still be saved by a shop with specialist tools?

Dave Mayer

Amen: this is why I never buy cartridge bearing hubsets. Yesterday at the bike Co-op we restored a bunch of 40 year-old absurdly neglected cup and cone hubs with a few pennies worth of ball bearings and hub cones salvaged from the inventory of a old bike shop. The highlight was restoring a 70s vintage Campagnolo hub to minty fresh condition by replacing a hub cup (yes a cup). This hub must have suffered decades worth of rainy abuse, with zero maintenance.

Anyway, my first plan of attack with this Novatec hub would have been to crack the seal of the crunchy cartridge bearing, completely degrease (with camp fuel/white gas), regrease and reseal. Takes a few minutes. That way, you don't have to worry about the risks of punching out bearings, or re-assembly. The risks being that the old cartridges are corroded tight inside the hub shell and unremovable. The risk on the reassembly being that the bearing starts to go in a bit sideways, and results in the soft (alu) hub shell being damaged.

The other downside in the middle of this process is that almost no bike shop is going to be interested in selling you new cartridges, or installing them. There are dozens of different bearing types, which they cannot stock, and bottom line is that they'd simply rather sell you another wheel (or better: a bike) than engage in frustrating, picky, risky work of changing out hub cartridges.

Helpful suggestions: you've done everything I would have done.. Taking this to a shop.... Hmm.

hokiefyd 

I have a great relationship with my local shop, fortunately. We both know each other by name and I'll probably take the bearings and the wheel down to them and ask them to press them in for me. 15 or 20 bucks at the most. They probably see this sort of thing fairly regularly (cartridge bearings). If they balk at it, no biggie, I guess. In the worst case scenario, I guess I just replace the hub with a Shimano Deore or similar cup-and-cone and re-lace the wheel.

For now, I've got the stock wheels back on the bike, cheap Giant GX28s with glass-smooth bearing balls. :-)

(The reason for the wheel change is unrelated to the hub type -- I downsized to 584mm wheels from the stock 622s, and these 584s came with the Novatec hubs. I thought, "cool, cartridge bearings!" I'm not a luddite for sake of being a luddite, but this seems more like a solution in search of a problem to me. Or...maybe the Novatec hubs are just really cheap with soft metal that damage easily, and this is a poor example for me to learn the ropes on.)

Kimmo 

I'd remove the ridge and reinstall the cartridge in the damaged side first, taking time to ensure it's going in straight. IME you have a degree or two of wiggle room before damage is caused; if you have a good eye you can just tap bearings in with a hammer and punch, carefully working your way around.

The problem is the expense of tooling for proper bearings. So much easier just to leave a cylindrical hole and fill it with something from a catalogue, and while we're being slack, leave out any means of preload adjustment, or maybe half-arse it.

hokiefyd 

I appreciate the encouragement. And, of course, it often helps to walk away from something and come back to it later.

I felt that my new disc side bearing was fully seated and straight in the hub (the non-disc side was the one that went in slightly crooked, and formed the slight ridge). And the original non-disc side bearing was good when I started all this. So I decided to leave the new disc side bearing in place, clean up the non-disc bearing hole in the hub (with some light work with 220-grit abrasive paper), and just re-install the original non-disc bearing. It went in straight and I was able to get a good adjustment. Installing the bearing "all the way" created a slightly tight axle, so I threaded a locknut on the other side of the axle and tapped it back until I had an easy spin without any axle play. Rudimentary I suppose, but it seems to work. Nothing seems to be binding and it's spinning smooth without any grit.

Job done. Experience gained. Lessons learned. Thank you all for the helpful advice.

speedevil 

I realize that I'm a little late to this party, but you can usually make bearings easier to install by putting the bearings in the freezer and warming up the hub shell with a heat gun (don't overdo it). The shell will expand slightly, and the bearing will shrink slightly. The combination usually makes it easier to get the bearing seated. But you need to move quickly, doing one side at a time. A lot of axles don't have a shoulder machined to position the bearings, they use a sleeve over the axle that contacts both inner races when the bearings are properly seated.

hokiefyd 

The freezer is a good idea.

This hub definitely uses an axle with a shoulder or integrated sleeve. And I think you're right that the bearings are not fully driven into the hub shells -- they're more positioned by the axle than anything else. I guess that makes it possible to shift the hub left or right a little bit on the bearings (and thus, the axle and locknuts), but this probably has no real impact on the assembly.

I guess I'll find out when I re-install the wheel -- I'll see if the brake disc moved any!