Replacement Rear Hub Motor 2018 RAD City

[carlosthetaxman]

Hi, I have a couple of RAD city bikes that we use to commute with and haul children. One is a RAD City 4 and the other a 2018 RAD City, don't know the model number, it's not the step through. To shorten the story we had a problem with the hub and messed it up and the motor case so we have good gears and rim and tire but are looking for an affordable replacement motor (comes with a Shengyi 750W 48V). After market is fine if we can make it work, we don't want to make it complicated or more expensive that getting a different one.

I can post pictures later if that would help.

Any advice is appreciated.

Carlos Nichols

 

[carlosthetaxman]

Here are the pictures:

 

[harryS]

What happened? Did the axle nuts come loose and spin the motor, twisting the cable and breaking it?

In the best of scenarios, you can find another direct drive motor like what you have, or switch to a geared motor like RAS has done in newer City bikes. You work around the possible connector differences, and it's a simple swap.

It might get more complicated if you did twist a cable and the shorted out wiring damaged something inside the controller. Then you might have to replace that part too,

Then again, if it's a twisted cable, and only damage is in the motor, those can often be repaired.

Unless you get lucky and find someone selling a used Rad City motor, any replacement will need to be spoked into the existing rim. It's usually cheaper to buy a entire new wheel/motor combo. You do have a motor with the Z916 motor connector. A new motor will likely not use that, in which case you're looking for an adapter or splicing the old connector onto your new motor,

 

[carlosthetaxman]

Hey, thanks for your reply. The problem started because I think they left it out in the rain a couple times, and it wasn’t free wheeling right, probably a bearing issue inside.

So when he took it apart to get to that, he broke another piece that was on the axle, and then he broke one side of the motor housing, so I guess it was educational, but it didn’t work out.

It rains, so often here that I get caught in the rain sometimes, but otherwise, I am very particular to keep my bikes dry. And our humidity is so high that an open carport is even a problem sometimes.

So there isn’t any problem with the controller. The challenge is to find a motor just like that to slip in and re spoke on the wheel. Just about all the motors that I see out. There are shorter and fatter. So we’ll have to try to get a rim, too. I guess.

I just hate to spend $350-$400. Somebody said on one of these forums that any 750. What motor would have the right connector. But I’m confident we can get that worked out. I’m not afraid to spice and solder wires.

So Z 19 is the number for my motor?

Thanks, Carlos

 

[harryS]

No Z916 is the connector on your controller. It is a 9 wire connector with three large visisble pins for the motor coils, plus 6 smaller wires for position sensors and a soeed sensor. The Z916 was picked by RAD because (1) it can handle higher motor currents and (2) no one else uses it. Other connectors like the Z91 are common and can handle 500W-750W motor ridden by adults,

You could probably pick any motor and with the connector spliced or adapted, it would work, In fact, most of the inexpensive motor kits don't use either of the above connectors. They would have to be spliced to your existing connector, There's a slew of direct drive 1000W motors on amazon for about $200 after shipping, THey come with the controller and other stuff you would not use.