Earlier in the year I had described my Elephant NFE adventure bike build. I built it with a touring triple crank with low climbing gears for my long rides. Other than changing the tyre setup and more recently switching from Honjo mudguards to SKS Bluemels I used it pretty much in the same configuration throughout the year.
While it has been a very comfortable and safe ride, I was not happy with front shifting on the touring triple, which was completely different from the wonderful experience of the Shimano 105 5703 triple on my Bike Friday. However, the smaller 20" wheels (ETRTO 451) on the BF provide low gearing even with standard Shimano cranks which can not easily be achieved with 700C or 650B wheels. One either needs a very large cassette at the rear or smaller chain rings at the front or combination of both.
Over the years Shimano got rid of triples on all road groups above Tiagra, which now means all 11 speed group sets (Dura Ace, Ultegra, 105). The smallest road chain ring is a 34T, which is basically the smallest ring supported by the 110 mm bolt circle diameter (BCD) of a compact double crank. Anything smaller would need something like 74 BCD as used for the inner ring of the older road triples. My 5703 triple uses a 30T chain ring and on my NFE I run a 24T inner ring, both with 74 BCD.
One problem with the shift quality is the interaction between the front derailleur (FD) and the ramps and pins on the non-Shimano chain rings. With Shimano STI, triples depend much more on ramps and pins to pick up the chain than with doubles. The cage of a double FD is much simpler than a triple cage, which is optimized for specific tooth count differences on the crank set.
Last year Shimano introduced the Tiagra 4700 group set, which still includes a 10 speed triple option. Its rear derailleur supports cogs up to 34 teeth, but only in a double. The limit for triples is 32. This makes for 30-32 as the lowest gear, still some 15% heavier than what I currently have on both of my bikes. Also, the Tiagra hydraulic brakes are flat mount callipers. There are no adapters for IS or post mount frames
One way to get lower gears without the pitfalls of a non-Shimano triple with Shimano STI shifters is to use a "compact plus" crank. These cranks use smaller rings than the 52/36, 46/36, 50/34 combinations offered by Shimano. Essentially their small ring is about the size of the inner of a triple while the outer is somewhere between the middle and outer of a triple in size. Usually they use a 110/74 BCD combination. Popular models are the Sugino OX601D, OX801D and OX901D as well as the White Industries VBC (Variable Bolt Circle) crank. Common ring sizes are 46/30 or 44/28. It's also possible to use a triple crank as a double, with a bash guard in place of the outer.
For my upgrade I decided on the Sugino OX601D with 42T/26T chain rings. With an 11 speed 11-32 cassette in place of my 10 speed 12-30 cassette, the 42-11 combination gives me almost the same top gear of the 46-12 while the 26-32 lowest gear will be very close to the current 24-30. The 42/26 front tooth count gap of 16 is the same as in a 50/34 compact crank. Because my frame is set up for the front shifter cable to run on top of the top tube, I will use the FD-CX10-BT top pull cyclocross FD so I will no longer need a pulley wheel to reverse the cable pull as for my Alpida-d triple FD (an Ultegra FD-6503 clone, I'm told). Alternatively I could have used the bottom pull FD-5800 or FD-6800 derailleurs which are designed for 11 speed (the FD-CX70 is a 10 speed part), but other NFE owners assure me the CX70 works great in their 11 speed setups.
At the rear I'll be using an RD-6800 GS medium cage derailleur, which is needed for anything beyond 11-28 (currently I use a 10 speed RD-6700 GS). A cheaper RD-5800 GS would also work, this is more vanity than functionality I admit
The GS Astuto wheels that Tim built for me are 11 speed ready. I just need to remove a spacer to install an 11 speed cassette instead of a 10 speed one
I could also have used a 10 speed 11-32 cassette and staid with an otherwise 10 speed setup (and kept money in my pocket). Possibly the 11-32 cassette might have required a rear derailleur upgrade, such as a 9 speed MTB RD, as the limit of the RD-6700 GS is supposed to be 30T.
However, by going down the 11 speed route, Shimano's hydraulic disc brakes became an option. Hydraulic braking road shifters are only available in 11 speed versions (with the exception of the flat-mount only Tiagra, see above). The ST-RS505 is Shimano 105 grade, while the ST-RS685 is Ultegra level. That's the one I went for. There is also the ST-RS785 for Di2 electronic shifting, but I decided against going Di2 because my frame is not really designed for it (no internal cabling or hiding the battery in the seat post, no cable mounts on the downtube, where do I install those two junction boxes and the battery?). Keep it simple!
While people argue the pros and cons of various cable operated disk brakes, everybody seems to love those BR-RS785 hydraulic calipers for their light touch and good modulation. I've used hydraulic brakes on my son's 29er MTB and loved them. My current cable-operated TRP Spyre SLC calipers with metallic pads don't need frequent adjustment, but the stopping power in the dry is only OK, not really overwhelming: I've had better braking from well set up 105 rim brakes. The benefit of the TRP disk brakes to me is that stopping power doesn't deteriorate in the wet. On the downside, in the rain they're noisy like screaming banshees - louder than most trucks or buses! The BR-RS785 should be a definite improvement.
Hopefully, in a couple of weeks I'll be able to post a ride report for the new configuration. My parts bin will grow by a few spare parts from the old setup and the odd part or two I'll be able to reuse on the Bike Friday.