First Ride: Cobble bashing on the Trek Domane SLR

KORTRIJK, Belgium — Yep, I had the same thought you did when I saw the new Domane and the front decoupler: Am I going to eat it like Hincapie did in the 2006 Paris-Roubaix? The steerer moves, after all. Flex leads to fatigue, and fatigue leads to failure, so it’s natural to be a bit wary.

But now I’ve seen it up close and have taken it up the Oude Kwaremont. I dove into corners, stood up to sprint, and hit potholes on purpose to see what the new Domane SLR would do. First and foremost, I can tell you this: You have nothing to fear. Trek designed the fork’s steerer specifically for this function, and because the entire steerer flexes — rather than relying on flex just at the top — force gets spread throughout the carbon construction.

Plus, despite the horror stories we’ve all heard, carbon is actually very difficult to break. That’s what’s so great about it: a well-designed layup can flex without breaking and withstand impacts. Can it fail? Sure. Is it likely to? No.

There are three key components to Trek’s new Domane: the adjustable rear IsoSpeed decoupler, the new front IsoSpeed decoupler, and the IsoCore handlebar. Each one flexes or dampens to keep road vibrations at bay, which has been the signature of the Domane since the first iterations in 2012. The rear decoupler adjusts using a sliding spacer between the seat mast and the seat tube: Lower it and compliance increases. Raise it and compliance decreases. If you like a stiffer ride with just a bit of flex, loosen the bottom bolt, slide the adjuster up, and pedal away. If you’re spending the day on washboard and/or cobbles, lower the slider to any position.

The front decoupler does not adjust, but it doesn’t really need to. You don’t want a whole lot of movement up there anyway, since you’d lose the road feel and have a sloppy steering problem on your hands. Trek relies on steer tube flex fore and aft, and a specially designed sleeve with bearings inside the head tube, to get what the company believes is the right amount of flex. There are three total bearings in the headset: one at the bottom cup — which does not move in the decoupling process — and two at the top, on the top and bottom of a preload sleeve. That sleeve and the bearings sit within a pivoting damping cylinder that’s fixed at two points to the head tube.

The IsoCore handlebar has a layer of a proprietary rubber between layers of carbon to dampen the last of the vibrations that could potentially reach the rider. Think of it this way: If the decouplers are chain saws, the IsoCore handlebar is the scalpel.

It’s an interesting bit of technology, one that should be met with expected skepticism. My primary concerns heading into the ride were the loss of ride feel or any connection to the road, and flex during hard efforts and climbing.

Bike Setup

Trek offers several fit and geometry options, so to be clear, here’s what I rode:
— Size: 56cm
— Pro Endurance Geometry
— IsoSpeed adjuster position: just past halfway, edging toward the stiffer end
— Bontrager R3, 700x28c (tire pressure: 70 psi )
— Wheels: Bontrager Aeolus 3 TLR D3 (19.5mm inner rim width)

Each setup decision can affect how well this bike rides, but that’s the beauty of it: there are so many options for setting the bike up exactly as you want it for the conditions that you’re likely to find that sweet-spot.

The Ride

Due to time constraints, I was only able to get about 40 miles on the Domane (I’ll be doing a long-term review once I have more rides on the bike). Part of those 40 miles included the Oude Kwaremont, the cobbled climb on which Fabian Cancellara wowed the Tour of Flanders crowd with a monumental effort to chase Peter Sagan to the podium. It was my second time up the Oude Kwaremont in as many days. On the first day, I rode a very nice but super stiff Focus Cayo; on day 2 I was on the Domane.

I was a minute and a half faster on the Domane going up the Kwaremont.

Now, before we lay that miracle at the feet of the Domane (or launch a discussion about my Boonen-esque cobble skills), let’s not forget that discrepancy has a lot to do with better drivetrain gearing (1X SRAM drivetrain on the Focus versus Dura-Ace with an 11-28 in the rear and 53/39 up front), fresher legs, and fewer crowds on the day I rode the Domane.

But the difference between the Cayo and the Domane is still remarkable: Whereas I found myself struggling to maintain consistent power over the cobbles on the Focus, the Domane soaked up so much vibration that I could get more out of my legs. Where the Cayo sent so much vibrations shuddering through my upper body that steering and braking became difficult, I felt completely in control and my neck and shoulders were no worse for the wear on the Domane. No disrespect at all to the Cayo — a stiff race bike you’ll likely enjoy everywhere but on consistent chatter — but it was immediately clear which bike was made for the cobbles and which one was not.

Like previous iterations of the Domane, the new SLR has a fairly tall head tube as part of the endurance geometry that keeps the rider sitting slightly more upright. The size 56cm endurance geometry Domane has a 175mm head tube; compare that to a 140mm head tube on the Madone. That has, in the past, led to a significantly flexy head tube, and that does not seem to have changed much on the new version. But the front decoupler also doesn’t appear to have compounded the issue at all; it is not noticeably more flexy than older model Domanes. So while Trek has never made any claims of precision steering on par with the Emonda or Madone, you should expect a bit of a vague steering feel.

With a long, 1,008-millimeter wheelbase and a low bottom bracket, though, the bike generally carves pretty well. You’ll notice the soft steering when you’re out of the saddle on climbs or sprints, not necessarily when you’re pounding out miles on smooth pavement. And you won’t notice or care at all about it when you’re on the cobbles or washboard dirt roads; the silky smooth damping more than makes up for any steering deficiencies.

I almost forgot about the IsoCore handlebar, which is easy to do considering all the other new tech packed into this bike. It’s a comfortable design in the drops, on the hoods, and on the tops, and my bars were double-taped for plenty of cushion. I didn’t necessarily notice the vibration damping that Trek promised with the layer of rubber between carbon layers, perhaps because I was being jostled around on the cobbles. It seems the vibration damping promised in the handlebars would be most noticeable on my home roads in Colorado, so we’ll save that for the full review.

Trek has engineered perhaps the best cobble bike we’ve ever seen. The question is, will the Domane be only a cobble bike? Or is it stiff and versatile enough to be the only bike in your stable? Stay tuned for a long-term review in the coming months.