Low Gears and SRAM 1x Road Derailleurs

People like to follow directions.  That’s why cookbooks are popular, and how to videos.  There’s evidence that we believe the first thing we hear on a given subject, which is what makes things like sketchy news sources so dangerous.  We’ll believe something, even if there is ample evidence to the contrary, if we heard the wrong thing first.  

Enter the popular thinking on SRAM’s 1x road rear derailleurs.  SRAM makes 3 of these that we deal with here at Analog.  I don’t know or want to know or care about the electronic equivalents of these derailleurs, so don’t write me asking about them.  The derailleurs in question are the SRAM Apex, Rival and Force derailleurs, identified by the number 1 after them, to seperate these derailleurs from SRAM’s derailleurs made for traditional road double cranksets.  

In the SRAM manual, which can be found online, these derailleurs are rated to a 42 tooth low cog, and no more.  SRAM sells these derailleurs as OEM spec only with a 42t cog cassette.  99% of all websites tell you the derailleur can only shift to a 42t cog, and so most people think, that’s it, it must be true.  

Since the current batch of SRAM 1x rear mechs landed, Analog Cycles has used them on 50 and 51t rear cogs.  How can we do that?  It shouldn’t work.  

Derailleur range is defined by a few things:  the drop of the parallelogram, the length of the cage (which primiarly controls chain wrap), and the length of the parallelogram.  These are the critical measurements, but smaller things like the angle of the parallelogram have a bit to do with it as well.

Measure a SRAM GX long cage rear mech, or an NX, or any 1x11 SRAM long cage mountain rear derailleur.  They’re all the same geometry.  Measure those 3 things.   Then do the same on a Rival 1 long cage derailleur, which again, is the same as a Force or Apex in the vital measurements.  They’re the same.  The difference between the road and mountain derailleurs has nothing to do with the three critical measurements mentioned.  Instead the difference lies within the cable pull of the two styles.  SRAM Road uses Exact Actuation, and the mountain stuff uses X Actuation.  You’d think they could have named those a bit differently to avoid confusion.  Cable pull is just how much cable is pulled or released by a shifter in a given shift.  

The difference between the road and mountain pull is minor, but it’s enough that they’re not cross compatible.  No worries, SRAM has a secret back door, in that the road rear derailleurs are the same as the mountain derailleurs, albeit with a different cable guide fin on the derailleur, which changes the cable pull.  The rest is the same.  I prefer the road derailleurs from a mainteance perspective, as they have a barrel adjuster on the derailleur.  Handy if you are running drop bars.  

I suspect that folks who have tried setting up ‘mullet’ drivetrains (not my term, I’ve never thought of a cassette as being a party zone) are missing something critical that would otherwise set them up for success.  Perhaps an incorrectly sized chain, perhaps a bad chain gap, which should be based on the manual for a mountain derailleur.  Maybe it’s a bend derailleur hanger, or critical for SRAM road derailleurs, a long smooth loop of housing between the barrel adjuster on the mech and the last housing braze-on on the frame.  Many folks set this up too tight, which causes friction.  Whatever the cause is, bad shifting on a 11-50 cassette isn’t the road derailleur’s fault.  It’s user error.  I think there are also false expections with wide range gearing.  The biggest cogs have large gear jumps, which do not shift as smoothly as say, a 11-13 tooth gear jump.  It’s more akin to a front derailleur in terms of shifting, in that you can be shifting over 8 teeth per click.  That larger gap requires more shift effort, and more strain on the chain.  The lower the gear, the higher the potential torque on the chain and cog, which can easily lead to rougher, tougher shifting.

Thumb your nose at the manual, and go low on your SRAM equipped gravel bike or ATB.