XT 775 Freehub Failure

The new 10 degree engagement oversize aluminum axles have arrived for Shimano XT in 2008. Great hub. Nice seals, quick engagement, light, and cheap. But what if these things aren't the workhorse we have been so used to.

What Happened?

Just at the end of a hike-a-bike section we were pushing up on our weekly Tuesday Night Ride a short pedal section put me back on the saddle. KLUNK, PING! WTF?

Push the bike the rest of the way to the top of the trail where it comes out to fire road to check out the problem. The freehub was frozen solid! Basically, the bike was now a fixed gear. Nothing we did could free it up. Amazingly, Ron had one of the best suggestions to try to fix this (WTF?). He said to drop the wheel onto the ground against the QR. Dana (a very good Porsche mechanic) and I both figured that this made a lot of sense. Sadly, it didn't work but it was worth a try.

Since any coasting would destroy a bunch of drivetrain parts, I had to break a brand new Dura-ace 10spd chain and coast the bike off the mountain while the group went up and had a great night ride without me. I drank one of my MGD 20's and scootered myself out for the next 20 minutes.

Real fun.

Freehub Failure

Forensic investigation showed that all 4 palls shattered and jammed the mechanism. Never seen this on a ride personally. Usually freehubs fail by skipping rather than seizing.

The Tale of the Missing Bearing

During the servicing of this hub and scavanging of the freehub body from another hub, I noticed an odd pattern. I noticed the same thing while teaching a friend how to service his hubs a few months ago. The main drive side bearings (3/16") count 12, but their is clearly space for thirteen including a tad extra. I had thought that one bearing had been lost before, but this time I made sure of the count. Could this have created some kind of 'paired couple rock' and caused the problem? Why does Shimano do this?