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Technical FAQ: 10- and 11-speed drivetrain component compatibility

Mixing and matching 10- and 11-speed drivetrain components

Dear Lennard,
I have a 2012 Cannondale SuperSix with an SRM Cannondale SI crank, which is a 2×10 with Dura-Ace. I’m thinking about upgrading to a new Cannondale EVO, which is 2×11. I want to take my SRM with me to the new bike.

An 11-speed chain is narrower than a 10 speed, correct? And the cog spacing on an 11-speed cassette is narrower than a 10-speed cassette? Does that mean the chainring spacing up front is narrower as well?

My bottom line question is this: if I put 11-speed chainrings on the SRM crank and slide it into a new Ultegra or Force 2×11 bike, will it work? Perhaps not optimal shifting up front, but will it work reliably? Under race conditions where I may not shift gently and carefully?
— Jim

Dear Jim,
While the cog spacing (or “cog pitch”) on an 11-speed cassette is indeed narrower than on a 10-speed cassette, the situation is not analogous on the front. Rather, the spacing between the centers of the teeth of the chainrings on 11-speed cranks and chainrings is not narrower than on 10-speed cranks and chainrings, and it is in fact even a bit wider on some of them. And in the informal survey I’ve done on cranks, I haven’t measured any that have thinner spider-arm tabs on 11-speed cranks than on their 10-speed counterparts.

I have used 10-speed cranks and chainrings on many 11-speed road bikes and have never had a problem. In fact, I right now own and frequently ride three 11-speed road bikes (representing all three drivetrain brands) and an 11-speed cyclocross bike that all have 10-speed cranks on them, and all but one has 10-speed chainrings on it. They all shift great.

So, I think your SRM crank will work fine as is on an 11-speed bike if the chainrings are in good condition, even in race situations. And it will work even better if you put new, 11-speed chainrings on it.
― Lennard

Dear Lennard
I am thinking about upgrading my Ultegra 10-speed triple system to 11-speed.

Can I keep the 10-speed front chain rings and crank on the 11-speed system?
KC

Dear KC,
Well, no, because it’s a triple crank.

You can certainly use a Shimano 10-speed double crank and chainrings with Shimano 11-speed chain, derailleurs, shifters and cassette, however.
― Lennard

Dear Lennard
I am thinking of getting a new Shimano Dura-Ace 9000 group, but I do a lot of hilly loops and so really like my compact crankset with an 11-32 cassette. Can I swap out an Ultegra 6800 long arm cage for the Dura-Ace short cage? If so, is shifting likely to suffer much?
Bob

Dear Bob,
The shift-activation ratio—the amount of lateral movement of the rear derailleur divided by the length of cable pull required to produce that much lateral movement—is the same for Dura-Ace 11 as for Ultegra 11. So the Ultegra long-cage 11-speed rear derailleur will work fine with a Dura-Ace 11-speed shifter and cassette. Other than slightly slower shifting due to the longer cage and inevitable longer chain, shifting will not “suffer much” at all.

If you’re asking about just the cages and not the entire derailleurs, you can interchange the derailleur cages between the two derailleurs, if you’d rather continue to have a Dura-Ace rear derailleur but want the longer cage of the Ultegra one.

I have a long-arm Ultegra Di2 11-speed rear derailleur on one of my bikes, and it shifts quite well, whether it’s an 11-25, 11-28, or 11-32 cogset on it.
― Lennard

Dear Lennard,
I was really interested in your recent Tech FAQ columns where you mention compatibility between various 10- and 11-speed systems. I would like to make the move to 11-speed in the most efficient manner, cost-wise and in terms of using components I already have.

In a recent column you wrote that one can use the old SRAM Red 10-speed rear derailleur in an 11-speed set-up, as long as it is matched with 11-speed shifters. That makes sense, as the derailleur lateral movement is determined by the cable pull per shift and ratchet mechanism in the shifters, not by the derailleur. I wonder if an older 10-speed generation front derailleur will be compatible with the current generation SRAM Red left shifter (i.e., is the cable pull and leverage in the front derailleur the same between the current and earlier 10-speed groups)?

I do hope the answer is yes, as I have sitting in the basement NIB SRAM Red derailleurs (10-speed), that I bought and intended to use in a build, but time and work demands did not allow at the time.

I also have a similar question regarding Shimano Dura-Ace 7900. Can I move up to 11-speed by simply upgrading to 11-speed shifters, and will they work with Dura-Ace 7900 derailleurs?

I suspect for the rear derailleur the answer is yes, but I am skeptical about the front derailleur’s compatibility, as the new front derailleurs have a much larger parallelogram for moving the derailleur sideways, suggesting the cable pull may be different.
Sebastian

Dear Sebastian,
Actually, this statement you made is incorrect: “the derailleur lateral movement is determined by the cable pull per shift and ratchet mechanism in the shifters, not by the derailleur.”

Rather, the lateral movement is most definitely a function of the design of both the derailleur and the shifter. The rear derailleur’s shift-activation ratio—the amount of lateral movement of the rear derailleur divided by the amount of cable pull to generate that amount of lateral movement (i.e., the number of millimeters of lateral displacement of the rear derailleur per millimeter of cable pull)—is built into the derailleur. It is akin to the leverage ratio in a rear suspension system (i.e., the magnitude of rear wheel vertical travel per unit of rear shock travel).

The design of the shifter determines how much cable it pulls with each click. If you multiply the derailleur’s shift-activation ratio by the amount of cable pull per click of the lever, the product will be the distance the derailleur moves laterally with each click. In order for the rear derailleur to shift properly on a given cassette, that resulting product must be equal to the lateral spacing between the centers of adjacent cogs in the cassette (the “cog pitch”).

You interpreted correctly that a SRAM 10-speed rear derailleur (road or mountain) paired with a SRAM road 11-speed shifter will shift properly with an 11-speed chain and cassette.

As for the front derailleur, a SRAM 10-speed road front derailleur will work acceptably with a SRAM 11-speed shift lever, but a front derailleur is perhaps the least expensive part of the drivetrain, and SRAM’s 11-speed Yaw front derailleur is a significant improvement over its 10-speed predecessor. Since your SRAM Red 10-speed road front derailleur is new in the box, you might consider selling it and getting the Yaw FD.

Forget about using Dura-Ace 7900 derailleurs with 11-speed levers. The derailleur’s shift-activation ratio is different for Shimano 11-speed rear derailleurs than it is for Shimano 10-speed rear derailleurs. Furthermore, Shimano 10-speed mountain and road rear derailleurs have different actuation ratios from each other, and the same goes for Shimano 11-speed mountain and road rear derailleurs. Prior to road 11-speed and mountain 10-speed, things were simpler; Shimano road rear derailleurs up through 10-speed and mountain-bike rear derailleurs through 9-speed all have the same activation ratio.

And your intuition is correct that a Shimano 11-speed shifter will not work well with a 10-speed front derailleur because the 11-speed shifter is designed to actuate the longer lever arm of Shimano 11-speed front derailleurs.
― Lennard

Regarding overheating road disc brakes:

Dear Lennard,
I just read your article about your 330-pound customer and his disc brakes, where you likened his situation to a tandem. My wife & I do ride a tandem that weighs about what you listed, and do have cable-pull disc brakes with sintered pads. On a trip in the mountains of Pennsylvania a few years ago we learned the hard way that even this system can overheat and stop working. There’s nothing scarier than going 40mph towards a 15mph turn and pulling the brakes as hard as you can and not having the bike slow down. Thankfully we somehow avoided a crash!

Even without boiling fluid, once the pads & rotors get too hot, they just don’t brake anymore.
John