What’s a bottom bracket drive electric bike?

by Peter on June 21, 2011

Bottom brackets? Electric bikes? What the heck are we talking about?

Good questions. First, let’s take a look at bike parts and what a bottom bracket even is!

Bottom bracket on a Kettler Twin

Bottom bracket on a Kettler Twin

A bottom bracket is the part of your bicycle that connects to the pedals and lets them spin freely within the frame. It is circled in the picture at the right. The bottom bracket is in the center of the bike and connects to the rear wheel via the chain, which incidentally also connects to the gears.

What does that have to do with electric bikes?

Another good question. You’re very inquisitive, Einstein asked a lot of questions you know? Of course his teachers hated him (no offense).

But seriously, the bottom bracket has a lot to do with certain electric bikes that have a motor housed within or connected to the bottom bracket. With these electric bicycle drive systems you get a few specific advantages with only one drawback. That drawback is enough to steer you glowingly towards a bottom bracket drive electric bike or make you distanced and uninterested.

So what’s the deal with a bottom bracket drive ebike?

The deal, my friend, is that a bottom bracket drive works the motor power through all the gears in the back of the bike. Who cares? I care! I care because it gives me the ability to run the motor through a lower gear when climbing hills and thereby take the strain off, conserving battery power.

Ahhhh, so that’s it! Yes, a bottom bracket drive ebike is more efficient and tends to have a longer range. So what’s the rub? Why wouldn’t everyone want a bottom bracket drive on their fancy electric bicycle?

The truth is this system caters to a certain kind of rider. Let me ask you: who wouldn’t want a bottom bracket drive system? If you don’t know the answer, chances are you would like this system. Otherwise you’re probably saying to yourself, “But how do I use the motor without pedaling? Wouldn’t a throttle make the pedals spin?”

That’s the crux of the bottom bracket drive ebike

Bottom bracket drive for Kettler Twin

Bottom bracket drive for Kettler Twin

With this system you have to pedal, and in fact, it’s designed to be used entirely with pedaling. So if you’re looking for an electric scooter type bike a bottom bracket ebike isn’t for you.

A bottom bracket ebike drive system is actually one of the oldest and most sophisticated designs. It reads how hard you press on the pedals with a torque sensor and gives you a proportional boost of motor power, matching or exceeding what you put in.

Well, there’s a lot more too it than that, but as we just got the new Kettler Twin electric bikes in I figured I’d do a quick run down on what makes these electric bikes special.

If it sounds like a bottom bracket drive ebike is for you, check out the Kettler Twin electric bike. It’s a fantastic modern example of this system.

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