Chain and Sprocket Guide for MX, Enduro and Road Bikes

Your chain and sprockets carry all the drive to the rear wheel.

Chain sizes explained

The size code tells you two things. The first digit is the pitch, the distance between the pins, in eighths of an inch: 4 means 1/2 inch and 5 means 5/8 inch. The last two digits relate to the roller width, so a 525 has the same pitch as a 520 but is wider. Your chain and both sprockets must be the same size. It is usually stamped on the side plates of your current chain and listed in your handbook.

Many of our chains list the models they fit, but you still need the right length, so count the links on your old chain or check the handbook. We also list 5 connecting links in 428 and 520 sizes, such as the ProX 520MX clip type link and the ProX X-Ring 520MXR rivet type link.

Non sealed chains are simple and free running, while O-ring and X-ring chains seal grease between the pins and bushes inside each link, so they last longer on enduro and road bikes. Examples by size: DID 420D Heavy Duty, EK 428 DEH, DID 520 VX3 X-Ring, EK 525 ZVX3 NX-Ring and DID 530 VX3 X-Ring.

Replace the chain and sprockets together

As a chain wears it effectively gets longer, rides higher on the sprocket teeth and wears them to match. A new chain on worn sprockets will not seat properly, wears quickly and can jump teeth, so replace the chain and both sprockets together. When you fit them:

• Tighten the rear sprocket bolts and the front sprocket nut or bolt to the torque in your manual, and replace corroded fixings. Our drivechain spares include sprocket bolts and front sprocket retainers for some models.
• Fit a clip type link with the closed end of the clip facing the direction the chain travels. Rivet type links need a proper riveting tool.
• Set the slack and wheel alignment to your handbook figures, then check the slack again after the first ride.

Gearing basics

Your final drive ratio is the rear teeth divided by the front teeth. A 13 tooth front and a 50 tooth rear gives 50 ÷ 13 = 3.85.

• More teeth on the rear, or fewer on the front, gives quicker acceleration but a lower top speed, with higher revs at any given speed.
• Fewer teeth on the rear, or more on the front, gives a higher top speed and more relaxed cruising, but softer acceleration.
• One tooth at the front changes the ratio about as much as three or four at the rear: 14/50 gives 3.57, between 13/46 (3.54) and 13/47 (3.62).

MX riders often add a tooth or two at the rear for tight tracks and take them off for fast, open ones. Bigger changes may need a different chain length, very small front sprockets tend to wear chains faster, and if your speedometer takes its reading from the gearbox it will read differently after a change.

How to count teeth

• Mark one tooth with chalk or a paint pen and count round until you are back to it. You will usually need to remove the front sprocket cover to count the front.
• Many sprockets have the part number and tooth count stamped on the face. JT part numbers end in the tooth count, so JTR1304.42 is the 42 tooth JT JTR1304 rear sprocket.
• Count both sprockets before you order, as a previous owner may have changed the gearing from standard.

How to check chain and sprocket wear

Chain

• Adjusters near the end of their range mean the chain has stretched.
• Pull the chain away from the back of the rear sprocket. If it lifts far enough to show half a tooth or more, it is worn.
• Turn the wheel slowly and check the slack at several points. Tight and slack spots mean uneven wear.
• Look for stiff or kinked links, rust, and damaged or missing O-rings.

Sprockets

• Hooked teeth shaped like shark fins, or sharp pointed tips.
• Teeth worn more on one side, which points to poor wheel alignment.
• Chipped, bent or missing teeth.

The front sprocket has fewer teeth, so it usually wears faster than the rear. On MX and enduro bikes, check the swingarm slider and chain guide too, as a worn slider lets the chain cut into the swingarm.

Find the right sprockets for your bike

The quickest route is our sprocket chart:

1. Choose your make from the list at the top.
2. Find your model and check your year falls in the range shown.
3. Open the front or rear sprocket listed to see the price, stock and full fitment table.
4. Choose your tooth count. 266 of our 390 sprocket listings offer more than one.

Or use the bike finder to see the parts listed for your make, model and year, browse the bikes hub or see all our fitment charts. Product pages that list fitment also have a fit check.

Chains and sprockets in our range

Browse chains, front sprockets, rear sprockets or the whole drivechain range, and keep a new chain clean and lubricated with chain care products such as Motoverde Drivetrain Cleaner and Maxima Clear Synth Chain Guard lube.

UK Next Day delivery is £7.99, free on orders of £100 or more, and you have 30 days from delivery to return an item. Return postage is yours to pay unless the item is faulty, damaged or wrong (see our returns page). Not sure which size you need? Email sales@apexpowersports.co.uk with your bike's make, model and year.