Cassette vs Freewheel vs Freehub: How to Tell Them Apart

People mix up three different parts of the rear hub. A freewheel is a gear cluster that screws onto the hub and contains the ratchet that lets you coast. A cassette is just the stack of cogs. A freehub is the splined body on the hub that the cassette slides onto. The ratchet lives in the freehub, not in the cassette.

If your bike was built in the last 25 years and it is not a cheap single-speed, you almost certainly have a cassette on a freehub. If it is a 1980s ten-speed, a department-store bike, or many single-speeds, you probably have a threaded freewheel. The two are not interchangeable. You cannot thread a freewheel onto a freehub, and you cannot slide a cassette onto a freewheel hub.

How to tell which one you have

They look the same from the saddle. Take the rear wheel out. Find the tool fitting in the center of the cogs, next to the axle.

1. Spin the cogs backward with your fingers.
2. If the tool fitting spins with the cogs, it is a cassette. The lockring is turning because it is part of the stack.
3. If the tool fitting stays still while the cogs spin, it is a freewheel. The ratchet is inside the freewheel body, and the tool splines do not rotate with the gears.

A cassette also usually has a small lockring with splines, and the cogs may be marked as separate pieces. A freewheel looks like one chunk threaded onto the hub.

What is actually different

	Freewheel (threaded)	Cassette + freehub
How it mounts	Screws onto hub threads	Cogs slide onto freehub splines, lockring holds them
Where the ratchet is	Inside the freewheel	Inside the freehub body
Typical speeds	5–7, sometimes 8–10 on oddball units	8–12 on most modern bikes
Axle strength	Bearings sit closer together. Older, narrower hubs were OK. Wide freewheel hubs can bend axles	Bearings can sit farther apart. Stronger for 130/135mm hubs
Replacing cogs	Replace the whole freewheel	You can often swap individual cogs, or just the cassette
Stuck forever?	Yes. Pedaling tightens it. A seized freewheel is a rite of passage	Lockring comes off with a tool and a chain whip
Parts in a small town	7-speed freewheels still show up in shops that have never heard of 12-speed	Easy in any modern shop. Harder in places that still sell 6-speed

Freewheel

Before the 1980s, this was the system. The cluster threads onto the hub. Pedaling tightens it, which is clever until you need to take it off. Then you need the correct freewheel remover (often 12-spline 22.6mm for Shimano-style units) and a long wrench. Sometimes a cheater bar. Sometimes heat and bad language.

The upside is compatibility. Threaded freewheels are standardized. A 7-speed SunRace will usually screw onto a 7-speed Shimano hub. That is useful on a vintage tourer or a bike you might have to service far from a boutique shop. Freewheels are also cheap. A basic 7-speed is still around $20–25.

The downside is everything else. Fewer gears, bigger jumps, weaker axles on wide hubs, and you replace the whole unit when the cogs or the ratchet wear out. High-count freewheels (9- and 10-speed) exist for some e-bike hubs. Most of them are junk compared to a real cassette.

Cassette and freehub

This is the modern system. The freehub body bolts to the hub and contains the pawls. The cassette slides onto splines. A lockring keeps it there. To remove it you need a cassette lockring tool (often Park FR-5 style, 12-spline 23.4mm) and a chain whip so the cogs do not spin while you crack the lockring loose.

You get more speeds, tighter steps on road cassettes, giant climbing cogs on mountain cassettes, and a hub design that does not try to snap the axle. You can replace a worn cassette and keep the freehub, or service the freehub and keep the cassette. Drive-side spokes are also less of a nightmare because you are not fighting a seized freewheel to reach the flange.

Compatibility is the tax you pay. Shimano HG splines are the common language. Campagnolo is not HG. Some SRAM cassettes want a different freehub body (XD, XDR, or a longer HG body). Check before you click buy. Hyperglide 8/9/10 often mix on the same body with spacers. 11- and 12-speed are pickier.

Should you convert?

Usually no. Moving from a freewheel hub to a cassette means a new hub or a new wheel, often a new chain, and sometimes a new shifter and derailleur if you are jumping from 6-speed to 11-speed. On a beater or a vintage bike that works, put a new freewheel on it and ride. On a bike you are rebuilding into a tourer, a modern freehub wheel is worth it for axle strength and parts, as long as the frame’s dropout spacing matches. Many old road frames are 126mm. Many modern hubs are 130 or 135. Steel frames can often be cold-set. Aluminum cannot.

If you tour in places where 11-speed cassettes are a special-order item, a 7- or 8-speed setup is not nostalgia. It is spares you can actually buy. I would rather have a slightly clunky drivetrain that I can fix than a 12-speed cassette with no replacement in the only shop in town.

Tools

• Freewheel: matching remover + a big adjustable wrench.
• Cassette: lockring tool + chain whip + wrench. Grease the lockring threads when you put it back on.
• Replace the chain when you replace the cogs if the chain is stretched. A worn chain on a new cassette will chew the new cogs.

If you do not work on your own bike, none of this matters much. A shop will have the tools. What matters is knowing which system you have before you order parts online. Measure, or use the spin test, then buy the matching cluster. Mixing them up is the most expensive way to learn the difference.

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