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Impressions

Days after buying my bike I regretted forgoing the Bosch speed motor option. My third generation motor is factory limited to 20MPH. I talked myself out of the $1,000 upgrade (!!) reasoning a slower bike was a safer bike and that the 28MPH limit would invite reckless speeding. But in the first week of crisscrossing San Francisco for errands and joy-rides it was plain that it was slowing me down. Even with SF's hills and traffic signals I found myself constantly running up against the limit. Two or three strokes from a cold-start I would feel the lurch of the motor de-activating and all of the bike's 65 pounds leaning into me.

Since I don't own a car my Mom drove me, my bike, and few boxes up the road to my new home in a suburban mountain town. So far shopping for groceries, a beach day, and visiting friends is all within reach of two wheels. There are enough bike trails and back roads that I feel safe enough to glance between errands without the threat of traffic. Even elevation (which there is a lot of here) is manageable now at 13 or 15MPH, steadily chugging up the hill to the hum of the motor with a watermelon and a case of beer in tow.

But distances are long – picking up toilet paper is a 16 mile round trip. The monotony of the long flats begins to grate while the motor, programmatically throttled, more or less sits idle between my legs while I keep slugging away at 21MPH. The bike has in some ways felt like a hindrance instead of an enabler to my mobility. So I bought a tuning chip from the Czech Republic that manipulates the controller's speed sensor readings to obviate the limit. Now, the Bosch motor continues to provide assistance past 20MPH with no noticiable degredation in performance (battery range aside). Installation was easy and has since "just worked". It has washed my bike of its limitations. I'm free again.

Installation

Unfasten the motor housing by removing 2 allen screws on the drive-side and 3 phillips screws on the non-drive side. The housing can be removed without pulling the crank.

Remove the display cable (2) and the speed sensor (3) and insert into the reciprocal Speedbox junction connectors. The battery (3) and light cables (4) can be left as is.

I nestled the Speedbox chip and cables into the seatpost tube and fixed their position with the battery cable.

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