Sram 10spd/11spd technical question

[Nooch]

Sram pulls 1:1 for both it's 10 and 11spd groups, so 10spd derailuers can be used with 11spd cassettes -- but does it work backwards? For instance, can I take force 22 or even, eTap shifters, dial in the high and low to only travel the distance of 10 cogs instead of 11, and subsequently have a 10spd group?

Curiosity getting the best of me today...

[David Tollefson]

No. The spacing per shift is in the shifter, not the derailleur.

[Nooch]

Right, but: the cable pull is the same. All the Sram 1x derailleurs tout that they can be run 10 speed or 11 speed. Which tells me that the cable pull is the same, the shifters just have one more indent to move one more pull.

From there, limiting the high and low to only move 10 shifts -- you don't think that's possible?

[93KgBike]

The 10 speed cogs are wider spaced than the 11 speed cogs. It will work, but you will have trim issues at some cogs, depending on the setup.

So yes, it can work.

If you have all that equipment to play with, give it a try and let us know how annoying the shift noise or mis-shifts are (or are not).

[tombtfslpk]

The 10 speed cogs are wider spaced than the 11 speed cogs. It will work, but you will have trim issues at some cogs, depending on the setup.

So yes, it can work.

If you have all that equipment to play with, give it a try and let us know how annoying the shift noise or mis-shifts are (or are not).
What he said.
We know an 11 speed cassette is wider, but is is not wider by one cog spacing from 10 speed (110%).
Sram cable travel is determined at the shifter, and the shifter needs to match the number of cogs on the cassette.

[Mark McM]

Right, but: the cable pull is the same. All the Sram 1x derailleurs tout that they can be run 10 speed or 11 speed. Which tells me that the cable pull is the same, the shifters just have one more indent to move one more pull.

From there, limiting the high and low to only move 10 shifts -- you don't think that's possible?

It's not quite that simple. It is true that both 10spd and 11spd have the same 1:1 cable pull ratio. What this means is that for every 1 mm of cable travel, the derailleur will move laterally 1 mm. 10spd cassette sprockets are spaced 3.95 mm between centers, so a 10spd SRAM has to pull the cable 3.95 mm for each shift detent.


But 10spd cassettes use up almost the entire space on the hub between the right flange/spokes and the drop out. If you just added an extra sprocket and spacer to a 10spd cassette, it just wouldn't fit into the space between the flange and dropout. In order to fit 11 sprockets into the same space as a 10spd cassette, the distance between sprockets had to be narrowed, so 11spd cassettes are only 3.80 mm between the centers of the sprockets. So to shift properly, an 11spd shifter has pull 3.85 mm of cable per detent. If you tried to use a 10spd shifter, it would shift a little too far. As you continued to shift across the cassette, the errors would continue to add up, until at the middle of the cassette the derailleur would line up between sprockets, instead of being centered under the sprocket.

[Nooch]

What he said.
We know an 11 speed cassette is wider, but is is not wider by one cog spacing from 10 speed (110%).
Sram cable travel is determined at the shifter, and the shifter needs to match the number of cogs on the cassette.

Fair enough. To play devils advocate, though, why are the 1x derailleurs compatible with 10 or 11 spd drivetrains?

https://www.sram.com/sram/road/products/sram-force-1-rear-derailleur

Edit: Posted before the above

[sandyrs]

Fair enough. To play devils advocate, though, why are the 1x derailleurs compatible with 10 or 11 spd drivetrains?

https://www.sram.com/sram/road/products/sram-force-1-rear-derailleur

EDIT: nevermind!

[Kontact]

Fair enough. To play devils advocate, though, why are the 1x derailleurs compatible with 10 or 11 spd drivetrains?

https://www.sram.com/sram/road/products/sram-force-1-rear-derailleur

Edit: Posted before the above

Because their geometry is the same, but the amount of cable being pulled to move the deraillleur the shorter distance between cogs is proportionally smaller as well.

In other words, if you have the same derailleur and the cogs are 6mm apart, your cable pull might be 4mm. When you switch to cogs that are 3mm apart, you'll need only 2mm of cable pull per click. Whether the cable is pulled 4mm or 2mm is built into the shifter.

The distance the derailleur moves for a given amount of cable is consistent, but since the cog spacing has changed the cable-per-click must also change.