Disc brakes are coming to the Domane.
Trek announced on Thursday night that two versions of its its endurance road bike will be available with the powerful brakes effective immediately. The new disc-ready Domane 4.0 and 6.9 models will feature improved tire and fender clearance and Trek’s Closed Convert dropouts, which allow users to swap between thru-axles (142×12 rear and 15mm front) and traditional quick releases, maximizing wheelset compatibility.
Only the 4.0 and 6.9 builds will get the discs at first, using Shimano’s new mechanical discs and the pricier R785 Di2 hydraulic systems, respectively. As Shimano debuts a wider range of disc groups, and SRAM returns to the disc party, expect disc-ready Domane options to grow. Retail price for the 4.0 is $2,100; $7,900 for the 6.9.
VeloNews received a Domane 6.9 Disc test bike in advance of the official launch. Read on for our first impressions.
Domane Disc in the shop
Trek has adopted most of the latest road disc technology trends, most importantly the inclusion of thru-axles — seen by many as a requirement for an effective disc system.
Thru-axles stiffen the frame/wheel interface dramatically, preventing any shifting of the wheel in the dropout as well as noticeably decreasing flex. They decrease disc noise — no annoying ting-ting-ting of rotor touching brake pad — and improve safety, as the forces acting on front wheels, in particular, can cause a poorly-attached quick release wheel to eject itself from the dropouts.
The Closed Convert system is clever, and an excellent choice, given the transition phase that discs are currently experiencing. It allows for the use of the vastly superior 142×12 thru-axle standard, but can also be easily swapped to accept standard quick release hubs. That means riders with extra wheels don’t necessarily need to enlist Craigslist or eBay right away. It also opens up the options for aftermarket wheels.
Swapping to quick release mode sets the rear end up with 135mm spacing, so any current quick release mountain bike hub will fit.
While Closed Convert is clever indeed, it does not solve one of the major problems with road discs: slow wheel changes. For this bike in particular it’s not a major issue, as the Domane is not strictly race-oriented, but down the road the problem must be solved. Some new thru-axle options, like those from Focus and Manitou, function much like a standard quick release, offering much faster wheel changes.
For now, the Closed Convert system is great. But once the industry passes through the disc transition phase, it must settle on one of the quick-releasing thru-axle designs. Trek says it will continue to reevaluate thru-axle options. “The future of thru axle is wide open,” Trek road brand manager Michael Mayer told VeloNews. “We are paying attention to all thru axle options at this point and right now believe that the DT Swiss RWS and the Bontrager Thru Axle are the best option for security, stiffness, cost, weight, and ease of use.”
The seat stays on the new disc models look similar to those found on the Madone, which also moves the brake off the seat stays and onto the bottom bracket area. Removing the brake arch takes away one of the pinch points for running big tires, so it’s no surprise that the Domane Disc models will take larger rubber. We threw a 30mm tire into our test Domane 6.9 Disc and it fit, barely. The standard Domane will barely take a 28mm tire.
Geometry appears otherwise unchanged, mimicking the standard Domane Endurance geometry — similar to the Madone H2 geometry, with a taller head tube and overall less aggressive position.
Trek did make some odd component decisions, though, at least at first glance. Most obvious is the decision to ship the Domane Disc models with 160mm rotors, despite Shimano’s assurances that 140mm is all we need on the road. When asked about the spec, Mayer said, “160mm is purely a safety measure. Basically, we need the 160mm rotors to meet the heat specification of our disc brake vendors.”
Perhaps Trek’s lawyers are simply a bit more cautious than Shimano’s. The Domane frames will accept 140mm rotors — it comes stock with 160mm adapters in place. Our testing has shown that for most riders, the decreased power of the 140mm rotors is actually a good thing; they seem to offer the best balance between power and modulation. Larger riders may want to stick with the 160mm version, though.
Tire spec is another head-scratcher. Bontrager’s 25mm R3 is a great all-around tire, but seems tiny with the Domane Disc’s new increased tire clearance, particularly given the relatively narrow rims that come stock. A bike like this begs for something larger, in the 27-28mm range, run at low pressure. The problem seems to be out of Trek’s hands, though, as Mayer explained: “We have some selling restrictions because of CPSC clearance models. We feel tire size is definitely a preference and 25c a great all around size. We cannot say we recommend a bigger size.”
Luckily, the CPSC doesn’t regulate VeloNews, and we can recommend a bigger size. Buy some 28s.
Domane Disc on the road
We have quite a bit of experience with the Domane line, including a full test of the 6.9 last year in Velo Magazine, and another of the aggressive, pro-geometry Domane Classics Edition in the upcoming June issue of Velo. It’s a platform that is universally accepted as one of the best endurance frames available; the ISOSpeed decoupler does work, and works well. The one complaint we have, and others have had, is the unbalanced feel of the bike, precisely because the rear end is so comfortable. The front feels harsh in relation. But at least your bum is comfortable, right?
The Domane Disc 6.9 that arrived at VN headquarters a few weeks ago feels largely the same. It has Trek’s Endurance geometry, providing a comfortable, albeit quite upright, riding position.
The Shimano discs are a dramatic improvement over any rim brake, even with the slightly grabby 160mm rotors. They are confidence inspiring, utterly controllable. They’d be even better with a bigger tire, too.
Weight is quite reasonable, 16.52 pounds, which will perhaps help quiet those concerned about the increased mass of disc systems. A swap to XTR calipers (not Shimano-recommended, but possible) would drop another 115 grams. Lighter wheels would put the bike near the 6.8kg UCI limit.
Like the standard Domane, the 6.9 Disc should attract riders looking for that endurance geometry without a major sacrifice in efficiency. This is still a road bike, not a gravel grinder. But the disc version does afford a good helping of versatility over the standard model, so those looking to do a bit of dirt road exploring, or anyone keen on the benefits of discs, should certainly give it a second look.