The Golden Wrench

A blog about bicycle repair and maintenance by the mechanics at Freewheel Bike.

Saturday, July 30, 2011

Fun project bonanza!

I've been saving up photos for the past few weeks to compile into one big blog post about fun repairs, so hang on tight...

First, let's reach back a few decades to the Golden Age of two- and three-speed internal hubs. A customer came in with a Bendix two-speed kick-back coaster hub (Yellow Band!) that wasn't behaving itself, even after a couple attempts to service it. So I pulled it apart for diagnosis:

In the foreground notice the Bendix wrench; yes, that one end is a 47/64". After cleaning everything I was able to find the problem--a broken coupler:

Notice the missing section in the foreground, which should be a closed rectangle like the hole on the opposite side (also notice the Sutherland's manual on the bench--trade secret!).

Unfortunately, though we have lots of old Bendix parts, we have long since run out of the fragile bits, so barring some lucky Ebay searches, this wheel will have to be retired.

Next up is a suspension fork that we don't see too often around here, Fox's 36 TALAS, their big-hit, travel-adjust fork. There's all sorts of fun stuff in this fork, including the granddaddy of today's 32 FiT damper forks, the big RC2 damper cartridge. Here's everything laid out:

Lots of stuff going on there! Notice the black rubber bladder in the lower right--Fox was using their FiT dampers in the big downhill forks for years before they finally came out with a smaller, cross-country version for their 32mm forks in 2010. Both FiT systems are designed to reduce weight by minimizing oil volume. Here's a look in the end of the damper cartridge just before the bladder is installed:

Our final stop in Taking Things Apart Funland is an overhaul on an Avid Juicy Ultimate hydraulic brake lever. This brake was exhibiting all sorts of undesirable behavior, including occasionally going all the way to the handlebar without engaging the brake AND pumping up to the point that there was no lever movement. I suspected the master cylinder piston seals, as both of those symptoms suggested oil was getting around the seals. It was also leaking brake fluid from under the reservoir cap, which suggested that the rubber parts in the lever were getting tired. Here's everything exposed to the light of day:

Notice the two threaded pieces on the right--the red part threads against the worm gear below it to provide freestroke adjustment (the point in lever throw where the pads contact the rotor). This is different than reach adjustment, which sets the starting point of lever throw. Though it's becoming more and more common, typically this kind of adjustment is only seen on higher-end brakes, as it adds a lot of moving parts to the system (equals more expensive).

Well, that's all I've got for now. See you out on the trail for the Murphy Time Trial Series!