Simple Question - Bike Chain
 

Hello! I have a question that I'm sure will be really simple for people who know about bikes; unfortunately I am not one of them.

I have a Bianchi Ocelot 21 speed mountain bike and I need a new chain. Someone is going to fix it for me (thank goodness), but I need to get the chain first. For the life of me I can't figure out what chain size I should get.

Is it a simple thing to find out, or how do I go about finding what kind of chain I need?

Thanks for your help in advance!

Any 6, 7, or 8 speed chain will work. I would get the KMC with a masterlink.

Count the number of rear cogs on your bike. That corresponds to the width of the chain that you need. It might say something like 6-7-8 speed chain.

When you buy your new chain it will be too long. You'll need a chain tool to cut it down to the right length. Assuming your old chain was the correct length, the easiest thing to do is to compare it with your new chain to figure out where to cut. Your new chain will actually wind up being a tad shorter than the old one, but you'll figure that out.

Absolutely agree on getting a chain with a master link; KMC, SRAM and Wipperman make them. When you compare the new chain with the old to figure where to cut it short, put them side by side and match the number of links. The old chain will measure slightly longer but the number of links is the important thing.

+1, except that older 6s chains were slightly wider than today's 7s & 8s chains. Anyway, it's simple math, your 21 speed bike has triple chainrings and 7 speeds on the wheel, so it's 3x7. Years ago we referred to bikes by the total number of speeds as you do, but for chain purposes you only care about the rear sprockets so you have a 7 speed and would buy any chain compatible that.

Agree you need a 6-7-8 speed chain if you've got 3x7 (21). Removable links make life easy.

You'll something like this to size it. Park Tool has good info for sizing and installing a chain here.

KMC 7-speed.