New Factor Ostro Gravel 'ultimate gravel racing bike’ is based on Tour de France stage-winning road frame

Factor has launched the Ostro Gravel - an evolution of its flagship all-rounder road race bike the Ostro VAM, claiming it is “the ultimate gravel racing bike that combines elite gravel performance with best-in-class aerodynamics.”

We spotted the new bike being ridden by gravel pro Dylan Johnson in Unbound and Crusher in the Tushar earlier in the year, but now Factor has officially released all the details.

Factor says the Ostro Gravel gravel bike draws inspiration from the Tour de France stage-winning Ostro VAM road bike (by Simon Clarke on the dramatic cobbled stage five in the 2022 race) and adapts it for the nuances of gravel racing in the form of lower-speed aerodynamics, more rugged construction, geometry and handling, and versatile mounting options.

Factor's existing gravel bike, the Factor LS, has exposed cables and relatively skinny tubes: by contrast the new Ostro Gravel frame with its deeper profiles and integrated bar/stem is barely distinguishable from an aero road bike.

According to the Taiwan-based British brand, it has applied its road and time trial expertise - which is considerable - to construct a bike that is fast across a variety of surfaces, but which is specifically designed with high-end gravel racing in mind.

In this discipline, Factor identifies a growing desire for optimised aerodynamics - especially over long distances such as 200km where small watt saving translates into a good chunk of time - and says the Ostro Gravel combines elite aerodynamics with gravel riding/racing design details “to deliver a gravel bike that is in a class of its own.”

Factor is up against new, aero-ised gravel race bikes such as the Pinarello Grevil F, which launched earlier this year.

Let’s have a look at some numbers.

Factor Ostro Gravel: the numbers

There’s 45mm of tyre clearance and Factor says the frame weighs in at 900g (size 54 fully painted frame in Naked Grunge). By comparison the Ostro VAM road race bike has a claimed frame weight of 830g in a size 54 in the Flicker paint scheme. 

The frame is constructed from a blend of TeXtreme, Toray and Nippon Graphite pitch-based fibre. This, says Factor, balances its signature lightweight design with a strengthened layup to handle the challenging conditions of gravel racing. 

It gets a T47A threaded bottom bracket, rounded steerer tube and fully-internal cabling and there are multiple mounting points for bottles and other gravel accessories.  

As for the geometry, it sounds as though there are some clever angles at work. Factor points out that many all-road and gravel bikes struggle to deliver steering that’s effective and confident both on and off-road, typically ending up with a compromise of soft handling and modest tyre capacity. As well as being wider, gravel tyres have a greater outside diameter which increases the trail of a bike; narrower tyres have a smaller outside diameter which reduces trail. 

Factor’s engineers made tyre size an integral part of the Ostro Gravel’s geometry, selecting a trail value on the slightly faster handling side for gravel use, given the bike’s racing focus, while prioritising head tube angle when selecting fork rake. This, says the brand, leads to a fast-handling gravel bike on 43mm tyres and an equally satisfying and precise all-road machine on 32s, with no low-speed wheel flop. 

The tops of the fork blades bear the legend 'Never. Status. Quo.' which neatly sums up Factor's innovative approach to the fork trail conundrum - but is sure to anger diehard fans of Francis Rossi, Rick Parfitt (RIP) et al.

Black Inc build

Factor’s sister brand Black Inc supplies the wheelset and integrated bar/stem.

The Black Inc Thirty-Four wheelset is engineered for gravel and all-terrain riding, with a hookless rim profile for 30mm tyres or wider, and weighing a claimed 1,489g. It runs on custom CeramicSpeed bearings and Sapim CX-Ray and CX-Sprint butted aero spokes. 

The Black Inc Aero Integrated Barstem has been developed to complement the frame. It has a gently flared design, which Factor claims also provides significant power savings of up to 9 watts compared to a regular bar stem set-up, as validated in Factor’s own wind tunnel testing.

Factor founder and CEO Rob Gitelis said: “Extending our current gravel offering to include a bike of this calibre is integral to Factor's development. We have invested heavily in the technology to create what we believe to be the world’s fastest gravel bike. Seeing it already succeed on the world stage is something we are extremely proud of."

Build options

The Factor Ostro Gravel comes in six complete builds or as a framesest.

• SRAM FORCE - $8,599 / £7,400
• SRAM FORCE + Power meter - $8,799 / £7,570
• SRAM FORCE XPLR + Power meter - $8,199 / £7,060
• SRAM RED - $10,499 / £9,030
• SRAM RED + Power meter - $10,899 / £9,380
• SRAM RED XPLR + Power meter - $9,799 / £8,430 
• Premium Package Frameset - $5,499 / £4,730 Includes frame, fork, seatpost, barstem, CeramicSpeed BB, CeramicSpeed Headset
• Premium Package Frameset + Black Inc Wheels - $7,499 / £6,450 Includes frame, fork, seatpost, barstem, CeramicSpeed BB, CeramicSpeed headset, Black Inc Thirty-Four wheels 

CW tech features editor Stefan Abram: my take

 As a race-focused gravel bike, the Ostro Gravel certainly looks the part: the sleek silhouette could easily pass as being part of the current crop of aero-climbing bikes – if you squint so as not to see the intermediate tread of the tyres.

Partly this is due to how the cables have been neatly tucked inside the frame, with no exposed routing flapping about around the bars. Similar to some other brands, Factor’s solution has left the Ostro Gravel being compatible with electronic / hydraulic groupsets only.

For top-end and World Tour race bikes this isn’t a big deal – even if the bikes are compatible with mechanical groupsets, the question of whether they’re actually sold with mechanical groupsets is quite different. But to not be compatible with 13 speed gravel groupsets such as Campagnolo Ekar is a bit of a shame for the Factor Ostro Gravel.

The other aspect of the frame design which gives it such a racey look are those chunky tubes with their kammtail trailing edges.

Now, the general rule of thumb is that the rider’s position is most important when it comes to aerodynamics, followed by the wheels and only then the frame. An aero optimised gravel bike with 34mm deep wheels could be construed as putting the cart before the horse a little bit.

Still, given that the claimed frame weight is 900 grams, painted, and in a size 54cm, whatever the benefits are they might as well be reaped – especially considering the speeds that gravel racing pros get up to.

Finally, it is nice to hear how Factor has considered the effect that different tyre sizes has on the handling, with the bike having a ‘road-like’ trail value when used with tyres around the 33mm mark. When 43mm tyres are specced, this increases the trail and slows down the handling, putting it within the bounds that Factor’s engineers wanted for use on gravel.

Sure, this is just a product of geometry. A change to the trail will happen with any bike if you switch up the tyre size – or, more specifically, the outer diameter of the wheel/tyre system – but hats off to Factor for showing their workings and being clear about the boundaries.

The Factor Ostro Gravel is on sale globally via Factorbikes.com and authorized Factor dealers from the end of September 2022.