Freewheels

BMX freewheel: the mechanism that lets you coast

A freewheel is a self-contained unit: teeth, body and pawl system all in one part that threads onto the hub. It is the historic BMX solution, still widespread on training builds and complete bikes, and it swaps out in a few minutes with the right removal tool.

Freewheel or cassette driver: do not confuse the two

On a freewheel, the drive mechanism sits inside the part you screw on; the hub itself is just a threaded drum. On a cassette-driver hub, the mechanism is built into the hub and you only fit a splined sprocket, which means it is a BMX sprocket you need to order, not a freewheel. Look at your hub before buying: visible outer thread and a thick block that turns as one piece means a freewheel; a thin sprocket held by a lockring means a cassette driver.

Threads and tooth counts available

• 30x1 mm: the thread used by small-tooth freewheels, the 15 to 18 tooth sizes raced today.
• 1"3/8 x 24 TPI: the classic ISO thread, kept for higher tooth counts and older builds.
• Tooth counts: 15, 16, 17 and 18 tooth cover the vast majority of BMX race gearing.
• Chain width: teeth machined for 1/8 inch or 3/32 inch, depending on the chain fitted.

Choosing your tooth count: gearing

Gearing is read as chainring divided by sprocket. Dropping a tooth at the rear makes the gear harder and favours top speed on long straights; adding a tooth makes it easier to spin up and suits steep gates and lighter riders. Always work in single-tooth steps, and write down the ratio you tested after every session, because it is the most rewarding adjustment on the whole drivetrain. Then match the tooth count of your BMX chainring to keep the ratio consistent.

Compatibility: hub, chain and tension

Check three things before ordering. The hub thread first, which must match the freewheel exactly. Chain width next: a 1/8 inch chain on 3/32 teeth floats sideways and derails on the gate, and the reverse simply will not fit. Alignment last: the teeth must sit in the plane of the chainring, otherwise the chain runs at an angle. Changing tooth count also changes the working length of your BMX chain, so keep a half link in reserve and re-check tension after fitting.

Pawls, engagement points and noise

The number of engagement points sets the dead angle before drive picks up. A freewheel with few pawls lets the pedal turn a little before it bites, which you feel when you power out of a turn. Close-engagement models cut that dead angle down. Freewheel noise is not a quality indicator, only a consequence of pawl design and the grease used.

The brands available

Shimano remains the historic reference on the screw-on freewheel, with proven reliability in training. Box Components and Tangent offer small race tooth counts. Insight rounds out the range on complete bikes and in the younger classes. On cassette-driver hubs such as Onyx or Excess, you should be looking at a dedicated sprocket instead.

Servicing and replacement

Replace a freewheel when the teeth take on a hooked shape, when the mechanism slips under load, or when a pawl fails to re-engage after a muddy session. Never remove one without the tool that matches the spline pattern: a screw-on freewheel tightens itself as you pedal and becomes very hard to crack loose. Lightly grease the hub thread on fitting.

The BMX RACING advice

Send us your hub reference if you are unsure between a freewheel and a sprocket: we will identify the drive type and the tooth count that suits your gearing. You can also browse our BMX cranksets to complete the drivetrain. Dispatched within 24 to 72 hours and you can spread the cost over 2 or 3 payments with Alma.

Which tooth count for which track? Our BMX race gearing guide compares the common ratios, ground measurement included.