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Power of one: the rise of the 1x groupset

In-depth
30 Jul 2021
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The 1x groupset is now ubiquitous on gravel bikes, but will it become standard for road bikes too? Cyclist investigates

Words Sam Challis Photography Tapestry

Since the birth of the derailleur, the biggest advancements in drivetrain technology almost exclusively involved the addition of more gears.

‘In general, more gears brings improvements in gear ratios for climbing or for speed, or improvements in cadence due to smaller gaps between the gears,’ says Shimano’s Ben Hillsdon.

Yet since 2015 there has been a faction of the bike industry championing the use of 1x – single chainring groupsets – on road bikes. It has been a slow burn, yet the trend has continued despite being at odds with common perceptions of drivetrain development in that 1x drivetrains mean you’re left with fewer gears, not more. So why has the concept endured?

‘I’d say it’s not for everyone, but 1x is simpler, quieter and more secure,’ says JP McCarthy, road product manager for Sram, a company that is a vocal proponent of 1x drivetrains on road bikes.

‘The aesthetic qualities cannot be understated either: 1x matches the clean lines of a road bike perfectly. I love knowing I’m not carrying components that aren’t entirely necessary or shifting in a way that I don’t absolutely need to.

‘Plus not having to shift at the front makes for a better ride experience. Front shifts require preparation, execution and recovery, whereas rear shifts can be made under power without a second thought.’

Shimano and Campagnolo, while both offering 1x groupsets in their ranges (albeit not ones aimed specifically at the road market), are far more reserved in their opinions towards their respective products’ suitability for road riding.

Both point to the scope of 2x drivetrains to maintain preferred cadences as one advantage, with another being the potential for this to help reduce the physiological cost to the rider.

McCarthy, however, argues that 1x could still benefit riders when it comes to correct gear selection: ‘On rolling terrain, when you’re on a 2x setup the tendency is to over-gear if the crest of a hill is in sight – you might just push through without front-shifting. That can end up costing the legs more heavily than if a lower gear can be accessed easily on a 1x setup. Considering the ease with which the rider can carry out a rear shift, they are more likely to find the lower gear and save their legs.’

A bit of R&R

Range and ratios are two of the major hurdles 1x struggles to overcome in the eyes of many. But since the advent of 12 and 13-speed cassettes, the idea that 1x drivetrains lack range is a misconception. For example, Campagnolo’s 13-speed Ekar drivetrain pairs its 38-tooth chainring with a 9-36t cassette option that essentially gives you the same range as a 50/34 double with an 11-30t cassette. P

ut another way, Sram’s widest 12-speed 10-50t cassette (a mountain bike product, but one that will work with the brand’s road components) with a 1x chainring provides 500% gearing range. That same 50/34, 11-30t 2x drivetrain only offers 485% range.

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There are concerns around the jumps between gears being bigger than in a standard 2x drivetrain, but even here the disparity isn’t as large as you’d think. Some 2x gear combinations are precluded by chainlines becoming too extreme and other gears overlap between the big and small chainring.

It means 2x11 and 2x12 setups only actually offer between 14 and 18 unique gears. However that is still more than is currently available on even the most progressive 1x systems, which is why Shimano still recommends 2x for road.

In a surprising development, the maker with the purest road heritage, Campagnolo, takes a softer stance towards 1x’s use following the release of Ekar. Giacomo Sartore, Campagnolo’s groupset product manager, states that 2x is unequivocally better for racing but he does suggest 1x can work for road riders.

‘Our Ekar cassette ratios were the result of extensive research into the needs of cyclists and, as a result, progress in a unique way,’ says Sartore. ‘The bottom six gears have one-tooth jumps between them, for when speeds are higher and the rider is more sensitive to changes in cadence.

‘The upper seven gears use incrementally larger jumps to create the range. While we think this solution is optimal for gravel riding and can work depending on the needs of the road riding individual, our 2x groups offer fine cadence control across the entire cassette and therefore are best for racing and performance riding.’ 

Framing another perspective

Gerard Vroomen has been a champion of 1x drivetrains since the trend first started. 3T’s Strada, a bike Vroomen designed, was the first 1x road bike on the market back when road drivetrains were still 11-speed at most.

He recognises the design was on the limit considering the state of drivetrain technology back then – which was perhaps the reason for the high-profile controversy concerning pro team Aqua Blue’s use of the bike in the WorldTour – but says Campagnolo’s Ekar cassette ratios are ‘perfect, making 1x within reach for everybody’.

Perhaps to be expected, Vroomen is quick to reel off numerous benefits of 1x gearing: ‘The drivetrains have the potential to offer a lower weight, better aerodynamics, less risk of chain suck, simpler maintenance, less noise, make cleaning easier, create a minimalist aesthetic and, especially for newer riders, nurture a much more intuitive shifting experience.’

Ian Hughes, an industry veteran and founder of British brand Vielo, expands on that. Vielo’s R+1 road bike has been specifically designed to accommodate 1x drivetrains – the result is that 2x simply won’t fit.

‘We see the advantages of 1x for regular bikes, but it’s when frames are purpose-made around the system that its true potential is realised,’ he says.

‘There aren’t many areas on a traditional road frame where substantial gains can be had anymore,’ says Trevor Hughes, Vielo’s co-founder.

‘Dropping the front mech and inner ring opens up all sorts of avenues to improve performance. The down tube can be wider and completely symmetrical when it enters the bottom bracket junction, for example, rather than having to make space for the inner ring. That change alone can improve stiffness by 32% in that area.

‘The seat tube design gets freed up too as it isn’t restricted by having to provide a front mech mounting point, so it can shield the rear wheel better and be made more aero. The chainstays can be wider and flatter but still offer wide tyre clearance. That is a critical feature. Most chainstays have a compromised shape to account for the extra chainring right where they bond with the BB junction. This is simply a better way to make a frame.’

Shifting opinion

If that is indeed the case, why is it just a few small brands that are exploiting the purported advantages of designing around a 1x drivetrain for the road?

‘In my experience, big brands have to produce a range of bikes that are within a set parameter for their global market,’ says Ian Hughes. ‘1x-specific frames are too much of a risk at the moment, but you will see more smaller brands doing it soon. That said, the big brands are dabbling. Take that as them testing the water.’

Hughes is referring to brands such as Specialized, which now offers a 1x spec for its Tarmac race bike. Vroomen says it’s still going to be a slow process though, because the successful adoption of new technology relies on the development of a complex mix of input from bike designers, groupset makers and consumers.

‘The whole dynamic of the road market is better set up for, and more accepting of, incremental gains than those who zig while everyone else continues to zag,’ he says.

It isn’t thought we’ll see any sort of meaningful re-emergence of 1x in the pro peloton any time soon to promote the system at the top of the sport, despite the consistent but occasional use in time-trials, for example.

‘I like to think of it as a speed differential between user groups,’ says Sram’s McCarthy. ‘If you look at the WorldTour groups, they’re fast. When you’re approaching a stage finish in the Tour de France they may be riding at 75kmh but still looking to push up a gear, so you have a precise high gear requirement. Yet on the same stage the same rider could also have a low gear requirement to hit that cadence and power sweetspot going up a long Alpine climb.’

That may explain why pros still prefer 2x, but Vroomen doesn’t think that’s important to most people.

‘Pros are irrelevant. Pro sponsorships are just about the money now and consumers are less interested,’ he says. ‘What we’re seeing is that the pure road bike is losing ground to the gravel bike, and to bikes that sit somewhere in-between. So for all the advantages, it might not even be the case that more pure road bikes will become 1x.

‘It may instead be that more people will choose as their road bike a bike that is really a gravel bike, and that will more often have 1x. Contemporary gravel bikes are better for the normal user than race bikes anyway: better geometry and more pertinent features.’

Technological advancement, more available OEM options, shifting consumer buying patterns… 1x’s route into the mainstream could be achieved via a number of mechanisms. Which one is still unclear, but the general feeling is that in future more riders, both on and off-road, will be persuaded by the power of one.

Shimano GRX Di2 1x

Approx £1,600 (dependent on spec). For more visit Freewheel

Shimano is the staunchest of the big three in its stance on 1x’s limited efficacy for road use. Yet it was the first to launch a dedicated groupset for gravel, a riding discipline that shares many similarities with road.

GRX is modular, making it possible to mix and match components. As it is still 11-speed, the disadvantage is that users must choose between a MTB cassette to get a broad range of gears or a road cassette for closer ratios, although it’s feasible to switch between cassettes for a given ride.

Campagnolo Ekar

£1,449. For more visit Condor Cycles

Ekar is a bold step for Campagnolo, being the first non-road specific groupset from the Italians for over two decades, as well as the first mainstream 13-speed drivetrain. Even though Campagnolo markets Ekar towards gravel, that extra sprocket makes it one of the most viable road 1x options too. It helps that Campagnolo has produced some really smart cassette ratios: a nine-tooth smallest sprocket creates plenty of range while still allowing for one-tooth jumps between the smallest six gears for fine cadence control at high speeds. Brands such as 3T and Vielo say Ekar has done a huge amount to legitimise road 1x.

Sram Force eTap AXS 1x

£1,890. For more visit Wiggle

As the most vocal proponent of 1x out of the big three groupset manufacturers, fittingly Sram caters extensively for road 1x setups. Each of its top three road groupset tiers has fully fledged 1x options, and Sram’s 12-speed cassettes minimise the compromise between range and close gear steps. eTap AXS’s wireless technology takes the clean aesthetic of 1x to the extreme too.

Intelligently, Sram has made all of its AXS components cross-compatible between its road and mountain bike groupsets, so Eagle cassettes and rear derailleurs work seamlessly with Force shifters and chainsets, meaning that there’s the scope to fully customise a 1x setup dependent on individual riding needs.