emily’s bike stuff
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Misc: Internal Routing and Prof. Ronnie

First, two YouTube recommendations:

  1. What makes a bike ride well? (well it’s not the frame!) — I love ronnie and everything in this video was worth watching. In particular, the demonstration of deflection on a fork (look how much your fork can bend!) and using a wheelbarrow to demonstrate low vs high trail geometries. ronnie’s videos are always nice with a bit of 420.
  2. Switching Lanes: A short documentary about how a cheap bike changed a life — Gorgeous footage of San Francisco and a monologue on how biking keeps you connected to your city. I loved that they were riding an old, lugged steel road bike with downtube shifters. Save forgotten bikes!

Second, internal routing in e-bikes! I just worked on an e-bike that needed its rear shift housing replaced. Most mid-drive e-bikes, including this one, have internal routing through the downtube and chainstays. That housing is routed under the battery and then over the motor into the chainstay. These Shimano motors have three interfaces to the frame on each side with a channel in the middle. You can see an example of this in this exploded view. There’s a group of cables/hoses zip-tied together above the motor. This makes it nearly impossible to pull the old shift housing out without removing anything. I’ve learned over time that it’s less time-consuming to do the thing that feels harder to make internal routing work — in this case, removing the motor entirely.

That involves removing the cranks, chainring, motor case, and finally the motor. All the cables into the motor unit (lights, power, speed sensor, cockpit computer) must be disconnected and re-connected. Sensibly zip-tying the cables and routing them when done takes a while. This all takes a lot of labor and is just a tradeoff of internal routing (and thus most e-bikes).

The motor cabinet of a mid-drive e-bike with various loose cables coming from the downtube and chainstay

This is why it’s a bummer that my e-bike doesn’t support Linkglide Di2 because electronic shifting would let me avoid needing to change my housing every year or so! However, my e-bike does have the shift housing exit over the motor cabinet without going around the entire motor and inside the chainstay. I’m looking forward to seeing if that’s any easier.