Technical FAQ

Technical FAQ: Future-proof shifting, derailleur and shifter compatibility, Mr. Tuffys

In this week's column, Lennard looks at firmware updates for electronic shifting, mixing mountain and road components, and using tire liners for additional tube protection.

Have a question for Lennard? Please email us veloqna@comcast.net to be included in Technical FAQ.

Dear Lennard,
Has Shimano/SRAM/Campy considered using software upgrades to future proof their electronic shifters? Instead of requiring the purchase of new shifters when they go to 12-speed.
Ryan

Dear Ryan,
In general, some of them might already have done so. On current Shimano wired electronic shifter systems, as long as the wire connections and number of conductors are the same, the shift button is just an electronic switch, and it neither determines nor cares how many gears are on the cassette; rather, the rear derailleur determines the number of gears it will shift. On other systems, the communication system can differ depending on generation.

I know nothing about Shimano 12-speed electronic and whether it even exists in any form currently. However, a Shimano Ultegra 10-speed ST Di2 shifter also works with 11-speed Ultegra, Dura-Ace, XT, and XTR derailleurs, as long as MTB and road derailleurs are not used together. (Said more clearly, if you are using an MTB Di2 rear derailleur, you must use an MTB Di2 front derailleur with it, and vice versa with road Di2. You cannot combine road and MTB derailleurs on the same bike; if you do, nothing will happen when you push a shift button.)

SRAM eTap satellite shifters, like Blips and Clics, are simply buttons, and compatible with 11- and 12-speed. They are wired directly to the drop-bar shifters; the wires and plugs are unchanged between 11- and 12-speed, and the buttons just give a shift input. However, SRAM drop-bar shifters and Blipboxes, the actual transmission units, are not compatible between 11- and 12-speed. SRAM uses a newer transmission protocol for AXS (i.e., 12-speed), which first-generation SRAM eTap (i.e., 11-speed) does not speak.

As for Campagnolo EPS, 11- and 12-speed components do not to work together. The shift buttons on 11-speed Campagnolo EPS are called “switch type,” while Campagnolo EPS shifters are “resistance type,” and the two do not talk to each other. So, you cannot use 11-speed shifters on a 12-speed EPS group, or vice versa. The only exception is that 11-speed Campy EPS bar-end shifters can be used with 12-speed EPS derailleurs and ErgoPower levers, as long as the 12-speed TT V4 interface is used.
― Lennard

Dear Lennard,
I may be literally the only person who is addicted to bullhorn bars for long distances, but so be it.

I am building a new gravel bike and am curious if Shimano’s Metrea 2×11 shifters could shift a GRX drivetrain. Please let it be so!

Perhaps a better one: have you heard of a mountain rear drivetrain (Shimano XT 11-speed) working with a road (GRX) 2x front? The chain lines are different but quite close. Would be using a Jtek Shiftmate to adjust the cable pull from the Metrea brifter.
Chris

Dear Chris,
Yes, Shimano GRX front and rear derailleurs are completely compatible with 11-speed Metrea Flat bar shifters.

As for the XT 11-speed rear derailleur and GRX front derailleur with the Metrea shifters, I’m sure that would work, as long as you use the proper Jtek Shiftmate on the rear derailleur to match the cable pull of the shifter and rear derailleur.
― Lennard

Dear Lennard,
I’ve read your columns regarding wiping tires and am curious as to why tire liners are not mentioned as a possible solution to pacify any flats-from-glass concerns and diminish your instinct to want to wipe off tires after rolling through glass.

From some people I’ve talked to (club racers mostly), I accept that some riders, riding decent tires, will feel the liner rather than the road and to them, that is not acceptable. They also obviously add rotational weight. But for the vast majority of weekend warriors, commuters, and daily urban trekkers, I would think no one could tell the difference and the main benefit (virtually no chance of a flat) far outweighs any aesthetic about “road feel”. I live in Chicago, where the streets are about the worst in the country and on the few days a year that the sun shines here, the streets sparkle with broken glass. After a few flats in sub-freezing weather (when patch kits don’t work) I settled on the combo of Schwalbe Marathon tires and Mr. Tuffy tire-liners and a flat is now an extremely rare event. Every so often, I deflate the tire a little and spend a half-hour with a knife blade picking out dozens of glass shards, of which I’m sure a significant number would have gone through the tire to the tube had it not been for Mr. Tuffy.

I know that your reader base skews racer, but I thought that many of your thoughts and recommendations on such things were more egalitarian. Am I just painting myself “Fred” for thinking Mr. Tuffys are a viable solution?
Ethan

Dear Ethan,
You are absolutely right; for commuters and daily urban trekkers on streets rife with glass, Mr. Tuffys can eliminate the time and aggravation spent on flat tires and can result in a consistent amount of time you can depend on for your commute. In those kind of conditions, you’re not only unlikely to notice them, but you also can enjoy the ride more with less worry.

Depending on what you mean by weekend warriors, however, Mr. Tuffys may or may not be an acceptable solution for that crowd.

While I have not measured it, I would guess that the rolling resistance added by a pair of Mr. Tuffys might be on the order of 50 watts. Given that nice, supple tubulars consume 45-50 watts, adding a stiff thing like a Mr. Tuffy might well add half that, or 25 watts per tire. If the weekend warrior is trying to keep up with other strong weekend warriors, he or she can ill afford to give up 50 watts. Even if I’m overestimating by a factor of two, 25 watts is still a lot to lose when trying to keep up with other riders of similar strength.
― Lennard


Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is also a custom frame builder (www.zinncycles.com) and purveyor of non-custom huge bikes (bikeclydesdale.com), a former U.S. national team rider, co-author of “The Haywire Heart,” and author of many bicycle books including “Zinn and the Art of Road Bike Maintenance,” “DVD, as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.”
He holds a bachelor’s in physics from Colorado College.

Follow @lennardzinn