Chainrings
Browse used BMX chainrings for sale from riders across the UK. On a BMX the front chainring is the sprocket, and it works as a pair with the rear driver — 25 teeth to a 9-tooth driver is the common setup on 20in bikes, with 28/9 giving a slightly taller gear for trails and racing. This category covers plain and guard sprockets for 19mm, 22mm and 24mm spindles.
What size BMX sprocket should I run?
Pick the pair, not the sprocket. A 25-tooth sprocket on a 9-tooth driver is the default on modern 20in bikes, 28/9 pulls a taller gear that suits trails and gates, and smaller combinations tuck the chain closer to the frame and clear ledges more easily. The sprocket also decides how exposed the teeth are on a grind, which is why guard sprockets that shroud the teeth behind a solid disc — the Odyssey La Guardia being the long-running example — are common on street bikes.
Does a smaller sprocket make the bike faster?
No, the ratio between sprocket and driver sets the gear, so a 25/9 and an old 44/16 pull almost identically. What the small pair buys is ground clearance, less weight swinging off the cranks and a shorter chain, which is why sprocket sizes dropped from the mid-forties to the mid-twenties over the years while the gearing stayed roughly where it was.
Which sprocket fits my cranks?
The bore has to match the spindle, so check whether your cranks run a 19mm, 22mm or 24mm spindle and whether the drive is splined or bolt-on. A sprocket bought for the wrong spindle simply will not fit and shimming one is not worth attempting. If you are replacing the drivetrain wholesale, buying several BMX components from the same rider saves working the compatibility out twice.
What wears out on a used sprocket?
Teeth first. A worn sprocket has teeth hooked over into a shark-fin profile and will skip under load as soon as you fit a new chain. Bent or chipped teeth come from ledges and rails, and a single bent tooth is enough to make the chain jump every revolution. After that, check the bore and splines for rounding or slop, and look at the mounting face, because a sprocket that has been ridden loose gets its seat chewed and never runs quite true again.
Is a used sprocket a good buy?
It is one of the better used parts: a 7075 alloy sprocket run with a well-kept chain outlasts several chains, and the damage that matters is all visible in a photo. Ask for a straight-on shot of the teeth and a close shot of the bore, then buy new if you want a specific ratio or a guard sprocket in a size nobody is selling. Sprockets often turn up when someone strips a bike, listed next to the bars and stem from the same build, and a bundle is usually the cheaper route.