- The curvature of my front derailleur matches the curvature of my round 50-tooth chainring quite well. But if that outer chainring were to get much smaller, like the 42T mentioned, when you move the derailleur down to keep it as close as possible to the chainring without touching, you’ll discover that the tail of the cage will be very far from the chainring when the tip of it is close to the ring. This will cause misshifts. Photo: Lennard Zinn | VeloNews.com
- This setup would not shift from the big Rotor Q-ring to the smaller one under load because the oval rings caused the teeth to be too far from the front derailleur throughout much of the stroke. In this crank position, the major axis of the Q-ring ellipse is oriented vertically so that the tallest part of the chainring is at the top, close to the derailleur cage. However, notice how far the tail of the derailleur cage is from the part of the chainring that is decreasing in size toward the minor axis, and as the minor axis passes over the top, it is far below the derailleur cage. Photo: Lennard Zinn | VeloNews.com
This week we’ve had an interesting mix of questions on electronic drivetrains, and mixing drivetrain components and chain sizes.
Dura-Ace 9000 compatibility
I’d eventually like to move to Shimano 11-speed, but I’ve got too much invested right now in wheels that will only accommodate 10-speed (without having to re-dish). My question is, can the new Shimano Dura-Ace 9000 Di2, which is 11-speed by default, be programmed back down to 10-speed? To me, it makes sense for Shimano to accommodate this feature, since it gets the new 9000 group in the hands of consumers and then allows them to transition to 11-speed when they are ready. Any insight?
From Shimano’s Wayne Stetina:
Sorry; the Di2 rear derailleurs cannot be reprogrammed between 10- and 11-speed.
Note that I did the first 2,000 miles of 11-speed drivetrain testing in 2011 with the 11T first cog removed from a CS-9000 11-25 cassette mounted on WH-7900 wheels. So I rode a 12-25 “10-speed” with a 12T lock ring and a 1mm spacer behind the cassette so the lock ring didn’t bottom out on the narrower 11-speed spacers. It’s also possible to use an 11-28. It unfortunately doesn’t work for those who require an 11T top gear.
V.P. R&D, Shimano
Trouble with Campy EPS
Today I lowered my stem about 1.5cm. My Campy EPS interface unit is mounted right under the stem. It took some wiggling to get the stem (which is, of course, hooked up with three wires to the unit) out of the steering tube. Once I was done with the stem, I could not get my rear derailleur to move up the chain to any larger cogs at all. I could only shift down to the smaller cog. Basically I had to pedal home in 50/11 the whole way. Did I just screw up the connection from the right SR lever to the rear derailleur in the process of lowering my stem? I am kinda freaking out right now because now I just cannot move the rear derailleur at all. Please help!!!
One last question. Can I use SRAM Red brake calipers with Shimano Ultegra Di2 levers?
The fact that it shifts one way indicates to me that the lever is still connected to the rear derailleur.
However, did you try to move the rear derailleur by hand? I’m betting that you did, or otherwise bumped it during your struggle. What that would have done is de-couple the derailleur from the motor. This is a nice feature of EPS and Di2 rear derailleurs that protects them in crashes and allows riders to manually select a gear to limp home in if the battery is exhausted.
Re-couple the rear derailleur by pulling the jockey wheel cage toward you; you will hear and feel a soft click as it snaps back into place. Then go back to the initial setting of your rear derailleur. This is described in Zinn and the Art of Road Bike Maintenance, 4th Ed.. You can also view a video here. When it says to shift the rear derailleur to the 10th (second biggest) cog, if yours will not go there, do the procedure on the largest cog it will get up to.
You have a Di2 bike as well? That SRAM Red brakeset will not work well with the Ultegra levers. Those levers are made for lower leverage and higher cable pull, so you will have to pull them harder to apply the brakes than they are designed for. All Shimano levers with shift cables under the handlebar tape are designed this way with lower leverage, and the corresponding brake calipers have higher leverage in order to be used with them.
Mixing road and mountain components
For my cyclocross bike I would like to install a mountain bike crankset (a SRAM Truvativ X9, 42-28) with SRAM Force (10-speed). Do you think it is possible? The front derailleur would work well?
I’m willing to bet that a road front derailleur, whether it’s your SRAM Force or any other one, won’t shift worth beans on that setup. That’s because the curvature of the derailleur cage won’t match the curvature of the chainring. As the chainring gets that small, when you move the front derailleur down to get close to it, only the front tip of the derailleur cage will be close to the chainring; the tail of it will be far from the chainring. So, the chain will not contact any of the shaped sections of the derailleur cage plates, and it will neither shift well only at the tip, nor will it control the chain well from jumping off when you hit bumps.
I tried to run 36-40 Rotor Q oval chainrings on my Campy EPS electronic ’cross bike (the major dimension of the 40T Q ring is the same as the diameter of a 42T round chainring). It was a complete disaster. Not only did I have the problem I described above, but the further problem of the chainring diameter constantly changing, getting closer to and further from the derailleur cage, made it impossible for the derailleur to do its job. It dropped the chain between the chainrings a lot, and it never could push it to the inner chainring. I couldn’t run it as a single chainring, which I tried, because disconnecting the EPS front derailleur causes the rear derailleur to go to sleep. So, I instead went with a round 50T outer chainring, which is too big for cyclocross, but it does make my bike far more versatile than my other ’cross bikes, which only have a single chainring — a 39T Rotor Q-ring. I also tried 36-52 Rotor Q rings, before settling on the and 50T outer chainring, but it would not shift to the inner chainring under load.
I suppose you could try to use a mountain bike front derailleur with that crankset. While, for instance, a SRAM 2X10 front derailleur will be the proper shape to mate with that outer ring and is designed for that shift, the problem would be the cable pull. I would be willing to bet that the SRAM Force lever would not pull the correct amount of cable to make that front derailleur shift correctly. It’s worth a try, though. Let me know if you do so.
Chain sizes and 11-speed Campy
For years I have used a 7/8-speed chain and an 8-speed cassette on a Campy 10-speed compact crank (34-50 chainrings) using only friction shifting. I was wondering if a 9-speed chain would work on an 11-speed Campy compact crank (36-52 chainrings) with friction shifting.
I haven’t tried either of the setups you mention. I’m surprised that the 7/8-speed chain works on a 10-speed crank. If it does, then I would bet that the 9-speed chain would work fine on an 11-speed crank, because the chain is thinner than the 7/8-speed chain, and 10-speed and 11-speed chainrings are almost identical, and the spider tab thickness is the same on 10-speed and 11-speed cranks.