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.
My 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, my SL4 weighs a not inconsiderable 10.01kg.
The Domane’s cables are routed through a guide below the stem. David Caudery / Immediate Media
The current Domane’s frameset has more angular, oversized tubes than before, including some with truncated airfoil shaping.
The broad top tube 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 drainpipe-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.
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.
Trek’s IsoSpeed decoupler permits seat tube flex. David Caudery / Immediate Media
With so much of the bike’s value tied up in that frameset – Trek retails the SL Disc frameset for £1,900 – 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.
The new Domane looks stunning, and on the road the Domane’s stability is immediately apparent. Its slack 71.9-degree head angle and 1,008mm wheelbase give 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.
A good-looking ride that’s let down by its overall weight. Robert Smith
On the flat, and especially downhill, the Domane was incredibly confident and covered ground with surprising speed. But as soon as gradients began to rise, the effort required to sustain my expected speed soon became overwhelming and speed fell away.
The frameset has incredible torsional rigidity, but as responsive as it is, your efforts are absorbed by the beefy wheels and tyres. 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 Giant’s TCR and its lower tyre volume.
I 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.
Trek Domane SL4 geometry
Seat angle: 73.3 degrees
Head angle: 71.9 degrees
Seat tube: 50.1cm
Top tube: 54.5cm
Head tube: 17.5cm
Fork offset: 4.8cm
Bottom bracket height: 27.3cm
Bottom bracket drop: 7.8cm
How we tested
This bike was tested as part of a five bike grouptest of bikes priced at around £2,000 that have been searched for the most online in the past year and are still available.
The bikes were tested against each other to find out which one provides the best blend of comfort and performance.
Bikes also on test:
- Cannondale SuperSix EVO Carbon 105
- Giant TCR Advanced 2 Disc
- Canyon Endurace CF SL Disc 7.0
- Ribble R872 Disc