Yesterday, the axle on my rear wheel snapped. I spent today trying to replace it with a new axle of same length. Before doing so, I checked bearings, and they seemed ok. When I put the hardware on the new axle, the axle spins (although feels a bit gritty), but as soon as I ride it, something tightens and the axle no longer spins, and I need to push the bike, dragging the wheel. What have I done wrong? ? Is it likely there is damage to the bearings/hub that I haven't spotted? ? Perhaps I have put in too many/too few ball bearings? (I didn't count them so have replaced with what looks right). Should they sit snug, some slightly above the others, or all on same level with slight gaps? ? Have I not used the lock nuts appropriately?
Just replaced axle on rear wheel. It is loose at first but as soon as I ride it, it tightens and wheel no longer rotates. Help!
Hi, Zen! Can you show us a picture of the rear hub? Is it a hub with cassette, or a coaster brake, a fixie? There could be multiple reasons for this problem. We need to narrow it down.– RobertAug 5, 2020 at 16:18
Thank you ! I stripped the axle back down so there's not much to show, but it was a rear axle within a thread on freewheel. I was trying to install it without taking the cassette off (because that was what it was like when the axle broke), so perhaps there's a mistake there. It was a rear axle with a cone at each end, with a lock nut on each, and then some washers and some spacers on the cassette side.– ZenAug 5, 2020 at 16:28
I have sometimes made the mistake of not tightening the locknuts enough, causing the rotation of bearings to drag the cone, tightening it enough for the bearing to bind.
The solution is to properly tighten the locknuts.
I'v been also in the situation of not having the right tools to remove the freewheel, which makes it more difficult.
What I've done to correct the situation is to properly locate the freewheel side cone on the axle, and then tighten it with its spacer and locknut when out of the hub. For this stage the axle and nuts must be free of grease and oil so they are more likely to keep the setting.
With this sub assembly done, put grease on the bearing races and put the balls. Grease is thick enough to hold them temporarily (I do not use the bearing cage in order to fit as many balls as possible. Also, some freewheels have a center hole so small that a cage can not be installed through it.)
Insert the axle from the freewheel side and thread the oposite cone. Adjust the preload and tighten the locknut of that side.
This last step can take a bit of trial and error for the once-in-a-while home mechanic.
My criteria for setting the preload is: Axle does not move side to side if trying to wobble it with my hand. If I try to spin the axle it is doable but won't spin freely (due to grease viscosity). Upon installing the wheel on the bike, it must not move sideways but should spin freely.
The worst case I had was actually a hub that was too worn and had damaged races, so at one point during usage, a ball broke and bind with the cone, dragging and tightening so much that it bent the center tube of the hub. (cheap steel hub).
Bottom line is check hub races, cones and balls for damage. Balls and cones are cheap, if you find surface damage or cracks or any deformation, change them. Some hubs, even some cheap ones have replaceable races. So, if possible and economically feasible, change then when damaged.
2Balls are cheaper than cones, and cones are cheaper than cups/entire hubs. The earlier you can catch damage, the cheaper the fix.– Criggie ♦Aug 6, 2020 at 1:19
1It's quite rare for a hub have "replaceable races." If a hub has a badly worn or damaged race, it (and, essentially, the wheel) is at the end of its life. It's typically awaste– JeffAug 6, 2020 at 1:31
1.. typically a waste of time and money to swap out a wheel's damaged hub when a new wheel costs less than lacing a new hub into the used wheel.– JeffAug 6, 2020 at 1:39
Perhaps I have put in too many/too few ball bearings? ... Should they sit snug, some slightly above the others, or all on same level with slight gaps?
All the balls have to touch both the cup and cone surfaces and therefore should not overlap. If the balls are overlapped they will bind up as the axle rotates.
Did you use a guide to rebuild the hub? Have a look at this Park Tool Repair Help article and this RJ Bike Guy video.