Pro bike: Amy Dombroski's Primus Mootry custom

Featherweight cyclo-cross ride for a featherweight rider

Up-and-coming cycling superstar Amy 'without a W' Dombroski (Schlamm p/b Clement and Primus Mootry) made an unusual move last month by walking away from Richard Sachs just six weeks into their contract. This put her on unfamiliar equipment – with unsure financial backing – right as the some of the biggest races were coming up. 

Whichever side of the story you wish to believe – Sachs says Dombroski wouldn't honour her verbal and written contract commitments; she claims she couldn't be competitive on the sponsor-supplied equipment – Dombroski will spend the rest of the year on an aluminium and carbon fibre frame custom made for her by local builder Joe DePaemelaere of Primus Mootry.

Dombroski may pack a lot of power in her legs but she is also one of the smallest and lightest racers on the pro circuit at just 1.55m (5ft 1in) tall and weighing only 48.5kg (107lb/7.6 stone).As such, she considers bike weight to be of prime importance and her new rig certainly fits the bill at a barely UCI-legal race-ready weight of just 6.88kg (15.2lb). Frame weight is just 1,340g (2.95lb). "Lightness is a huge thing because you are picking it up and so much of 'cross is acceleration," said Dombroski. 

Lying at the bike's core is a TIG-welded butted 7005 aluminium frame punctuated with a carbon fibre top tube and down tube from Edge Composites to both shave grams and soften the ride. The front triangle is devoid of fancy shaping with round cross-sections throughout; DePaemelaere instead relies on the carbon tube's directional layup to get the desired performance characteristics.

It's a different story out back as the S-bend stays are more dramatically massaged. The Dedacciai SC61.10A seatstays are flattened out below the brake bosses to ameliorate the pounding of rough courses and help maintain drive and cornering traction, while the tapered chainstays are tall and thin for drivetrain stiffness and mud clearance. 

Up front, a standard non-tapered head tube surrounds a Ritchey WCS Carbon fork while DePaelemaere fits the special machine with an oversized BB30 bottom bracket shell. In total, Dombroski says her new machine is over 2kg lighter than her previous setup and yet is still as rigid as she wants it to be. "It's snappy and responsive when I accelerate and sprint on it, and it's wicked smooth as well," she said. "There's also no fork chatter."

Also contributing to the bike's feathery weight is the premium build kit. SRAM provide their Force drivetrain and transmission (though technically second-tier, it's virtually the same weight as Red), Reynolds supply their MV32T UL carbon tubular wheels, FSA and Fizik the seating and cockpit components, and TRP lend their ultralight EuroX Magnesium wide-profile cantilevers.

Dombroski's tyre sponsor is Clement – a brand who recently came back into the limelight but don't yet have product to supply. Her bike was fitted with Challenge Grifo tubulars when we caught up with her a few weeks ago.

Two notable breaks from the standard Force group include a Red Powerdome cassette – which Dombroski says she only uses for dry conditions – and the crank setup, which includes a single elliptical Rotor Q-Ring and secure-looking outer and inner guides from AceCo. The left-hand DoubleTap lever is free of shifting internals to save weight.

Dombroski's unusual circumstances necessitated an accelerated timeline. DePaemelaere reportedly built her two frames in the span of about a week and mechanical sponsors Excel Sports bolted them together in even less time than that, using fit numbers from the Boulder Center for Sports Medicine and the measurements of her outgoing Richard Sachs bikes to make the switch as seamless as possible.

Dombroski received the bikes at 5pm on 6 November and her first ride was her warm-up lap for a local race the next day – which she won. She has gone on to win more since then, taking the top step on both days at the recent Super Cross Cup in Southampton, New York.

Earlier in the year – and before the break with Sachs – she had hoped to make a trip to the UCI World Championships in Tabor, Czech Republic. That's now out of the question as her next sponsorship agreement with the Luna squad will kick in on 1 January and she says they've asked her to back off from 'cross to prepare for the mountain bike season.

Dombroski is understandably disappointed but at the same time realistic. Even at the ripe young age of 22, contending a full road, 'cross and mountain bike season takes its toll. "Worlds was my goal," she said. "But at the same time, next year I'll hopefully be going even faster and will be able to do that much better in Europe. They'll be plenty more times to go there."

The revised list of goals now focuses on the upcoming US National Championships in Bend, Oregon, and the previous weekend's races in nearby Portland. As for her chances at another stars-and-stripes jersey – Dombroski holds the US U23 title in both road and cross-country – she's hopeful but realistic.  After all, also planning to attend is none other than current 'cross queen Katie Compton (Planet Bike).

"It's clear that Katie's on a different level," Dombroski said. "It was awesome to be able to race with her in Boulder and even for the short period that we were actually racing with her, it was cool to try and stay on her wheel. I lasted not very long – a lap or something like that – but it was very similar to Providence when I was trying to stay on Katerina's [Nash] wheel.

"They have the power and finesse down to an art. Out of every corner they're just so powerful but they go into it and don't even touch their brakes. It's just so effortless and efficient, and that's something I've been working on. She's the best rider in the world right now. She's phenomenal."

Complete bike specifications 

  • Frame: Primus Mootry custom, butted 7005 aluminium w/ Dedacciai SC61.10A MTB seatstays and Edge Composites carbon fibre top and down tubes
  • Fork: Ritchey WCS Carbon Straight
  • Headset: FSA Orbit X CX
  • Stem: FSA OS-99, 9cm x -6º
  • Handlebar: FSA K-Force Compact, 40cm (c-c)
  • Tape/grips: Fizik bar:tape
  • Front brake: TRP EuroX Magnesium w/ TRP carbon-specific pads
  • Rear brake: TRP EuroX Magnesium w/ TRP carbon-specific pads
  • Brake levers: SRAM Force DoubleTap
  • Front derailleur: SRAM Force
  • Rear derailleur: SRAM Force
  • Shift levers: SRAM Force DoubleTap w/ empty left-hand lever
  • Cassette: SRAM OG-1090, 11-25T (dry conditions only)
  • Chain: SRAM PC-1090R
  • Crankset: SRAM Force BB30, 170mm, w/ 42T Rotor Q-Ring
  • Bottom bracket: SRAM Force BB30
  • Pedals: CrankBrothers Candy 4ti
  • Wheelset: Reynolds MV32T UL
  • Front tyre: Challenge Grifo 32
  • Rear tire: Challenge Grifo 32
  • Saddle: Fizik Antares k:ium
  • Seatpost: FSA K-Force SB0
  • Accessories: AceCo K-Edge outer chainring guard and inner chain watcher; Gore Professional derailleur cable set

Critical measurements  

  • Rider's height: 1.55m (5ft 1in)
  • Rider's weight: 48.5kg (107lb)
  • Saddle height, from BB (c-t): 633mm
  • Seat tube length, c-t: 495mm
  • Seat tube length, c-c: 450mm
  • Tip of saddle nose to C of bars (next to stem): 435mm
  • Saddle-to-bar drop (vertical): +10mm
  • Head tube length: 100mm
  • Top tube length: 500mm
  • Total bicycle weight: 6.88kg (15.17lb)

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