Forum home Road cycling forum Workshop

Dura-Ace 7850 freehub lubrication

geebee2geebee2 Posts: 248
edited March 2011 in Workshop
A few days ago a fairly loud clunk started coming from my 7850 rear hub when freewheeling at speeds above about 10mph. I bought the wheel last September, I guess it has done about 1,000 miles.

It's once per revolution of the rear wheel. On a stand, I can get the noise with the wheel stationary by turning the pedals backwards.

I removed the freehub body and added some lubrication. I didn't fully remove the seal ( the inner one closest to the spokes ), because I was worried about damaging it, I just moved a small portion aside so I could drip a bit of oil in.

This has improved matters - the clunk is now quieter and only occurs at higher speeds, barely noticeable when riding.

I'm just about satisfied this isn't a big problem, but do you think otherwise?
Any ideas on what exactly is going on within the freehub body?
Anything else I should be doing? What kind of lubricant?
I don't think a warranty claim is justified, although I have considered it.

Posts

  • keef66keef66 Posts: 13,123
    I just did a bit of preventative maintenance on my 105 freehub since it had done 3 winters without missing a beat. I did carefully fish out the seal (ooh, look at all those tiny bearings!) and with the thing standing upright, trickled copious oil through it until it was pouring out of the other end. Left it to drain for a while, refitted the seal (needed quite a bit of persuasion to fully seat) and reinstalled it on the bike. It's now purring like a kitten.

    Since yours went clunk, I'm not sure if that points to simple lack of lubrication, some internal corrosion, or failure of some component. Given the price of Dura-Ace kit I think I would be tempted to pursue a warranty claim, and keep quiet about the fact you've disturbed the seal.
    I recall reading somewhere that DA freehub bearings sit further inboard than those on the cheaper Shimano ranges, and so are, in spite of the name, less durable. Possibly something to do with weight saving?
Sign In or Register to comment.