From Nose to Tail: Factor OSTRO Gets Comprehensive Aero Upgrade

by thebestworldevents.com 15 February 2024 · Cycling

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The OSTRO is the bike that encompasses Factor and its presence worldwide. It’s the most recognizable (IMO) and appealing of its offerings and helped shape the mold for powerful road machines with a slippery silhouette. The new OSTRO doesn’t move far from the original starting point but goes all in on minute aero updates for larger gains.

OSTRO VAM Headtube front on — (All images: Factor Bikes)

When it came time to redesign the bike, the Factor design team looked to balance stiffness/comfort, real-life aerodynamics, and beauty. The team added some cool extra bits like unique aero bottle cages and a new set of ultra-fast (and very good-looking) Black Ink 48/58 Wheels.

Factor OSTRO – Aero Makeover from Nose to Tail

Developing the 2024 OSTRO, Factor looked at every tube and focused on understanding how the bike’s shape could strategically guide air around the rider. They started at the leading edge and worked backward.

While presenting the new OSTRO, the Factor design/aero team explained that Improvements at the front impact elements at the rear, creating a snowball effect of gains and losses. The Factor design team divided this aero-challenge into five ‘zones’ to achieve the most aerodynamic edge while maintaining the bike’s overall ride integrity.

Zone 1 — Fork and Headtube

The fork impacts the aerodynamics of the entire bike as the central part of the bike’s leading edge. The CDA (drag coefficient) was reduced by minimizing the frontal area and increasing shape efficiency. The newly reduced fork crown height improves the new OSTRO’s stiffness and feel. The ride feel and responsiveness are a hallmark of the OSTRO, and the team didn’t want to lose that feeling amid aero gains.

Factor then gave the new OSTRO’s headtube a more hourglass shape, reducing the frontal area. Adding a nose on the headtube allowed the team to move the leading edge of the fork forward, creating a smoother transition for the nose with the headtube.

Aero Fork on the inside: Small surface details were added on the inside of the fork leg that work with the rotating wheel to promote better flow. The dropout and brake mount surfaces are modeled to move the air from the axle. All these small details add up to create a nice chunk of aero-gains.

Zone 3 — Headtube to Toptube

The updated head tube made way for a look at the overall airflow coming to the top tube. The team focused on smoother flow from the headtube to the bike’s rear. A streamlined headtube-to-top-tube transition enhances flow attachment and creates a more slippery design. This slimmer top tube paves the way for an overall reduction in seat tube size for a streamlined profile.

Zone 4 — Seat Tube

Now that the UCI has removed the 3:1 rule (about two years ago) for components and reduced the minimum tube thickness required, the design team at Factor could develop a slim seat tube that worked well with the aggressive tapering on the top tube.

The team’s objective was to maintain stiffness while reducing frontal area. As a result, the lower sections of the seat tube remain as wide as the OSTRO frame. It tapers into the bottom bracket zone (zone 5) and requires additional carbon layup magic to combat the dreaded torsional flex.

Zone 5 — Bottom Bracket

The industry trend is to make the bottom bracket wider, taller, and slightly boxy (like the Trek Madone). Factor added their spin on this with the new OSTRO, creating a smooth yet boxy bottom bracket junction. The team started, “Balancing shape efficiency and maintaining volume and rigidity is key to power transfer. Here, we had to manage the pedaling forces in one plane while promoting airflow retention in the other.”

As for the height, the design team meticulously fine-tuned the volume above the bottom bracket, balancing airflow while keeping it tucked away from the riders’ legs. Once again, the Factor team found a slight gain in aerodynamic efficiency, adding another tick in the faster direction.

Black Ink 48/58 Wheels:

When Factor drops a new bike, it usually means another cool wheelset, and the BLK Inc 48/58 is no exception. The newest BLK Inc. wheels feature a high-flange carbon spoke hub and weigh in at a super light (for this deep) 1270g. The wheelset is aero-designed and tested for maximal performance with 28mm tires.

The increased leading-edge radius improves flow attachment at larger yaw angles, and the high-flange hub increases ride feel and lateral stiffness.

Factor design team explains: “The increased radius creates a more gradual rate of curvature change, promoting flow attachment at larger yaw angles. In addition, the rounder profile and more gradual change in curvature means that the aerodynamic stall onset is gentler, giving the rider a better feeling of control in gusts and strong crosswind situations.”

Aero and Tube Specific Water Bottle Cages

Not only are these new Factor/BLK Inc cages aero, but they are tube-specific. Unlike other aero cages, they do not require a specific bottle or an attachment.

Black Ink–Tube Specific Bottle Cage: The BLK Inc OSTRO downtube cage bridges the gap between the downtube and the water bottle. It promotes longer flow attachment and reduces localized drag — plus, it holds a water bottle!

Ostro Sprint Cage: The Factor design team chose a different aerodynamic approach for the Sprint Cage. It acts as a high-speed flow management device. It’s most aerodynamically functional when a rider ejects their bottle before the final sprint. The foil profiles and precise spacing with the seat tube funnel air tightly across the tube and transition it to the rear wheel. Making you faster for the times when it’s absolutely needed — like a tour stage or a town line sprint.

The Full Picture — Factor OSTRO 2024

So, how much faster is the new Factor OSTRO compared to the previous generation? The new design saves 7 watts. Now I know what you’re thinking: “All that for 7 watts?!” But that’s a lot when it comes to an already super-aero bike.

The Factor design team explains: “As for aerodynamics, the net gain is roughly a 10% improvement in aerodynamic efficiency with all variables controlled and normalized in a wind tunnel. This is, on average, a 70-gram reduction in drag vs. the original OSTRO. This is about 7 watts at 48km/h, which converges with our simulation data. In addition, the aerodynamic benefit increases as yaw angles become closer to real-world expectations (5-10 degrees).”