New cassette - with shark fins.

[Steelo]

Been riding my Dahon Speed D7 for about 3000 miles through 2.5 winters (not my main bike, but i do like it a lot!) Thought i'd get a new chain and cassette (I measured the old chain and it seemed to have stretched to the point where this was recommended).

Not many places seem to stock the 11-30T 7 speed suntour cassette, so I ordered one (and a chain) from the official parts distributor.

When it was delivered today, it was not really what i was expecting. The teeth are not really very uniform at all, with lots of uneven teeth and "shark fins". I attach a couple of photos (one of the main body and one of the two extra sprockets) - sorry about the quality.

Is this usual? Should i send it back? Frankly, it doesn't seem much better than what is on the bike at the moment! Any advice much appreciated!

 

[Hacienda71]

I think that this is fairly standard. The different shapes of the teeth help when changing gear. So they are designed like this.

 

[Fattman]

I think that this is fairly standard. The different shapes of the teeth help when changing gear. So they are designed like this.

+1

It's all fine and dandy - Wikipedia helpfully says this on the subject (under 'Improvements in Shifting').

 

[Fattman]

Oh, and it occurs to me - 3000 miles for a cassette is not that much, though; if the chain isn't super-stretched you will probably find the existing cassette will work fine with a new chain. I believe the rule of thumb is 1 cassette for every 3-4 chains. I have ridden my commute bike ~15000 miles summer and winter and have gotten through 5 chains and I had to replace the cassette on the 5th chain change.

So the upshot is, you may still have a roadworthy spare cassette at the end of the day!

 

[Zoiders]

Changing the casette or not is never a measurable thing.

I have seen people ruin the drive train on a bike in a very short period - often less than a thousand miles - just through failing to clean it.

 

[Steelo]

I'm relieved. I didn't want the hassle of sending it back.

Thanks for the advice. The existing cassette looks ok, so i may just clean it and change the chain for now then.