I think these are both just types of cassettes, one all the rings come apart, and the other it's just one big piece all welded together.

Can someone please tell me what the difference is?

The hub is the body at the center of the wheel containing the axle. It is more or less just some bearings in a pair of cups that rotate around the axle.

The freewheel is the mechanism that locks when pedaling forward (forcing the wheel to be driven by the chain) and spins freely when coasting or pedaling backward.

Both wheels have hubs, but only the rear wheel has a freewheel.

These are two variations on freewheel design, taken from the Wikipedia article linked above:

older freewheel newer freewheel

On most modern bikes with multiple gears, the freewheel is built into the rear hub and the whole assembly is called a freehub. The cassette is just a set of gears bolted together, without any moving parts, that slides onto the hub and is held in place with a lockring.

On older bikes, the hub was just a hub with some threads on one side. The freewheel was built into the rear gear cluster and that whole assembly screwed onto the hub.

freehub and cassette vs. freewheel

Single speed bikes are still (typically, though variations exist) built like older bikes, with the freewheel and the gear being one piece and screwing onto the hub.

If you want to read more, the Freehub article that I linked to on Wikipedia has a section comparing freewheels and freehubs.

The ever helpful Sheldon Brown also has a very detailed article (which the above photo was taken from) outlining the difference between freehubs and freewheels.

  • Typicaly, modern bikes which have freewheels are either single speed / fixies or low quality bikes (e.g. bso's). The main issue with a freewheel is that its hard to build one with more than 7 speeds and keep the rear axle strong. – Batman Apr 30 '14 at 14:44
  • @Batman Most of today's BSO's that I've taken more than a passing glance at are "24 speeds" with a cassette and a freehub. Admittedly, I don't pay too much attention to the bikes at the big box stores. – jimchristie Apr 30 '14 at 23:28
  • Might be where you are or which level of BSO you see. Most of the time at Walmart, I see 18 or 21 speeds (3x6 or 7). I suspect in richer parts of the US, you'd likely see better BSO's though... – Batman May 1 '14 at 1:20
  • @Batman Or it could just be that I seriously don't pay very much attention to them. Generally, the only things I get from that part of the store are water bottle cages. – jimchristie May 2 '14 at 17:41

Perhaps you are not asking the question that you think you are. See here for the difference between a cassette and a freewheel. A hub is the center point of the wheel that the freewheel or cassette attaches to. And sorry if I misinterpreted your question.

  • It should be noted that there are hubs on both the front and rear wheels. But the OP has likely been confused by the term "freehub", which is the ratchet mechanism that is used to attach a cassette to a hub, in the newer (non-freewheel) style rear hubs. – Daniel R Hicks Apr 30 '14 at 15:39

One point not mentioned is the location of the bearings in the hubs. The more advanced free hub design has the sprocket side bearing much closer to the frame's dropout than the freewheel type.

What this means is, with more distance between the bearing and frame dropout, the axle on a freewheel hub is more likely to bend than the more advanced free hub type.

  • +1 It’s a very important point – Swifty Aug 17 at 17:16

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