Trek Domane+ SLR 6 review

The Trek Domane SLR 6 is designed to pack in the ride qualities of non-assisted Domane endurance bikes with the benefit of pedal assistance.

The bike uses a new TQ Harmonic motor, delivering 50Nm of torque, complete with handy hood-activated remote control buttons.

In testing, the ride proved as smooth as a Domane’s should be, and the assistance was generous without being overpowering.

Trek Domane SLR 6 frame details

Trek is now onto its third iteration of the electrically assisted Domane . The original used Bosch’s powerful but weighty CX mid-motor, which gave the bike a hefty 17.5kg weight.

Next came the ultra-light Fazua mid-mount system, which helped reduce the weight to a respectable 13.8kg (58cm).

This latest generation switches to the new TQ Harmonic Pin Ring electric bike motor and integrated 360Wh battery for a complete weight of 12.56kg (58cm), making this the lightest Domane yet.

TQ claims the motor weighs in at just 1,800g including the battery. Its compact dimensions also mean the Q-factor (the distance between the outside faces of the cranks) of 135mm is slim and around the same as a regular road bike (anything around 140mm is standard).

That means unlike some of its predecessors, this Trek feels very much like a non-assisted bike.

The carbon frame features Trek's IsoSpeed decoupler to cushion the rear end of the bike.

The Domane faithfully follows the tube shapes and aero-profiling that debuted with the latest fourth-generation Domane SLR. There are Kammtail profiles for the head tube, seatstays, seat tube and top tube.

Even the enlarged down tube (to incorporate the 360Wh battery) still has the same aero-profile style.

The Domane frame has tyre clearance to spare, with space for a maximum size of 700x40c, or 35c if you take into account the frame and forks' mudguard provision.

Trek Domane SLR 6 geometry

The geometry of the Domane is close to that of the current Domane SLR, which means an endurance-biased riding position.

The 611mm stack is tall without putting you upright and the 380mm reach is sporty without stretching you out.

The 1,027mm wheelbase brings stability at speed, and a 63mm fork trail provides neutral and balanced handling – neither too snappy nor too sedate.

The 73-degree seat angle pitches you over the cranks and the 72-degree head angle adds to the smooth, neutral handling.

Trek Domane SLR 6 build

The SLR 6 I tested sits as the ‘entry’ into Domane ownership, although the £7,850 price tag makes it anything but ‘entry-level’.

The range tops out with the SLR 9 at £11,500 for a Dura-Ace Di2 (or Red AXS) model with Aeolus RSL37 wheels and carbon Bontrager finishing kit.

The SLR 6 gets a great specification, though. It’s driven by Shimano’s impressive 105 Di2 with a Praxis carbon crankset (standard Shimano cranksets aren’t mid-motor compatible).

Trek has chosen 52/36-tooth chainrings and an 11-34 tooth 105 cassette.

The bike rolls on Bontrager’s excellent Aeolus Pro 37 carbon wheels. The 37mm-deep carbon rim has a 21mm internal width and a hooked design. It’s a great match for the specced 32c tyres.

The R3 Hard-Case Lite tyres are set up tubeless and though it isn’t the fastest tyre Bontrager offers, it’s arguably a smart choice for the extra heft of an electric bike, with a reinforced casing and superior puncture protection.

The cockpit combines Bontrager’s slick cable-tidying RCS Pro stem with a carbon Pro IsoCore handlebar wrapped in luxuriously comfortable Bontrager Supertack bar tape.

At the rear, an aero-shaped carbon seatpost is topped with Bontrager’s comfortable and on-trend Verse short saddle.

Trek Domane SLR 6 ride impressions

On the road, the most impressive trait about the Domane is that it rides very similarly to the standard Domane.

The IsoSpeed-infused rear end not only makes short work of rough surfaces and energy-sapping vibrations, it also helps the bike feel balanced and composed at speed.

The rear-end compliance combines with the way it makes the back end feel planted carving through corners. Allied to the low-down weight of the motor and battery, it makes the Domane an unflappable partner for fast descents and tight, twisty cornering.

The 105 brakes and 160mm rotors provide masses of braking force that’s easy to subtly deliver thanks to the progressive feel of the lever.

The TQ motor has a claimed 50Nm of torque, but it feels punchier than that. It certainly feels as though it has much more torque than both the Orbea Gain M10i and Wilier Filante Hybrid, which both use the nominally more powerful 55Nm Mahle X20 motor.

The TQ’s motor control is smart too. Flush-fitted into the top tube is a bright clear monochrome digital display with a 5cm-long screen.

This also serves as the on-off switch and a way to move between the information available on the screen.

A clear 10-segment battery icon gives a good indication of remaining overpower and you can connect to the system through Trek’s Central app.

The app enables you to tune the assistance in each of the three modes, and how quickly the motor responds to pedal input.

It also records all your stats, will sync automatically with Strava, and enables you to download routes from Komoot.

However, the best element of the TQ system is the addition of control switches that mount in the inner faces of the hoods.

These enable power mode shifts without taking your hands from the bars.

The buttons click positively, but I found the alloy hook-shaped brackets that slide under the hood covers tended to bend outwards if I was a bit forceful, which meant the occasional road-side readjustment.

I’d like to see a properly secure bracket more in line with the remote switches Orbea fits onto the Gain.

The three modes are very distinct. The lower level gives subtle assistance that kept me hovering around the bike's 15.5mph motor limit on steady inclines with ease.

Level 2 does much the same but on gradients of up to around 7 to 8 per cent.

In the most powerful mode, I found I could get up some of the steepest, sharpest local climbs with double-digit gradients at around 15mph, whereas on a non-assisted bike, I’d be at more like 10mph and busting a gut.

Like all good performance ebikes, the Domane is most impressive when you put in the effort. Rely on the motor to get you around and it’ll do it, but the ride will be less fun, and it will have a largely detrimental effect on range.

The Domane has ample range, though. My 90kg frame, atop this 58cm test bike, achieved consistent distances of around 100km/62 miles.

My first outing saw 99.94km/62.1 miles, with 1,026.8m/3,368.8ft of ascent. Further rides saw 99.10km/61.58 miles with 1,070.12m/3,514.2ft and 100.58km/62.5miles with 1,021m/3,349.7ft.

If range anxiety is a genuine worry, you can add a 160Wh-capacity range extender that mounts to your bottle cage. Trek claims this will increase the range by up to 44 per cent. It costs an extra £489.99.

The charge time of the TQ system is impressive, taking only 2 hours and 10 minutes to refill a completely depleted battery.

Trek Domane SLR 6 bottom line

The Trek Domane+ SLR 6’s powerful, quiet and smooth TQ motor system helps make this the Wisconsin brand’s best e-road bike yet.

The frame is as comfortable as you could hope for, while the handling is confidence-inspiring with good integration of the electric tech.

If you are looking for a pedal-assistance enhancement to your road bike efforts, the Domane+ is a very worthy partner.