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I have an older bike (between 10 and 15 years old), which has a alivio derailleur. It's an 8 speed, and I just replaced the cassette, chain and crank set. I noticed that there was a large amount of play in my derailleur, so I reckoned it's time for a new one. Will this shimano acera derailleur fit instead of a new alivio one? They are quite a bit harder to find, and I'll just go for this if it's the easiest option.

Thanks!

EDIT:

I replaced it this afternoon and it worked perfectly; thanks for all the advice.

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  • It can be tricky, but usually if you find one with the same number off speeds it can be made to work. And occasionally even when not the same number of speeds. (Hint: See if a local bike shop has a used unit they will sell you.) – Daniel R Hicks May 4 '18 at 22:03
  • It has the same number of speeds, but since a derailleur has quite a lot of moving parts with all different dimensions, I reckoned it would be trickier to find the right one. – Joost May 4 '18 at 22:27
  • First (even before the number of speeds) you need to check the mounting scheme. Most use something similar to the Shimano unit you linked, but there are exceptions. Then you need to check the cable routing. Most run the cable in from the back, like the Shimano, but there are exceptions. Then you need to check the 'tooth capacity" of the unit (max take-up of chain slack) and the min/max rear cog size accommodated. – Daniel R Hicks May 4 '18 at 22:37
  • Generally, if it looks about the same dimension as the one its replacing, then you're good to go. If the gap between the two jockey wheels (length of cage) is smaller then you may have issues. A longer cage will just use a longer chain, without any bad side effects other than decreased ground clearance. – Criggie♦ May 5 '18 at 5:16
  • If the play is in the jockey wheels, you might consider buying a new top one. The bottom one is less important. – Criggie♦ May 5 '18 at 5:17
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The derailleur you linked is compatible.

In general, Shimano shifters for 9 speeds or less for off-road series and 10 speed or less for road series are interchangeable if the mounting scheme fits. 7-speed cassette is narrower than 8-speed, but the derailleur probably has enough room for adjustment to fit the wider cassette (edit: actually, it was 7-8 so it definitely should work).

The derailleurs for more speeds require a corresponding shifter to work correctly. Derailleurs from other brands are also not compatible without tricks with adapters, with the exception of some old SRAM units specifically marketed as Shimano compatible.

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  • I'll buy and install it this afternoon. Will update once it's working. (or not). – Joost May 5 '18 at 9:54

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