Start with the right bike when converting to an electric bike

September 6, 2010 · 2 comments

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Every electric bike conversion project starts with both a bike and a conversion kit. In this post I’ll share with you what I look for in a bike to determine if it is suitable for an electric bike conversion.

After completing four electric bike conversions to date, I have a really good idea of what to look for and the problems that can crop up.

Once you have a bike and a conversion kit that are compatible with each other, you can get started assembling it all into a finished electric bike.

By making sure that everything is compatible before you start assembly can save you hours of frustration.

In future posts, I’ll explain the details of conversion kits and how to put it all together into a working electric bike. I’ll do an electric bike conversion from start to finish and show you step by step what I’m doing and why.

Why not just buy a complete electric bike?

Before I talk about what kind of bike would be good for converting to electric, I want to point out that there are other options to owning an electric bike other than building your own.

There may be some good reasons why you should just buy a complete eBike

  • You find one that you really like
  • Has a price point you are willing to pay
  • You aren’t mechanically inclined
  • You don’t want to take the time to do your own conversion

If some of those points apply to you, maybe just buying one is the best way to go, nothing wrong with that.

There are several reasons why you would want to make your own

  • You can’t find a pre-made eBike that you like
  • You want higher quality components at a better price point than a manufactured eBike.
  • You want to select the components that you want
  • You like working on your own projects
  • You are mechanically inclined or want to learn how to be
  • You want to learn more about the electric bike system by working with it
  • Want to learn all about your eBike so you can service it
  • You like the satisfaction gained by making something yourself

There is a third alternative to buying or building and that is paying someone to do a conversion for you. Maybe you just want to buy an eBike but don’t like the manufactured ones. There are many bike shops now that are doing custom conversions with excellent results. They usually sell complete electric bikes too. This way you can get the benefits of an eBike conversion without having to do the work yourself.

If you have read this far and are ready to build your own electric bike, then read on.

The features to look for in a bike for an electric conversion

There are many aspects of a bicycle that will make one easier to convert than another. I’ll share with you my opinion and experiences that will hopefully make your bike selection easier and make for a successful electric bike conversion.

Safety
Make sure the bike that you are starting with is safe to ride. This includes many issues that I am not going to list here. Take your bike to a bike shop and have them check it out. This is very important. Maybe get a tune up while you’re there. It’s easier to start with a bike that is in good working order.

Brakes
The brakes need to be of good quality, have good pads, and be adjusted properly. This is extremely important. If you have any doubts about your brakes, have someone check them out before riding with or without electric assist.

Brakes on an electric bike are a critical component. After adding heavy batteries and a motor, it is going to put a lot of pressure on your brakes. Just like in any vehicle, the stopping distance is going to increase as the weight of the vehicle increases even with good brakes. With faulty brakes, you might not be able to stop at all.

The brakes can be rim brakes and sometimes they can be disk brakes. It depends on the type of motor selected. If you have a particular motor in mind, check with the brake options that it allows. Some hub motors have a disk rotor mount. Otherwise, they will require rim brakes. Mid-drive systems are the most flexible in that they allow whatever braking system the bike comes equipped with.

Comfort and fit
Make sure the bike is comfortable and fits your body dimensions. If the bike doesn’t feel good before the conversion, it probably won’t after the conversion. There are some changes you can make like a different seat or handlebars. There are some things that are not practical to change like frame geometry.

Wheel size
Depending on the kit, almost every wheel size is supported in some fashion or another. Some sizes make for better conversions than others. Wheel size depends on the type of kit.

If you want to use a hub motor, most kits come with a complete wheel in a variety of popular sizes. Typically the sizes will be 20”, 26”, and 700c. Some kits offer other sizes as well.

If you can’t find a kit that comes with a pre-built wheel in the size you need, you might be able to get the hub motor, spokes, and rim and build your own. This will be hard and I don’t recommend it. It will be much easier to use a complete wheel with hub motor.

The most common wheel size for hub motor kits is 26”. It will provide a smoother ride than smaller wheels and provides more torque than larger wheels.

There are several 26” wheel bikes to choose from too. Many quality bikes can be found used at a discount. Maybe you already have one.

If you are going to use a mid drive electric bike conversion kit, tire size is not an issue in bike selection. The main restriction will be if the conversion kit has a mounting system for a particular bike. Check with the kit supplier for the type of bikes it is compatible with. Mid-drive kits are nice but hub drive motors allow you to use a wider range of bikes and are generally easier to install.

Frame and Fork
You will need a strong frame to handle the extra weight of the motor and batteries as well as the torque of the motor.

I like to use mountain bikes or cargo bikes. They are built to take more stress than lightweight road bikes and won’t flex as much with the added weight. Cruiser bikes and comfort bikes made of steel are good candidates too.

If you want to use a front hub motor, you will need a very strong fork made of steel. The width between the dropouts usually requires 100mm.

If you want to use a rear hub motor, you will need space between the rear dropouts of 135mm.

Don’t know what motor to choose? My Motor Selection Guide will give you all the details of how I choose motors for my projects and why. Enter your info here and I’ll send you a link to it.

If you are going to use a rear hub motor, you will need a rear derailleur. Rear hub motors typically come with a 6 speed freewheel. You can find other speed freewheels but you’ll have dropout width spacing issues to solve unless you can find a 5 speed freewheel. Some bikes will be setup for 7 speed or higher shifters. The shifters may require replacement if going with a different speed freewheel.

Personally, I like using the 6 speed freewheel and replacing the shifters. I don’t miss having extra gears with an electric motor. The shifters sometimes need to be replaced anyway to allow for a throttle and brake levers with motor cutoff switches anyway.

Conclusion

This post talked about the main features that you need to consider when finding a bike that will be a good candidate for an electric bike conversion. There are other considerations but I think I’ve covered the go-no-go features.

Keep in mind that for your bike selection you’ll need to have selected your conversion kit too. They have to be compatible with each other. More about this later.

I presented a lot of technical details that you might not understand completely. No worries. I’ll be going over all of these details in future posts as I build my next electric bike. I’ll show you step by step what I’m doing and why. I’m working on an electric bike conversion right now with blog posts and videos on the way. Stay tuned.

If you have questions, please send me a message or leave a comment.

P.S. For more details on electric motors and how I select them for my electric bike projects, enter your information here and I’ll send you the link to my Motor Selection Guide.

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{ 2 comments… read them below or add one }

1 fred elliott September 7, 2010 at 3:33 am

Having re-built an adult trike and electrified it, I want to do more. The more I know about the options, the better I think the finished project will be. I’m partial to the mid-drive system as it allows for changing the speed/torque possibilities.
Thanks,
freddie

2 Dan September 7, 2010 at 5:13 pm

Thanks for the comment Freddie. I like mid-drive systems too. I really enjoy my e-bikeE with ecospeed:
http://electricbikebuilding.com/bikee-is-ready-to-ride
I have several new projects in mind that will use a mid-drive kit. I’ll be posting all the details about it.

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