Explaining the Cassette
A standard road cassette would be 11-25 made up of 8,9,10 or 11 rings ranging from the smallest with 11 teeth to the highest with 25 teeth. A cassette, being at the back, works with the smaller rings being for speed & the largest being for hills.
To cope with our terrain, and to improve performance on the hills, it makes sense to change the cassette to one with bigger rings such as an 11-28 or even an 11-30
Now you are able to be in easier gears on the hills.
These are made by the major manufacturers, Campagnolo, Shimano & Sram, who make theirs compatible with Campag & Shimano.
The cassette on a road bike is made up of individual rings and the whole thing sits on a freehub which provides the free wheel when you’re coasting downhill etc.
The manufacturers are now making bigger & bigger cassette rings. Hope have just released a 40 tooth ring which sits behind your existing cassette & replaces one of your middle rings. This is potentially a great idea because it would mean that you do not have to change your existing crank set for a triple or compact. Gives you climbing ability without costing a fortune.
If you have the tool to unlock your cassette lock ring then it makes changing & cleaning really easy as you can remove it in only a few minutes.
This video shows you how: http://youtu.be/bYejbxf2epM