Technical FAQ: Make 11-speed shifters work with 10-speed

Lennard Zinn considers one product that may solve drivetrain compatibility puzzles and revisits flat bar shifters for road bikes.

Dear Lennard,
I think I have read all (or most) of the Tech FAQs related to SRAM 11s/10s compatibility, but wanted to confirm an assumption since my goals are different from most.

Can I change my SRAM front shifters (currently Force 10s) to Rival/Force 22 hydro (disc) and leave my rear cassette and derailleur (and chain) as 10s? Presumably, tightening down the lower limit screw to keep the shifter from seeking out an extra (low-end?) cog. I assume this will hold, since I understand the cable pull remained the same in going from 10s to 11s shifters.

My motivation in keeping the back end the same is that I have multiple wheelsets that have no easy upgrade path to 11s, but I’d like very much to switch over to hydro disc (and there is no 10s SRAM hydro option) — and then slowly start rebuilding my rear wheels.
— Hans

Dear Hans,
No, that will not work. The shifts will not line up across the entire range, because an 11-speed cassette is not just a 10-speed cassette with an extra cog stuck on at the same spacing. Rather, the spacing between 11-speed cogs is narrower than between 10-speed ones, and since you’d be using the same derailleur with either setup, the shifter determines what cassette it will be compatible with.

The shift activation ratio is the same on 11-speed and 10-speed SRAM road derailleurs: approximately 1.3, so you’re fine there. However, and contrary to your contention, the cable pull is most definitely different on 11-speed and 10-speed SRAM road shifters. If it were not, then the cog pitch (the distance between the central planes of adjacent cogs) would have to be the same on 11-speed and 10-speed cassettes, and it is not. Cog pitch can easily be measured; it is the the thickness of one cog and its adjacent spacer.

The shift activation ratio multiplied by the cable pull is equal to the cog pitch.

The cog pitch of SRAM (and Shimano) 10-speed cassettes is about 4mm, and the cog pitches of SRAM, Shimano, and Campagnolo 11-speed cassettes are all about 3.8mm. Solving the above equation with these cog pitch numbers and the 1.3 shift activation ratio, you can see that the cable pull of SRAM Exact Actuation 10-speed road and mountain shifters is approximately 3.1mm, while it is around 2.9mm for SRAM Exact Actuation 11-speed road shifters.

You can measure the cable pull — how much cable your shifter pulls with a number of clicks, and divide by the number of clicks. I just checked on my SRAM 11 hydro disc bike and got 20mm of cable movement for seven clicks of the shifter, which is 2.9mm of cable pull per shift. I also tried it on a SRAM 10-speed road bike and got 28mm of cable movement with nine shifts, or 3.1mm/shift.

In short, if you switch to SRAM 11-speed hydraulic levers, you can keep your derailleurs, but you would need to upgrade your chain, wheels, and cassettes to 11-speed.

But you didn’t write me to hear that you have to buy a bunch of expensive cassettes and freehub bodies and re-dish your wheels or get new ones. So here’s another solution that should work, but I haven’t tried it. The Jtek Shiftmate alters the cable pull of a shifter, and Jtek makes a number of different models to adapt various shifters to a variety of derailleurs and cassettes. The Shiftmate Y should do what you want, according to the Shiftmate Compatibility Chart; scroll down to the last model at the bottom. It’s certainly worth trying; it’s a modest investment and could do exactly what you want right away and would still allow you to do your planned upgrade to 11 speeds over time.
― Lennard

Dear Lennard,
I bought a cross bike with SRAM CX1 to use more for dirt roads and rail trail during the summer and cross racing in the fall. I had a ‘cross bike before and hated the gearing on it while riding roads and rail trail. I figured that a 50t ring with an 11-36t cassette would give me all the flexibility I would need in terms of gearing. I cannot, however, find any literature to tell me if that combination is compatible. The bike has a SRAM CX 1 medium-cage derailleur, and I also have a new chain to throw on with the new setup. Apart from big jumps between gear ratios, do you foresee any problems with the setup?
— Stu

Dear Stu,
If you are asking if you can get more range by using a double in front with a front derailleur and 34x50t chainrings, that will not work. The CX1 X-Horizon rear derailleur does not have enough capacity to deal with front shifting.

If you are asking if you can use a single 50t chainring, the answer is yes, you certainly can. SRAM says that the medium-cage rear derailleur will handle an 11-36. Here are the X-Sync chainring options.
― Lennard

I got a lot of feedback about flat-bar shifters for 11-speed, and in addition to the correction from Andrew that I put in last week, here are some other options:

Dear Lennard,
In addition to the Shimano SL-RS700 Rapidfire shifters for flat bars running 11 speed derailleurs, MicroShift makes the “Centos” flat bar shifters that apparently run 11-speed Shimano (I know they work fine, ’cause that’s what my wife’s new Specialized Sirrus came spec’d with Centos shifters with 105 11-speed).
— Rick

Dear Lennard,
I have found that road shifters work nicely on bull horns, sort of upside down — but very well-positioned. This provides some of the benefits of flat bars (upright). Braking can be enhanced by a set of those little inline brakes put near the stem.
— Jeff

Dear Lennard,
As well as your suggestion of using an MTB rear derailleur and shifter, another option is the [Jtek; see above] Shiftmate model 8, which allows use of either an 11-speed Shimano road shifter with Shimano 11-speed MTB derailleur or an 11-speed MTB shifter with 11-speed road derailleur.
— Nick

Dear Lennard,
Eric wrote to you looking for a shifting solution for his wife’s bike, and I wonder if the new Lindarets Tanpan shift adapter could work. It’s designed to run road shifters with mountain derailleurs, but I think if you turned it around, it’d do the opposite. Thoughts?
– Tim

Dear Tim,
I checked with Marc Lindarets, and this is what he said regarding your question:

“I wish that I could help, but we go the other direction. I was thinking that he might be able to mount the pulley backward or, but the cable alignment would be off, and mounting the Tanpan backward in a cable stop would be awkward if it worked at all.
— Marc Lindarets
Lindarets LLC”

Interesting idea, Tim, but no go.
― Lennard

Regarding the motor found in a pit bike at cyclocross worlds:

Dear Lennard,
I was reading your response to a question regarding the Vivax Assist system. The motor and battery weigh only 1.8kg. The weight you were mentioning was for the entire carbon frame with motor. We’ve looked extensively at this system and other similar ones. It is by far the most robust and reliable at this stage. I rode it for the first time in 2012 on an Alpe d’Huez-like climb outside the leading reseller of it in their frames. They have two bikes weighing 8.9kg. and 9.9kg. I rode the Kitzhorn, and it was the most fun I’ve ever had on a road bike on such a climb. Made me feel like Marco Pantani all juiced up without the side-effects. Steinbach has been selling its e-assist line with the Vivax-Assist for nearly five years.
— Patrick

Dear Patrick,
Ah, that makes sense; I was looking at this, and I suppose in retrospect that it’s clear that the weight is for the entire system including the frame, fork, and headset, and perhaps seatpost, even though it’s not pictured.

Still, my contention remains that a bike that weighs 1.8kg (4 pounds) more than Van den Driessche’s motorless bikes would be a dead giveaway to a mechanic. The thought that a mechanic could unknowingly prepare a bike for the world championships that didn’t belong to Van den Driessche is far-fetched enough, but if it also weighed an extra four pounds — well, that’s just about impossible for me to believe. And she has given up trying to convince us of that.
― Lennard