Factor releases new Ostro VAM as “the benchmark aerodynamic, lightweight race bike”

Factor has officially launched an updated Ostro VAM which, it says, is “the benchmark aerodynamic, lightweight race bike”, outperforming the Specialized Tarmac SL8 and Cervelo S5 in terms of aero efficiency while dropping a little weight compared with its predecessor.

Factor says the new bike – which everyone who was even remotely paying attention spotted being raced by Israel–Premier Tech riders in the Tour Down Under last month – saves 7 watts of power at 48km/h (30mph) over the first Ostro VAM which was launched in 2020, and that it’s 267.8g lighter when fitted with the new Black Inc wheels that the brand is also unveiling today, although most of that weight saving comes from the wheels.

> Check out the best road bikes 2024 — the best drop bar, skinny(ish)-tyre bikes for riding on the road

If you want more stats – why the hell not? In for a penny, in for a pound – Factor reckons that Michael Woods would have had an additional time advantage of 2:21mins on his Stage 9 victory at the 2023 Tour de France if he’d been on the new Ostro VAM instead of the old one. 

What?!? Whoa, whoa, whoa! Let's back it up a bit here. Michael Woods was in the original break of 14 riders, and spent most of the stage in a chasing group behind breakaways from this breakaway. He put in an amazing solo shift up Puy de Dôme (13.3km at an average of 7.7%), but 2:21mins quicker on a different bike? 141 seconds? We're guessing that Factor has calculated how much time the new Ostro VAM could theoretically save over the old one across a kilometre and the type of terrain tackled, and scaled it up from there, but that's not how racing works, is it?

[Note: We have since spoken to Factor about this claim. The assumptions upon which it is calculated are a 0.06 CdA (coefficient of drag) improvement and a 300g weight saving by switching to the new Ostro VAM, and the numbers are run as if Michael Woods rode the entire stage solo – so an idealised situation rather than something that would ever happen in a race.]

Okay, that’s plenty of claims to be going on with. Like you, we always raise a quizzical eyebrow when it comes to brands’ claims about their new bikes, but whether or not you buy into the details, they at least give you an idea of where Factor is coming from with this update. 

Factor believes that version one of the Ostro VAM was light and stiff – there’s only so much weight you can lose before dipping below the UCI’s 6.8kg minimum weight limit for racing, or reaching the end point of what’s possible with current materials and technology – and that it matched the benchmark aero bike on the market (the 2019 Cervelo S5) in terms of aerodynamics while being significantly lighter. 

“The idea [with the redesign] was to make a bike that improved on the aerodynamic performance but didn't take away the positives of the old one,” says Factor’s director of engineering Graham Shrive. “Those positives were ride quality, ride feel, weight, usability… We wanted to make sure we retained that character while still improving the performance.”

> Best aero road bikes 2024 — wind-cheating bikes with an extra turn of speed

Why redesign the bike, other than the obvious reasons: to shout about the updates and sell more of them? Factor says it wanted to take advantage of UCI rule changes – notably the removal of the 3:1 rule which meant component depth couldn’t exceed three times the width, and the ability to reduce main frame tube profiles to less than 25mm – the introduction of wireless Shimano Di2 shifting (allowing a skinnier seatpost and seat tube), improved computational techniques, and to solve issues with the existing design.

“[Our] engineers sought to find balance across weight, stiffness and aerodynamics; refusing to concede any one of these three critical components at the expense of another,” says Factor. “The result is a modern racing bike for riders who demand pinpoint handling, immediate power transfer, comfort on unforgiving roads and low weight for optimum performance on the climbs.”

We’ll give you a few specifics… Factor says that, based on lessons from developing the Ostro Gravel, it focused its efforts on the areas of the bike where gains could be greatest – makes sense – and that meant the leading surfaces. 

> Factor launches the Ostro gravel

“Our approach to the aerodynamic development was to learn how the bike’s shape could steer the air favourably around the rider,” says Factor. “The leading edge of the bike has the greatest impact on flow behaviour for two reasons. One, because it meets the cleanest airflow. And two, because it can be made to manage the air for all elements of the bike that follow. Starting with this concept, we focused on the front of the bike and worked backwards.

“Improvements in aerodynamics at the front have a cascading effect on the elements at the rear – both positive and negative. The goal is to capture the positive gains and propagate them downstream. In some cases, changes made in the middle of the bike even influenced the drag generated upstream. For this reason, we continually reassessed the front as we worked our way rearward.”

With the fork, for example, Factor says it reduced drag both by minimising the frontal area and improving the efficiency of the shape.

“This included an exploration of flow management around the crown and down tube junctions to better work with larger tyres,” says Factor. “We also found gains from the synergies between surrounding components, such as the brake calliper mount and axles. This led to localised gains and more predictable flow into the zones downstream.

“A reduced fork crown height coupled with the lower frontal area decreased the overall surface area of the fork, allowing us to place material in areas that would improve stiffness and ride feel while maintaining the same weight.”

Factor says that extending the leading edge of the head tube allowed it to move the leading edge of the fork forward, while a smoother transition between the two enabled it to fine-tune the frontal area and reduce the downstream impact of the airflow.

Meanwhile, the head tube was given a smaller frontal area as a result of an hourglass shape while retaining the same bearing sizes as before (1-1/8in upper, 1-3/8in lower).

“The variable profiling allows for much longer flow attachment and therefore reduced drag,” says Factor. “Multiple head tube profiles and sizes were simulated before landing on a shape profile that yields exceptional results at both 0 degrees [with the wind coming head on] and higher yaw angles.”

We won’t go through every design change in detail (if you’re interested, it’ll all be available on a white paper) but, briefly, Factor says that the top tube captures the smoother airflow from the new head tube profile and maintains it through to the rear of the bike, while the narrower seat post (reduced by 36% to 15mm) and seat tube (reduced by 20%) permitted under new UCI regulations lead to a significant reduction in overall drag.

“The lower section of the seat tube was shaped so that the tyre and wheel complete the aerodynamic profile,” says Factor. “This was achieved by shaping the rear of the tube to properly nest a 28mm tyre and tuning the forward shape to be the leading edge of a continuous, integrated aerodynamic profile.”

Factor has also developed a set of Ostro VAM cages designed to reduce drag. As Giant does with the cages for its Propel aero road bike, Factor has made one cage specifically for the down tube and another for the seat tube.

> Check out our review of the Giant Propel Advanced Pro 1

“In the case of the seat tube bottle, I was sitting on an aeroplane and I’m sure we've all seen as we prepare for takeoff or landing that they extend the leading edge slat,” says Graham Shrive. “That allows the airflow to stay attached to the wing section a little bit better, a little bit longer at high angles of attack. 

“Most World Tour riders will throw either one or both of their bottles in the last five or 10k of the race, and I thought we had an opportunity here to sort of cheat the UCI rules a little bit and create a fairing without it actually being a fairing. In this case, what we’re trying to do is encourage flow attachment across the seat tube when the bottle is removed. The net result is that when you pull out that second bottle and toss it, the bike gets a little bit faster.” 

Of course, the rest of us aren’t all ditching bottles towards the end of races, but that’s the rationale.

As mentioned, Factor has also developed a new Black Inc 48/58 wheelset alongside the Ostro VAM.

“Providing a predictable ride feel without compromising on weight or aerodynamics, the rounded profile is optimised for 28mm tyres with a 23mm internal rim width, promoting aerodynamic performance at larger yaw angles and giving the rider a greater feeling of control in gusts and crosswinds,” says Factor.

The high-flange hub is designed to increase the lateral stiffness of the wheel, Factor says, while the rim’s offset spoke bed is intended to provide balanced tension across the carbon spokes. A ‘mini hook’ system is used to hold the tyres in place. The Black Inc 48/58 wheelset has a claimed weight of 1,270g.

The results... according to Factor

As is usually the case, Factor first modelled its design concepts using CFD (computational fluid dynamics) – a virtual wind tunnel, if you like – before wind tunnel verification and real-world testing. 

Factor says, “[Our] rapid design iteration, analysis and optimisation process has resulted in a 70g reduction in drag (a seven-watt saving) [at 48km/h or 30mph] compared to the previous Ostro VAM frame, with aerodynamic benefits becoming more pronounced at 5-10° yaw angles that most represent real-world riding conditions.”

Yeah, okay, but don’t we hear similar aero claims with every new bike launch? The new model is always the best in the history of the universe.

“There's a million different ways that you can manipulate the results in the wind tunnel,” says Graham Shrive. “In our case, we chose to be as transparent as we possibly could, as well as repeatable as possible, so we decided to go with a straight average across the sweep, as well as just using a bare bike and wheels only.”

There’s tons of debate about the best way to go about wind tunnel testing – that’s a whole feature in itself – but Factor measures at 48km/h (30mph), up to 15° of yaw on both sides of the bike, and averaging all yaw angles. Not too many of us are getting around at 30mph on a regular basis, but that’s the speed that Factor has chosen to use here.

How does the Ostro VAM stack up against the opposition, according to Factor? Funny you should ask; it took the Specialized Tarmac SL8 and the Cervelo S5 to the wind tunnel along with the new bike to find out. It first tested ‘as-sold’ bikes with uniform drivetrains, and stock wheels and components from the relevant companies (graph below).

“While the S5 excels in 0-degree scenarios, the Ostro VAM is significantly faster once yaw angles approach 5° and the margin increases dramatically up to 10°,” says Factor.

“Averaged results across all yaw angles show the Ostro VAM to now be the benchmark aerodynamic, lightweight race bike. While the Ostro VAM bests the S5 by 6% across the averaged yaw sweep, the SL8 almost matches the S5 due to deeper wheels, narrower tyres, and a deeper bar. The Ostro VAM bests the SL8 as sold across the yaw sweep by 6.8%.”

Factor also compared the bikes with “normalised components” (graph above) with the aim of isolating the impact of the frame and wheels. For these tests, all bikes were fitted with the same tyres and Black Inc 48/58 wheels. The SL8 was tested with the Black Inc Aero Barstem, though this wasn’t possible on the S5 owing to its design.

"Normalising these bikes as much as we could, we were able to see quite a big improvement over them,” says Graham Shrive. “With the same handlebars and the 48/58 wheels, we see about a 14% improvement over the SL8 and then about that same 6% improvement over the S5.” 

Of course, these are Factor’s figures, and we’d be stunned if a brand ever published data showing its product trailing behind the opposition. That almost goes without saying. Factor must be honest, but it gets to pick various test variables/protocols, and decides which figures it wants to release. It also decides on the weight it gives to wind tunnel measurements at each yaw (relative wind) angle.

Factor treats all yaw angles equally in deriving its averages – so measurements at 10° and 15° yaw (where Factor’s figures say that the Ostro VAM is considerably more slippery than its rivals) are treated as being as important as measurements where the air is coming head on (where the Cervelo S5 comes out on top). Other brands prefer to use a weighted wind averaged drag that makes some measurements more important than others in an effort to reflect reality more closely. There's certainly no industry standard.

We’re sure that every other brand would give us data that demonstrate beyond all doubt that their bike kicks ass too. You know how it works. Factor has, though, explained how it derived its statistics, so you can take ’em or leave ’em.

Weight

Here are the claimed weights for the various parts that Factor includes in what it calls its Premium Package:

Frame (54cm) 820g
Fork 463g
Seatpost with hardware 168.6g
Small parts 268.4g
Black Inc Aero Barstem (110x42) 376g
Total of Premium Package 2,096g

Black Inc 48/58 wheels 1,270g
Total of Premium Package with wheels 3,366g

The Premium Package total is 48.8g lighter than the equivalent version of the first Ostro VAM, according to Factor's stats.

The Black Inc 48/58 wheels are 219g lighter than the previous Black Inc 45s, so the Premium Package with wheels is 267.8g lighter than before. The vast majority of the weight savings comes from the wheels, then.

For comparison, Specialized claims 685g for its Tarmac SL8 frame in a 56cm size.

As mentioned way up there somewhere [wafts hand vaguely], Factor says that weight saving wasn’t a priority with the new Ostro VAM frameset, the redesign was focused on improving aero efficiency.

“We weren't looking to make it any lighter because we felt like we already had one of the lightest bikes in the world,” says Factor CEO Robert Gitelis. “We did find some weight savings as a byproduct of the development we did, but this was all about how to make the bike faster while staying true to the Ostro heritage. It was really important not to diverge too much from what we had already done, but to make something great even better.”

With the Ostro VAM easily able to make the UCI’s 6.8kg minimum weight limit, does Factor’s lightweight O2 (pictured below) become redundant?

> Factor launches new O2 VAM as “the world’s fastest climbing bike”

“The O2 is still very competitive with other bikes in the WorldTour, it’s just not quite as fast as the Ostro VAM,” says Rob Gitelis. “It still has a place for some uphill finishes. I think we will see the HPH [Human Powered Health Cycling] women’s professional team riding it quite a bit. 

“Having spent the last couple of weeks with the [Israel–Premier Tech] team, one thing that’s striking is that a number of riders are quite keen on it. Jakob Fuglsang, for example, won't ride anything else. 

“One of the things the team talks about quite a bit is where they win the races and how does the bike perform in those situations. The O2 is really designed around aerodynamic performance at lower velocities – so when you’re climbing, for example – without giving too much back at higher speeds. Jakob knows that if he’s going to win a race it will be typically on a climb or on a stage where you're limited by the braking on the descent more than anything. 

“We challenge the riders to look at how they’re going to win that race and then choose the most appropriate tool for the job. We don't try to force the riders to do anything. “

Factor Ostro VAM prices 

Factor has kept the Ostro VAM prices the same as previously:

Premium Package frameset £5,499
Premium Package + Black Inc 48/58 wheels £8,900
Premium complete bike, Shimano Ultegra 8100 Di2 £8,999
Premium complete bike, Shimano Dura-Ace 9200 Di2 £10,799
Premium complete bike, SRAM Force eTap AXS + Quarq powermeter £9,299
Premium complete bike, SRAM Red eTap AXS £10,999
Premium complete bike, SRAM Red eTap AXS + Quarq powermeter £11,399

Find out more at factorbikes.com.