Rad Power Bikes has stopped operating, and for owners the question that follows is a practical one: when the controller on your bike fails, can you fit an aftermarket kit instead of hunting for an original part? The honest answer is that it depends on which model you own and roughly which year it was built. For some bikes the answer is a straight no, and knowing which group yours falls into before you spend money is the whole game.
The short answer, by model
Compatibility here follows the testing published by Area 13 Ebikes, who build KT-based upgrade kits for Rad bikes around a 35A controller paired with an LCD8H display. Their results sort the range into three groups.
Fits without modification: the 2016–2018 RadRover, and the 2019–2021 RadRover up to Rover 5.
Fits, but needs work: RadCity, the older RadWagon, Runner, RadExpand 5 in the cadence-sensor version only, Mission, and Runner Two/Plus. Installation is possible on these, but plan on adapting the mounting or the wiring rather than swapping one part straight across.
Not compatible: Rover 6, RadWagon 5, and any bike running the newer 500-lumen headlight system.
Why 2021 is roughly the dividing line
Earlier Rad bikes used a conventional layout: a controller in its own housing, wired out to the motor, display and battery through connectors that follow patterns the wider industry also uses. Later bikes went the other way. The controller became integrated into the frame, and the battery compartment and harness are proprietary. Once a manufacturer builds it that way, a third-party controller has nowhere to physically live and nothing standard to plug into. That is the structural reason Rover 6 and RadWagon 5 sit on the "no" list rather than the "difficult" list — it is not a matter of trying harder.
The headlight worth a paragraph of its own
One warning deserves separating out: the 500-lumen headlight system on newer Rad bikes can destroy an aftermarket controller. If your bike has that lighting system, treat the bike as incompatible rather than looking for a way to work around the light.
Size is a real constraint, not a detail
A kit controller is not necessarily the size of the part it replaces. The Area 13 unit measures 7.5 by 3.25 by 1.75 inches, which is larger than the original controller on several models. On those bikes it will not drop into the factory controller location, and you will need to fabricate a bracket to mount it. Measure the cavity you have before ordering, not after the box arrives.
Why the display goes with it
A controller swap is really a communication problem, on any brand. KT controllers speak the KT protocol and pair with KT displays such as the SW900 and the LCD8H family; a display from another protocol family will not talk to them. Three rules make this messier than it first looks. Same model number does not guarantee the same protocol, because firmware versions differ and some displays can be switched between protocols through a parameter setting. Same brand does not guarantee compatibility either, for the same reason. And a connector that plugs in with a screen that lights up proves nothing about the data link — a lit display can still fail to read speed or change assist levels.
That is why these parts are sold as matched kits, with controller, display and harness tested together, instead of as separate pieces. We have written about the same problem seen from the display side, and about what the wire colours on a controller harness actually tell you.
Three numbers to check before ordering
Whatever your model, three electrical figures have to line up. Voltage must be the same across battery, controller and motor. Current matters in both directions: the controller's rated current has to stay within what your battery can deliver continuously, and reach what the motor asks for. Power follows from that — a controller rated below the motor's rated wattage will lose speed on hills and can fail outright.
One thing we cannot confirm
Rad's assets were taken over by Life Electric Vehicles. Whether that restores a supply of original replacement parts, and for which models, is not something we can confirm at this point. Until it can be checked directly, treat any claim about factory parts being available again as unverified.
Placing your own bike
Start with the model and model year, then look at the bike itself: is the controller a separate housed unit, or built into the frame? Does it have the 500-lumen light? Will the replacement physically fit the space? If you are replacing a wheel or hub motor in the same project, dropout width becomes a fourth question — fat-tire builds in this class settle on either 170 mm or 190 mm, and those are not interchangeable, so measure the frame instead of assuming. For the wider picture on sourcing parts now that official support has ended, see our guide to where to get Rad replacement parts.