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I want to convert my trek cross bike to a electric bike. I have 700c rear tire. The kits wheels seem to come in inches. What should I do?

closed as unclear what you're asking by Daniel R Hicks, mattnz, paparazzo, Benzo, Neil Fein May 10 '17 at 15:32

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  • Best thing to do is match the sizes of your existing wheel, 700 in diametre and whatever the width of the rim is. – Criggie Apr 26 '17 at 7:30
  • Edited to remove shopping question aspect – RoboKaren Apr 26 '17 at 17:18
  • If you have the money, E-BikeKit makes several front and rear motor kits for 700C. I'm not recommending them per say, just letting you know they exist, they are not cheap however, be prepared to drop $1000 on a conversion with the battery, motor kit and controller. – Nate W May 1 '17 at 19:34
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Most ebike kits with hub motors are sized for 26" mountain bike tires and not the larger 700c road/hybrid tire. There are numerous reasons for this:

  • the smaller the wheel the more torque it can handle as well as deliver *conversely, the larger the wheel the larger the hub motor has to be (adding to weight) or it has to be a geared hub motor, adding to complexity. In either case, hub motors for larger wheels are more expensive.
  • mountain bike frames are built more solidly and can take the extra weight and abuse
  • contemporary consumers tend to prefer the mountain bike styling and as a result cheap MTB frames are much more commonly available than 700c frames
  • if you only want to stock one SKU you'll stick with the most common one. It doesn't hurt that a 26" wheel is cheaper to ship than a 700c one

As a result, it's much harder to find an off the shelf 700c rimmed hub motor compared to a 26" one. In most cases, you have to get a hand laced 700c rim on a hub motor. This adds cost and expense and is non-optimal as the motor was likely wound for a smaller wheel and will deliver weaker performance in a 700c.

Most end users give up and instead get a cheap 26" mountain bike for their donor bike rather than using their 700c bike.

And if you have to ask: no, it's not possible to put a 26" wheel in a 700c frame -- not without considerable pain and expense. Seriously, just get a 26" BSO frame or be prepared to pay more for a boutique 700c hub motor.

Ps. If you're intent on keeping the 700c frame, a better option may be to use a bottom bracket (also known as mid-drive) motor. Bafang is the most common vendor of aftermarket BB motors and if you google (bafang bottom bracket) you'll find vendors. However, they do tend to be more expensive than hub motors.

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    Spot on. On the other hand the few 700c wheel kits out there seem to be better quality - and more expensive - than a lot of the 26" budget kits that dominate the market. – Chris H Apr 26 '17 at 5:56
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    700c ehubs are by definition boutique items so yes, they tend to be higher quality. – RoboKaren Apr 26 '17 at 6:11
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    What surprises me a little is that there isn't a lot aimed at 29" MTBs now that they're popular. I guess because they're only just trickling down to the BSO level where the volumes are. – Chris H Apr 26 '17 at 6:33

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