The original 4-speed Sturmey Archer hub (usually the RK4) relies on an electronic shifter — and that’s where everything goes wrong. They're fragile, unreliable, and Error 44 is a constant headache. Our conversion replaces it with a 2-speed hub that shifts mechanically with no electronics at all. It’s simple, rock-solid, and built to last.

Not really. We install a rear sprocket with 4 fewer teeth than stock, which helps close the gap in gear ratios. First gear is a bit heavier (you’ll feel it more on hills), and second gear is slightly lower than the original 4th — so at top speed, you'll just pedal a bit faster than before. For city riding, it’s a great balance.

Nope. The A2K shifts automatically based on your pedalling speed. No buttons, no app, no motors — just a smooth mechanical shift.

If anything, it’s better. First gear is slightly heavier than the original, but because the 2-speed hub is built to take real-world torque, you can stand up on the pedals and push hard — no problem.
With the original 4-speed hub, standing up and mashing the pedals was a gamble — it’s how most hubs failed. The internal pawls would just explode under load, leaving you with a dead hub and a pricey replacement.
With the 2-speed setup, you can ride the way you want — no babying it.

Yes — but only when the bike is standing still. That error simply means the original electronic shifter isn’t detected (which is expected, since it’s gone). Once you start riding, the error disappears and the display works normally, showing your speed and battery level as usual.

Not at all. The motor, torque sensor, and pedal assist all work exactly the same as before. We’re only changing the rear hub.