TREK DOMANE SL4
£2100 A well-equipped bike that could lose some weight
When Trek first debuted the Domane with rear IsoSpeed, the endurance bike market changed for good. The advent of front IsoSpeed then balanced the ride feel of bikes it was fitted to because the original front end always felt firmer than the rear.
Our new Domane SL4 is the cheapest 500 Series carbon Domane with front and rear IsoSpeed and disc brakes. It’s the cheapest carbon disc Domane full stop because the only bikes below it in the range are the rim brake-only Domane AL2 and AL3, at £595 and £750 respectively. Trek says that the all-carbon frame and fork with double IsoSpeed is much lighter than the preceding aluminium Domane frame but in 56cm size, our SL4 weighs a not inconsiderable 10.01kg.
The current Domane’s frameset has more angular, oversized tubes than before, including some with truncated airfoil shaping. The broad top tube (1) houses both IsoSpeed systems and Trek’s new hidden cable design. All four control lines turn sharply after exiting the bar tape and pass through a guide beneath the stem, then alongside it before plunging vertically in to individual holes behind the headset and IsoSpeed. It looks unwieldy at first, but doesn’t affect the controls or steering and does tidy things up.
As well as utilising the void within the huge head-tube area, Trek didn’t let the drain pipe-like down tube go to waste. A lever that protrudes to the right of the down tube bottle cage can be turned 90 degrees to release a panel, which takes the cage with it, revealing a cavernous space (2). As well as plastic mounts for small spares, it contains a 30cm long fabric roll designed for an inner tube, tyre levers, CO2 cartridge and inflator head that is a snug fit when empty. If you
need more storage, the Domane has a third bottle mount beneath the down tube, and mudguard mounts complete its practicality.
With so much of the bike’s value tied up in that frameset – Trek retails the SL Disc frameset for £1900 – the component specification is generally of a different level to its immediate competition. The drivetrain is Shimano Tiagra 10-speed with a Praxis Alba M30 chainset, and the wheels, tyres and finishing kit are all Bontrager. Shifting is good, if occasionally clunky under load, but the brakes have typical Shimano power.
Aesthetically, the new Domane looks stunning. On the road, the Domane’s stability is immediately apparent, its slack 71.9-degree head angle and 1008mm wheelbase giving the impression that it’ll roll straight over any road impediment. Supplied with 32mm tyres that measure 33mm on the generous Affinity rims, I tested with 70 to 75psi, which only served to enhance the bike’s planted feel. Max clearance is 38mm, so you could fit something a little wider and grippier and leave tarmac far behind.
On the flat, and especially downhill, the Domane is incredibly confident and covers ground with surprising speed. But as soon as gradients begin to rise, the effort required to sustain my expected speed soon becomes overwhelming and speed falls away. The frameset has incredible torsional rigidity, but as responsive as it is, your efforts are absorbed by the beefy wheels and tyres (3). It’s a little disappointing, and even its inspiring handling doesn’t make up for the additional uphill workout.
IsoSpeed has a positive effect on the Domane’s handling, helping the tyres to maximise grip. But compared to the seated comfort from the cushy Arvada Comp saddle and carbon seatmast-topped IsoSpeed Decoupler, the bump smoothing feeling through the handlebar is no more refined than with the TCR and its lower tyre volume.
We love its solidity, confident handling and practicality, but wish it was faster. A simple tubeless conversion, or costlier wheel upgrade, should revive its climbing ability.
With fantastic looks and lots of neat touches, the SL4 deserves to go faster