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I want to replace my cassette which is 7 speed 14-34 shimano. The problem is I can't find exactly the same one. All I saw its 13-34 or 14-32 cassettes. So the question is: It is possible to replace my cassette with 14-32 or even lower e.g. 13-26 without replacing a chain or any other replacements? Thank you in advance.

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You mean like this: [Shimano 14-34 Thread-on 7-speed Freewheel "Megarange" ](…) (I Googled "7-speed 14-34" and got at least a dozen good hits.) – Daniel R Hicks Feb 24 '12 at 1:01
Yep possible, I just check it on eBay. – Alexander Feb 24 '12 at 15:39
up vote 2 down vote accepted

As long as you're not adding larger cogs than you've got on right now, your existing chain should be a functional length.

One more thing to consider is that if your current chain has significant wear, running it with a new cassette can damage the cassette (effectively very rapidly turning your "new" cassette into your "old" cassette), so even though your old chain should work fine with your new cassette, it may be worth it to replace it anyway.

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So if I will change the chain do I need to replace chainrings for the same reason? – Alexander Feb 24 '12 at 15:56
That depends on how worn they are. If a worn chain stays on for too long, it can damage the cassette and the chainrings, and all three should be replaced together. But, because of the larger diameter, chainrings don't wear as quickly as cassettes, so it is quite possible that your chainrings are fine. You should visually inspect the chainrings. If it has been worn, you should see asymmetric wear on the teeth, often described as resembling a "sharktooth". – prototoast Feb 24 '12 at 16:48

If you're replacing it with a similar range (1-2 teeth at either end) you should be fine. I wouldn't recommend changing the gear range significantly.

I replaced my cassette with a much smaller biggest (in terms of number of teeth) gear and it wouldn't shift into the top couple of gears. I believe the length of the pivot arm on your derailleur is tuned (to a certain degree) to the range of your cassette.

I agree with prototoast that you should probably replace your chain at the same time.

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Also verify that it is a Shimano compatable cassette.It doesn't have to be a Shimano brand just Shimano compatable.

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Does anyone even sell 7-speed cassettes that aren't Shimano-compatible? – Mike Baranczak Feb 25 '12 at 14:59

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