Brennan’s Bike from Gravel Nationals
In a field of mass-produced carbon bikes, it’s refreshing to see a national championship won on a custom-built metal frame. Brennan’s Mosaic GT-1 iAR is the latest all-road offering from the Colorado maker. With an Enve Gravel fork and Mosaic’s All-Road chainstays, Brennan’s bike juuuust clears the 44 mm-wide Snoqualmie Pass tires. The upshot of the relatively tight clearances is a road-bike chainline.
The frame is made from double-butted titanium tubing that’s custom-selected for each rider. A custom frame, both in its dimensions and its tubing selection, is especially useful for Brennan: Compared to most racers, he is tall (196 cm / 6′ 5″) and heavy (92 kg / 200 lb), and he puts out more power than most other pro racers.
Brennan explained: “This frame is the culmination of what we’ve learned with a few other bikes we’ve done before. It’s a blend of oversized and lighter, more compliant tubing, but it’s definitely on the stiff end of the spectrum.” As one would expect for a rider with Brennan’s build and power.
Why race on the all-road bike and not his gravel rig? Brennan: “It’s what I raced last year, when I also made it onto the podium, and it was a perfect setup then. If it ain’t broke, don’t fix it! Seriously, I wanted my setup optimized for the high-speed finish. That’s also why I was running slicks. Last year, I was on the 38 mm Barlow Pass Endurance. These days, the 44 mm Snoqualmie Pass Endurance are my goldilocks tires. People sometimes ask me, if I could keep only one bike, which one would I choose? There’s no doubt in my mind: It would be this setup.”
Brennan runs deep-section Enve SES 4.5 wheels with an inner width of 25 mm. He explained: “I agree that the aero benefits mostly disappear with wide tires, Perhaps I notice an advantage in cross-winds, especially cross-tailwinds, but the main reason to run these wheels is the greater stiffness of the taller rims and shorter spokes.”
Brennan’s components are a mix of Shimano Ultegra, Dura-Ace and GRX components. He laughed: “I have to pay for my own components, so I don’t just automatically choose top-end parts.” The front derailleur is from the GRX gravel group, because it offers extra tire clearance. At the rear is an Ultegra road derailleur with Ceramicspeed pulleys to reduce friction to an absolute minimum. Cassette and chain are Dura-Ace, with the chain a pre-lubed Ceramicspeed ‘Racing’ chain. The SRM Origin cranks provide reliable power measurements, and they work with Dura-Ace chainrings. Brennan enthuses: “They are super-stiff and light. I really like them.” The Dura-Ace road pedals are equipped with Ceramicspeed bearings.
Gearing consists of “the largest road chainrings in the program” (54×40), coupled with an 11-34 cassette. The shift levers are Ultegra Di2 wireless 12-speed. The brakes are also Shimano Ultegra, with Dura-Ace 160 mm rotors front and back.
The Formcycling ThrOne RS saddle comes from a local San Francisco brand, chosen for its comfort. The Enve Aero handlebars are 44 cm wide. “That’s measured in the drops, they are just 39 cm wide at the hoods for a more aero position,” explained Brennan.
A Garmin Edge 840 Solar computer finishes off the cockpit. Brennan recalled: “I didn’t look much at the readouts today, going off feel instead. I knew that if I rode to my normal race numbers, I’d blow up. I looked at the map to see upcoming turns, also wind direction, and the distance to go.”
The Arundel Grypto bottle cages are extra-strong—necessary because Brennan uses extra-large one-liter bottles. He explained the fueling needs for the 131-mile (211 km) race: “I carried Osmo Power fuel in my hydration pack. One of my bottles was plain water, the other Osmo electrolyte hydration. I carried another bottle with plain water in my jersey pocket, mostly for dumping over my head if it got too hot. The race started at 6:30 a.m., and the morning was cool, but over the 5:50 hours of racing, it heated up a lot.”
To deal with the ever-present risk of a flat tire, Brennan carried a CO2 cartridge in his pocket, another strapped to the bike’s seat tube. A small Dynaplug is integrated into the bar plug, with a larger Dynaplug strapped underneath the top tube. A Rene Herse TPU tube serves as backup if all else fails. Fortunately, Brennan didn’t need any of them.
Asked about the weight of his bike, Brennan admitted: “I never weigh much of anything on my bike, so I don’t even know the total weight of the bike. What’s more important: The bike is carefully assembled and tuned by the folks at Above Category in Sausalito, California.” And finally, Brennan really liked the sleek race numbers at Gravel Nationals: “Usually in gravel races, we get big, huge, obnoxious numbers on front of bike, so it was nice to have our number on the seatpost instead.”
Click here for Brennan’s report from the race.
