If you've been riding hard lately, you've probably realized that your 20 bmx bike rear wheel takes way more of a beating than almost any other part of your setup. It's the component that handles the impact when you case a jump, the sideways stress when you're learning 360s, and the constant friction from your brakes if you run them. Eventually, every rider reaches a point where "just truing it" isn't enough anymore, and you need to look into a replacement or a serious upgrade.
Choosing a new wheel isn't just about picking something that looks shiny. It's about understanding how you ride and what kind of abuse you're going to put that wheel through. BMX wheels are surprisingly technical for how simple they look, and the rear one is especially complex because it houses the drivetrain mechanism.
The Battle Between Cassette and Freecoaster
When you start looking for a new 20 bmx bike rear wheel, the first big decision you have to make is whether you want a cassette hub or a freecoaster. This choice will completely change how your bike feels when you're riding fakie (backwards).
Most complete bikes come with a cassette hub. It's that classic BMX sound—the loud clicking or buzzing when you're coasting. People love cassettes because they offer instant engagement. As soon as you step on the pedals, the bike moves. They're usually lighter, easier to maintain, and very reliable. If you like doing pedal-pressure tricks or you just love that "click-click-click" sound, a cassette is probably your best bet.
On the flip side, freecoasters have become incredibly popular over the last decade. A freecoaster allows you to roll backward without having to pedal backward. This opens up a whole new world of lines and tricks because you don't have to worry about your pedal timing when you're coming out of a 180. The downside? They usually have "slack," which is a little bit of a delay when you start pedaling forward. They're also heavier and require a bit more mechanical knowledge to keep them running smoothly.
Why Double-Wall Rims are a Must
If you're doing anything more than just cruising around the neighborhood, you really shouldn't settle for a single-wall rim on your 20 bmx bike rear wheel. Single-wall rims are essentially just one layer of aluminum. They're cheap and light, but they fold like a taco the second you land a bit sideways.
Double-wall rims, as the name suggests, have an internal bridge that creates a second layer of support. This makes the rim much more rigid and resistant to flat spots. When you're looking at specs, always check for this. A good double-wall rim can be the difference between a wheel that lasts three months and one that lasts three years.
You'll also see different rim widths. Some riders prefer a wider rim because it gives the tire a larger contact patch and better sidewall support, which is great for street riding where you're jumping off high ledges. Others prefer something a bit narrower to save a few grams of weight. Honestly, for most of us, a standard wide double-wall rim is the way to go.
Understanding Axle Sizes and Hub Spacing
The standard for any modern 20 bmx bike rear wheel is a 14mm axle. Back in the day, some bikes used 3/8" (10mm) axles in the back, but those almost always bent under the pressure of street or park riding. If you're buying a new wheel today, it's almost certainly going to be a 14mm.
You also have to choose between a male and a female axle. A male axle is the traditional style where the threaded rod sticks out past the dropouts, and you tighten it down with a nut. These are super robust and easy to work with. A female axle uses bolts that thread into a hollow internal axle. These look a lot cleaner and are less likely to snag on your shins or a ledge during a grind, but they can be a bit trickier if you manage to snap a bolt inside the hub.
Spacing is pretty much standardized at 110mm for BMX frames. Unless you're working on a very old vintage bike or a specific racing frame, any standard 20-inch rear wheel should drop right into your frame without any issues.
Spokes and Lacing Patterns
It's easy to ignore the spokes, but they're the glue holding your 20 bmx bike rear wheel together. Most BMX wheels use 36 spokes. You might occasionally see 48-spoke wheels, which were the "gold standard" for heavy-duty street riding in the early 2000s, but modern rim technology has made 36 spokes plenty strong for almost everyone.
The "lacing pattern" refers to how the spokes cross each other. The most common is the 3-cross pattern, where each spoke crosses three others between the hub and the rim. This provides a great balance of strength and weight.
Also, keep an eye on the material. Stainless steel spokes are the way to go because they don't rust and they have just enough flex to handle impacts without snapping. If you're building a custom wheel, don't cheap out here—getting high-quality brass nipples (the little nuts that hold the spokes to the rim) is also a smart move because they won't corrode and "seize" onto the spoke over time.
Keeping Your Wheel Straight and True
Once you get your new 20 bmx bike rear wheel bolted on, your job isn't quite done. New wheels usually have a "settling in" period. After a few solid sessions, the spokes might stretch a tiny bit or find their seat in the hub flange. This can lead to the wheel going slightly out of true.
It's a good idea to learn the basics of using a spoke wrench. You don't need a professional truing stand to keep things running reasonably straight. Just flip your bike upside down, use your brake pads (or a zip tie around the frame) as a guide, and slowly tighten the spokes on the opposite side of where the wobble is.
If you let a wheel stay wobbly for too long, the tension becomes uneven. Some spokes get way too tight while others get loose, and that's when you start snapping spokes or permanently bending the rim. A little bit of maintenance every few weeks goes a long way in making that investment last.
Final Thoughts on Choosing Your Wheel
At the end of the day, your 20 bmx bike rear wheel is the heart of your bike's performance. If you're a beginner, a solid, mid-range cassette wheel with a double-wall rim is probably the best bang for your buck. It'll be reliable, easy to fix, and won't break the bank.
If you're more advanced and you've found yourself doing a lot of technical lines that involve rolling backward, maybe it's time to give a freecoaster a shot. Just be prepared for a bit of a learning curve when it comes to that pedal slack.
Whatever you choose, just make sure you keep your chain tensioned properly and your axle nuts tight. There's nothing worse than having your wheel slip in the dropouts right as you're about to hop. Take care of your gear, and it'll take care of you out there on the streets or at the park. Happy riding!