10 / 11sd compatibility

Question

I own a road bike with a SRAM Red 10 speed 110 BCD crankset and chainrings. I am upgrading the bike to the SRAM 11 speed shifters, cassette, chain and derailleurs.

Do I have to buy a whole new SRAM red 22 110 BCD crankset or can I just get the Red 22 outer and inner chainrings to fit my current 110 bcd arm?

In other words, will SRAM 22 Red 11 speed 110 BCD chainrings fit on a 2012 SRAM Red 10 speed crankarm?

thanks for all the responses. i realize that my terminology may be misleading. i actually wish to upgrade to the 11spd chainrings. what i needed to confirm was if they will fit on my my current red 10 spd spider arm i.e the hole dimensions are the same. if not i will have to buy the complete new crankset which is an additional US$226 vs just the chainrings. what i will do is purchase the small 11 spd ring which is less expensive and confirm that its holes match my spider

Answer 1

You probably don't have to change the chainset at all. An 11-speed chain and front mech will run fine with a 10-speed chainset.

A good article by Lennard Zinn who is the last word on mixing and matching drivetrain.

10 / 11 speed drivetrain compatibility

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.

— 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.

― Lennard

Read more at http://velonews.competitor.com/2015/03/bikes-and-tech/technical-faq/technical-faq-10-11-speed-drivetrain-component-compatibility_362722#Lr6GsYmPACvo8CY7.99

Answer 2

To answer your second question, yes the chainrings will fit.

Answering the first question is where things get murky. The issue arises when you look at the distance between the two chainrings, otherwise known as tab thickness. Are those the same? From what I can find out they do appear to be.

The 10S chain rings and 11S chainrings are definitely different. The chainring plate profiles are all different (including within different combinations of chainrings i.e. 52/36, 53/39, etc)

However, the spider’s tab thickness on the crankset is the same, so all of the spacing difference is in the rings. This means you can put new 11-speed rings on the 2012 Red 10-speed cranksets.

Chainring and cog profiles changed, too. They’re not just thinner, and they even might be thicker in parts. The big changes are in the shapes of the teeth, ramps and pins. And the chain. The only similarity between 10- and 11-speed chains is the distance between the pins. Plate profiles are all new.

http://www.bikerumor.com/2013/04/15/sram-22-unveiled-all-new-red-force-11-speed-road-groups-tech-weights-first-rides/