Shimano 600 HB 6400 front hub issue (dead cone?)
 

I've bought second-hand wheelset based on Shimano 600 HB 6400 hubs. Upon arrival I didn't check if hubs were greased or not (my mistake), hovewer there were no issues whatsoever until last Saturday ride. I hit deep pothole while descending at 50 km/h and then hit another one one more time. Silent ticking noises were telling that something went a little bit wonky with bearing balls. When I disassembled the hub, one side of the hub lacked the grease completely and by one ball at either side. I fixed that. Noises gone until next few kilometers. Then I disassembled the hub again and saw the grease at one side somehow finds its way out, leaving bearing balls with very thin coat. Is that indication that the cone is dead or just the rubber washer needs replacement?

What kind of grease are you using?

Any suitably thick grease isn't going to disappear in a few kilometers.

Phil Wood or something of that consistency is what you should be putting in hubs.

The cone needs to be replaced if it is pitted or scored on the ball track.
The seal needs to be replaced if it is worn or damaged. You can compare to the other side if necessary. These don't usually need replacement unless they are damaged during servicing.

Check the exploded diagram on the Shimano site and make sure you're putting it all together correctly.

Have you been riding in the rain? Clicking/cracking sounds are often due to rust from water intrusion. I would open up the wheels again and inspect for pits on the cones and hub races.

Litol 24. It's pretty viscious. With these hubs there's nothing that can be damaged or assembled incorrectly, in my opinion. They're simple.

Yes, I do ride in the rain alot, however the weather was sunny these days. Hub races are nice and clean, pits on the cones are okay too. There are no scuffs, scratches, sand or dust particles... Everything was degreased and greased back correctly, hence my curiosity.

Grease will initially be push aside and away from the balls as they plow through the freshly lubed hub. Some of this grease will be squeezed out past the cone and dust cap/seal. Some will get pushed deeper into the hub/axle cavity. In a short time the balls will only have a thin coating and the piled up grease right next to the balls will feed them a thin coating for a long time. Or until enough water gets in and takes up space that otherwise would have had grease.

Take care with the number of balls in these hubs. It's easy to place one more then proper in the hub and think all is well. far better to leave one out the have one ball too many. Andy.

That's interesting. Care to elaborate?

If the clicking/snapping has come back, there are other potential causes. Perhaps a little piece of grit made it in when you regreased the hubs, or rode the bike. Or the rim eyelets could be rusty: Rim noise (Jobst Brandt)

The ft hub with it's smaller balls and shallower race make how the balls fit into the race a bit less "positive" then the rear. Also "classic" Shimano ft hubs are even shallower then other brands. If the dust cap isn't removed it can be difficult to fully view the balls and their fit against each other.

I've seen many with too many balls in them. Usually the rider does a fix/servicing and then note the wheel is binding after or has gone out of true. With one too many balls on one side the wheel will cock off center and this offness will it's self rotate (at half the wheel's rotational speed) so the out of true seems to move (which it is doing). The cone sticks out by only a very small amount so the fit back into the fork is almost as it was. If there's a ball less then proper then not much changes from normal. Andy.

Thanks for clarification, Andrew R Stewart!

ThermionicScott, thanks for you input!

FYI, the FH-6400 front hub requires 10 x 3/16" bearing balls per side which is the same as most older Shimano front hubs. Some of the newer ones use 11 x 3/16" balls per side but not the 6400.

HillRider, thanks, given what Velobase datasheet says, you're right. Then why there's space to fit another (eleventh) ball? Just curious.

This is but one reason why it's easy to end up with too many balls. The design wants almost complete ball count, enough to handle the loads and not allow the cone/axle to move off center but not so many that the balls rub against each other with more then a light touch. Andy.

Fair enough, but still it's unclear why the space is so wide that it is possible to put another ball. In old USSR-made bikes hubs were also made with some spaces left to allow balls move freely back and forth along the races, however one couldn't install more balls than required by data sheets. Those balls had so low quality that it was pretty common practice to lose some during the ride on rough road surfaces.

Extra space or not, 10 is the correct number. As Andrew noted, the space gives the balls a bit of clearance with each other. Assembled, lubed and adjusted correctly, the hub will roll very smoothly and last nearly forever. Nothing is going to fall out.

Thanks! I detached by 1 ball from either side already today.