Review: Trek Domane 4.5

While many brands have introduced “endurance” road bikes over the last few years, few have taken the idea to quite the extreme as Trek. The Domane was developed with considerable input from Swiss pro cyclist Fabian Cancellara, who is known for his steam-engine riding style, using his massive power output to crush cobblestones in the fabled Spring Classics. He is said to enjoy the bike so much that he rides it year-round, even in the Tour de France, choosing it over Trek’s racier Madone model.
The frame features the intriguing IsoSpeed decoupler, an ingenious system that separates the seat tube from the top tube and seatstays, and allows the seat tube to flex and pivot at the mounting point. If you stand next to the bike and put your weight on the saddle, you can see the seat tube flex slightly, but while riding it is imperceptible until you hit a bump.

Make no mistake: IsoSpeed is not a suspension system, and this is still a high-performance machine. If you’re expecting something akin to a suspension seatpost, think again. The frame’s ride quality is distinctly carbon—a muted road feel with less of that high-frequency vibration you feel from some aluminum frames, but still generally stiff.

IsoSpeed makes itself most noticeable when crossing railroad tracks or other high-speed, sharp impacts that would normally require you to lift or shift your weight on the saddle to avoid being bounced. Not having to do that means you can keep your cadence smooth and the power high. The system seems so extreme some might think it’s a gimmick, but I’m convinced. Trek is as well—the technology will soon be adapted to its line of hardtail mountain bikes.
At the other end of the bike, the fork deserves some of the credit. It was developed with an asymmetrical steerer tube that is slightly thicker side-to-side than front-to-back, giving it a touch of compliance, but it never felt soft or shuddering.
The difference between the Domane 4.5 and the higher-end models is in the stiffness of the carbon fiber itself, and that this version uses a standard 27.2mm seatpost rather than a seatmast that is integrated into the frame. I actually prefer the standard post, as it can be swapped for countless alternatives and provides an easy spot to clamp the bike in a workstand.

Other frame details include a spot for Trek’s DuoTap hidden speed and cadence sensor, an integrated chain guide to eliminate dropped chains and more generous tire clearance than most frames. It also has removable fender eyelets, so you can keep the clean look if you’re not using them. For an even smoother ride, you can ditch the tubes and set up the Bontrager Race wheels tubeless—another technology that is easy to dismiss until you try it, as I did for a review in Issue #22.
It would be a mistake to write off the Domane as a “comfort” bike for weekend warriors. Despite accommodations for a smooth ride, it is as stiff and race-worthy as I could ask. Yet the slightly longer wheelbase makes it extremely stable, and it’s one of the few bikes I’ve ever plunged downhill at 40mph with a crosswind while still feeling relaxed. The fit adds to the comfort factor, as the slightly taller head tube gives you a more head’s-up position than Trek’s race bikes. Paired with a set of shallow-drop Bontrager handlebars, I felt great in each of the riding positions, an essential element of a long, comfortable ride.
The adage “laterally stiff and vertically compliant” has gone beyond cliché to become something of a running joke in road bike circles. The notion that a bike can be a stiff-as-heck race machine and still be comfortable over rough pavement on long rides is not unlike a unicorn—a magical beast that surely can’t exist. But on the Domane, initial acceleration is direct and instant, with the massive, squared down tube and BB90 bottom bracket all but eliminating lateral flex.
Back in Issue #16 I reviewed the Volagi Liscio, which also features an unusual seat tube arrangement—the seatstays bypass the seat tube and connect to the top tube. While the Liscio was smoother than the Domane in a straight line, it can’t compete with the Domane in terms of power transfer and handling accuracy. The Domane makes no sacrifices in these areas.
The Shimano Ultegra build kit performed flawlessly, as I expected. The compact crankset paired with an 11-28-tooth cassette offers tons of range for tackling the steepest pitches. The 105-level brake calipers offer power to spare, as a single finger is often enough to bring the bike to a stop.
Hitting the street for less than $2,800, the Domane 4.5 struck me as a steal, considering the high-end frame technology and the smart build kit. While it will likely be pitched to riders looking for a high-performance ride for centuries and gran fondos, the Domane is a race bike at heart that won’t beat you up on the weekdays.

Vital stats

• Price: $2,730
• Sizes Available: 50, 52, 54, 56, 58, 60 (tested), 62cm
• Weight: 18.12lbs