How does a pro-level mountain bike from the XC World Cup compete against a gravel bike? Is it the better choice when the tarmac ends? We tested the Trek Procaliber 9.9 SL Race Shop Limited to find out.

Here you’ll find our current group test on the best gravel bike.

Trek Procaliber 9.9 SL RSL | 9.02 kg | € 7,999

Despite a suspension fork, wide tires, 29″ wheels, and a whole bunch of mountain bike components, the 18.5″ frame size of the Procaliber weighs in at just 9.02 kg. Light enough to put the € 7,999 Trek Procaliber 9.9 SL right in the middle of our gravel test-field. Sure you can get even lighter XC racers, but we all know that weight isn’t everything – within reason.

The IsoSpeed technology is the standout feature of the Procaliber. As a roadie you may have seen this already on the Madone and the Domane. An alloy pivot allows for decoupling of the seat tube from the top tube and seatstays, providing for more vertical flex and added riding comfort. The almond-shaped taper in the lower part of the seat tube is supposed to provide for even more comfort. All this sounds great in theory, but in practice we weren’t able to fully appreciate the perks of the IsoSpeed technology – and this really depends on the riding style; the IsoSpeed technology only shows its benefits when riding seated. While roadies tend to steam through the pavé of the Paris-Roubaix in the saddle, most mountain bikers spend far less time seated. This means mountain bikers might enjoy the benefits of the IsoSpeed on technical uphills, but will eventually get out of the saddle when the climbs get harsher. In addition, the bigger volume of mountain bike tyres also puts a limit to the efficiency and purpose of this technology.

Despite not being as stiff as the Trek Crockett 7 Disc cyclocross bike, the Procaliber 9.9 SL sprints swiftly when accelerating. The light DT Swiss XMC 1200 carbon wheels combined with the lightly-treaded 2.2” Bontrager XR1 Team Issue tires roll incredibly well on the gravel, offering a great blend of comfort and traction. Only on damp and soft surfaces do the narrow shoulder knobs result in imprecise cornering and poor traction on climbs. In these conditions the narrow cyclocross tires of the Trek Crockett dig much deeper into the ground. Where the Procaliber definitely shines is on the uphills. It makes any sort of climb feel effortless thanks to the broad range of the twelve-speed SRAM Eagle groupset with a huge 10-50 cassette and an incredible 500% range. However on even terrain and gravel descents the 34 t chainring quickly runs out of steam.

Tuning-Tip: Stiffer fork and stiffer front wheel, More defined grips

The biggest concern voiced by our test crew was the Trek’s poor steering precision. The reason for this is the combination of the relatively soft carbon frame, rather soft carbon wheels, and the slender construction of the 100 mm Fox Factory 32 Float fork. All of which results in little torsional-stiffness. The step-shaped recess on the lower fork leg, which creates space for the brake rotor and gives the Fox 32 the “Step-Cast” name, is proof that the fork was designed at the limit of its possibilities. The soft foam grips also affect riding precision, at least if you have sensitive roadie hands. This might sound weird, but it’s true. And it’s also the reason all of our test riders preferred the Trek Crockett Disc or other gravel bikes on singletrack and gravel paths. It was only on technical terrain that we started noticing the advantages of the trail-oriented geometry, the 720 mm wide flat bars and the 100 mm suspension fork.

Increased riding confidence was going to be the ultimate argument for the Trek against its gravel competitors …

The high-end version in our test comes with an SL-suffix in its name, which denotes a higher quality carbon fibre and a better carbon layup which shaves 250 g off a regular carbon Procaliber. In addition, the top of the range version comes with the Control Freak cable routing, which allows for tidy and safe cable management and is just a very nice touch! Matching the diameter of the wheels to the different frame sizes gives the Procaliber a few extra bonus points. Especially with smaller riders who will enjoy better handling characteristics of smaller wheels. Frame sizes up to 15.5″ come with 27.5″ wheels.

Helmet POC Octal Raceday | Glasses 100% Speedcraft | Jersey Mavic Crossride | Shorts Mavic Crossride | Socks Stance Empower | Shoes Giro Empire VR90

The Trek Procaliber 9.9 SL RSL in detail

Drivetrain SRAM XX1 Eagle
Wheelset DT Swiss XMC1200 Carbon
Brakes SRAM Level Ultimate
Tires Bontrager XR1 Team Issue
Weight 9.02 kg
Price € 7,999

Soft front: the combination of soft carbon wheels, lightly treaded tires, and a fork with very little torsional stiffness reduces steering precision and riding confidence.
IsoSpeed-technology: through an aluminium pivot you can decouple the seat tube from the top tube and seatstays to increase vertical flex.
The Fox Factory 32 Float can be locked out from the handle bars and adjusted with two pressure settings. On our test bike the dialler got stuck.
Very nice: the Control Freak cable routing makes for a tidy and clean look!

Geometry of the Trek Procaliber 9.9 SL RSL


Unfortunately the killer looks and many clever details don’t make up for the poor steering precision of the Trek Procaliber 9.9 SL. Increased riding confidence was going to be the ultimate argument for the Trek against its gravel competitors, but in practice it only made a difference on technical terrain. You could stiffen up the front end by swapping around some of the components. But you’re probably better off with the Trek Crockett Disc from our group test if you’re after real fun on gravel paths and flowy trails – especially if you’re a roadie who demands razor-sharp precision and honest, direct feedback.


– SRAM Eagle
– Rider height-specific wheel sizing
– Control Freak cable routing


– Poor steering precision
– Soft wheels

More info at:

Here you’ll find our current group test on the best gravel bike.

Alle Bikes im Test: Festka One Gravel | Legor Cicli LWTUA | Merida Silex 9000 | Moots Routt RSL | Open U.P. | Rondo Ruut CF2 | Salsa Cutthroat Force 1 | Specialized Men’s Diverge Comp |
Specialized Sequoia Elite | Trek Crockett 7 Disc | Votec VRX Elite

Words: Robin Schmitt, Manuel Buck, Benjamin Topf, Hannah Troop Photos: Valentin Rühl

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