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Adjustable rear IsoSpeed decoupler, bigger tyre clearance and now the front decouples too + a host more changes

Trek has launched a new Domane that aims to build on the success of the first model, launched four years ago, with an adjustable IsoSpeed decoupler at the rear and an IsoSpeed decoupler at the front, plus a new IsoCore handlebar, all aimed at producing a bike that isolates the rider from rough roads and cobbles more than the previous Domane.

We spotted the new Domane at the Tour of Flanders over the weekend. We're now at the worldwide launch, where Fabian Cancellara himself was on hand to reveal the new bike. We're riding this new bike tomorrow so we'll be able to give you an indication of how it performs.

Here are the key developments and changes:

  • Adjustable rear IsoSpeed
  • Front IsoSpeed - so now the front of the bike moves with the terrain too
  • IsoCore handlebar
  • New fork
  • Increased tyre clearance
  • 12mm thru-axle on the disc bike
  • Di2 function box port

Adjustable rear IsoSpeed

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The new Domane provides a wider range of compliance - the amount it moves when it encounters a bump in the road, ranging from the stiffness of the Madone, to 14% more compliance than the previous Domane.

It can be easily adjusted. Jjust a single bolt needs to be loosened to adjust the slider in the seat tube. It’s not a change you can make on-the-fly. The bolt is neatly integrated into the lower bottle cage mount.

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This sliding lever changes the level of compliance, from the lowest position which is claimed to offer 14% more compliance than the current Domane, to the top setting, which makes it as stiff as the Emonda.

The bike features a pair of seat tubes, connected via the IsoSpeed decoupler with a lower bolted joint. The slider adjusts the space between the two halves of the twin seat tube, allowing the seat mast to deflect rearwards. 

Adjustable Rear IsoSpeed detail.jpg

“The slider contacts both the lower seat mast tube and main frame tube to limit the fore deflection of the lower seat mast per the user’s preference,” says Trek. 

“If the slider is towards the bottom (near the bottom bracket), a user will experience greater compliance because of the greater vacant space that allows the lower seat mast to deflect more. If the slider is near the top (towards the IsoSpeed decoupler), a user will experience less compliance because the slider is inhibiting deflection in the vacant space below it.

“In the test lab, vertical stiffness testing at the saddle shows that for a 56cm frame, the compliance ranges from approximately 99N/mm to 144N/mm throughout the slider’s adjustment range.”

Front IsoSpeed

While the evolution of the rear IsoSpeed is impressive enough, more interesting is the development of the front IsoSpeed. It works very much like the rear IsoSpeed and addresses my biggest complaint of the previous Domane - that the front end is much stiffer than the back. 

IsoCore Bar.jpg

Trek describes the front IsoSpeed as a decoupler that allows the steerer tube to move back and forth, which results in a claimed 10% increase in vertical compliance. Stem length is a factor in the amount of deflection. 

It’s essentially a pivoting collar that allows the top of the head tube and allows the steerer tube to move back and forth by a very small amount. This collar is bolted into the top of the steerer tube on both sides using elliptical nuts, and is free to rotate a small amount.

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Slotting into this collar is a preload spacer, with an IsoSpeed head tube cover sitting on top. With these parts in place, the headset bearings are added, the compression spring, headset top cap and finally the stem.

This rotation allows the top of the steerer tube move back and forth, providing the deflection that should help smooth out impacts with cobbles.

We'll have more details on the exact workings of this front IsoSpeed decoupler soon.

IsoCore handlebar

Front 3:4.jpg

Trek has also developed a new IsoCore handlebar that contributes to the front-end compliance. It’s based on the IsoZone handlebar but has a “ thermoplastic elastomer” integrated into the carbon fibre layup, throughout the entire handlebar, that is intended to dissipate vibrations by a claimed 20%. It does this anywhere on the handlebar, whether you’re riding on the drops or in the hoods. 

Direct mount brakes, disc brakes and new fork

The new Domane is available in rim and disc brake versions. The rim brake version moves to direct mount brake calipers, and Trek has developed a new fork for the rim brake bike that is claimed to increase compliance by 7%. 

Tire Clearance Direct Brakes.jpg

For the disc bike, the company is using a fork with a 12mm thru-axle, which is increasingly looking like becoming the disc brake standard. Trek is also using the flat mount standard, as most new disc brake bikes are these days. 

Extra tyre clearance

Trek recognises that more people are mixing up the surfaces they’re riding. Gravel and adventure bikes are hugely popular at the moment. The direct mount brakes on the rim brake version allow 28mm tyres to be fitted, while the disc version will take 32mm tyres with mudguards fitted. It’s a road race bike that is adaptable enough to be ridden on gravel roads or rough tracks, reckons Trek.

It certainly makes it appealing to British cyclists seeking a road bike with increased tyre clearance. And with the hidden mudguard mounts carried over from the previous Domane, it's ready for winter riding.

Control Centre

A port in the down tub, in other words. It’s something that first featured on the Madone, and is simply a port that the Di2 junction box is concealed within. It’s located under the bottle cage on the down tube. It’s a nice idea and removes the junction box strapped to the stem situation.

Domane_SLR_6_Disc 3:4.jpg

Pro Endurance Geometry

This is H1 fit but with endurance geometry, meaning a longer wheelbase, lower bottom bracket and shorter head tube, which is the same as the Madone and Emonda H1 fit. 

Testing, testing...

Fabian Cancellara was instrumental in the development of the first Domane, and he was again with the new model. He rode the first prototype and did extensive testing, including riding a bike rigged up with measurement sensors, over the cobbles of Paris-Roubaix.

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Furthermore, Trek constructed a 100 metre cobbled test track at its headquarters so it could run simulations through the development period of the bike, saving on long haul flights from the US.

Domano SLR prices

There will be five models of Domane SLR, two with disc brakes, and two framesets.

  • ​​Domane SLR 6 - £3,600
  • Domane SLR 6 Disc - £4,000
  • Domane SLR 7 - £4,400
  • Domane SLR 7 Disc - £4,800
  • Domane SLR 9 eTap - £7,600
  • Domane SLR Disc Frameset - £2,550
  • Domane SLR Frameset - £2,400

More details on the new Domane soon...

David has worked on the road.cc tech team since July 2012. Previously he was editor of Bikemagic.com and before that staff writer at RCUK. He's a seasoned cyclist of all disciplines, from road to mountain biking, touring to cyclo-cross, he only wishes he had time to ride them all. He's mildly competitive, though he'll never admit it, and is a frequent road racer but is too lazy to do really well. He currently resides in the Cotswolds.