What was in the stand yesterday (and today)?

So I had a rather interesting limited edition bike come through the shop for an appointment for general servicing and, as some projects occasionally do, it had a complication that was a good call for photos and explanation of a component that shifts the bike through an internally geared hub developed by SRAM around 2006 called an iMotion 9 hub.  It has nine gears or varied range and changes the gearing with moving the chain.  A wire cable runs from the inside of the hub to a long barrel adjuster and then up the frame of the bike to the shifter. The bike is a limited run of commuter style Cannondale hybrids with a Headshock lefty fork and no non-drive side chain or seat stays, hydraulic quad piston brakes, slick commuter style tires, and a fully enclosed chain.  Take a look:


The client mentioned shifting issues, which usually happens with most bikes as the cables stretch.  Tighten them up to the correct tension and the cable pulls the gears in the hub into an easier or harder gear each time you twist the shifter (smoothly and quietly).  I initially installed a new cable and with a bit of a learning curve and several adjustments of cable length (pretty specific without using up one of the two available barrel adjusters)(I would also mention maybe trying an additional one as an inline adjust about a foot from the shifter).  I went to test it outside (where it was much nicer) and after sever shifts I noticed the cable went slack so I felt the shifter and could feel a bit of play in the cable and stopped the bike.  Once back in the stand, I noticed something I had not previously seen due to it’s hidden position behind the chainguard housing.  A crack in the entry point of the cable into the hub had separated about half of it’s cylindrical length (about 7mm).

WP_20150504_002(This is inconveniently located in my photo underneath the greased up axle bolt.  I will take a photo of the fixed piece or possibly the still broken piece if I can’t repair it today.)

This part is made of plastic and, after a bit of research, I realized that apparently none of these parts are sold separately, even in the normal version of this hub.  This is when a little fabrication and small detail work will hopefully save the day.

I took apart the wheel and have opened the hub to examine any other issues and make fixing the piece much easier.  A little epoxy was applied to both pieces after greasing the cable running through (proprietary piece of cable that can’t be removed) so I can reinforce it with a collar of sorts today.  Here are a few photos of the hub being taken apart.  The spring in the third photo will likely be a challenge to get back into the shell, but can be done with a bit of concentration and effort (and persistence). The first photo shows the plastic threaded piece coming out from the circular housing.  The spring keeps enough tension on it in the photo to join the broken piece with the rest of the body, but moves significantly under load.

I will take a few more photos today and update the situation in tomorrow’s article.  It’s supposed to hit the upper 80’s around DC today.  Make some time and go for a ride!  I will certainly be taking thorough test rides after tuneups today.  Follow @pixalias on Twitter for updated photos and good tech that rolls through the shop!

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