Geared hub motor for RadCity with Bolton kit

[TechButterfly]

I have a 2020 RadCity ST3. I really love the bike except for the lower torque of the DD motor. I just installed the Bolton 35a controller and really appreciate the better acceleration and climbing ability. I think a geared hub motor would really take it over the top, but don't know enough to know what I need to order that would work with my RadCity and current electronics. In another thread, @AHicks mentioned he used a MAC 12t but they are really hard to get. What other geared hub motor could I buy that would work with my current setup? Thanks!

 

[AHicks]

What's you motor connector look like? Are you going to be good with matching the controller wiring with the motor wiring if they aren't the same? In other words, how skilled are you when/if it comes to something like that?

My first choice for a practical conversion would be a REAL 750 watt Bafang geared hub (750 will be in the model number). Question would be regarding if the wiring will match up to your controller, or if it's going to need to be adapted.

 

[TechButterfly]

Matching up wires shouldn't be a problem if necessary - I've built and designed multiple 3D printers, and have a background in RC. In a previous life, I was an aircraft electrician in the Army. That said, I'd prefer to have a plug and play solution. The Bolton kit is designed to be plug and play with the RadRover, which has a Bafang geared motor. Do all the Bafang have the same motor connector? Or do I need to look for a particular kind? Also, I'm concerned whether the geared motor would fit on the RadCity, with the same gears and brake disc, etc. Amazon has a Bafang 48v 750w geared motor - is that all I need to order? Do I need a cassette or freewheel version? Sorry for all the questions - I don't know much about bikes in general, though I'm trying to learn!

 

[AHicks]

Cassette or Freewheel will depend on the motor you get. Pretty sure they're available both ways. Just select the one for whichever motor. The rest of the bike doesn't care as long as it's a 7 speed.

I believe there are 2 different motor plugs. That's something you're going to want to do some research on to confirm/make sure of what you have now, and what you are getting.

Something to watch is the "dropout width", the clearance required for the width of the motor. A motor set up as a "fatty" is going to be way too wide.

Check out this add on Amazon. It goes through some of the differences, and it looks like he sells just about all of the different Bafangs-

Amazon.com

Be happy to check out a link to something that interests you. -Al

 

[harryS]

Be careful on your dropout size. Most 750W Bafang motors that I've seen for sale are for fat tire bikes, and have an axle width (O.L.D. is the spec) of 175mm, while your non-fat tire bike widths are 135mm.

EDIT. Now I'm looking at the listing above. The fat tire motors also use a higher current connector. You can see it in the photo in the above amazon listing. Female plug vs a male plug. You can separate the connector on your RAD to see which type you have.

Could you buy a 500W motor and pump 1000W into it? A lot of people do that. me included. Not the same though as having the real thing.

 

[AHicks]

I agree. If you are buying a wheel motor combo, for whatever it cost to go from a 500w to a REAL 750 would be worth it....

 

[legsofbeer]

Something to watch is the "dropout width", the clearance required for the width of the motor. A motor set up as a "fatty" is going to be way too wide.

Good call. The rad city rear dropout width is 135mm, the radrover (geared hub motor) is 170mm. Source, radpower website (for each bike scroll down to "geometry" section).

 

[TechButterfly]

Thanks @harryS - that information about the dropout size is a critical piece I was missing. I know now what to look for as far as the mounting width goes. @AHicks I had been looking at that Amazon listing but I can see now that the 750 won't fit my bike. I haven't found any true 750 geared motors that fit 135mm dropouts - yet, anyway. I did see this - an 1800w DD hub. I know the connector is different, but assuming I could change the connector or get an adapter, would a motor like this be compatible with my Bolton controller setup? Would there be some advantage to going to the 1800w DD? My main interest is torque for acceleration and climbing. https://ebikemarketplace.com/collections/hub-motors/products/36v-tdcm-motor

 

[legsofbeer]

Would there be some advantage to going to the 1800w DD?

Since bolton mentions the controller being successfully used to drive a radcity stock DD motor, I would assume it can be programmed for another DD motor. The parameters you would have to figure out are P1 and P2, as described here:

There's also C2, if a sine wave controller is necessary.

The other issue is that 1800W will be above that 672WHr battery's C rating, which will at the least cause it to shut down temporarily due to thermal buildup, and possibly damage the battery. But you can tweak the bolton controller's power draw settings with C5 and C14 to try to dial in a 1400-1500w cap. Be advised that using 1400w continuously is going to drain that battery in less than 30 minutes.

 

[TechButterfly]

Okay, that makes sense. I guess I should just ride with the 35a controller and stock motor for a while. I already know it adds a lot of torque, but we're having a cold snap here and I haven't been able to ride more than 15 minutes or so. It'll warm up again pretty soon and I'll have a better idea if I really need more power. Thanks everyone for the input!

 

[Deleted member 4210]

I have a 2020 RadCity ST3. I really love the bike except for the lower torque of the DD motor. I just installed the Bolton 35a controller and really appreciate the better acceleration and climbing ability. I think a geared hub motor would really take it over the top, but don't know enough to know what I need to order that would work with my RadCity and current electronics. In another thread, @AHicks mentioned he used a MAC 12t but they are really hard to get. What other geared hub motor could I buy that would work with my current setup? Thanks!

You will most likely need a new controller too, when you switch from direct drive to geared drive. Sensors are usually different, and speed may not monitor correctly. I'd sell the ebike, and buy a better one, with geared motor already on it. Bolton makes a small fortune from Rad buyers, wanting to upgrade the power or speed on these Rads, and it seems sort of ridiculous to throw good money after bad, on such a mediocre product. Hardly any quality ebike oem, supplies a direct drive motor on a recreational or commuter style ebike. Direct drive on a Cargo ebike, for sure. Makes sense there. Sort of Makes one wonder if Rad was anticipating their prototypical buyer of this model would be on the heavier side of average. Especially since they have stuck with it for so long. Very odd spec choice, given how they are using geared hubs on most of their line up.

 

[AHicks]

You will most likely need a new controller too, when you switch from direct drive to geared drive. Sensors are usually different, and speed may not monitor correctly. I'd sell the ebike, and buy a better one, with geared motor already on it. Bolton makes a small fortune from Rad buyers, wanting to upgrade the power or speed on these Rads, and it seems sort of ridiculous to throw good money after bad, on such a mediocre product. Hardly any quality ebike oem, supplies a direct drive motor on a recreational or commuter style ebike. Direct drive on a Cargo ebike, for sure. Makes sense there. Sort of Makes one wonder if Rad was anticipating their prototypical buyer of this model would be on the heavier side of average. Especially since they have stuck with it for so long. Very odd spec choice, given how they are using geared hubs on most of their line up.

Mike, he won't need a new controller. Using a KT controller nearly idintical to the one Bolton sells, I swapped a Leaf 1500w DD for a MAC 12t geared hub and the only change required was to match the wiring and install an external speed sensor. Took me about 2 hours. That bike has worked out REALLY well in the 2 years since. Clearly you have little experience with conversions - or with RAD.

I do agree with you on Rad's choice of motors for the City. Still, that in mind, there are a LOT of very happy 'City owners - proving both our opinions are just that (2 people vs. thousands)- and reflections of our personal tastes.

I really enjoy the MAC geared hub powered 'City. The ONLY reason I went with my latest bike was to go with 4" tires. Figured while I was at it I would try out the Bafang Ultra mid drive - one of the few drives that can hang with the MAC for hybrid/street use.

As far as a 135mm Bafang 750, they're out there. Check out the Juiced CrossCurrent. Pretty sure they use "real" 750w motors. Just going to be a matter of sourcing one.

As far as ANY direct drive hub, I find they are completely gutless at speeds from -0- to 15mph which is where I spend the vast majority of my time riding. A gear drive, even one with a 500w rating, will provide much "sportier" performance in the -0- to 15mph range and will still crack 20mph pretty easily (the CrossCurrent is rated for 28mph). Where the direct drive might shine is where you are going to be spending a lot of time at speeds over 15mph - as in somebody using the bike as a commuter. That's about the only application I know of where the DD work well - until - you start talking ginormous batteries used by some riding fully modded bikes. They like them for their ability to shed heat way better than a geared hub or a mid drive. -Al

 

[kmccune]

I have a brand new "fattie' I am trying to sale along with a 1500 watt controller, it supposedly has the larger stator,I would sell both for 180$ if someone would pay the postage, the thing is the DD motors have the potential for "regen" and regen would really help on brake life around here. This motor is similar to one I had in a fat tire cruiser and that thing punched above its weight.

 

[TechButterfly]

I hope you find a buyer - sounds like a great deal. I decided to do what I should have done in the first place. I sold my RadCity ST and ordered a RadRover ST. I already have the Bolton upgrade controller, and eventually I'll get a true 750w Bafang to go with it.

 

[AHicks]

Most people are flat landers, and could care less about regen - with good reason really. For those that like to play in an area with a lot of hills regen is a great feature. I'm a BIG guy though, so even with a 1500w DD hub, I find the DD's questionable when it comes to power. My point is the lack of power available with direct drive more than off sets the regen feature. I'd MUCH rather have the extra power!

Good price for the pair though!

 

[kmccune]

II hope you find a buyer - sounds like a great deal. I decided to do what I should have done in the first place. I sold my RadCity ST and ordered a RadRover ST. I already have the Bolton upgrade controller, and eventually I'll get a true 750w Bafang to go with it.

Good deal, enjoy your bike after I finished my current build( more for sentimental reasons than anything else) I have vowed never to build another, found out one thing though-the better components you start with the better the end result. I will not recover the money I put into that bike, just want it gone.