10 speed shifters and hydraulics in ebike conversions?

[Supertux1]

Hello ESers!

I've got a few dumb questions. I'm kind of new to bike tech and ebiking in general, just bought my first donor bike! (It's a 29er hardtail from bikesdirect)

So I bought a bike for my build, but it's got a 10 speed SRAM X7 shifter, S7 rear derailleur and hydraulic brakes.
I'm thinking about an ebikes.ca or one of Cellman's geared MAC hubs on the rear, both of which take a 7-8 or 9 speed freewheel depending on how much I want to stretch the rear dropouts or not (it's a 6061 frame).

So the question is, can I get away with leaving the 10 speed shifter and on there with a less than 10 speed freewheel, or should I find an appropriate trigger shifter with the correct number for the hub freewheel? (eg SRAM X3 for the 7 speed). I'm thinking that things will be better indexed if I do, and if I don't there will be rough gear changes and disasters when switching into the lower 2-3 gears?

Second question, what do you do with hydraulic brakes and cut off switches for the motor that are mechanical in nature? Should I just replace one brake (say the rear one) with a mechanical pull or is there some kind of reed switch (eg BionX) that can be stuck to the hydraulic pull? (My brakes use DOT 5.1)

 

[d8veh]

Why not get a Bafang CST motor that has a spline for cassette gears, so you don't have to change anything on your gears?

If you do a seach on "hydraulic Brakes", you'll find loads of solutions, but most require a bit of DIY. Magura do inline switches, which are not too expensive; however, you have to cut and bleed your brake lines. You can also buy ready-made systems from Tektro with switches already installed, but not easy to find: TEKTRO AURGIA E-SUB-F

The easiest solution is to fit a cable brake to the back with one of those in-line brake sensors:
http://www.bmsbattery.com/459-hwbs-hidden-wire-brake-sensor.html

Finally, many ready-made ebikes come with hydraulic brakes with switches. You can get the brake assembly as a spare part, though fairly expensive. You didn't say where in the world you are, but if in Europe, you can get them from Juicy Bike for about £100.

 

[MadRhino]

You will find soon that 10 spd is too many on your ebike.
If you are really into pedal assist, 7 will be enough.
Those who are building fast ebikes are usually happy with a single cog.

 

[dogman dan]

If you can get the 9 speed freewheel, it should index tolerably good on at least 5 gears. Most of us just need the high gears, so you can just adjust to index best on the small cogs.

If you go to 7 speed, then you have issues with the chain being wide for use with your current derailurs. That is, if you still shift any at all. Many of us just put it in one gear, and leave it there for a long time.

But if you do have to shift to the large gears, a bit of clicking is no disaster. Just takes a simple barrel nut adjustment to make it go away if you need the low cog, like to limp home broken.

 

[Supertux1]

Thanks for the info. I plan on using some PAS to extend the range and so forth, would also like to be able to use it as a non electric at times with minimal adjustment, for camping trips and riding with friends. I picked up a cheap SRAM X3 left shifter that has the same 1:1 tech as the X7, so in theory it should work wth the SRAM derailluer but if it doesn't work - no big loss. I'll see what I can rig up for brake switches.

 

[dogman dan]

When you go to wider chain for the 7 speed freewheel, you will likely have trouble with your existing derailurs being tight. But you can pick up used 7 speed ones fairly cheap someplace.

I often say, "don't wreck your best bike putting a motor on it". While a cheap bike rides like a dream with the motor.