Pedal Assist: Not What I Thought It Was

It’s been a few years since I started wanting an e-bike, but for a long time I was put off by physics. We live at the top of a steep hill, and I’m fat and out of shape. So all those sprightly 250-watt bikes and front-wheel kits simply weren’t going to cut it.

This spring, I saw someone in the neighborhood on a Radpower utility bike (750 watts) and asked them if it could go up our hill. They said it could. And what the heck, 14-day free return policy.

So I ordered, waited a few months for delivery (while enduring a constant stream of email trying to get me to buy one of their other bikes) and ended up with this:

RadRunner Plus

750 watts, 5 levels of pedal assist plus throttle, 300 pounds of payload, front and rear hydraulic brakes.

The throttle part is easy: you turn it and the bike goes. I’ve started using it to get going, because 70 pounds of bike is hard to start moving, especially when the pedal assist doesn’t kick in for those crucial first few seconds.

Pedal assist isn’t what I thought it would be — which may be a good thing. I have a frightening annual bill from Adafruit, so of course I’d imagined some complicated system with strain gauges and accelerometers (and probably a 3-axis gyroscope for good measure) that would sense just how fast and how hard I was pedaling, and then dole out a precisely calibrated extra kick to deliver just the right enhanced riding experience.

Nuh-uh. That would be the automatic transmission version. What this bike has, as far as I can tell, is much simpler: When the pedals are moving (well, a couple seconds after they start until a couple seconds after they stop) the motor is on. It delivers whatever level of assist you’ve chosen with the arrow buttons on the handlebar, from about 35 watts at level 1 to about 740 watts at level 5. The engineering for that is much less baroque.

(The simple engineering also means that the amount of assist will depend on your battery level — expect about 100 watts less of assist at the top end when your battery is just about done. Oh, and the battery-level meter will report based on how much assist you’re using: level 1 typically shows a bar or two more than level 5.)

I’m getting used to it. The lowest level is like regular bicycling, only as if I were young and in shape.

The higher levels are sort of like a pushbutton alternative to regular gears, at least around where I live. On a conventional bike, for this rider, going up a slope means downshifting until the bike is moving at a fast walking pace while I pedal madly until I reach the top or run out of breath and have to walk the bike up. On the Radrunner, going up a slope means kicking the pedal assist up a notch, maybe two. If it’s a serious slope, I can downshift a gear or two and slow down while the electric motor continues to do its thing. I still have to work, but it’s not a losing battle. The top level of assist even gets me up the hill by our house — the one that neighbors without 4WD sometimes park at the bottom of in the winter

The pedaling part of pedal assist is still a bit new for me — if I’m zipping along on the flat and the bike seems to be freewheeling, it feels natural to stop pedaling, as you would on a conventional bike. But when I do, two seconds later the electrics kick out, and the whole thing sags down the behemoth it is. So I have to learn to keep my legs lazily moving.

And although I’d expected electrical assistance to make the physical job of riding a bike easier, the psychological effect may turn out almost as important. I can ride anywhere in my small town (or maybe even to the next village over) without worrying about whether I’ll have enough endurance to ride back. I can also ride on roads without worrying about being mowed down by even the slowest-moving cars. Now, if I can just figure out how to keep riding during the winter…

A few other things I’ve learned:

  1. It’s also loud. Not so loud that people can hear you coming, but between the motor and the fat tires loud enough that the conventional cycling experience of being able to hear nothing but the wind in your hair is gone.
  2. Unless you work at going slowly, you will go faster than you would on an unassisted bike. No real surprise there, but old intuitions about overtaking pedestrians and other bikes have to be adjusted. (Oh, and kudos for the built-in bell).
  3. This bike doesn’t really like to turn sharply. Which mostly isn’t a problem.
  4. There’s a lot of space between the frame and the interior of the front wheel (and rear wheel too. You will need a bigger bike lock.
  5. Say goodbye to range anxiety. No, the battery has a limited capacity, but unless you’re way fitter than I am, that capacity is likely greater than yours. I always had to gauge rides on a conventional bike by whether I would be able to ride back after riding out, but pedal assist and throttle. (20km and 135 meters of climb are less than 40% of battery — a real cyclist on a serious ride would laugh at that, but a real cyclist on a serious ride is not who the Radpower utility models are aimed at.)
  6. Check your tire pressure. Those armored exteriors are stiff, and will defeat your conventional-tire intuition about squeezing a tire to see if it needs air. The difference in rolling resistance between underinflated and properly is about one gear or one level of pedal assist.

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