f4rrest

I have c24 9000 wheels that are maybe a couple years old ridden mainly in dry conditions. Roughly 6000 miles on them.

If I put the bike in the stand and run through the gears, when I get to the highest gear (50 - 11) and spin the pedals at a riding speed, I hear a slight rattle out of the rear hub. I don't hear or feel anything when riding in this gear, though.

There is no lateral play in the wheel, and it spins freely. The hub has never been serviced since it was new.

With the wheel removed, when I push radially on the end of the freehub, I can feel a slight bit of play from the freehub itself. The prawls are noisier than when it was new. I suspect it needs some grease.

What do you think is causing the slight rattle at speed in the stand? Are these easy to grease?
My understanding is they cannot be disassembled, and the Morningstar Tool is no longer offered for sale.

Andrew R Stewart 

Many/most freehubs (and freewheels) have a slight slop to their "bearing adjustment" to better insure no drag when coasting. Not enough to bother indexed shifting though. If the interior of the freehub has gotten dry of lube then the parts can rattle when shook about. Dripping in a light wet lube should help this. But when pedaling the freehub is loaded with the pedal pressure and the parts won't tend to be able to rattle. So I wonder if your issue is from the chain engaging cog teeth. Andy

blamester

I have heard a rattley rear hub recently and it turned out the cassette was not correctly instaĺled.
It was missing a spacer. The sprockets where loose and rattled against each other.
It had been ridden for a year like that. No real damage but he did mention it didn' t shift as good as it had.

f4rrest

I'd think if it were chain engaging teeth, then it would sound similar on other cogs.

It's definitely louder and more rattley in 11, slightly in 12, and not at all in other gears.

I'll drip in some lube next time it's off.

f4rrest

I'm pretty careful about spacers and use a big torque wrench to get to 40nm.

Shifting is fine. It's di2.

Andrew R Stewart 

No, not so. Besides the obvious index/cable tension aspect of chain meshing onto teeth is the chordal effect of the chain's changing tension WRT the cog's rotation, a tooth at a time. Basically as the cog gets fewer teeth the more the meshing power pulses. This can be heard as engagement noise with the momentarily increases of force causing the chain and tooth to rub/slide and not just roll. I know I'm not explaining this well but it's real. Andy


2.2.1 Chordal Action

f4rrest

Thanks for the link, and I understand, having past experience in acoustics.

Actually, it seems that the energy from the chordal action is of sufficient frequency to cause the end of the freehub to vibrate and rattle the most at a particular chain speed, so it seems to be resonating.

davidad

6000 miles is too far to go without service. I I service my hubs at 2500 miles and haven't had to replace any parts with that schedule.

f4rrest

It turns out I wore the chain past 1/16 (measured over 12 links) and ordered a new one.

Having the chain off, I figured I'd check the hub.

There was plenty of clean, original grease, and everything looked fine, so I just reassembled.

With the new chain, the hub adjusted, and the cassette torqued to spec, I cannot recreate the issue.

Andrew R Stewart 

Good job! Andy