Lightweight rear hub kit

Hi, first post here, and I'm hoping to get some advice from you knowledgeable folk.

I converted a couple of bikes for myself a few years back from individual components, but now I'm Iooking for a rear hub kit for my wife's new bike (an Islabike Joni). The kit has to be as light as possible as my wife has rusty wrists and knees, though she still only wants a low level of assist. The most suitable kit I've found so far is the Aikema 85SX from Woosh, but it doesn't seem to be available in a 27.5 rim and I'd prefer a smaller battery - around 6-8 Ah ideally. Is there any other suitable integrated kit available in the UK?

Hi Malcom,

Bike wheel sizes are a real mess and misleading. I'm not 100%, but I think 27.5 is the same as 28 which is 700c. I know!

It's worth a check with Woosh.

The other way is to buy a motor and lace it into a wheel yourself. Many on here have done it and it's not the nightmare you might imagine.

 

I've just looked at this and now I'm even more confused:

https://www.sheldonbrown.com/wheels.html

Presumably you're getting 27.5 from the tyre size ? If so this may help.

https://bikepacking.com/gear/700c-to-650b/

 

700c is 29er not 27.5.

27.5" is 650b size. The former is mtb wider tyre size and the latter for gravel or cross type bikes with not so wide tyres.

I doubt one will find anything in that size, a hub will have to be laced and trued in to such a rim. A 650b bike might take a 700c rim ( if the mudguards allow clearance).

 

27.5"/650b rims are 584mm, 700c are 622mm.

 

Imv the best such lightest rim would be either the Akm or a Bafang G370 front hub that rides unpowered pretty much as a normal bike does.

For small motor options and different wheel sizes then usually one has to go the self build route.

Edited March 9, 20224 yr by Nealh

Thanks for the replies!

 

If there aren't any suitable kits with a 27.5/650b rim I guess I could use a 26" rim and put a larger tyre on it. I think a 700c would be a tight fit.

 

I'd really prefer a complete kit, or at least a hub/controller/pedal sensor package that is already configured to work together well.

 

I did a quick search for a G370 hub and controller, but could only find front hub motors, which are no good as the bike has a carbon fork. I'll contact Woosh and ask if they have a smaller battery. Will keep you updated.

G370 is yes a front hub motor only.

It was just a suggestion, it isn't a large power hungry hub but still has good power.

My one takes my 84kg and trailer without complaining in generally flat terrain.

Of all the hubs I have used I am suitably impressed with it's performance so expect the AKM not to be to dissimilar.

One can always change the forks.

Thanks, I appreciate the suggestion Neal. I'm trying to avoid putting more weight on the front of the bike because my wife has arthritis in her hands. She had an old Giant ebike with a front hub and found the front end too heavy and the steering rather sluggish. It was fine in a straight line, but not so good over kerbs or on winding trails.

 

I guess there are fewer kit options for rear wheels because they're a bit more difficult to set up. I've also thought about doing a mid-drive conversion using a small hub motor, but it's a step-through bike so there's not much space.

Yosepower finally have a rear 250w motor kit in both 700c and 27.5

 

https://yosepower.com/collections/e-bike-conversion-kit/products/e-bike-conversion-kit-36v-250w-rear-motor-kit-for-cassette-with-36v13ah-battery-and-charger

Yosepower finally have a rear 250w motor kit in both 700c and 27.5

 

Thanks, any idea which motor that is and how much it weighs?

All of the yose hubs are yose branded bafang swx* hubs so about 3.5 - 4kg each.

Thanks Neal, that's a bit heavier than I want.

It is rare to find a lightweight hub kit for sale as woosh sell and also the switch expensive kit, mostly these hubs are sought by us shed/garage guys direct from China sellers or manufacturers.

 

All I can reiterate is that so far imv the G370 I have is by far the best hub I have bought.

The Aikema/Q 100 H/CST would be a good choice at around 2kg, but would mean buying from China and building up yourself.

http://www.topbikekit.com/akm100cst-cassette-36v250w-ebike-rear-driving-hub-motor-3236-holes-p-728.html

The Aikema/Q 100 H/CST would be a good choice at around 2kg, but would mean buying from China and building up yourself.

http://www.topbikekit.com/akm100cst-cassette-36v250w-ebike-rear-driving-hub-motor-3236-holes-p-728.html

Apologies for butting in on this thread, but this is the motor that I have been looking at to fit to my wife's bike - and that does seem to be the most comprehensive website by far - is there an available online primer/guide as to how to navigate the rather daunting array of options when trying to spec your intended build? I know precisely what my requirements are (not dissimilar to the OP), but would like to be able to make the right choices first time around to the greatest possible degree, as ordering from China can be a bit of a slog - any pointers would be greatly appreciated - MH

On the same home page select the controller on the header bar and once on the controller page select the kt T06S or T09s controller from there select compatible items from the drop down box. This will differ if one is going down the integrated battery/controller route.

 

The akm 100 should be limited to about 18a so if wanting to do so opt for the T09S and limit the current from the display otherwise one will melt the nylon gears with heat and possibly demagnetise the windings.

 

From the drop down box select the following;

1. Display lcd 3 , 4 or 5 or any of the ones that takes your fancy. the lcd 4 is by far the most discreet.

2. 9 pins one will want this cable usually 100cm is plenty long enough, 60cms may be too short.

3. Brakes. Sensor not really needed if throttle not used. Other wise fit a sensor type to suit your brakes.

4.Cable. One will be needed if using throttle and brakes then 1T4, if not using a throttle then simply fit the 1T2 cable for slightly neater look.

5. Throttle only if needed.

6. PAS yes, show a pic of your cranks/BB to advise.

If the conversion is for a rider sub 13st and not in a too hilly area then one of the light front motors may be a good option esp if steel forks are used. Also with small light front hub it will climb hills if one also utilises the bike normal low gears to spin up them rather then grind up them in a gear that is too high.

 

The G370 is only suitable for steel forks as there is no option to fit torque arms, one should also probably limit any controller current to 15a or so.

Edited March 13, 20224 yr by Nealh

[mention=9614]Nealh[/mention] - thanks so much for taking the trouble to reply - I shall have another look at the options, and try to grasp the implications of the various decisions that need to be made - the plan is to be as lightweight and discreet as possible, and just provide a bit of extra oomph - I do have quite a few questions, which was why I was hoping that someone had produced a kind of idiot's guide...

If not sure then ask away, much better then buying wrong.

In the past front motors were a bit of a handful giving vague control/torque steering and wheel spin due to them being very heavy and powerful, the smaller hubs are very different and as I mentioned ok for someone up to about 13st. With the heavier/larger more powerful hubs one had to make sure that torque arms were fixed securely to prevent spin out and motor cables shorting. I had a Bafang BPM partly spin out because the torque eventually snapped the front fork drop outs, fortunately not causing any cable damage.

In the past front motors were a bit of a handful giving vague control/torque steering and wheel spin due to them being very heavy and powerful, the smaller hubs are very different and as I mentioned ok for someone up to about 13st. With the heavier/larger more powerful hubs one had to make sure that torque arms were fixed securely to prevent spin out and motor cables shorting. I had a Bafang BPM partly spin out because the torque eventually snapped the front fork drop outs, fortunately not causing any cable damage.

These are exactly the issues that persuaded me that rear drive might be the way to go, but I had not considered the hill climbing issues you mention - my wife is a very experienced cyclist, and would like a bit of gentle assistance rather than a completely altering the riding experience - the frame is bespoke handbuilt steel (Steve Goff) and I think the forks are 531 - are there any downsides (apart from cost) to the Cytronex C1 system? I am doing this as a silver wedding anniversary present, and I want to get it right!

A few years old, but look at https://www.pedelecs.co.uk/forum/threads/pro%E2%80%99s-and-cons-of-buying-cytronex.32165/

The system was clearly not right for us, but could well be right for your wife. The shop is quite close to us; we've been in a few times, considering their system and for other general bike issues and they've always been very helpful.

 

It is a proprietary system which has its downsides when it comes to spares and repairs. I can't remember the details but I have a memory of people with their earliest system having lots of issues getting replacement batteries. That was some time ago though, and it may be a distorted memory.

My small G370 hub is simply fitted in to nice Surly chromoly steel forks, all that resists rotation is the tight fit and one anti rotation washer and the nuts nicely tightened in the dimples. The motor cable exits the hub in a way that doesn't allow a torque washer on that side, unlike most hubs the thread uses std SA or alfine threaded nuts on 10mm axle. The axle shaft is 10mm in dia and the only part that has opposing flat sides is the tiny bit that sits in the drop outs, this motor is low power but quite pokey for a lightweight install. It isn't designed for high power usage and must be fitted in to a steel drop out rather the soft aluminium.

All I will say is the cytronex kit is bepsoke and quite expensive, for spares one is tied to cytronex.

All I will say is the cytronex kit is bepsoke and quite expensive, for spares one is tied to cytronex.

Up to now I have not been considering front hub kits, and the Cytronex stood out as having had a great deal of thought going in to it, not least the control software - I might look again at putting something together myself, but it does seem that there are pitfalls... Woosh is also an option I might revisit - previously dismissed due to the weight of their rear hub kits - MH

Any hub kit to get the best out of them is one with high internal gear ratios as this allows for more unassisted riding without the treacle affect often associated with hubs. The larger hubs 129mm or greater tend to be mostly 4:4:1 geared down where as the smaller lighter hubs are much higher geared, the larger hubs being heavier means all the weight is centrally located so one has to over come the inertia of that central mass when unpowered. It will feel like motor resistance but it isn't internal resistance as they freewheel but the gearing internal gearing does make a big difference.

 

The direct drive hubs are massively heavy at over 5kg and nearly 20kg for the 8kw monsters, these have no freewheeling or are geared inside and are near impossible to ride without power.

 

So for any geared hub one needs to know the internal gearing if wishing to ride with less power or no power.