Rear hub motor, 130mm width, cst and disk

[Kittenrainbow]

Hello Guys

I am planning to convert my citybike to an ebike, to help me to commute to my workplace and back (7Km one way). First I planned to use the Q100C Cute motor, with casette freewheel, but then I saw, that it's too wide (134mm). (Bending or stretching the frame is no option)

Before I go with a front motor (which I just like less, because it looks clumsy and less stealthy) I wanted to ask if there is a motor which has a (Shimano) Casette freewheel and is disc brake compatible. I don't need too much power, the desired end speed would be about 30 km/h (20km/h without pedalling are legal here) in a 26" wheel.

Best regards Kittenrainbow

 

[dogman dan]

Actually, flexing the frame 2mm on each side is an option. Alloy frames can easily flex that much with no damage.

 

[d8veh]

Why do you say bending or stretching the frame is no option? I've done lots of frames as much as 150mm.

 

[motomech]

Actually, the install of the Cute CST on my Rocky Mountain requires one of the kit supplied änti-rotation spacers inside the chain stay to line-up the brake disc to caliper and a flat washer inside the chain stay on the cassette side to keep my 9-speed cluster from rubbing on the chain stay. It also provides a little more "mating surface"against the chain stay when the axle nut is torqued.
So the motor ASM, including spacer and washer is about 139 m/m in total width when ready to install.
All that is needed for the axles to drop down into the dropouts, is very gentle prying with a long flat screwdriver.
The Alum. chain stays are NOT "bent or stretched" is any way. "Flexed"would be the correct verb.
Once the motor ASM is removed, the chain stays "springs" back to their original position with NO Lasting Change in width.
All this is easier to do than to explain.

The lasting modification is the deepening of the dropouts that, as far as I know, every hub motor installed into bicycle dropouts require.
To worry about "stretching" to frame/chain stays, while dis-counting this seems to be a case of misplaced concern.

More time consuming is the severe "dishing" required to center the rim.
I have done two, the kit supplied rim and an aftermarket, and while it takes awhile to get it right(the more of the dish, the harder it is to true), the dish is not so extreem as to require two different length spokes.

The only other CST mini is a MXUS version that D8veh is familiar with. But he felt that it was an under-performer given it's size.
The next step up would be the large geared BPM CST.

Go ahead and front mount, it works just as well with low-power mini-motors. And opens up the option of using the Q100H 260, I.M.O., the best all-around mini-motor.
But be aware, front mounting requires "opening-up" the dropouts in the fork. Something harder to put back to original than anything you can do with a rear mount.

You can't have a Prima Donda attitude when it comes to mounting hub motors. If dis-figuring your bike will cause loss of sleep, get a cheaper donor bike.

 

[Drunkskunk]

30kph sustained just needs a motor rated for 350watts or more, so the Cute Q100C would work. It is a CST and disk brake compatible.

135mm is the standard width for a rear motor. If your frame is narrower and can't be stretched, you have a problem. For 99.9% of the bikes in the world, stretching an aluminum frame an extra 2.5mm per side isn't an issue. If you have one of the 0.1% of the bikes that can't be, because of a cast frame or some other oddball design, you need to look at custom made parts. Also post some pics of the bike. googling "Citybike" comes up with hundreds of different bikes.

 

[Kittenrainbow]

Hey Guys

Okay, it seems like I overrated the flexing part of the frame, but I am really worried when I read "deepening of the dropouts".
This would then be a bigger modification.

Is it still possible to insert a normal hub afterwards?

I would really like to still use my normal bike, because I like it very much, but rendering it unusable without a hub motor is not my goal.

 

[Ykick]

I’ve installed several wide Q100C mini hub motors into aluminum frames. Flexing a few mm using a pry tool (long screwdriver) isn’t an issue but it can be complicated if using what I consider mandatory steel washers on the inside of the dropouts.

If you don’t use washers in that location, the steel axle shoulder can and will dig into the softer aluminum dropout and may eventually loosen the attachment enough to become a problem. I normally use the thinest steel washers I can find but just be aware it’s an extra hassle to install the wheel while flexing the dropouts apart with washers on the inside of the dropout. A little practice and it becomes fairly easy.

As far as dropouts being deep enough? Well, that’s a case by case basis - maybe post a picture of how it looks? IMO, it never really hurts to file a few mm deeper but I understand the reluctance on an expensive frame.

My rule of thumb is that as long as the flats of the axle are completely seated into the dropout slot so that no portion of the flat sticks out/above the slot, that’ll be good enough using a good torque arm.

What our good man Dan always suggests - if you have a really nice bike and you're very fond of it, perhaps find something else to stick a motor kit system into?

 

[Drunkskunk]

Some dropouts are very shallow. A normal 9.9mm quick release axle sits most of the way in them and it works without issue. But when you add a 12x10mm Hub motor axle, you end up with 1/3 of the axle out of the dropouts, and the wheel nuts hang off the edge of the frame. that isn't safe. In that case, you need to deepen the dropouts by filing around 2 to 3mm of metal from the end of them. on most bikes, that is harmless, and doesn't affect anything except a small derailleur and brake alignment when using your stock wheels. But other bikes have deep dropouts and need no alteration at all. It's really a case by case basis.


However, it sounds like you like this bike a lot. Converting a bike to electric changes it fundamentally. nothing about it will feel the same with the motor installed. If you like riding the bike you have, it's usually a better idea to buy a cheap used bike to convert. Craigslist is full of unloved high end bikes that need to be re-homed, often for under $100. I just saw a Trek 820 for $20 in my local Craigslist. The 820 is a perfect example of a near ideal bike to convert.

 

[d8veh]

It's no problem to deepen the drop-outs if you need to. Your old wheel will still fit OK. I've done it loads of times on high-end bikes, which I've changed from rear motor to front motor or crank-drive and back again. In the worse case, you need to add a couple of washers under the brake caliper if you have disc brakes. I've also stretched many frames, which makes it easier to remove and refit the wheel if you get a puncture. You just jack it wider a bit at a time until it takes a permanent set at the width you want. It doesn't do any harm.