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I just bought an 11-34T 8 speed rear cassette and noticed that it is a Megarange cassette with a substantially large jump between the lowest and 2nd gears.

Will this work with my existing Alivio rear mech or do I need to get a different one? (Such as in this question here)

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My Alivio mech is the standard type with normal sized cogs and length of cage. I will give it a shot with this mech and update as to how it works. – decvalts Aug 16 '14 at 14:43
Generally, the mountain group is long (enough) cage to do 34t. – Batman Aug 31 '14 at 12:23

It will probably work. The one thing you need to look at is the length of your derailleur cage. With that really large cog, you might have to adjust your chain length, and then your derailleur might not be long enough to properly tension the chain.

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You'll check that the derailleur does not come into contact with the cassette! – Carel Aug 15 '14 at 17:41

One thing I have noticed about the mega range derailleurs is they all seem to have very large jockey wheels. The megarange seem to run with 16-20 teeth vs 10-14 teeth. It may be a cost saving issue or part of the design. I am basing this on the small sample of bikes I have on hand. If your Alivio has the smaller standard tooth count wheel it may work but be a little clunky going on to the big gog.

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I've noticed this as well. I figured it was a cost savings thing, because I always saw it on low quality bikes. That said, I've never seen a megacog on a high quality bike, so I don't have a good point of comparison. – stranger Aug 15 '14 at 19:42
up vote 1 down vote accepted

Yes, it works.

My existing rear derailleur (Shimano Alivio M410) was suitable to work with the largest 34T cog. The B-screw (angle adjustment) on the derailleur will need to be tweaked to prevent rubbing of the cassette/jockey wheel/chain. In my case the B-screw was turned almost all the way in, but it works great. The change between the 2nd-largest and the 'Mega' cog is actually smoother than I expected, despite the big jump.

I have fairly small front chainrings, so the tensioning of the chain was not an issue. (I was fitting a new chain at the time anyway)

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