Bike Test: Trek Boone 9 Disc

Since the first day we experienced Trek’s IsoSpeed decoupler featured on the Domane road bike, we’ve always felt the suspension system would make great sense on a ’cross or gravel bike. Apparently, the engineers at Trek were thinking the same thing. Trek’s proprietary decoupler is a pivot point located on the top tube just in front of the seat tube, which allows 33mm of movement in what would normally be a fixed joint between the two tubes. This allows greater vertical compliance of the seat tube (when the saddle is weighted) without any downside that we’ve found, other than the approximate the 50 grams in weight it adds.

Compared to the Domane, the only difference between the two decouplers is their location on the frame, with the Boone’s being mounted in line with the top tube so the bike could be shouldered more comfortably. Also aiding in the bike’s compliance at the saddle is the same Ride Tuned seat mast design used on Trek’s other high-end bikes.

Four models of the Boone are available— two with disc brakes (Boone 9 Disc, Boone 5 Disc) and two without (Boone 9, Boone 7). Thru-axles failed to make their way onto the Boone disc models since Trek feels that racers would prefer the lighter-weight quick-release skewers.

Geometry is in line with traditional cyclocross numbers that give it a bottom bracket drop of 6.8cm (56cm size frame) for better pedal clearance compared to the 7cm drop commonly found on road bikes. The numbers round out with a long 102cm wheelbase, a 73.6-degree seat angle, and a relaxed head tube angle of 72 degrees. The fork itself uses Trek’s E2 taper that goes from 1 1/8-inch at the top to 1 1/2-inch diameter at the crown. Since cyclocross bikes are often purchased because of their versatility rather than just their merits on the racecourse, Trek gave the Boone hidden fender mounts and a second bottle-cage mount, in addition to internal cable routing that’s fully compatible with mechanical and electronic drivetrains.

THE PARTS

With all four of the Boone models receiving the same 600 Series-grade carbon, it’s simply the parts spec list that separates them. Our Boone 9 Disc represents the highest-end model in the line, and comes equipped with a Shimano Ultegra Di2 group with RS785 hydraulic disc brakes and a fantastic wheelset in the HED Ardennes+ that uses a 25mm outer rim width for exceptional tire sidewall support, which is especially important with wide ’cross tires. The hubs use Shimano’s Centerlock design with 160mm IceTech rotors mounted to them.

The smaller details of the build are definitely oriented to a true cyclocross setup rather than an all-around gravel/ adventure bike, with the 46/36 gearing up front and the narrow 32c knobby tires. Out on the racecourse, 32c tires may well be the ideal width, but when it comes to dirt road or singletrack riding, they’re simply not enough to enjoy the ride. Switching to a 35c semi-slick at the same tire pressure made a noticeable improvement in handling and comfort. Tire clearance allows up to a 38c tire to be used.

THE RIDE

Since our review took place before the cyclocross season kicked off, much of our ride time on the Boone 9 took place on dirt roads rather than the racecourse itself. Regardless, things like its low weight are going to be equally advantageous whether you’re accelerating out of a corner in a race or climbing a hill on a gravel ride.

Where the Boone shone brightest, though, was when the conditions deteriorated into rough, pocked terrain. We could stay in the saddle and maintain power through bumps that would otherwise prove too rough. The IsoSpeed decoupler did more than just take the edge off the bumps; it dramatically smoothed out the terrain. In a ’cross race, being able to pedal through choppy corners while having the rear wheel follow the ground’s contours rather than bouncing is going to be a distinct advantage. Out of the saddle the Boone felt stiff in the front end when sprinting up to speed; although, just as thru-axles gave the Domane Disc a noticeable improvement in stiffness, we’re sure the same would hold true for the Boone.

THE VERDICT

Trek nailed it with the Boone. It’s an impressively efficient bike that benefits greatly from the IsoSpeed decoupler. No other ’cross bike we’ve ridden shares the Boone’s ability to be pedaled through the rough stuff. The parts spec’d on the Boone 9 are some of the best options available, especially when it comes to the HED Ardennes+ wheels. For us, dirt road riding was improved by going to a wider tire with greater air volume than the 32c race tires that come stock. The Boone series starts with the Boone 5 at $2839.99.

STATS

Price: $6299.99, $2299.99 (frameset)

Weight: 18.3 pounds

Sizes: 50, 52, 54, 56 (tested), 58, 61cm

See this bike and more at trekbikes.com

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