You’ve got two options: a front hub motor or a rear hub motor. (There are actually a few electric bicycles with hub motors mounted as mid-drive motors, but that’s outside the scope of this article.) If you search around, you’ll probably find that the same hub motors are offered in both front and rear hub motor kits, so “what’s the difference?”
Of course you determinate to what you need exactly when deciding between a front or rear hub motor. Let’s start with weight.
Generally, you don’t want to have all the weight located in one area so you want to try to spread the weight of your electric bicycle out as much as possible, front to back. It’s important for weight balance. Most batteries are mounted in the middle or rear of an ebike. It’s meaning that a front hub motor helps spread the weight forward and can improve weight distribution of your electric bike.
Bikes with heavy rear hub motors and batteries also mounted far to the rear, such as on a rear rack, are inclined to “popping” wheels during acceleration. This is especially happen if the motor has fairly high torque and/or the wheels are smaller diameter.
While it may sound fun, this wheelie behavior can become rather annoying when it happens every time you accelerate after a red light or stop sign. It can also be dangerous if it happens when you aren’t expecting it, such as on a slight uphill. Letting someone test ride your ebike and having them flip it over on the first try isn’t good either.
Another point is that traction is affected by hub motor placement. While moving a hub motor forwards to the front wheel solves the problem of weight distribution but it can reason to different problem: traction control. Because there is already very little weight on the front wheel of the e-bike compared to the rear and a front hub motor has less traction.
Hub motors and flat tires. You are more likely to pick up road wreck ensue in a drilling to your rear tire than your front tire. Because your front tire often kicks up objects laying on the road, such as glass shards, puncher etc that were initially laying flat. Once they bounce up from the impact of your front tire though, again you’ll be unlucky enough to have it land perfectly aligned to spear your rear tire as it gets passed over for the second time.
Rear hub motors still have their advantages
Many people like their electric bicycle to look like a standard bicycle of their “assistance”, so to speak. Many small hub motors nearly disappear behind the gears of a rear wheel, and are often covered by the disc as well. This gives the bike an extra hiddenly look and hides the dead giveaway of a naked front hub motor.
Powerful hub motors are also more suitable for a rear assembly because the higher power can be better handled by stronger dropouts in the rear of the bike.