Tech Talk: Sound Off
Around two years ago the notion of 1x (pronounced one-by) set-ups was starting to be introduced into the road market. By this, we mean a single front chainring with your normal 10/11 speed cassette on the rear. Now at this stage, the 1x drivetrains were nothing new to cyclists, having been around the MTB rigs since 2012, and not long after they were available for cyclocross bikes. The move towards 1x for off-road bikes was aided by more cogs becoming available in the rear cassette, with 10 then 11 speed coming into the market, meaning the double and triple cranksets of the past were overkill. Simplicity was the key to the new system as bigger rear cogs could compensate for no small front chainrings. It was only a natural progression to see them appear on road bikes shortly after that. SRAM was the big manufacturer who was predominately responsible for the new push for less gearing up front with their MTB drivetrains, followed later by Shimano.
Moving on a few years, and we don’t know about the crew that you regularly ride with, but no one we know was riding a 1x set up on their roadie or TT bike until very recently. So, why hasn’t this set up taken off for the road market like it has for the off-road segment? One major reason is that the biggest player in the road game, Shimano, hasn’t followed SRAM in developing their own road ready 1x set up. This in itself probably answers the question, in that Shimano don’t see a market in 1x for the road – at this stage. To go further and see why this setup isn’t being seen on Grand Tour riders’ bikes we have to look at the pros and cons of 1x, and where its application for the road might fit best.
The Brownlee brothers have also chosen this drivetrain option throughout the WTS, and were winning on it. — The Test Lab
Firstly, by removing the front derailleur off your bike, there can be a reasonable weight saving in the order of 200g. With this change up front, there is also one less chainring required saving a little more weight. For the aero inclined amongst us, we see a slight reduction in drag associated with the front mech (and potentially derailleur hanger) being taken off. Better airflow around the front chainring may also reduce the drag coefficient with some independent testing showing a few watts being saved around the front crank. We also get a small weight saving by no longer needing a front gearshift lever, which can be taken off a TT bike if desired, however, unless you’re a super weight weenie, you’re not likely going to hollow out a road shifter to save a few grams. This weight saving is countered somewhat if the rider adopts the preferred clutch rear derailleur for the 1x build, which is slightly heavier. Also, adding some bulk are the big cogs – from 28 teeth up to as far as 36 or even 40t – more metal equals more weight.
Proponents of 1x drivetrains also see the narrow/wide (shape of the teeth on 1x) chainrings as being more secure for the chain, reducing the likelihood of chain drop. This reduction in chain drop is aided by the clutch rear derailleur giving the rider better chain tension. This basically means no chain slap that you can get on rough roads with a regular road derailleur and no need for a chain catcher. As we mentioned earlier, this all leads to a simpler, lighter and potentially more efficient drivetrain requiring less maintenance. Why wouldn’t you choose to ride this?
The main reason we at The Test Lab see the adoption for 1x not taking off for the road market as it has for MTB/Cyclocross, is that there are much larger gaps in gear ratios. Road bikes generally have wider speed ranges than their off-road cousins, meaning the space between ratios is magnified more on a road bike. Descents of 70kph might require a 52/11 (biggest front ring/smallest back cog) while low-speed climbs of 10kph or less might call for 36/25 gearing. We can ride with a 1x set up of a 52 front ring with an 11-36 to match the above 2x set up but we also need all those gears in between to help keep our cadence in manageable increments in order to maintain an efficient pedalling style. By dropping the front ring to 50 or 48t we get better climbing gears but lose high-end speed, and vice versa by keeping a 52t front but dropping to an 11-25, 26 or 28. For most road set ups, these jumps are just a little big to manage.
We also see a difference in chain line with a 1x system where the high and low cogs are slightly off centre compared to the 2x system, which may increase friction in the chain and potentially reduce wattage very slightly. This is more likely an issue with the bigger cog as it’s closer to the front ring meaning it has a greater angle from front to back, while the smallest cog isn’t affected to any great degree as it sits further back relative to the front ring.
Riders who can’t go without their Di2/eTap will also be a little left out as there are no dedicated electronic options as yet, but we hear SRAM is in the process of changing this, as the eTap system is more adaptable to going 1x. We have seen some custom engineering of Di2 wires to turn a 2x into a 1x, but this is outside of expertise as well as limiting you to using a Di2 derailleur and not the recommended clutch option. We’ve also seen some Shimano XTR Di2 MTB rear derailleurs being used.
The other factor we need to consider is cost. This can go either way depending on whether or not you have a bike with 2x already installed and want to go 1x, which may be more costly, or whether you’re starting from scratch, which will likely be cheaper. Either way, if you’re looking at doing the 1x thing right you’ll need a new a 1x crank, like the SRAM Force or Rival, that has the narrow/wide tooth profiles, a clutch derailleur to reduce chain slap and chain drop that can deal with larger cogs and potentially a new rear cassette to gain the higher gears that you may lose without your small front ring. On the other hand, you won’t need a front derailleur, or a double or, heaven forbid a triple chainring (although you can retrofit a narrow/wide to a triple), or a front gearshift mechanism and the cables going to the derailleur.
We think 1x is a great way to make those marginal gain you might be looking for. — The Test Lab
So, back to the point of this article – what applications do we see this 1x system being best used for, for those of us who like our roads sealed? Unsurprisingly we think triathletes can make the best use of the 1x system to make us faster, by being a bit lighter, more aerodynamic and making it easier for us to keep our speed machines in great working order, with more simple maintenance. As more of our best pros and elite age groupers are seeking those 1% gains, we are beginning to see more and more 1x rigs in competition. Jordan Rapp was one of the first to adopt the set up for long course racing, while the Brownlee brothers have also chosen this drivetrain option throughout the WTS, and were winning on it. We’re even seeing some of the world’s best time trialists such as Germany’s Tony Martin and Meike Kroger featuring the simple set up.
So, why does it work for triathletes and TTer’s better than road racers? Simply put, most triathlon and time trial courses aren’t hilly enough to warrant needing the bigger gaps in cogs that come with 11-36 cassettes. For most, a 50 or 52t front ring with an 11-25 to 28 rear cassette will be more than enough for most races we enter. A 52t/28 ratio is equivalent to the old 39t/21 we used to ride up the steepest of hills around Melbourne. We don’t think the lack of electronics is really that much of an issue either. With SRAM coming up with the 1x eTap, this will actually be much cheaper than a full Di2 build. Mechanical shifting is still a very reliable option, with most bikes having hidden cables all the way to the rear mech.
Unless you’re planning on making the Alpe d’Huez triathlon for your A-race this season, we think 1x is a great way to make those marginal gains you might be searching for. You might wish to choose this option in order to step one level higher on the podium or just to make your bike set up less complicated. We’re sure the other big manufacturers apart from SRAM, like Shimano and Campagnolo, will see that the market for 1x is growing and will come to the party with some great electronic and mechanical offerings.
Look out for our next instalment of tech talk, where we show you how easy it is to go 1x.