This is part 2 in a series of articles about our experiences with disc brakes for road. It's been a bit longer than we intended since our introduction to this series. The reasoning for this will become clear as we go on and may speak to the viability of the road disc platform itself. Read part one here.
For starters, let's talk about our test machine. As previously mentioned, we built a Gaulzetti Corsa in disc configuration. Aside from brake mounting, this Corsa differs not at all from every other bike of the current generation that we've built. In this case, our test bike is a 51cm stock geometry Corsa that we painted in a custom Candy Blue with Embro Green logos. For the fork, we specified the Enve Composites tapered disc fork - again, the same fork we normally use, just in disc version. We chose the readily available Avid BB7 SL calipers with Avid HS01 6-bolt discs in 140mm for our initial test brakes. We built the bike up with a Campy Chorus groupset with Deda 35 cockpit parts and a Selle Italia Superflow 135 saddle. Pretty standard stuff around here for Gaulzetti builds, really, but that's where the simplicity ended.
We ran into huge issues trying to source wheels for the test. We wanted something disc-specific, meaning we wanted to shy away from wheelsets that were essentially disc versions of non-disc wheels. More specifically, we wanted something without a rim brake track and we wanted to start with something out of a box, as opposed to a custom wheelset. This proved elusive. In the end, we settled, reluctantly, on a set of Easton EA90XD wheels. Our reluctance was not due to a prejudice against Easton wheels, but rather because these are billed as a cyclocross-specific tubeless wheel; not the road-specific option we originally wanted. But, they were the closest to our ideal that we could find and, in the flesh, these wheels are good looking and after a few initial rides seem stiff, sturdy and generally competent and nicely-riding wheels. Plus, they have a wide rim, which is a perfect match for our preferred 25mm tires, in this case the Michelin Pro4 Endurance. The XD wheels are also tubeless road compatible, which adds another element of flexibility for setup if tubeless is your thing.
Despite our good first impressions of the wheels, they only exacerbated our build issues. We ordered the EA90XD wheels in the Shimano/SRAM flavor and also ordered an Easton freehub body for Campy so as to make it compatible with our build kit. We discovered that the Campy freehub bodies available for Easton wheels are incompatible with the hubs on the XD wheels, which Easton calls the M1 hub. Our plan B was to use a Dura Ace 9000 cassette, which while not ideal to some, and downright sacrilegious to others, would be functionally compatible with the Campy 11 speed drivetrain. Alas, this proved impossible as well. We installed the 9000 cassette only to realize the Easton freehub body for Shimano was not 11 speed compatible. This elicited a call to Easton, who informed us that 1) they did not and would not be making a Campy freehub body for the M1 hubset and 2) their 11 speed Shimano/SRAM cassette body for these wheels would not be available for at least another month.
So, we ended up with a nice set of wheels that were, for all intents and purposes, useless for our desired build. We don't blame Easton for this inconvenience and feel it's worth noting we've found their customer service to be top-notch. They quickly responded to our issue and put an 11S freehub on backorder for us. Also, wheel companies are not, and should not be, the prime movers for road disc, nor is it reasonable to expect them to be able to react immediately to all the current shifts in the market, across their entire lines. But, the reality is that we had a wheelset that we couldn't readily use for the project.
So that's the end, right? Of course not. We were not going to let a little thing like this stand in our way of disc brake road bike glory. After all, we had group rides and races to attend and we needed to do this astride our Candy Blue Corsa. Now, we have to stress that what we're going to describe next is something you not attempt and something we would never do if this bike was destined to a customer. By virtue of some careful machining, we were able to modify Easton's Shimano freehub body to accept all 11 cogs on the Dura Ace cassette. This process can go poorly and result in bad things if not done properly. Fortunately, it worked out and our Easton wheels became 11 speed compatible with good clearance and no alignment issues to speak of.
So, with freehub modified, cassette installed and any warranty on our brand new wheels blown absolutely to smithereens, we installed the wheels on our frameset and moved to disc brake setup. We opted for the BB7 SL cable-actuated disc brakes because they are readily available and time-tested, having been used in some configuration on mountain bikes for at least a decade. While there are some intriguing products on the horizon, at the time of this writing there are no viable road hydraulic disc systems available. To be clear, we do not consider the currently available hydraulic conversations to be viable. Some decorum must be maintained and a large, unsightly hydro unit mounted on our stem is a bridge too far.
The BB7 SL proved easy to set up and adjust, once you understand the fundamentals of centering the calipers and then adjusting each pad accordingly. Most disc cable setups will require use of full length housing for the front and rear brakes and ours is no exception. With increased cable housing comes the reality of increased cable drag. For this reason, we paired our setup with SRAM's Slickwire XL brake cable and housing system. This system uses their PTFE coated cables paired with extra long, compression free housings. When set up, the brake actuation was incredibly smooth and effort-free; shockingly so, actually. How this system fares over the long-run will be one of the main criteria we evaluate as our test continues.
There are a couple things worth noting about the BB7 SL setup: First, it is absolutely more finicky in the setup than road calipers - there's just no other way to put it. Now, some of this is undoubtedly due to our experience level with discs versus rim calipers, but we feel its an inescapable fact that disc road brakes require more time and effort, setting and resetting, to arrive at the desired outcome. Secondly, riders who don't like much throw in their brake levers should not consider this system, period. In order to get our wheels to spin freely we had to set up the BB7 brakes to allow a large amount of lever pull.
We've always been taught that some level of initial caliper / disc contact is acceptable on mountain bike builds; that this rubbing clears up after just a few applications of the brakes. We've also noted over the years that most mountain riders accept some level of disc-on-pad contact as standard operating procedure for their bikes. This is absolutely NOT ok on the road. We'll state it clearly: for disc to be at all viable on the road, it is imperative that the disc never be in contact with the caliper without the express input of the rider. No level of friction or noise should be acceptable on high end road builds, ever. On our setup, the only way we could avoid this was to set the brakes fairly loose, with ample lever throw. Fortunately for us, this is our preferred setup, but for those favoring a tighter brake feel will find this particular setup a non-starter.
Initial Ride Impressions
We did finally get the test bike set up to our standards, with wheels spinning freely, derailleurs accurately hitting all the cogs and the bike liberally oozing Candy Blue badassery. The first ride was exactly the sort you want, which is to say it was uneventful. The bike rides like a Corsa should: stiff and very reactive to power inputs with good road feel, fast but stable handling and just the right amount of personality and attitude. In fact, the first ride was characterized by a lack of anything noteworthy at all. Perhaps the greatest lesson to be gleaned from riding the disc Corsa, so far at least, is just how infrequently we get on the brakes in normal riding conditions and how similar the disc brakes feel to standard calipers in most situations.
We think this is worth keeping in mind for the rest of this test: That in normal riding conditions, disc brakes are altogether unremarkable. They activated smoothly, with little lever effort and progressive, natural-feeling modulation. In fact, for most of our first rides, the only reminder that we were activating disc brakes instead of rim brakes was the distinctive metal-on-metal noise of pads squeezing discs. Similarly, we did not note any marked increase in braking power as compared to dual pivot rim calipers. One thing we did note was that the rear brake was a bit grabbier than the rim brakes we've used recently. We first noticed this in a series of 90 degree turns through corners still strewn with winter sand build-up. In a couple cases, the rear wheel locked up momentarily as the tire skidded across the sandy ground as we executed the turn. Of course, this is attributable to rider error, specifically not being used to the amount of braking pressure required on this system. Nevertheless, the rear brake does appear more powerful than rim brakes, or at the least, stickier. For the moment, we'll reserve judgement as to whether or not this is positive.
The test will continue and we'll be delving deeper into this project over the next few weeks.