I'm having a hard time finding an appropriate replacement chain for my bike. Its a 21 speed, Wal-mart brand mountain bike. My local bike store has chains that were up to a 10 speed. I know I need a chain tool, and to measure the new chain using the old chain, but I'm unsure what type of chain to buy.

Thank you!

PS I'm in the market for a new bike, as I currently commute to and from work on my bike. I've been using the cruddy Wal-mart bike because it was a gift. As for now, I want to tune it up and make sure it can survive another couple months of riding! It got rather rusted this winter when I stored it in my apartment building's basement.

  • As Andy suggests, you want a 7-speed chain. Jun 1, 2015 at 0:52

1 Answer 1


Since you say the bike has 21 gears, it must have 3 at the front and 7 at the back.

So you need a 7 speed chain. Any bike shop would have one.

I suggest you take your bike to a shop and ask them to fit a new chain.

But I'm curious why you think you need a new chain. If it's due to rust then just oil it and ride it some.

Other rust will probably be superficial, and can be cleaned with a plastic pot scrubber and a greasy cloth.

A cheap bike can give no end of trouble, but they are also an opportunity to learn basic bike maintenance skills, if you're interested. Check out posts under the [maintenance] tag (added to your post).

  • These days, you're probably going to get an 8 speed chain for a 7 speed bike (I use SRAM PC-850).
    – Batman
    Jun 1, 2015 at 3:15
  • My current chain is terribly rusted, and I noticed that even after adjusting my derailleur, my chain will slip or just not shift correctly. Also, based on riding my bike to and from work nearly daily for almost 2 years, almost every post and blog about bike maintenance is pointing towards a new chain. Thank you so much for the added tag! I'm looking forward to learning more about caring for my bike before I upgrade to a high quality one. I want to make sure I can properly maintain and care for what I buy!
    – hannathing
    Jun 2, 2015 at 3:51
  • Yes, sounds like it. Check if the rear gears (cassette) is worn. If the teeth look like shark teeth it would pay to replace both at the same time.
    – andy256
    Jun 2, 2015 at 4:04

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