New build, Mid Drive or Hub?

Have just bought this one for my second build, it`s a british built Whyte Malvern 29er, ticks most boxes for what i need, hydraulic disc brakes, front sus, 700c wheels etc



having previously done a BBS02 750w i`m tempted to go for the HD version again but looking at some of the hub conversions there seems to be less to go wrong and leave you stranded.

It will be used mostly on rough road surfaces in a hilly part of the country so its a case of torque over outright speed.

Already have a spare 48v 13aH battery so would want to hook up that.

Suggestions appreciated!!

Nothing is as simple and reliable as a dd hub. It is also more simple to ride because you don't need to shift gears. The downsides are that they need more power to come alive, and they are not at their best in a large diameter wheel. A slow winding does make it, though you need to do some research. The battery that you have may not have a high enough C rate to feed a DD hub the power to make it a good climber, that is something to consider too.

Well, you just said big wheel, hilly, and the word torque. So unless you want to feed a hub motor enough watts to get that torque, and weigh as much as a big hub does, you are back at mid drive.

But if you need mad reliability, and moderate torque, then a slow wind 500w rated DD hub in a tiny wheel can shine pretty nice.

But as you can see, this bike, built specifically to tow a trailer up steep hills on 1000w or less, does not resemble your project bike very much. max speed 18 mph, so no hot rod. But it will carry 400 pounds total weight up steep hills.

I'm not saying you can't build your bike with a 700c hub motor, and run it on 1000w or less. But it will have less torque than your mid drive. It just depends on how steep your hills are, what your weight is, and so on.

If you are under 200 pounds, the lighter 500w rated dd motors will still get you up 10% grades with no sweat, at about 15 mph, with brisk pedaling. But they wont haul more weight up steeper hills very well, without overheating. Or, being bigger motors, running much more power. About 25-30 mph depending on the wind, and battery.

Lastly, the geared motors are not unreliable. So again, if you don't weigh 300 pounds, you might like one of those better than a dd. More torque, less weight, same 1000w, similar top speed to the dd.

Assuming that you want to ride it like a normal bike, a 500w geared motor will be perfect. In Europe the normal selection is the Bafang CST if you have cassette gears, Bafang BPM if you have or don't mind freewheel gears, or the Bafang SWX02, which comes in both gear versions. Another good choice is the Q128C from BMSbattery. At 48v, they all give a lot of torque. The SWX02 can go up to 20A, the Q128 25A and the big Bafangs 30A, though I doubt that you'd need that much power. Your battery will be limited to a lot less than that anyway - probably 20A unless it has modern cells in it.

With a hub-motor, the motor's maximum rpm is a very important characteristic. It affects speed, torque and power, so you need one with a speed that suits your needs. You need to choose a maximum rpm something like 25% faster than your modal speed.

I can't see that a heavy DD motor would suit that bike. It would be a complete waste. They're much better suited to cheap strong bikes that you want to use as a workhorse with little or no pedalling.

thanks for the advice so far guys, i`m leaning towards the geared Bafang 500w

another one that crops up is the Xiongda 2 speed, any thoughts on that one?

i`m beginning to think that big 700c wheel might not be the best for some hub motors, stands to sense i suppose, motor has to turn a bigger circle compared to a 20 or 26"

The two speed motor has 0.5mm laminations, so no 72v. I don't think you want 72v anyways. It has a 400w power limit. Will probably be fine at 500w. On a 26 inch rim @ 48v, low gear=16 MPH, high gear=22 MPH. Will be faster on 29 inch. That is some basic information. I hope it helps.

Also the lighter gearmotor on rough roads should ride better. Heavy dd motors on rough is hard on parts, tires, arse etc..

tommie said:

i`m beginning to think that big 700c wheel might not be the best for some hub motors, stands to sense i suppose, motor has to turn a bigger circle compared to a 20 or 26"

Click to expand...

26" and 700c tend to have nearly same diameters (comparing mtb tires vs touring tires respectively), so don't worry about that. On my bikes, the 700c wheels actually need less power because - well in my case it is a difference between 40watts rolling resistance for the 700c, and ~100 watts rolling resistance for a mountain bike tire (and in my case worse aero on the bike).

With about 300 watts, I can do 19mph on the 26" bike, and 22-23 on the 700c bike (motor only).

Thanks all, at the minute i have the BBS02 and one of the things i like about it and it`s very important is `Noise`, or the lack of it!!

With the BBS its just a gentle whirrrr, nobody notices the bike approaching,

what about the Q128 or BPM hubs, how do they compare on noise?

Just throw the BBSHD on there and be done with it, you'll be happy with the extra power and it will run on that bike nicely with the 48v battery and is super quiet, I have a similar setup 700c commuter with 48v 10.4a battery and the power level is perfect.

nice bike!
But, are you running it single speed?

chas58 said:

nice bike!
But, are you running it single speed?

Click to expand...

or an IGH possibly??

Yip 8 speed IGH, made it nice and easy to install, I only use around 4 gears 99% of the time and its quite hilly over here.

Until you say you are on the light side of normal weight, and the hills not really that steep, you are still back at another mid drive.

But if you only weigh 200 pounds, and the hills are mostly less than 10%, or very short, then a geared motor like the bafang will work fine. Simpler install, less strain on the chain, you get more flexibility what size front gear, etc. Won't be any noisier than the bafang BB, run at 800w cruise.

I'm NOT knocking the mid drive. just saying the geared motor will have less torque, but more reliability and ease of install and use. which makes it the prime choice for commuters that just want a fast reliable ride daily.

some interesting observations here,

My first ebike was a rear hub powered folder, 20" wheels and a 250watt motor. It just didnt cut it when it came to the steep hills around here. As well as that the spokes were a pain to keep tight and it wasn`t the quietest, it `growled` at low speeds.

Next up is my present ride, a converted MTB with the BBS02 750w and an Alfine 8 hub. So far it`s done all i`ve asked of it, great climber, very quiet, it just purrs along. Haven`t had it long enough to see how reliable it would be compared to a hub.

To answer a previous question i`m well under the 200pounds mark and the hills here could be described as short but sharp, not a lot of flat land around here being well off the A roads.

btw the battery i`ll be using is a 48v 17.5aH made with Panasonic GA cells.

Only good argument for a hub would be price. They are very cheap compared to md setups. Also in the last couple years they have gotten better and lots of choice of vendors/manuf. now.

I have always seen the advantages of middrive . Keeping the motor in it's happy zone. weight dist. hook it to any drive train you want.. .

I have a mac hub 10t on a 700c rim, 52v 26.6aH battery 40a controller 2000w from ev3ev. Top speed 30mph with range of about 40miles at 30mph. At 40amps this thing takes off! Iv put about 5000miles on it no problems. I ride at 40 amps daily but you have to watch your temps at 40amps it gets hot fast!

craigsj said:

dogman dan said:

...but more reliability and ease of install and use.

Click to expand...

Don't think any of these claims can be defended. The BBSHD is proving reliable at "800 watts" compared to an unnamed geared hub and it is arguably easier to install and just as easy to use. Chainring choice isn't really a problem for a 700c commuter either and the BBSHD doesn't lock you into terrible drivetrain components like many hub motors do. While some hub motors will be adequate under lighter loads, the mid drive will work better. No need to build a custom wheel or mount an external controller with a BBSHD.

dogman dan said:

...which makes it the prime choice for commuters that just want a fast reliable ride daily.

Click to expand...

Don't agree with this either, especially the first time you have to fix a flat on the rear wheel...which you will on a daily rider. Not a single compelling point is being made for a low powered hub motor here, just a list of circumstances where one isn't so bad that it must be ruled out. Hardly a prime choice, more like merely acceptable as long as expectations aren't great.

Click to expand...

You make some good points, about the only problem at 800w is the weak spot clutch, which is cheap,and easy to replace, and ought to be in every kit. Not a wear issue, more likly a bad part. Spring fail i think.

harmonist said:

Yip 8 speed IGH, made it nice and easy to install, I only use around 4 gears 99% of the time and its quite hilly over here.

Click to expand...

Is that the Alfine 8?

Using that one with my BBS02, I agree with the 4 gears comment, i double click all the time. Didn`t think it would hold up on the HD version though,

any problems so far??

tommie said:

another one that crops up is the Xiongda 2 speed, any thoughts on that one?

Click to expand...

I've been using a Xiongda for 3 years. It's done about 4000 miles so far and I love it. I run with 48v and 15 amps. Low gear is winch-mode. It'll climb anything with a little help from the pedals, but it goes right down to 4mph for the steepest hills (30% incline or more). Max speed in low gear is about 12mph so you're around 10 mph when climbing normal hills. Max speed in high gear is about 23 mph, so It's good for cruising at 20 mph. For reference, I'm 100kg naked (220lbs).

To summarise, if you want an electrically assisted bicycle that's light and easy to pedal with a top speed of around 20 mph and can deal with any hills, the Xionda could be a good choice. It has all the advantages of a crank-drive without the disadvantages.

There is one draw-back. It's a bit wider than normal hub-motors so you have to widen your frame a bit if you want to use 7 or 8-speed gears (rear motor). That's no problem. I've done a few. With 8-speed gears, the rim offset would need to be a lot, so I prefer to stretch a bit more and put a spacer on the brake side, but then you need to bring the brake caliper inboard by adding a few washers on the caliper adapter equivalent to the width of the spacer. For 7-speed, you can get away with just dishing the wheel. The front motor fits directly if you don't have a disc brake, but if you do have a disk, then you have to use non-suspension forks because they need to be sprung a bit for the extra width. You can't do that with suspension forks.

They have a couple of other advantages too. they can be bought pretty cheaply if you buy directly from Xiongda (bonnie@xiongdamotor.com.cn) and then, if anything breaks, they send you free parts to fix it. I personally didn't have any problems during those 4000 miles.

Hmm, I don't think I was suggesting a low power hub motor. 500w rated motor, run at 1000w.

Change that to 250w, and a rider over 150 pounds, and you'd be a complete idiot to run anything but a mid drive. I do think the mid drives blow their controllers days are long over, and I am assuming you have enough sense to not ride so as to wear out your chain all that fast. ( I once owned a mid drive, that blew its controller every 40 miles or so)

But with a hub, you can ride any gear you want, the motor cares not. ( provided you aren't the fat guy, as I said before) Wrong gear in a mid drive, with big power, can stress chain, gears, battery, and controller. So if not actually one bit more reliable, a hub is at least a little bit idiot proof. If you want to put in high gear, and leave it there a year, then its the hub.

Id certainly have to ride a mid drive more miles, 20,000 or so, to make a fair reliability comparison with hub motors. So I can only say that the hubs ARE plenty reliable. I never said a hub motor would easy to change the tire on. But if you have a flat that a re pump can't fix, you are late to work either way. Torque arms do slow you down on the tube change, by at least 5 min. If they slow you more than that, you just didn't carry the right tool kit for dedicated commuting.

Did I not say get the mid drive anyway? I only said get the hub if you weigh under 250, and preferably more like 200 or less. Over load that hub, and yer stupid.

As for clutches breaking, I have not been able to break one on a good quality motor, ridden at 1000w exclusively off road. I did shear the key once, seeing how much jumping it could stand. the key should shear before the clutch breaks.

Shit cheap ass hub motors, are another story, much like the cheap ass mid drive I once had. I never said, or will say, the cheapest kit out there is highly reliable in any way.

Nobody has hired me to go out and try to break the BBs02. But I have been trying to break E bikekit brand stuff since 2009, and in normal use, not overloading them, I fail every time.

One guy that had me test some cheap hub motors, never did that again! :lol: I broke his controller, broke his motor, etc. Easily.

The clutch spring in a bbshd is like half a pen cartridge spring. Just a weak spot.

Either way, broken clutch in a mid drive, broken clutch or shear pin in a geared hub, you'd still be able to pedal.

I learned a thing about reliability commuting by bike for 5 years. The unreliable thing was the bike itself. So most likely you will be late for work because of bike parts, rather than a mid drive motor part. In most cases, the bike did not stop you getting there, it just meant you lost one wheel braking, had to stop to pump a few times, or needed to tighten some spokes before the return home, shit like that.

I did learn to carry a chain breaker, so I could repair a broken chain on the road.

I still think though, if you want to worry about the motor the least, then go with the one with one moving part. the DD hub. (at least 750w) Far from the best choice, but damn hard to break those motors in normal use.