Specialized Tarmac SL9 vs Factor ONE - The Modern Speed Equation

The Factor ONE and the Specialized Tarmac SL9 are two of the fastest road bikes to ever exist. How do they compare to each other?

To answer that question, you really have to start with what it even means for a bike to be fast. For much of the history of the bicycle, a fast bike meant a light bike. Less mass to drag up a hill meant it was easier and you’d go faster. If it was flat and you wanted to go faster, it wasn’t complicated: push the pedals harder.

At some point, this changed. Maybe LeMond and his historic Tour de France win using a time trial helmet was the moment. Or maybe not, but regardless of the exact tipping point, the reality of the current era is that the UCI minimum weight rule is making raw weight less of a differentiator. At the same time, our ability to process the complex algorithms that simulate aerodynamics and load dynamics is expanding exponentially.

That is a fancy way of saying bike companies can test variations of tube shapes faster than ever, and that means aero is king. At least in many of the ways that matter when it comes to making a bike fast.

Still, there’s a tension there. How much do you weigh one thing versus another? Can you make a faster bike that’s heavier? What about the human element of actually riding the frame that spits out of all these simulations? Or how about the production processes for the crazy tube shapes a computer algorithm dreams up? Or what if you get crazy and just ignore the UCI?

That gray area is exactly what sets up the standoff between the Factor ONE and the Specialized Tarmac SL9. They represent two entirely different ways of answering the modern speed equation. Because of that, it isn’t the obvious face-off for everyone. Lots of people might think the two bikes belong in different categories. The thing is, neither Specialized nor Factor seems to believe that. Each bike is marketed as the ultimate expression of modern speed, and plenty of riders are cross-shopping the two. I’ve put significant miles on both—here’s how they differ and what makes them similar.

The Specialized philosophy

In the marketing of the Tarmac SL9, Specialized states, “We’re focused on building the fastest bike in the world by engineering around the moments that truly decide races.” What you have to understand about that line is that Specialized is playing a bit of a game here. The company is trying to claim superiority in every way but not tell you quite the whole story.

The Tarmac is not aerodynamically the fastest bike in the world. There’s no getting around that, but it’s also not a mistake. The only trick is that Specialized doesn’t really want to say that the premier aero bike from the company that owns a wind tunnel isn’t the fastest aero bike. Instead, you have to read between the lines a bit. The point Specialized is making is that aero isn’t everything, and a balance of aero, weight, and ride feel makes more sense for a product people ride and race.

Which is not to say that the Tarmac SL9 isn’t aerodynamically fast. Independent testing has consistently placed the Tarmac among the fastest bikes on the market—it’s just not the fastest. It’s also not the lightest, but this is where the UCI rules step in as a backstop for a variety of brands. It might not be possible to build the absolute lightest bike as aero as the Tarmac, but Specialized doesn’t have to worry about it. The UCI gives Specialized an out: just hit the minimum weight and make the bike as aero as possible within that consideration.

The Specialized philosophy is to focus on winning WorldTour races. It doesn’t matter if the consumer can ride a bike that’s lighter or more aero. The brand is banking on the fact that race wins sell bikes, choosing to make compromises in specific areas if that means a better overall race bike. The whole game is to hit the minimum weight while being more aero than any other bike that hits the minimum. It might be more aero to have deeper tubes, but that adds weight, so it’s not worth it. A lighter bike is possible—check the Specialized Aethos 2 for confirmation—but once you go below a 6.8kg complete bike, it’s irrelevant, so you might as well add some weight to make it more aero.

The Factor philosophy

At the surface level, the Factor philosophy is comparatively simple: make the fastest bike possible in the wind tunnel. The reason every bike on the market doesn’t follow this path is that no matter what you do, there will always be a weight compromise inherent in that pursuit.

A more aerodynamic bike uses deeper tubes, and deeper tubes are heavier. How heavy those tubes are is constantly shifting as carbon fiber technology improves. More powerful computers also allow for better simulations, which lets companies reduce the layers of carbon used, and access to those computers is always improving. Factor is also particularly good at things like thinner frame joins, and the materials themselves are always advancing.

But those advances raise the tide for everything. The reality is that less carbon will always be lighter. Apply those same manufacturing improvements to smaller tubes, and you end up with less mass. There’s no magic way around that physics formula, but the UCI currently provides a workaround in the form of rules. Because there is a minimum weight limit, the goal is just to hit that 6.8kg number. If you can make a bike as aero as possible in a wind tunnel and still hit 6.8kg, weight becomes irrelevant.

There are two issues here, though. The first is that the absolute most aerodynamic bikes don’t hit 6.8kg yet, which plays out in the Factor ONE with its additional weight. The second is that consumers don’t necessarily care about UCI rules. You can sell a bike that’s lighter than 6.8kg and there is a massive market for it. With the ONE, Factor is choosing to prioritize aero first and let the weight fall where it may.

The other part of the aerodynamic story is that no matter how slippery a frame is, the rider makes up a much greater percentage of the overall drag. Rider position is where you can make the biggest gains, and that’s where the Factor ONE is actually the most innovative.

The ONE is among the first wave of bikes offering progressive road geometry, which is all about getting the rider low and stretched without ruining the handling. If you simply use a lower stack and a longer stem, you get into a more aerodynamic position, but few people can actually hold it. The solution is to rotate the entire rider position forward around the bottom bracket, dropping the head while maintaining an open hip angle. You can hack this on a standard bike by slamming the saddle all the way forward and running a massive stem, but that negatively impacts handling. Factor instead uses a long top tube paired with a short stem and an optional zero-setback seatpost right out of the box.

Boil it all down, and the Factor ONE starts with an exceptionally aerodynamic frame, then actively helps the rider maintain an aero position for longer. The ONE considers weight, but only in terms of making an aero shape as light as possible.

Riding the Specialized Tarmac SL9 vs the Factor ONE

The Factor ONE takes aerodynamics and makes it the primary focus. Unsurprisingly when you ride the bike, you feel it. The number one thing you will notice about the Factor ONE is its availability to hold speed and remain stable. It’s still a bike so this is about nuance but in comparison to other bikes the Factor ONE wants to go forward and do so at speed. It doesn’t feel as snappy as some bikes and the faster you go the more it comes alive. Even at speed though, it never has a lot of snap to it.

This is the bike you want to settle into. On the Factor ONE I often find myself sitting at high speed and pedalling for long periods of time. I like to refer to these moments as yoga on the bike and it’s all about time seeming to slow down at speed. You can certainly jump with this bike but it’s not the bike that makes you search out those moments of quick acceleration. Instead it’s the bike I find myself searching out moments where I can get down low and focus on my breathing and position. Go fast and stay focused, empty my mind, and just pedal. That is what this bike feels like to me.

What is not surprising about the Factor ONE is that it is very stiff. When you hit a bump, you will feel it and you will feel it at the front tire then again at the rear. It’s not unrideable though, I’ve personally covered two double centuries with it. The geometry is such that the stack is actually slightly taller on the Factor ONE compared to some of my bikes and it also gives a bit of extra room in the reach so my elbow angle is more sustainable. This is a stiff bike but as long as you understand that you’ll be fine on it for long or short distances.

The Specialized is almost the opposite of the Factor ONE in most ways you’d think about a bike. Right away it is a much more forgiving frame. It’s still a race bike but it’s almost approaching endurance bike levels of compliance. It never feels like it’s actually giving up anything when you push against the pedals but it’s much more of a spring than the Factor ONE.

Which also plays out in the ride characteristics. The Specialized Tarmac SL9 is perhaps not the snappiest bike that’s ever existed but Specialized has always been a company that prioritizes that sense of wanting to jump. Quick accelerations feel really good and the bike pushes you to attack often.

Where this bike truly comes alive though, at least for me, is in the mountains. If you want a climbing bike that’s aero look at the Tarmac. Stand on the pedals and dance your way to the top and you will feel like a hero. Not only because it’s lighter but something about the way that Specialized has engineered the compliance just lends itself to getting to the top first even if you aren’t the strongest climber.

The final verdict

There is one more thing I want to highlight when I think about these two bikes, and it’s part of why you might pick one versus the other. The Specialized Tarmac SL9 looks like a regular bike. Not just a regular bike, either. The Tarmac is an incredibly well-known bike that hasn’t appreciably changed for multiple generations. There’s a group ride I sometimes join that has multiple SL8s and a couple of SL7s. They all look the same, and they don’t especially stand out. In some ways, that is part of the charm. Like a Porsche 911, you buy into the family and you know exactly what you are getting. Upgrade after a number of years and sell the old one. It’s easy.

Then there’s the Factor ONE. The bike looks unlike anything else on the market; it is incredibly distinctive. Everyone, whether they know bikes or not, looks at the Factor ONE and feels that wow factor. If you think Factor isn’t aware of this, well… you are wrong. There’s a Bugatti version and a SpongeBob version. Factor understands that this bike turns heads, and the brand has intentionally leaned into a shape that says this is the fastest. It doesn’t matter if it’s 1 watt or 20, you know it’s faster, and that’s what counts.

The other thing you have to keep in mind is price. The Factor ONE and the Specialized Tarmac SL9 S-Works are pretty evenly priced, but very few people in the world have access to bikes at that level. There is no budget version of the ONE. You can get Force instead of RED, but this is an expensive bike. Meanwhile, Specialized offers the Tarmac SL9 in a huge range of prices. It’s certainly still a premium-priced frameset, but the slightly heavier version is drastically less expensive and realistically offers the same ride. You can also, as I already mentioned, tap into the massive used market for Tarmacs. Can’t afford an SL9? Grab an SL8 used for an even lower price and the performance is nearly identical. Far more people have access to a Tarmac compared to a ONE, and it’s an incredible bike.

As for myself, I am not a good climber. I climb when I need to go to the top of the hill, but my days of climbing for the sake of it are long behind me. I love the feeling of the Factor ONE coasting forever and feeling like a rocket on the flats. I also prefer riding ultra-endurance distances, and when you are in the saddle all day, that aerodynamic efficiency is paramount. As much as I love the Tarmac—and I absolutely do—I prefer riding the Factor ONE, partly because it’s audacious and partly because it perfectly matches my riding style. Let me know in the comments where you fall on this debate.