Sprocket Guard

A sprocket guard is a ring or plate that covers the teeth of a BMX sprocket. It lets the sprocket slide over a ledge or rail during a grind without the teeth biting in or the chain catching. The guard can be built into the sprocket, which is called a guard sprocket, or bolted on as a separate part.

What it does

On most BMX bikes the sprocket and chain sit on the right side. During grinds on that side, such as double peg grinds, feebles and smiths, the sprocket sits close to the edge of the ledge. If the teeth touch the edge, they can catch and stop the bike dead, throw the chain, or chew up the teeth and the ledge.

A guard sits just outside the tips of the teeth. It gives a smooth, round surface that slides instead of biting. It also helps protect the chain from being knocked off when the sprocket clips a rail or coping.

Grind side and drive side

Riders who grind on the side away from the chain have less need for a guard. Some street riders set up their bikes left-hand drive, with the chain and sprocket on the left, so the drive side and the grind side are different. Others grind on both sides and fit a guard so either side works.

Types and standards

Type	Description	Pros	Cons
Guard sprocket	The sprocket has a solid outer ring or a raised plate around the teeth, made in one piece or permanently joined	Neat, strong, one part	Heavier than a plain sprocket. Replace the whole thing if the guard wears out.
Bolt-on guard	A separate plastic or alloy guard that bolts to the sprocket, often sold with it as a replaceable part	Cheap, replaceable, can be added later	Must match the sprocket. Extra bolts to check.

Some complete bikes for children use a plastic disc or a chain cover. That keeps clothes and fingers away from the chain, but it is not built for grinding.

Plain sprockets and partial guards

Some sprockets have a small raised edge or flat spots rather than a full ring. These give a little protection and save weight, but they will not slide as smoothly as a full guard.

Sizing and compatibility

1. Tooth count. A guard has to sit just outside the tips of the teeth, so it is made for a particular tooth count. Guard sprockets such as the Odyssey Utility Pro Guard, Shadow Sabotage Guard and BSD Guard are usually offered in 25 and 28 tooth sizes.
2. Mounting. Bolt-on guards need to line up with the sprocket's holes or bolt pattern. Check the maker's list of compatible sprockets.
3. Spindle size. Guard sprockets fit 19 mm, 22 mm or 24 mm spindles, like plain sprockets. Many come with adaptor rings or washers to suit more than one size. See cranks.
4. Chainline. Check that the chain still lines up with the rear driver after fitting a new sprocket or guard.
5. Frame clearance. The larger outer diameter must clear the chainstay.
6. Pegs. If you run pegs on the drive side, the guard and the peg work together. The peg takes the weight and the guard stops the sprocket catching.

Materials

Material	Notes
Aluminium alloy	The most common for guard sprockets. Light and strong. Wears down on rough ledges.
Steel	Very tough. Heavier. Some guards use a steel ring on an alloy sprocket.
Plastic (nylon)	Common for bolt-on guards. Slides well and is cheap to replace. Wears faster.

A guard sprocket weighs more than a plain one of the same size. A plastic bolt-on guard adds the least weight.

How to choose

1. Check which side you grind on. If it is not the drive side, you may not need a guard.
2. If you grind on the drive side often, pick a guard sprocket for a clean, strong setup.
3. If you want to keep your current sprocket, look for a bolt-on guard made to fit it.
4. Choose plastic for low cost and good slide. Choose alloy or steel for longer life.
5. Match the tooth count to the gearing you want. See sprocket for gear ratios.
6. Think about the rear of the bike too. Hub guards protect the driver side of the rear hub in the same way.

Maintenance

• Check the guard bolts regularly and use a little thread locker if they work loose.
• Replace a guard before it wears through to the teeth.
• Look for bends after a hard grind. A bent sprocket or guard can rub the chain or the frame.
• Check chain tension and alignment after any hard hit to the sprocket.
• Clean grit and wax off the guard, since it can work into the chain.
• See BMX maintenance basics.

Related parts

Sprocket, cranks, chain, hub guards and pegs.