In the previous installment, I went over a bit of history and discussed how we got to this point, where drop-handlebar bikes gradually moved from no disc brakes at all, to mass-market adoption.
As with many of his contemporary bikes, Hyro has open dropouts; 100 mm front hub spacing and 135 mm rear hub spacing; and post-mount hardpoints. This leaves him in a funny little limbo in that it limits his possible upgrade paths.
Let’s start with the hubs first. Unlike everything else here, their interface with the bike is non-negotiable. There is no way to fit through-axle hubs on a bike with open vertical dropouts. That said, perhaps it’s testament to Giant’s construction methods that I’ve never had any problems with frame and hub rigidity, nor its symptom of brake rotor rub, over the last five years…despite running quick-release hubs. Besides, many 135 mm/100 mm QR-axle hub options still exist, and they’re not going away anytime soon.
While TRP’s Spyres are great mechanical disc brakes, they cannot overcome the inherent weaknesses of the brake cable: you still need quite a bit of hand force to get the brake calipers to actuate, especially from the hoods. The calipers themselves have rather stiff return springs, which can be potentially fatiguing on longer rides with lots of braking. Riding around the Philippines, where anyone and anything can become a sudden obstacle, any brake force multiplication you can get is welcome, in my opinion.
Four years on, with lots of kilometers logged, Hyro’s Shimano 105 5700 drivetrain is still strong, but aging. Shifting to the big chainring, even with fresh ones mounted, yields intermittent sticking in the left STI lever, although it improved after dripping some Boeshield T-9 into the mechanism. Also, having enjoyed Shimano’s new brake hood shape and profile after riding a Lynskey ProCross equipped with Tiagra 4700, I realized that the 105 5700 hoods are just a tad too bulky and wide for my hands.
With all this considered, I might as well go big and upgrade to a modern 11-speed groupset with hydraulic braking. That goal was on my mind for a number of years, but the cost had been prohibitive…until now.
The bulk of the expense of a groupset is in the STI levers. With hydraulic disc brakes, the brake calipers have to be sold in a set with the STI levers because the latter contain the master cylinders, which jacks up the cost even more.
Now that the road cycling world has largely moved to Flat Mount for its disc brake needs, I got a good deal on the ST-RS685 + BR-RS785 combo. Shimano calls this the “J-kit” version, meant for original equipment manufacturers.
A J-kit hydraulic brake system is pre-bled, and already has the barbs and olives hooked up to the critical end points. For the rear brake, all you need to do is affix the STI lever and brake caliper to where they should go, route the brake hose through the frame (if needed), and then link up the two hoses via this in-line connection exclusive to J-kit systems.
Done correctly, assembling a J-kit system into a bike should require no bleeding at all. Building this up should be interesting.
The BR-RS785 caliper is essentially a Deore XT BR-M785 unit for mountain bikes, remade for road use. The main difference is the banjo fitting gets swapped for an in-line brake hose connection. In case these BR-RS785s give up the ghost, it should be easy enough to replace them with any Shimano mountain bike unit.
The J02A finned resin brake pads boast half of Shimano’s IceTech technology. The idea is to help dissipate heat and combat brake fade under prolonged braking by radiating it to the atmosphere via fins and better materials. A metallic-compound J04C version of this pad is available, and these can be swapped with non-finned G02A or G03S pads if needed.
The ST-RS685 STI levers predated Shimano’s introduction of hydraulic braking into its road bike groupsets. The nomenclature does quietly indicate that they are Ultegra-level parts of the 6800 generation, meaning this is a 2×11-speed STI lever set.
Cosmetically, they look very similar to Ultegra ST-6800 levers, save for a taller profile and a touch longer reach. This was Shimano’s first attempt integrating a brake master cylinder and mechanical shifting into the brake hood. Steve Tan of “Hands on Bike” took a deep dive into the ST-RS685, and noted how the hydraulic piping is built into the aluminum bracket, lending even more of a “prototype” feel. When Shimano finally baked hydraulic braking into the Dura-Ace R9100 groupset, it returned to lightweight resin for the brackets.
The ST-RS685 has this white stopper wedge installed on the right lever as packaged. When in place, this prevents both shifting and braking actions, thus keeping the seal on the J-kit sleeve connector intact before the hydraulic lines are mated.
This angry, angular looking thing is a Shimano 105 RD-R7000-GS rear derailleur. Shimano yaks about the Shadow technology offering better protection in a crash, but it doesn’t tell you that rear derailleurs of this ilk have a much stronger P-knuckle spring, increasing chain tension and reducing chain slap. This is the real step up from the older Ultegra RD-6800 and 105 RD-5800 units, and there should be no problems mating this with the ST-RS685. It’s officially rated to handle a 34T biggest cog.
Also borrowed from mountain bike tech is the cassette. The CS-HG700-11 unit sports an 11-34T range. Since Shimano didn’t resort to the 1.85 mm freehub body extension on mountain bikes, this particular 11-speed cassette will fit on a 10-speed freehub body, because the 34T cog is large enough to be dished over the spokes. No other 105-level 11-speed cassette has this kind of backwards compatibility, and this will allow me to keep using my current Giant S-X2 wheelset for a little longer. Its gear jumps are relatively big, though, with many cogs in two-tooth increments.
Last on the drivetrain upgrade parts list is the Shimano 105 FD-R7000-F front derailleur for braze-on mounting. This contains the cam-actuated mechanism on Dura-Ace R9100 and Ultegra R8000, but was actually first seen on the 105-level FD-5801 unit, which was a mid-life update of the original long-armed front mech. These new front derailleurs now come with onboard cable tension adjustment, negating the need for an in-line barrel adjuster.
A number of friends have suggested replacing the 2014 TCX frame with something more modern. I don’t see why I should. Sure, it’s a dead end, but it’s not hopeless, and this is a good opportunity to push Hyro’s potential to the limits of his design.
I will be documenting the build process here. Watch this space.
the accidental randonneur 