Bike Parts and Repair Tools: Tubes, Drivetrain, Fit

Wheel size, tube width and valve length: three numbers to match

A tube or tire must match the wheel diameter and the width range printed on the sidewall, such as a 20 in tube for 1.75 to 2.125 in tires. The valve type, Schrader or Presta, has to match the rim hole, and its length must clear the rim depth, which is why deep rims need longer stems than a 32 mm one. Read the sidewall markings on your tire before you search.

Tubes list a width range rather than one width, so any tire inside that span works. Tires also show an ISO number such as 559 or 622 mm, the true rim match behind names like 26 in or 700c. Brake pads, cables and levers also depend on brake type, since rim, disc and coaster brakes do not share parts.

Freewheel or cassette, pegs and fasteners: parts that only fit one way

A freewheel screws onto the hub threads and carries its own ratchet, while a cassette slides onto a freehub body and is held by a lockring. They are not interchangeable, and the number of sprockets must match the chain and shifter. Replacement cogs, chains and derailleurs should be matched by speed count. Footpegs and similar parts also vary in axle size, so measure the axle thread or check the stated fit.

Anti-seize paste or sticks stop aluminum and steel parts from seizing on threads and seatposts, but carbon parts need a carbon assembly paste instead. Primers prepare surfaces for threadlocker or adhesive, and neither should reach brake pads or rotors, because they contaminate the braking surface. Use sparingly and wipe off any excess.

Questions about Bike Parts and Repair Tools: Tubes, Drivetrain, Fit

How do I pick the right inner tube?

Match three things: the wheel diameter printed on the tire, a width range that includes the tire's width, and the valve type and length. A 20 in tube marked 1.75 to 2.125 in suits a tire of that size, and a deeper rim needs a longer valve stem.

What is the difference between a freewheel and a cassette?

A freewheel is a single unit with the ratchet inside, threaded onto the hub. A cassette is a set of sprockets that slide onto a freehub body containing the ratchet. You cannot swap one for the other without changing the hub, and the speed count must match your chain and shifter.

Can I use anti-seize on every bike part?

No. It suits metal threads and seatposts, but carbon fiber needs a special carbon assembly paste, and none of these products belong on brake surfaces. Use a thin layer, and follow the instructions on the pack for the metals involved.