The majority of people that have come to contact with either part have mistaken them to be the same thing, and no they are not the same thing. Despite their similar look, they operate differently from one another, but they are both intended to do the same job. I know this sounds a bit confusing too but today everything is going to get clear for you. We are going to explain both the freewheel and cassette and what makes them operate differently but look almost the same.
The freewheel (also known as a threaded hub) is a traditional system that was very popular throughout the 80s – every bike that was made that decade had it. What sets a freewheel cycle apart from the cassette is that it comes slightly recessed into the axle and bolted together with the sprocket. The tool fitting doesn’t spin together with the whole system here, instead, it stays locked in place. The axle may show the splines with some freewheel cycles, but this is mostly the case with cassettes, the splines are also recessed even deeper in the body and usually sit around the axle.
There’s no distinctive bulge present on a freewheel cycle and their ratchet mechanism is outside the hub body. They also don’t have the option for you to only change the sprockets, and you are not even able to swap them, because of the way they are built. Their design is made to fit the large external thread which can be found on older bikes. Their ratcheting mechanism comes out together with the cogs when you unthread the freewheel – this is how it usually gets removed from the bike. If you have an older bike a freewheel is going to be the right tool for the job, or rather, part.
Also known as the freehub, has certainly replaced the freewheel as the standard in newer bikes, because of the newer style system hub that they use. Their system has a type of clutch mounted to the body of the hub and the cylindrical mechanism ratchets counter clock-wise for coasting but locks clock-wise when you want to drive the bike pedalled. This freehub type of body also has a whole series of splines on the outer shell and the “cassette” sprockets also slide over these splines.
Unlike the threaded hub system that the freewheel uses, the cassette has the rockling splines turn together with the sprockets when spun backwards. The location of the coasting mechanism presents a major difference between the two, as it allows you to only replace the sprockets and not the whole mechanism. This is the case because the ratchet mechanism is located in the hub body. With cassettes, there’s a lockring threaded in the freehub to hold the cogs and sprockets in place.