manuelgabriel

I recently purchased an 8 speed Claris Rear Derailleur and I want to use an 8speed megarange cassette sprocket (11T-34T)?

I was told that there is a maximum number of teeths you can use on a specific rear derailleur. Will the Claris Rear Derailleur be compatible to the 34T sprocket? Thanks in advance

jimc101

If you read the tech doc that came with the RD. all that info is supplied by Shimano as to the min and max capacities

SkyDog75

There are two ratings for your derailleur that you'd need to know: max cog size and wrap capacity.

The max cog size for a Claris 2400 derailleur is 32 teeth. 34 would exceed the derailleur' stated capacity, but it might be close enough to work.

Wrap capacity is just a little more involved to figure out. Your big chainring & big cog gear combo requires a longer chain than the small ring & small cog combo. Your derailleur needs to be able to take up the chain slack between those two chain lengths. To calculate the wrap capacity you need, add the difference between your smallest and biggest cogs (34-11=23) to the difference between your biggest and smallest chainring.

According to Shimano's web site, a Claris SS (short cage) rear derailleur has a wrap capacity of 37. The GS (medium cage Claris 2400 rear derailleur has a wrap capacity of 41 according to a few vendors.

If those numbers are right and you have a short cage (SS) Claris derailleur, then the biggest and smallest chainring on your crankset must be no more than 14 teeth apart if you're running an 11-34 cassette. If you have a medium cage (GS) Claris derailleur, your chainrings can be up to 18 teeth apart with that same cassette. (Assuming you can get a Claris derailleur to do a 34 tooth big cog.)

manuelgabriel

This has been a HUGE help. I cannot thank you enough.