How easy is it to change the rear motor

coalmarx

New Member
I've just bought one of these and i'm really happy with it, except that the torque is pretty poor. I'd happily fork out a bit more for a decent rear wheel motor if it was compatible with the existing battery and controller set up. I don't need to go far.
https://www.ebikes.co.uk/peak-electric-mountain-bike-blue.html
Where could i get advice on this and how easy would it be? Does anyone have any rear motors they could recommend? Could someone handy do it or does it require a mechanic.

Please don't say "why did you get that one, you should have got the other one, etc..." - its the result of a long search that fits my needs, all except the torque!

Thanks!
 

6zfshdb

Well-Known Member
A good bike shop should be able to lace a new motor in your rear wheel as long as the number of spokes match. The biggest problem is the motor controller. It may not be compatible with that particular motor. Other electric components could also be a problem. Wiring, connectors, fuses and perhaps the display may have to be replaced as well. Check with the bike maker to see if there are any options available.

You could retrofit the bike with a more powerful e-bike kit but the cost would be prohibitive. Unfortunately, your best option might be to sell the bike and put the money toward a more powerful model.

Good luck and welcome to the forum!
 

rich c

Well-Known Member
Usually the first approach is changing the programming in the controller. 2nd is to replace the controller with a higher output version. The motor only puts out the wattage that the controller sends from the battery. New motor on your old controller may still not give you what you want.
 

indianajo

Well-Known Member
The bafang motor in post 2 is also a 250 W 36 v motor. The only possible improvement is if the motor you own is a direct drive motor. Lift the back wheel or turn the bike over (protect display) spin the back tire forwards & backwards without power. If it spins easily in the forward direction and not in the backwards, then you already have a geared hub motor. The bafang would not be an improvement. If your hearing is good just push the bike unpowered on the ground. A geared hub motor whines going backwards and is silent going forwards.
UK laws are strict, you may not be able to buy a hub motor stronger than that. I can buy a 500 W Mac12 in the US, but customs may stop import of one into the UK.
 

coalmarx

New Member
Have had a go and the assist is just really catchy, which reflects the price of the bike i think. Maybe a bafang would solve that? Or maybe i just need to pedal more!

I thought the assist was more down to newtons than wattage? If i could find a rear drive Bosch kit i'd go for that but i think they see it as beneath them.
 

rich c

Well-Known Member
Have had a go and the assist is just really catchy, which reflects the price of the bike i think. Maybe a bafang would solve that? Or maybe i just need to pedal more!

I thought the assist was more down to newtons than wattage? If i could find a rear drive Bosch kit i'd go for that but i think they see it as beneath them.
Beneath them? Why compete with the cheap Bafangs on hub drives when they make them by the millions? I don't know what you mean when you say the assist is really catchy? Power flow is set in the controller, not the motor. There is more than one assist level, each one allowing more wattage to the motor.
 

coalmarx

New Member
It just seems to be very erratic as to when the assist comes on. The thing with the Bosch's is they seem to get a lot more torque out of the 250w than the bafangs.
 

Sierratim

Well-Known Member
It just seems to be very erratic as to when the assist comes on. The thing with the Bosch's is they seem to get a lot more torque out of the 250w than the bafangs.
This may have more to do with the Euro regulatory environment that the major mid-drive motor manufacturers sell into. As I understand it the 250W Euro power limit is under a specific set of operating conditions the majors go to lengths to meet. Under 'real life' conditions these mid-drive motors can produce much more power than their nominal ratings would imply. Bench tests of several of the more popular mid-drive models show thatvthey can produce peak power outputs to to 560W at torques up to 90Nm. The Specialozed Mission Control app reports that the Brose motor in my Vado peaks at 800W when I'm at max effort. Prettru impressive for a 250W rated motor!

None of this helps you, but maybe clarifies mid-drive motor ratings and performance...😎

BTW - It might be worth your time to research a replacement ebike wheel and controller set, rather than lacing in a new motor. @rich c has an excellent point re the existing controller being a potential limiting factor to improved performance. A replacement wheel/controller combo could address both issues. Note that the mileage available from the 317Wh battery will drop as the motor power/torque increases.
 

indianajo

Well-Known Member

coalmarx

New Member
Again, before shopping, I suggest you check your bike to see if you have a geared hub motor or not. The bike website says it is 250 W. However well known the bafang is, I doubt if it is much stronger from stops & climbing grades than a 250 W geared hub motor you have already.
OK thank you for the reminder - is complicated

Aye - its a geared hub motor. But my sense is its the controller not really using the motor well.

And if there's any way of disabling all the pointless limiters that would be good too ;)
 

Sierratim

Well-Known Member
OK thank you for the reminder - is complicated

Aye - its a geared hub motor. But my sense is its the controller not really using the motor well.

And if there's any way of disabling all the pointless limiters that would be good too ;)
As @rich c mentioned getting programming access to the controller is key here. If you can ID the controller you may be able to Google to check if this is possible or not.
 

kmccune

Active Member
You could check and see if the controller has a "speed limit" wire you can unhook, to let it put out all it can.I was amazed at the highest top speed I could get with an 11 tooth high gear and the Bafang Hub drive pulling over a 1000 watts according to the memory on the display on that very slight downgrade PAS5 and putting all I could on the pedals it was 39. something or the other.I never tried it again, my bike was starting to get wobbly and if a whitetail had ventured in front of me, the Forum may have been minus a recent member( I think the sub 30 mph legal cap might not be such a bad idea after all.)
My new bike is probably never going to see speeds like that, I actually like to look at things around me, the old crappy road I rode a few times over 12 miles total( probably closer to 14) Went by faster than I could have imagined, during the cold mornings in October I lamented the type of clothes I was wearing till about 10 oclock in the sunshine.After dodging the "anklebreakers" and the trail bike club,I just fancy I will avoid that road in the future which is sad, because these places to ride were I live are rare.
 

theemartymac

Active Member
Just keep in mind that it only has an 8.8ah battery as well. If you do lace in a higher power motor, you will not have much range with higher assist settings you will want in order to benefit from the power with the higher motor. You also have a relatively light duty bike with possibly cable disc brakes? You can very quickly over spec the power, and find the rest of the bike components aren't up to the task. By the time you upgrade the rest, you will be over the cost of a better bike.
 

harryS

Well-Known Member
Your controller is probably limiting your current. A different motor will act the same. Here's a bunch of controllers that I accumulated. Their max currents are 13A, 20A, 25A, and 25A.

Running on 36V, if I were to lift the wheel off the ground, they would all spin the motpr in a 26" wheel to around 20 mph, But with a a rider on the bike, the first one will have a hard time going past 16 mph. The others will go progressively faster.

So first thing to do is find a higher current controller that uses the same display. If not available, then you have oi upgrade controller/display. That can be a lot of work. AFter that, you raise the voltage.
 

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kmccune

Active Member
Some of them limit the speed(yes) the main thing to remember on these motors, is this, the voltage controls the speed(rpm) of the motor(basically) within reason a larger wheel will give you a little more speed at the expense of torque applied and yes there are motors that are"wound" for speed. Its very convenient on a 36V motor because the RPMs on these usually fall within a class( hub motors)
It's different on the higher voltage motors, they spin faster with a little more torque. Some of these have to be governed for example my daughters 48v ECO Tric is limited to class 2 while the little folder I didn't not keep would go to 28 mph( class 3) on 48 volts, ( that thing had no endurance on the battery- while my Daughters bike goes on and on with a slightly larger battery)
"overvolting" is perhaps the easiest way to speed up a bike on the level- to get more"hill power"(torque) you need to increase the current.
 

coalmarx

New Member
Thanks. I think I've concluded that the bike is faulty and am going to send it back. Something's causing the power to cut out and be erratic. At first i thought it was my noobness to electric bikes but now i'm convinced its more than that.