The IsoSpeed
“decoupler” on 
Trek’s new Domane classics bike breaks new ground in its approach to smoothing out
the ride over rough roads. Skeptics dismiss it as being akin to a flexible
seatpost (or even a suspension post) integrated into a more expensive and
overly complicated frame but after a four-hour ride* including several of Ronde
van Vlaanderen’s
fabled cobbled climbs, we can emphatically say that it’s not
what you think – it’s probably better.

IsoSpeed is no gimmick

First things first: the IsoSpeed seat cluster on the Domane really
works. In fact, it works far better than we anticipated and doesn’t
feel like we imagined it would. Belgian cobbles are genuinely less violent on your rear end by a
substantial amount – sort of like switching from 60tpi tires to 220tpi ones, times 10 – and reasonably high-quality
road surfaces turn to glass. It’s the closest thing we’ve ridden to a properly suspended road frame in terms of small-amplitude impact absorption, and
IsoSpeed’s ability to, well, isolate your rear end from road harshness is so
effective that at times, it’s almost eerie.

The movement is essentially what frame designers try to work into their
bikes already but in a greatly amplified fashion – you don’t just feel the flex
(in a good way) in the saddle, you can see it, too. Whereas those other
bikes are essentially a cantilevered spring from the seat cluster up, the spring
length of the Domane is the entire seat tube. With two bottles mounted, you can
actually see them moving towards each one on a big hit as the seat tube adopts
a slight ‘J’ shape under load.

That being said, the motion – which is undamped aside from whatever is
built into the seat tube itself – never seems excessive,
at least not for this tester’s 72kg weight. The movement is very controlled,
surprisingly lacking in bounciness and essentially invisible except for the
fact that things that would normally jolt you are tamed down. There
is, however, an extremely slight rhythmic fore-aft motion that we noticed on
other riders’ test bikes but it’s so slight that we never noticed it
ourselves and none of the other journalists on site made mention of it.

Despite the motion of the seatmast cap being both up-and-down and fore-and-aft, any change in cockpit length was so brief as to be virtually imperceptible. If you’re the type of rider who cherishes an intimate connection with the road surface through every contact point, though, the Domane will disappoint you. IsoSpeed isolates you so completely from the pavement that in most situations you barely feel anything at all through the saddle.

The Domane feels like a regular, well designed, ‘normal’ bike in every other respect. It pedals at least as efficiently as a current Madone (Trek claim even more so, in fact), the front triangle stiffness and steering precision feels inline with other manufacturers’ flagship carbon race bikes (again, the Domane fork is supposedly stiffer side-to-side than a Madone’s) and it’s very light, with the IsoSpeed bits comprising just 50g of the claimed 1,050g 56cm frame weight. Our 52cm test bike was just 7.01kg (15.45lb), as pictured but without pedals – not bad at all for something so comfortable.

The IsoSpeed concept is no gimmick – it definitely works

IsoSpeed is awesome but it
doesn’t extend tip-to-tail

Trek’s work on the front end – with the fork’s radically raked geometry,
aggressively tapered blades and rear-facing dropouts, and the IsoZone
cushioning in the handlebar – is readily apparent, too, but the improvement here over
a regular Madone isn’t nearly as dramatic. Even Trek claim just a modest seven
percent bump in fork comfort as compared to nearly 50 percent out back. 

Therefore, hitting the cobbles at speed still rattles your hands – just
perhaps slightly less so. Road texture that we couldn’t feel at all through the
saddle was still transmitted up through our hands. It wasn’t a
particularly offensive sensation – realistically, the Domane front end ranks
very highly in terms of comfort – but all the same, it’s a slightly disjointed
feel front-to-back that some might find off-putting. On the positive side, the
aforementioned riders who might bemoan the near-total lack of road feel will
find it here.

As promised, the new Bontrager RXL IsoZone handlebar provides a noticeable boost in cushioning without adding exterior bulk

Even more apparent is the Domane’s lower frame (down tube/bottom bracket/chainstays) stiffness. This keeps the drivetrain very efficient but also sends bigger impacts straight into the bottom of your feet. As BikeRadar’s US editor, Matt Pacocha, says, racing on cobbles is like “someone pounding on the bottoms of your feet with sledgehammers”. In fairness, we didn’t notice the issue on more typical road surfaces and many riders may never subject themselves (or the Domane) to that sort of torture test, anyway.

Fit handling: Not as
tall as we initially thought, ultra-stable geometry

Trek road product manager (and former team liaison) Ben Coates touts
the Domane’s new Endurance Geometry as offering “all of the stability
that you’re looking for paired with all of the raciness that you’ve come to
love”. Trek have certainly nailed the stability half of that equation on the
Domane. Relative to the Madone, the chainstays are roughly 1cm longer, there’s
a full centimeter of additional bottom bracket drop on some sizes (the Madone
was already among the lowest among major manufacturers’ stage racing bikes),
the head tube angle is 1-2° slacker and the wheelbase is about 2cm

As a result, the Domane is incredibly stable, particularly on very
rough and slippery sections of road that would normally conspire to ricochet
the front and rear wheels in different directions. Sitting up to strip off
layers is child’s play and even riding no-handed in crosswinds is seemingly
less dramatic – with 50mm-deep wheels fitted to our test bike, no less.

However, Trek contend that the increased fork rake (48-53mm, depending on size) still maintains “the handling of a race bike”. Indeed, the
greater rake does offset the increase in trail relative to a Madone nearly
completely (varying by just 0.1-0.4cm depending on size) so the bars feel
hardly heavier in your hands when initiating a turn. However, it’s impossible to completely mask the longer rear end and

The new Trek Domane fork features radically forward-swept legs that flex a bit more than straighter legs under impact 

The Domane obediently followed the directed path on just about every
road surface we threw at it but some riders might actually find it to be a bit too stable. It still rails
corners well once you set an arc but it’s not quite as easy to alter your line
in mid-stream, so crit racers looking for additional cush should look
elsewhere. That being said, we’ve long found we can corner faster on slightly
softer bikes on account of the additional traction and we’d bet IsoSpeed will
only enhance that, especially with deteriorating road conditions.

Fit-wise, the Domane is certainly taller up front than a comparably sized H2-fit Madone. Head tube
lengths increase by 5mm (as on our test bike) to 15mm (on the
largest sizes) though it’s a cumulative effect with the increased bottom bracket drop. Provided you don’t run a particularly aggressive position,
though, most riders should still be ok with the stem slammed and a short headset cone

Is the Domane for me, or
should I go with a Madone?

The Domane vs Madone discussion essentially revolves around three things:
ride quality, fit and handling. Shopping for a Trek and looking for a faster
handling machine, a more aggressive position and a firmer ride? Easy – go
Madone. Otherwise, the Domane’s superior comfort, more sedate handling and
more accommodating position is better suited to how most road riders actually
spend their time. That the Domane is otherwise so impressively efficient and lightweight
blurs the lines further but ask yourself what you’re really going to be doing
out there and we suspect the answer will be a little clearer. 

* As we’ve only ridden the Domane for four hours and our test bike had a custom spec, we’re going to hold off giving it a score at this stage. Look out for a full review on BikeRadar once we’ve put some miles on a production model.