Complete Electric Bike or Conversion Kit?

© Ken Kalb 2009

You saw the light. You got it that the combination of two of humankind’s greatest inventions -- the bicycle and electricity -- marry in a mystical synergy to create a transportation device that combines fun, health, mobility, freedom, economy and is beneficial for the planet. You want an electric bike. You are now confronted with the big decision…

Should you convert a bike or buy one of the better complete machines?

Almost everyone is concerned about saving money. And most everyone already has a bicycle. So the inclination to slap one of the electric conversion kits on a bicycle is natural. But is this a good idea and does it make a good electric bicycle?

In a word, generally my answer is...no. You usually transform a good bicycle into a mediocre one and create a marginal electric bike. Yes, it will work, but will it soar down a hill at 35 mph safely and handle around the turns well? Will it be comfortable and trouble free?

Generally speaking, an electric bicycle needs to be designed and built from the ground up. An Ebike uses bicycle technology, but it is really a hybrid machine -- a cross between a bicycle and a motorcycle, though it transforms into a breed all of its own.

There are many critical requirements. Electric Bicycles need to have a sturdier frame, beefier wheels with stronger spokes and rims, better brakes, and a heartier kickstand to support the extra weight. They need to position the battery and the motor in such a way as to retain the critical balances which a bicycle is. They need to integrate the different modes in a seamless manner where the pedaling, powering, freewheeling and handling all blend together with an intended intelligence. They should also have features which are proprietary to its new purpose -- from the gearing and transmission -- all the way down to the spokes and tires.

Electric bicycles also need to have braze-ons, cable guides and special mounts for the electronic components and wiring, as well as waterproof cabling between them. The motor controller needs to be mounted and positioned in a protected and unobtrusive manner. The costly battery must be located in balanced and safe position where it may be locked securely, but also easily removed. It also must not rattle.

Another big issue with front wheel conversion kits is the front fork. A solid steel fork is recommended, so you are limited both in your choice of frames and lack of front suspension for comfort. Steel torque arms are recommended because of the powerful twisting motion of the motor which can shatter and aluminum fork. Now, with a rear wheel conversion kit, you place all the weight and complexity of the motor, cluster, gearing and battery on the back of the bike. That does not create balance. Do not expect a bike with a 15-20 pound motor and a 10-20 pound battery on the rear to handle correctly. There is one conversion assembly -- the BionX -- which places a locking battery in the triangle of the frame, though costs $1700 for just the kit alone and does not work with modern cassette gearing. I have been prodding conversion kit developers to position the battery where in the triangle where it really needs to be. And with lighter Lithium Ion batteries being able to be manufactured in different shapes, this configuration is surely soon to arrive.

You also don’t need as wide a range of gears on an electric bike, eliminating the need for a front derailleur and multiple chainrings. Personally I like the Nexus hub gearing, which also eliminates the rear cluster and derailleur and shortens the chain. The best things are the simplest. And a good electric has the lighting systems integrated into the main battery, a battery condition guage and other many other special features.

Euclid once said that “the whole is greater than the sum of it’s parts.” A good electric bicycle has undergone vigorous research, development and testing and been fine-tuned into an integrated machine. By the time you line everything up and get it all together, you’re likely to have more time and expense invested than you would on a complete Ebike which works a lot better. Then there is the issue of a warranty and what is covered and what is not.

On the other hand, some pretty nice kits are emerging in the marketplace with decent motors, wheels, and batteries. If you’ve got a favorite spare bike which lends itself to candidacy as an Ebike, you may be able to convert it successfully into a pretty nice machine. But beware of the cheap kits, they can be a genuine nightmare. Another possible advantage of a conversion kit is power. There are some kits out there that can produce some awesome speeds, though they do not conform to the electric bicycle laws. But you will spend a lot plus need costly additional battery capacity with questionable mounting systems. And safety becomes an issue at higher speeds carrying all of those batteries. Then again, if you’ve got some time to tinker, and have the Tom Swift spirit in you, a conversion bike might be a fun project.

But if you’re depending on your bike for transportation or recreation or just want to feel the magical whoosh each and every time you twist the throttle, you’ll probably want to go with complete. A good electric bike is an absolute joy, besides making all the practical sense in the world. Wishing you miles of electric smiles!

Ken Kalb has been involved with bicycles since he was a child. He helped start the Re-cycled Bicycle Shop in Isla Vista in the 70’s, been a triathalon champion and avid tourer, and been involved with Electric Bicycles since the mid-90’s. He has sold and serviced virtually every product entry during their entire evolution, and consulted on the design and development of several Ebikes. He is the owner of Electric Star, www.electricstar.org.