Bicycle casette, what does shark fin mean?

Question

I took my bicycle wheel to the bike shop to get repaired. The poblem is that somthing is stripped because the cassette turns freely on the wheel in both directions. The repair man said my casette is showing sign of shark finning. What does that mean, and do I really need a new cassette right away? Also, what do you call the part that he is replacing to fix the original problem? thanks!

Answer 1

Shark finning refers to the shape of the teeth. As the teeth wear they take on the appearance of shark fins rather than a more symmetrical shape.

If your not experiencing difficulties changing gears then you could probably leave it a while longer. If it were my bike I would stick on a new cassette, a new chain and have a good look at the chain rings.

To get the most life out of components measure your chain regularly. It should measure 12 " exactly between pins over 24 half links. When it measures 12 1/16" change the chain. Hang the old chain on a nail (oiled and in a dry spot). When you get to about five chains the sprockets will be worn you can then reuse your old chains until they are 12 1/8"

After the second time through your cassette and chain wheels will be pretty well stuffed. You can keep riding until you can take it no more then change the lot.

The part that is already broken is called a freehub.