My front hub Joytech D341RCC have 9 1/4" balls, same as my rear Joytech hub. But they say that front hubs have 10 3/16" balls.
There is no law mandating a certain size ball for hubs. It's whatever the manufacturer thinks will work best.– Daniel R HicksJul 10, 2022 at 21:18
Has the hub been serviced since new? Its possible the wrong size bearings were used.– mattnzJul 10, 2022 at 21:48
Yes, but those 1/4" balls fit perfectly in cups and cones, and it seems intended to be so. Axle protrusion beyond locknuts on the left side the same as on the right side, while cone-locknut on the rotor side were initially fixed to the axle. Only non-rotor side cone was available to adjust. I think with 3/16" balls there will be smaller amount of protrusion at non-rotor side, thus unequal– Trump PenceJul 10, 2022 at 22:55
1I might actually have the same hub (certainly a Joytech 6-bolt QR front), but I've retired it in favour of a dynamo wheel. Maybe I'll get the chance to check– Chris HJul 11, 2022 at 8:08
"They" are over-generalising if they don't say "usually".
I've just had a look at my front JoyTech hub. It looks the same as yours (also QR and 6-bolt disc), but has no branding on it. It was built into the original front wheel on my genesis, and hasn't been serviced as I replaced it with a dynamo hub.
I've taken out a couple of balls, and they don't just look the same as rear hub balls, they measure at 6.34mm on my Vernier calipers. So they're 1/4".
Yes, there are front hubs that use 1/4".
If you wanted to corroborate which is right, you could look at:
- How well the race of the cones match the radius of a 1/4" versus a 3/16" ball.
- If you had the wrong size installed, on most hubs there would be some kind of clue in terms of any seals present not fitting together right, the OLD being off by more than just a "noise" amount, the wrench flats of the cone not being located right to be accessible, etc.