The combined low weight and non-invasive nature of the Fazua motor system creates a marvellously natural feeling e-bike.

Product Overview

Trek E-Caliber 9.9 XTR


  • Almost zero negative transition when pushing the E-Caliber past the motor cut-off.
  • The combined low weight and non-invasive nature of the Fazua motor system creates a marvellously natural feeling e-bike.


  • Front and rear end offer different performance characteristics.
  • Range is disappointing.
  • You could buy a Supercaliber or a Slash, and a Rail e-bike for less than the cost of the E-Caliber 9.9 XTR.


Trek E-Caliber 9.9 XTR: first ride on £10,750 XC e-racebike


Price as reviewed:


The new Trek E-Caliber 9.9 XTR electric XC mountain bike has got the looks, spec and price to turn heads and could be a glimpse into the e-bike future.

Read more: Best electric mountain bikes, E-Bike of the Year

Trek E-Caliber 9.9 XTR need to know

  • Fazua Evation 1 motor-assisted version of Trek’s World Cup XC racer
  • Trek’s unique IsoStrut Fox Factory rear suspension delivers just 60mm of travel
  • Featherweight build spec rivals many non- motorised trail bikes in weight
  • Ships with dummy battery/motor box to drop weight and run/race 100 per cent human powered


In the established pecking order of motor assisted mountain bikes, it is generally recognised that more is better than less. More torque, more travel and more battery capacity are often the most touted features. It’s no coincidence that most of the best selling e-bikes are usually based on a brand’s longer travel trail and enduro platforms.

Read more: Trek Procaliber 9.7 review

The Trek E-Caliber however, has none of these box-ticking features, and instead takes its inspiration from a very unlikely source – World Cup XC racing. You heard that right, the E-Caliber is (on paper at least) a bike that technically should be the absolute anathema to the very riders Trek seems to be aiming it at.

Even the controls look discreet and have a quality feel

In other words, riders with the legs and lungs to put out more watts than a motor. Long-travel, slack-angled e-bikes are easy to understand, but the E-Caliber is a different beast altogether.

The E-Caliber is based around Trek’s Supercaliber full-suspension XC race platform and features just 60mm of rear wheel travel. The IsoStrut rear suspension design is integral to the frame structure and the shock is a completely bespoke design.

trek e-caliber 9

Rear shock is neatly integrated into the top tube

The outer can of the shock is actually moulded into the upper part of the extended seatstays and wraps around a Kashima coated central shaft. The shaped top tube houses the shock mounts and the clever design blends the shock into the frame, so from some angles it is difficult to tell there are actual moving parts.

It’s a flex-stay design too, relying on the bow of the whippet-thin seat stays, in fact the actual shock only provides 55mm of movement with flex in the stays contributing the additional 5mm.

trek e-caliber 9

Only battery cover gives away the e-bike function of the Caliber

Trek has gone to the trouble of adding a proper lower pivot, located above the bottom bracket, along with decent sized bearings to keep things as stiff as possible.

One thing that does stand out is how impressive the Iso Strut suspension is. Trek has managed to make it feel incredibly composed and effective, and the well-damped and progressive nature makes it feel like it provides far more than just 60mm of movement. It is very sensitive to adjustments in rebound, but once it is dialled in it is buttery smooth and refined.

Thin stays are designed to flex an additional 5mm

It’s only the larger diameter down tube – housing Fazua’s Evation 1 motor system – that gives you any indication of the difference between the E-Caliber and Supercaliber. The Evation’s party piece is its modular design, enabling you to swap the motor and battery for a plastic dummy unit if you so wish, instantly dropping the weight of the bike by nearly three kilograms and giving you the ability to ride the bike as a standard ‘analogue’ machine.

Read more: E-bike motors, Shimano v Bosch v Fazua v Panasonic v Giant v Brose

Like most e-bikes, the Evation 1 system provides up to 250W of continuous support, however the battery has a relatively small 250Wh capacity and Fazua cites weight reduction for this small size. Torque is also lower than many other motors at 55Nm, but this translates to a far more natural feeling ride quality than more powerful systems.

Finesse the e-power and the pedalling for maximum fun and range

One of the standout features of the E-Caliber is how the Evation 1 kicks in at almost any pedalling cadence and gear selection. Something that Fazua has improved with its Black Pepper software update and also a trick that gives it an edge over more powerful systems.

The system is controlled by a simple handlebar mounted on/off button that incorporates two touch sensitive pads that allow you to cycle through the three power modes: Breeze giving 100 watts of assistance; River with 210 watts; and finally Rocket for the full 250 watts.

Ride quality and speed enhanced by Bontrager tyres

Trek has made some nods towards the extra power and speed that the E-Caliber promotes and has upped the travel at the front to 120mm and has also specced the more trail-oriented Fox Step Cast 34 fork for increased stiffness.

The brakes have been upgraded – Shimano’s XTR brakes are flagship models and the four-piston versions fitted to the E-Caliber, coupled with 203mm front and 180mm rear rotors provide effortless stopping power.

Shimano XTR M9100 rear mech is suitably top spec

The rest of the spec is as you would expect from a bike costing nearly £11,000. The cockpit and seatpost can be used to summarise the riding experience of the E-Caliber – it’s the embodiment of a reverse mullet bike; all party at the front and business as usual at the back end.

You have a front end that encourages you to really push into trails at speeds that a typical trail bike with the same front end would have no issues with.

But the rigid seatpost on the Trek makes it hard to lower your centre of gravity without hanging completely off the back and unweighting the front tyre.

This results in the rider employing the brakes a lot sooner than he or she might like and it also makes dealing with rooty steps and drops a little more of a cautious affair.

I come from an XC race background, and am normally fine with a high saddle height, but everytime I hit a fun bit of downhill I was screaming at Trek for the lack of a dropper post.

World Cup racers are using them, so why isn’t one specced on the E-Caliber? This is one of only two models in a six bike range without a dropper post. To save, what, 300g?

How it rides

To ride the E-caliber you really do need to recalibrate how you ride an e-bike. If you simply stick it in full power Rocket mode and try and rely on the motor to do the work you will be pretty disappointed.

Riding it like this around my Welsh test loop rinsed the battery in just 18km. But retune your brain to think of the E-Caliber as an analogue bike with a bonus power boost for those few occasions when you really need it, then the E-Caliber starts to make sense and the range extends.

The key saviour here is the low weight and minimal rolling resistance of the Bontrager tyres and wheels. These, coupled with the minimal drag of the Fazua motor allow you to maintain speed far beyond the normal 25kph motor cut-off. With most e-bikes you pay a price for pushing beyond the motor, but not so with the E-Caliber, it actively encourages you to pedal.

And the range? When utilising the low power mode (still enough to give you a boost), switching off on downhills and flow trails and only using the higher power modes occasionally, I was able to eke out 56km and around 1,500m of climbing. Although better, I could still ride further with a heavier bike and larger capacity battery.

After putting in a lot of hours on the E-Caliber, I’m still a little confused as to who this bike is for. With its XC geometry, rigid seatpost and low weight it’s hard to see the Trek E-Caliber 9.9 as anything other than a pro XC racer’s expensive training/recovery tool. The minimal torque and range also point to this.

But I can also see the Trek E-Caliber 9.9 appealing to riders who eschew gravity- fed mountain biking, preferring distance on easier terrain. A spare battery would extend the range for all-day rides too.

Whoever the Trek E-Caliber 9.9 appeals to, it definitely shows that Trek is nailing its colours to the mast, embracing the world of motor power as being a big part of the future for all forms of mountain biking.


Frame:OCLV Mountain Carbon
Motor system:Fazua Evation 1.0
Battery:Fazua 250Wh
Shock:Trek IsoStrut Fox Factory w/remote lockout, 60mm (60mm measured)
Fork:Fox Factory 34 Step Cast w/remote lockout, 120mm
Wheels:Bontrager Kovee XXX Carbon, Bontrager XR3 Team Issue 29x2.4in
Drivetrain:E*thirteen E*spec Race Carbon 34T, Shimano XTR M9100 shifter, Shimano XTR M9100 r-mech
Brakes:Shimano XTR M9120, 203/180mm
Components:Bontrager Line Pro OCLV Carbon 750mm handlebar, Bontrager Kovee Pro 70mm stem, Bontrager XXX OCLV Carbon seatpost, Bontrager P3 Verse Pro saddle
Sizes:S, M, L, XL
Weight:16.33kg (36lb)
Size tested:L
Head angle:67.4°
Actual seat angle:72.9°
Effective seat angle:74.4°
BB height:315mm
Front centre:753mm
Down tube:740mm
Top tube:643mm