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I put stronger bearings and axles in my wheels
I am a little taller than the average cyclist, and a little fatter. Which makes me heavier than a lot of cyclists. I ride longer distances than many cyclists, and a lot of my riding is on rough tracks. When I started riding fat bikes, I would bend or break the axles in the back wheels. The hubs had cup and cone bearings, with freewheels.

I am not really that heavy. Many people are heavier than me. I believe it is a design fault. In the wide hubs of fat bikes, they still use the same thickness axles as they used on narrower hubs. Then freewheels get more gears, making the leverage on the axle so much, that axles bend and break easily.

I made an adapter which reduced the bending of the axle. This depended on the rigidity of the frame. I found out frames are not completely rigid, but flex a little. https://forums.bikeride.com/thread-8031.html

I also found out, even if you stop the axle bending, the cones still wear out rapidly.

I spent a ridiculous amount of time constantly repairing my bike.

So I inquired if I could buy cartridge bearings which fit the hubs, to replace cup and cone bearings. I found out I could.


The ideal bearings for my hubs are 6200 2RS. These have a 30mm outside diameter, a 10mm inside diameter, and are 9mm wide. They also have rubber seals, to prevent water getting in.

Not all hubs are the same. Anyone doing this, should check their hubs.

With some hubs, it is relatively easy to remove the cups. With other hubs, it might be difficult.

I found, some hubs have a 30mm internal diameter, and the bearings go in easily. Other hubs seem to have a 1 5/32 inch internal diameter, which is approximately 29.4mm. 29.4mm hubs made of thin sheet steel, stretch a little, and the 30mm bearings can be tapped in. With cast 29.4mm hubs, the bearings will not fit. But you can put the hub in a lathe, and enlarge the internal diameter.

For the axles, I used 10mm threaded rod. I mostly used nuts for spacers. On one bike, I used a washer for a little extra width.

The bearings have a tiny amount of clearance on the threaded rod. So when the wheel is off the ground, you can wobble it a tiny amount. This does not affect the bike when riding it. Anyone wanting to do this professionally, should make axles, or have axles made. For personal use, 10mm threaded rod does the job.

With the fat bikes, these bearings resulted in a noticeable improvement in rolling resistance.

I have only replaced the bearings and axles in back wheels. My front wheels are still standard.

Do these 10mm threaded rod axles bend? One day I was going down a hill at a reasonable speed. It had been raining a lot. I could see water running across the road. I didn't realize until I was close, that the water had washed away a section of road. There was a 3m wide gap in the road. I was going too fast to stop, so I lifted the front wheel, and went flying across this 3m gap. The front wheel landed on top, and the back wheel hit the side of the bank hard. I continued riding as normal. At a later date, I had the back wheel off, and noticed the threaded rod axle had bent a little, much less than standard axles would have bent, and not enough to be a problem riding the bike.

I have now done over 5000km on the first bike I put these bearings in, and they are still as good as the day I fitted them.

Since then I have bought a new mountain bike, and have put these bearings in the back wheel of my mountain bike.
Here is a picture of the bearing in the hub, with the threaded rod for an axle. On the freewheel side, I found four nuts normally provide suitable spacing.

The 10 mm threaded rod is a fraction of a millimeter smaller in diameter than the inside of the bearing, making it a tiny bit loose. A bike can be ridden with the axle a tiny bit loose.

Those wanting to make an axle which fits well, can have one machined.

Those wanting to make an axle which fits well inexpensively, can wind some wire around in the thread of the threaded rod, in the places which will come in contact with the bearings, then glue it with super glue. After the glue sets, file it to fit inside the bearings.
Thank you for sharing your detailed experience with replacing cup and cone bearings with cartridge bearings in your fat bike hubs. It sounds like you've encountered some significant challenges due to the design limitations of fat bike hubs and the stresses put on them by your riding style and weight.

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