My SRAM x5 rear derailleur got caught on something and broke. I went to order a new one and learned there are different cage sizes. I don't know which size cage I currently have. While trying to figure out which one I need I figured out that I need to know my Total Drivetrain Capacity. All of the sources that I have come across say
Maximum Chainring Difference + Maximum Cassette Cog Difference = Total Drivetrain Capacity
Not sure what the formula is when you only have 1 chainring. The answer to this question appears to just be
Maximum Cassette Cog Difference = Total Drivetrain Capacity
Is that correct? So in my case it would be 34 - 11 = 23? So a medium cage would be plenty? The sources I have come across say if in doubt, get a large. I would rather have a smaller cage though to hopefully not have it catch on something again.
My current setup
Crankset: alloy arm with 34T single ring
Shifters: SRAM x4 9 speed
Rear Derailleur: SRAM X5, 9 Speed
Rear Cogs: SRAM PG950 Cassette, 9 Speed, 11-34T
SRAM x5 medium cage specs
Largest Cog: 34
Chain Wrap Capacity: 37
SRAM x5 long cage specs
Largest Cog: 36
Chain Wrap Capacity: 45