Modifications to my Downtube 9FS bike

So I got a Downtube 9FS in 2015, with the intent to modify it to a eBike with a Bafang BBS02 motor. Then take it on an epic tour through the Carribean islands.

A bike out to the festival and camped.

A bike out to the festival and camped.

The Downtube is a folding bike, permitting multi-modal travel. Take it on a bus, no problem, train, no problem, trunk of my wifes Honda Civic… tight fit, but no problem. So it has some big pluses. After I’ve put 2000 ebike miles on it, I understand its utility a lot better.

The bike

First, with the Bafang ebike motor, you get to use the gears. And the 9FS has 9 gears. Big plus as I live in a hilly area of Austin. I chose the 44T chainring model as I wanted more torque over speed.  Wow, does it climb hills,  up 20% grade hills at 9mph in bottom gear pulling only 16amps.

Second, I put on big apple tires, 2.15″ tires. Gives more cushion, steering feels less twitchy, but the big tires caused some derailour problems and I lose my lowest gear due to clearance to the tire. I’m thinking these maybe too big for the back wheel._1320029

_1320031Third, the battery is heavy, like 15# and now the bike is very back heavy and prone to accidental wheelies.  Part of that is I chose a handlebar throttle and not a thumb throttle. So I accidentally can throttle sometimes. And part of that is the handlebar throttle is not very linear. Turn it 1/2 way and nothing, 3/4 and you are at full throttle. Somewhere at 11/16th you start to feather into the throttle. Not a good throttle and I should get another, but I’m cheap.

Fourth, my pattern is using under 5 amp-hours for 95% of my trips. The bike normally can do 2.5 miles per amp-hour of battery. So 5 ah= 12.5 miles of range.  But I’m lugging either a 20ah battery or a 26 ah battery around when i should have a 5-8ah battery. Preferably one mounted in a bottle rack.  For instramentaion, I went with a WattsUp wattmeter to tell me how many amp-hourss I have left, because

The blue WattsUp meter will tell me how many amp-hours I've used. Not as good as a Cycle Analyst, but more appropriate and low profile.

The blue WattsUp meter will tell me how many amp-hours I’ve used. Not as good as a Cycle Analyst, but more appropriate and low profile.

the Bafang has no useful power readings.  Bear in mind the only measurement you really want to worry about is amp hours. You run outta those and you have to pedal home.

Sixth, speaking of racks, putting a rack on this bike was a pain to research what would work. I eventually went with a Biologic rear rack (https://www.amazon.com/gp/product/B006OSYSUA) and a Axiom Journey Lowrider rack

Biologic back rack

Biologic back rack

for the front fork (https://www.amazon.com/gp/product/B0081FQW4E)

Axiom front rack for suspension bikes.

Axiom front rack for suspension bikes.

Then I bought Axiom panniers for front and back.

Seventh, after all that I realized that most carribean islands I want to tour are so damn small I should just take a light folding bike with no motor. Even Aruba can be toured in a day. So I need to buy a Nova and put on a rack and I’m good to go.

 

Ultimately, I’ve discovered that this ebike excels at letting me ride around town, out of town, and all around, and then I can take other modes of transportation back. It is a keeper.


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