Question 1

What size should I use for a 36 -11 casette?

Accepted Answer

Forgive me, but you are asking the wrong question.The cage size is controlled by the maximum amount of slack chain created by the combination of chain rings AND cassette. This is called "Chain Wrap".To formula for chain wrap is (Big Chain Ring - Small Chain Ring) + (Big cassette Cog - Small Cassette Cog).  So if you are using a compact double chain ring (50-34) and a 11-36 cassette the numbers work out to (50 minus 34) + (36 minus 11) or 16 + 25 = 41.  This means that if you shift from a big-big combination to a small-small combination, your derailleur has to be able to handle 41 teeth of loose chain, which calls for a long cage.  On my bike a have a single 40 tooth chain ring and a 11-42 cassette so the chain wrap works out to (40 - 40) + (42 - 11) = 0 + 31 = 31.   So even though I have a huge cassette I only need a medium cage because I have no front derailleur to create more chain wrap.Hope that helps.

Question 2

what is short, medium.long cage?

Accepted Answer

It has to do with chain wrap capacity. Small=30t Chainwrap Capacity, Medium=35t, Long=47t. The wrap is just the difference between the number of chain ring teeth plus the difference between the cog teeth. For example a 53/39 with a 12-25 cassette requires 14 + 13 = 27 teeth of wrap capacity needed from the RD.

Question 3

Will this work with Shimano Ultegra shifter

Accepted Answer

No, actuation will only work with sram.... The good news is that it will work with both sram 10 speed road and Mtb... Unlike the newer 11 speeds witch are road or mtb specific.

Question 4

Can this be used with a shimano  11/42 cassette ?

Accepted Answer

I used it with a sunrace 11-42 cassette but I needed a longer b tension screw(which was not provided) so you will likely run into the same issue.

ASIN	B00V8RZ9SW
Best Sellers Rank	#109,020 in Sports & Outdoors ( See Top 100 in Sports & Outdoors ) #56 in Rear Bike Derailleurs
Brand Name	SRAM
Case Material Type	Aluminium
Color	Black
Customer Reviews	4.4 4.4 out of 5 stars (745)
Global Trade Identification Number	00710845771835
Included Components	Rear Deraille
Item Dimensions L x W x H	12"L x 8"W x 2"H
Item Type Name	SRAM derailleur gx type 2.1 long cage 10 speed black
Item Weight	157 g
Manufacturer	SRAM
Manufacturer Part Number	00.7518.080.000
Material Type	Aluminum
Model Number	00.7518.080.000
Mount Type	Standard
Number of Items	1
Number of Teeth	10
UPC	757183591480 710845771835 784427964175
Warranty Description	Limited Warranty

SRAM GX Type 2.1 Rear Derailleur - 10-speed

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