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I need your advice.

I have a Giant Escape 2014 UK model bike and it's time to change the chain and the original cassette/freewheel, which are worn out.

My question is, if I get this Sram PG850 8-speed cassette, will it fit nicely instead of the original Shimano MF-TZ31 Tourney 7-speed freewheel? They say Sram cassettes are Shimano compatible but I just want to be sure, I'm rather a newbie to cycling.

Will it combine well with the bike's current Shimano Tourney TX55 6/7 speed rear derailleur and Shimano EZ FIRE 40 21 speed shifters? (I don't mind having only 7 speeds on the new cassette).

Thanks for helping!

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SRAM Cassettes are compatible with Shimano Cassettes, but a cassette and a freewheel are different components. You will not be able to use the SRAM Cassette to replace your Shimano Freewheel. You will need to replace your freewheel with a freewheel.

The difference between a cassette and a freewheel is that a cassette is just a bunch of cogs that slides onto a free hub. This allows the wheel to spin without the chain moving. With a freewheel, the cogs and freewheeling mechanism are all in a single assembly, and this is screwed onto the hub of the bike.

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  • Moreover, you need to match the number of cogs on with the number of shifters. You're best off buying the Shimano TZ31 14-34 freewheel again. As for a chain though, you can get a 7 or 8 speed chain ( I normally use SRAM PC-850).
    – Batman
    Commented Aug 13, 2015 at 21:10
  • That's very clear, thanks @Batman. I was wondering because I noticed that Giant used to put SRAM PG 830 - which is a cassette not freewheel - on its 2013 model. So I thought they might be interchangeable. giant-bicycles.com/en-us/bikes/model/escape.3/11500/55833/…
    – Jan
    Commented Aug 14, 2015 at 9:53
  • You can use the same freewheel, or get one with slightly different gearing. If you don't use the 34 tooth cog at all, then you can get a freewheel that has something smaller in it's place. Most people won't need a cog like that unless they are not in good shape or carrying a heavy load or trailer. Might also be useful if you have some really steep hills in your area. But with a 28 on the front chainrings, a 34 tooth cog probably isn't use a lot.
    – Kibbee
    Commented Aug 14, 2015 at 14:30
  • @Jan - Giant sells different bikes in the US and in the UK, and it changes from year to year. Make sure you're looking at the right country and model year. But freewheels and cassettes are not interchangable.
    – Batman
    Commented Aug 14, 2015 at 14:34
  • Thanks, everyone, you've made things clear to me. Yeah I noticed from the beginning Giant sometimes puts different parts on same models in the UK and in the US. @Kibbee, special thanks for the advice, as I'm looking at this one 14-28 freewheel to install, I never used the 34-tooth sprocket anyway. I guess this one would fit no problem. amazon.co.uk/Shimano-14-28-Speed-Screw-Freewheel/dp/B000WFHUKQ
    – Jan
    Commented Aug 19, 2015 at 11:42

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