Whether you are converting a standard bicycle into an electric bicycle or buying a ready-to-ride commercial ebike, one of the many choices you’ll have to make is the wheel size on your ebike. While it might seem trivial compared to other issues like battery voltage and motor power ratings, your electric bicycle’s wheel size will have a big impact on how it rides and handles.
Bicycle wheels come in many different sizes. The standards range from tiny 12 inch diameter wheels up to massive 29 inch diameter wheels. When it comes to an electric bicycle though, you’ll likely have one of three options: 16, 20 or 26 inch. A few tiny folding ebikes come with 12 inch wheels, but those are so rare that we won’t cover them here. If you’re curious though, just take all the disadvantages of 16 inch wheels listed below and amplify them.
Now back to the regular wheels sizes. Like nearly every important decision you’ve ever made or ever will make, each wheel size has its own advantages and disadvantages.
Breakdown of electric bicycle wheel sizes
First let’s look at when you might encounter these wheel sizes. A 16 inch wheel will almost definitely be found on a folding bicycle (unless you’re trying to electrify your little niece’s 16 inch “Dora the Explorer” bike). Folding bicycles use smaller wheels to reduce weight and keep the folded size as compact as possible.
Similarly, 20 inch wheels will also likely be found on a folding bike, and are much more common than 16 inch wheels. There are also many non-folding bikes with 20 inch wheels, such as BMX and children’s bicycles, but the one’s you’ll likely be looking at for an electric conversion or retail ebike will most likely be folding bicycles. If you don’t want a folding bicycle, you can pretty much rule out 16 and 20 inch wheels right now.
On the other end of the wheel spectrum, 26 inch wheels are the most common wheel size and can be found on everything from mountain bikes to road bikes to beach cruisers. There are even a few folding 26 inch wheel bicycles out there, if that’s your thing. (If you plan on paratrooping into a war zone but want to bring a full size electric bicycle with you, consider starting with this bike for your next ebike conversion.)
Effects of wheel size on ride quality
Now let’s look at what these different size wheels mean for your ride. One of the main advantages of larger wheels is their ability to roll over obstacles easier. This is due to something called the “angle of attack” of the wheel. Imagine a 1 inch thick stick in the road. It would be difficult for a 2 inch skateboard wheel to climb over this obstacle. On the other hand, a 26 inch bicycle wheel can climb it easily, because the angle of attack compared to the axle is much lower for the bicycle wheel. This becomes important for many different types of riding, including taking your ebike off-road where you’ll encounter rocks and roots or riding in cities where you’re dealing with curbs and pot holes. The larger your wheels the easier and more comfortably you’ll roll over obstacles and imperfections in your path.
Potholes are another good way to demonstrate this principle. Imagine a pothole that is 8 inches wide. A 16 inch bicycle wheel will fall fairly deep into that hole, which would be quite jarring for the bike and rider. A 26 inch wheel will pass over the hole with much less tire dropping down inside, resulting in a much smoother ride.
Another advantage of larger wheels is their ability to better store inertia. Once you get up to speed on a 26 inch bicycle, letting go of the throttle will result in a longer period of coasting than on a 20 inch bicycle, assuming everything else is equal (motor, battery, etc). It also takes less energy to maintain constant speed on larger wheels because they store their inertia better.
Big wheels also come with their own disadvantages though. They require the bicycle to have a longer wheel base, resulting in reduced maneuverability. Whether you’re wiggling down a trail or zig-zagging between pedestrians on the sidewalk, small wheels and a shorter wheelbase will give you increased maneuverability, especially at lower speeds. Conversely, larger wheels and a longer wheelbase are more stable at higher speeds.
Big wheels are also slower to accelerate. You’ve got a lot of mass sitting further away from the center of the wheel, meaning the moment of inertia of the wheel is greater. This results in slower and less efficient acceleration than smaller wheels. Bigger wheels also transfer less torque to the ground for the same motor compared to a smaller wheel.
What it all comes down to is a comparison of the advantages and disadvantages of each wheel size and determining how that stacks up against your own needs. If maneuverability and a small package is key for you, a folding bike with 16 or 20 inch wheels will do the trick. If ride comfort and efficiency at speed is more important to you then you’ll definitely want to stick to larger wheels. At the end of the day, the best ebike wheels are the ones you have.
photo credit 1