The past, present and future of bike fit: How the guidance has changed, and how a treadmill could revolutionise our sport

A few weeks ago, I spent time at the Specialized headquarters in Morgan Hill, and alongside my tour of the brand’s various facilities, a morning in the wind tunnel, and a few lunch rides, I was offered a bike fit on the Tarmac SL9 with Jason Williams, long-time bike fit guru and the personal bike fitter to Remco Evenepoel.

This was the first time I’d seen Williams since he fitted me to my own S-Works Tarmac SL6 in 2019. As we spoke, he pulled up my old data to see how they compared, and it was a fascinating confirmation of the trend that has occurred in road cycling bike fit over those years.

Going back to that 2019 fit; I’d not long joined Cyclingnews, was a keen road racer, and I went on holiday – we called it a training camp – with my friends to Majorca. By sheer coincidence we found ourselves staying at the same hotel as Bora-Hansgrohe during their December training camp.

Upon seeing a horde of Specialized T-shirts, I reached out to a contact and was soon invited to see the team's makeshift performance room (a conference room in the basement) and offered a slice of the pro rider experience. I felt like a football fan pulled from the crowd to fill in for an injured player.

Within that experience, I met Williams, alongside one of Retül's co-founders, Todd Carver, and was offered a Retül Fit.

Williams' recommendations removed a knee pain that had plagued me on-and-off for years and had already reared its head on the first ride. It threatened to derail the trip, but I rode pain-free for the rest of the week.

Retül, founded in 2007 and acquired by Specialized in 2012, tracks 16 points on the body (eight on each side) in relation to the bike to sub-millimetre accuracy. These are then used to measure how the body moves through space as you pedal; things like knee angle at various points throughout the pedal stroke, hip angle, reach, whether your knees wobble under load, how much bend is in your elbows, and so on.

It has collated data from hundreds of thousands of fits, and uses the averages to offer normative ranges for each measurement to quantify whether yours are similar to the rest of the cycling population. As such, for 99% of riders, they represent a perfect sweetspot of where and how they should fit onto a bike.

But Williams works with the 1% – WorldTour pros – and so he sees the ranges like a chess grandmaster sees a board. It's fascinating to watch his brain work, using the ranges as a guide while calculating in real time that injury X could be due to knee position Y adding workload to muscle Z, and that since flexibility issue A means muscle B is switching off, pushing outside of the suggested range might actually be better if paired with strength exercise C.

It’ll be no surprise to anyone that I’m a data-driven person, so all these measurements and ranges put me at ease. I once had a bike fit where the guy primarily stood across the room and eyeballed these measurements. I trust he is brilliant at that, but I came away feeling less confident in my position than when I started.

The nerdy section: How did my fit change between 2019 and 2026?

Higher, further forward, narrower… is this starting to sound familiar? The comparison between my new fit and my old fit is akin to reading a summary of the wider industry's trends over the past seven years.

At the most basic level, it's interesting to see that in 2019, the suggested ranges were singular and for all riders, but in 2026 that's shifted to discipline specific. A road racer doesn't necessarily want the same position as an endurance rider, and they especially don't want the same as a time triallist. This distinction alone is a big step forward in ensuring that each rider gets a better baseline to work from.

But for me specifically, the changes start with a significant shift forward on the bike, from behind the pedals to right on top of them.

The biggest changes in the entire dataset are in my knee position, with knee-forward-of-spindle (the offset of the knee marker relative to the pedal spindle at 3 o'clock in the pedal stroke) increasing (moving forward) by an average of 72mm (averaging the variance of left-right). Back in 2019, my knee tracked 47-69mm behind the pedal axle, even after that fit had already moved me forwards. By 2026, it's sitting 13-15mm in front of the axle; a massive shift forward and solving a likely imbalance that went unseen before. While the exact millimetre difference could be affected by marker placement or where I chose to sit on the saddle, the overall direction of travel is unmistakable.

Elsewhere, the bars are now 12mm higher and 12mm closer relative to the bottom bracket, but interestingly, my back angle has barely changed. Rather than making me noticeably more upright, the extra stack, shorter reach, and forward saddle position have been absorbed through more elbow bend (162° to 145°) and a 3° more open hip angle. That suggests I've gained a lot of comfort without giving away much aerodynamically.

And speaking of aerodynamics, my cockpit went dramatically narrower too. The distance between my hands has shrunk from 378mm to 345mm, a 33mm reduction. It's very much in keeping with modern aero thinking, with the 2026 fit showing my wrists sitting 14-20mm inside my shoulders, rather than in line with them as they were before.

And to round off the game of modern bike fit bingo, I'm also now on shorter cranks, although that wasn't a change we made on the day; that's baked into the Tarmac SL9's specs, at 2.5mm shorter than previously specced across the whole size range.

This means my 58cm frame puts me on 172.5mm cranks, although Williams agreed that my hip flexor tightness would probably be a strong case for dropping down another size to 170mm.

Subtle but significant shifts

If you'd asked me six weeks ago to name some progressive brands that are designing with modern fits in mind, I wouldn't have said Specialized, but my mind has been changed.

According to the geometry charts, the Tarmac SL9 handlebars are only 2cm narrower than before, and are stated as 42cm in my 58cm frame size, but that's misleading. The 42cm measurement is taken outside-to-outside at the drops. They actually measure 36cm centre-to-centre at the base of the hoods (ie, where they clamp, which is where most brands take their measurements.

As mentioned, cranks are shorter across the size run, bottom brackets lower to account for bigger tyres, which are now specced at 30mm instead of 26mm. And you can buy 0mm offset seatposts if you really want to chase the progressive position.

This is all done to balance accommodating the small percentage of Specialized's customer base that want to chase this modern position, without losing the geometry of the Tarmac that the rest of the customer base knows and loves.

The future

I'm not a betting man but I don't expect we'll see the change we've seen in bike fit trends over the past seven years to continue as drastically for the next seven. But that's not for a lack of innovation on Specialized's part.

In my time at Morgan Hill, I was also given access to the building's latest instalment: a treadmill.

No, Specialized isn't getting into running (even if Nike is rumoured to be targeting a resurgence in cycling). Instead, it is able to look at the biomechanical implications of different equipment designs on different surfaces and gradients.

In fact, it's the company's fifth version of a treadmill, although, to my understanding, this is the first time an outsider has been told about their existence, let alone given a demonstration.

The treadmill itself is an enormous rolling belt of slats that can have plates bolted onto it at select intervals to create any desired frequency and intensity of bumps; everything from 1mm square-edge plates to 3D-printed recreations of cobbled surfaces.

And by knowing the speed at which the 'road' is moving beneath the rider and thus removing aerodynamics from the equation, the treadmill enables the isolation of other metrics and thus the measurement of them with much greater accuracy. Not dissimilar in theory to the Pedalling Efficiency Rig we've used for some of our CN Labs tests, but with the added realism of both wheels, natural weight distribution and the need to balance and steer.

On its own, the potential prospects include tyre rolling resistance testing and suspension tuning, for example, and earlier iterations have already been used to drive shifts in mountain bike geometry.

But by then pairing this technology with a metabolic cart (for testing a rider's oxygen uptake) and a 32-sensor EMG system (which measures the electrical activity in muscles when they contract), Specialized can then measure how a rider's biomechanics respond to different setups.

Most pertinent here is that those setups can include different positions on the bike.

It's nothing new for professional athletes to test their oxygen uptake alongside a new bike fit position, especially on time trial bikes, but this generally happens on an indoor trainer with much reduced realism, not least the removal of any need to steer or balance.

Here things get more realistic and comprehensive. Theoretically, Remco Evenepoel could be tasked with repeatedly riding a recreated section of the Oude Kwaremont in multiple different positions in order to quantify which is least taxing.

That's a frightful thought if you're one of a very select handful of Evenepoel's rivals, but what about the rest of us?

Exclusive expertise, open to all

Williams' expertise isn't just reserved for Remco, it powers the Retül system and flows through every Body Geometry product in Specialized's lineup.

If you go to your local Retül-equipped bike shop or fit studio, the person you see will have been trained on what ultimately boils down to Williams' knowledge. The Retül system is designed to transfer his expertise and his research to every user, equipping them with the power to offer you the same bike fit experience that Remco Evenepoel receives when he goes to Morgan Hill, California.

And through Williams' research and close connection to Specialized's product teams, that same expertise is distilled into the bikes, such as the aforementioned bike geometry shifts; shoes, such as the new Ares shoes; saddles, with Mimic and Mirror technology, and so much more.

Sure, Remco might get the new products before the rest of us, but we can all benefit hugely from the work being done.

And as Williams spends another seven years (and likely more) working with Evenepoel, Demi Vollering, and dozens of other Specialized-sponsored athletes both on the road and on the trail, I'd be surprised if he doesn't unearth some currently unknown nuggets of go-faster gold.

Whether those are positions that ensure a rider can be even more aero without losing metabolic efficiency, or positions that recruit more muscles more effectively than we currently can, is unknown. It's impossible to predict, but it's clear that Williams isn't slowing down in the pursuit of getting his riders to the finish line faster.