After several years riding the various system and equipment options, talking to industry insiders and crunching the weight, price and drivetrain numbers, what’s the reality of joining the single-ring circus?
No longer restricted to mountain bikes, we consider the pros and cons of dropping a chainring to simplify your shifting. Read on to see if you should be joining the single-ring circus...
Single chainring transmissions dominate more expensive mountain bike specifications and are becoming increasingly common in the dirtier side of drop bar riding, such as cyclo-cross and gravel. But what are the pro and con realities of going single ring and will we ever see it send the double ring the way of the dodo on the majority of road bikes?
Keep it simple
We’re talking just one front chainring, with no front mech, no front shifter and no front gear cable. We’re not talking about singlespeed with just one cog at the back. Single-ring bikes use a conventional rear wheel and, depending on the cassette and shifter, you still get up to 11 gears at the back. That can give you a theoretical gear spread of as much as 511 per cent [the top gear being 511 per cent of the bottom one - divide 46 by nine, then times by 100] if you go for a radical cassette like the two-piece 9-46t from E13.
Getting rid of an extra cable, chainring and front mech is pleasing from aesthetic and marginal aerodynamic gain points of view, and getting rid of the extra hardware reduces weight, although the scales show that’s not as big a deal as you might think.
Single rings first became popular on mountain bikes as designers struggled to fit double chainrings, front shifters and chain lines around tyres up to 3in/70mm wide. Obviously tyres aren’t that wide, even on road plus bikes, but shorter chainstays can still make finding clearance around the chainstay/seat-tube area tricky.
Dominic Mason from Mason Progressive Cycles explains: “Single front chainring systems open up all sorts of possibilities from a design point of view. The wide-range rear cassette allows for a smaller front chainring, which means we can
increase clearance around the tyre where the chainstays meet the bottom bracket shell. This area has always been super-difficult ‘packaging’ wise when designing a frame.”
So far only 3T has really exploited the single ring ‘packaging’ advantage on its radical single-ring-only Strada, fat-tyre aero machine, which gained a load of attention at the Eurobike trade show, and has just been confirmed as the official race bike for Irish Professional Continental Aqua Blue Sport team for next season. This will be high-profile proof – or not – of whether single ring can spin to win at the highest level.
Just simplifying the frame moulding and removing cable guides and front mech mounts on the new Whyte Wessex One has saved nearly 100g over the standard frame. In both cases it also creates a better aerodynamic match to that other future must-have – a wider, smoother rolling rear tyre – as well as a really neat and clean-looking chainset area. Most other complete bikes supplied with a single ring still have space for a double and front mech.
Going single ring removes the brain strain and trial and error from shifting. No more trying to work out which gear ratio comes next in the sequence and whether that involves shoving the chain across onto a different chainring as well as a rear cassette shift. Instead, shifting is just a sequential up or down no brainer with the size of jump dictated by the ratios of the cassette you’ve chosen. All the changes can be done with a single right-hand shifter, making it simpler for new riders to navigate.
Even though front changers are now better and faster than ever, having to shift ring and rear sprocket to hit the next gear in the sequence will always be considerably slower than a single rear shift. Using a single chainring also gets rid of the problem of almost identical, redundant ratios achieved through different chainring and cog combinations.
There’s none of the wear-multiplying extreme chain line or incorrectly set up chain grind of a front mech arrangement either. Done right, single chainring setups don’t drop chains in rougher off-piste/cyclo-cross situations like double/triple ones can. Clutch rear mechs also stop the chain slapping against the frame, knocking off paint and creating a right racket if
Going single ring removes the brain strain and trial and error from shifting
the bike is bouncing around. Mountain bike use has proved that increased contact area on chainring teeth and chain rollers reduces overall wear and tear compared to a double ring setup.
The result is a transmission that’s physically quiet on the bike and means a quieter experience for the rider. From a bike design perspective, it’s faster for bike manufacturers to fit, means less parts to order and gives more freedom for future frame shapes, and it’s particularly well suited to the latest generation of fatter tyre gravel and adventure road machines. But do you get enough of a gear range to make it usable for regular road riding?
The gear thing
In theory, a single chainring setup has half the number of gears of a double. However, essentially duplicate gears in different chainring and cassette combinations can reduce the number of noticeably separated gears dramatically.
Ian Alexander from Whyte points out: “If you flick on the Syncro Shift - sequential gear selection function in Di2 – a 2x11 drivetrain can have as few as 13 usefully different ratios.” That’s with a princess and the pea attitude to pedalling speed too, and the wider your bandwidth of acceptable changes in cadence is the fewer distinct gears you’ll feel. Extreme gears such as big chainring to biggest cassette sprocket or vice versa are often off limits due to front mech or chainring interference, or lack of capacity in the rear mech. The overall range of gears is closer than you would think with a wide-ratio block too. “The standard Whyte Wessex is a 50-34 with an 11-32 cassette. This gives a bottom gear of 28.7in and a top gear of 122.7in. The Wessex One is specced with a 44t chainring and a 10-42 cassette, giving a bottom gear of 28.3in and a top gear of 118.8in,” says Alexander.
Most of the time, gaps between the gears might not be the major problem. “A 10-42 cassette has three sprockets to go from 10-14, while an 11-32 has five sprockets from 11-15. Above that, both cassettes have the same size jumps between them all the way up to the 42 or the 32,” Alexander continues.
Transmission is quiet on the bike and means a quieter experience for the rider
Those larger bottom end sprocket gaps are fine for steeper, slower riding or where the surface/gradient/speed changes frequently. Or if you’re a recreational rider not really bothered about always pedalling the perfect ratio.
If you’re a time-served, sweet-spot spinning racer living on a strict diet of A-grade club runs, they’re going to feel notchy and jumpy. If you’re that calibre of rider, you’ll be fine using an 11-36 (four sprockets to cover the 11-15 spread and a 33-108in overall range), 11-32 (fivesprocket 11-15 and 37-108in range) or even an 11-28 (five-sprocket 11-15 and 42.4-108in range). If you’re smooth on the pedals that’s a 50kph top end before your cadence gets too bouncy. If you’re prepared to lose top-end sprint/pedalling descent speed you can obviously drop the front ring size down to put your close gear sweet-spot where you need it.
The numbers turn out more favourably for single-ring when it comes to drag Halving the number of chainrings doesn’t halve the number of usable gears
Cash, weights and watts
You’d reasonably assume that removing the innards of your left-hand shifter and losing the front mech, inner chainring and front gear cable would create a significant loss of both weight and cost, but the reality is surprising. The rear mech of SRAM’s 1x systems uses a straight parallelogram X-Horizon mechanism rather than a traditional slant parallelogram, and it has a chain tensioning clutch. That makes it heavier as well as more complicated and expensive to make. Wider range rear cassettes are also heavier and more expensive. That means SRAM Force 22 is only 72g heavier overall than SRAM Force 1 and £100 more for the drivetrain without brakes. Rival 22 is only 8g heavier than Rival 1 but £69 cheaper.
The numbers turn out more favourably for single-ring when it comes to drag. Spin the cranks backwards on a conventional drivetrain and you’ll feel noticeably less resistance than a single chainring system with a clutch mech tensioning the lower chain section. However, research done by friction reducing specialists Ceramic Speed and Diamondback shows that larger jockey wheels and narrow/wide chainring teeth mean there’s only 1.5-2 watts more drag under power with a single-ring system. That’s the same levels of drag you get from
using extreme cross-chain gears in a double setup.
One for all and all for one?
The advantages and disadvantages you’d assume in theory aren’t necessarily true in reality. For a start, despite fewer components the weight loss of going single is at best minimal, unless you invest in a very light chainset and stay away from clutch mechs and wide-range cassettes. Equally perversely, single-ring drivetrains cost more than double-ring equivalents, on official over-thecounter costs at least.
On the plus side, halving the number of chainrings doesn’t halve the number of usable gears. It doesn’t have to mean massive jumps in pedalling rhythm either if you match the ratios to the riding you do. Most importantly single ringing simplifies the process of changing gear mechanically and mentally. It makes your bike quieter, keeps the chain on over rough terrain, looks neater and opens up whole new tyre and tube shape combinations for designers by removing the space needed for an inner chainring, the swing of the front mech and the cable alignment to pull it.
Whether that’s enough to see it make double chainring setups as rare as triple chainring ones are these days we don’t know. We do know there’s going to be a lot more equipment and bike development around single ratio systems, and we are really looking forward to seeing where that leads.
Above Top right Right The One saves nearly 100g over the standard Wessex frame Whyte specs SRAM’s wide-range 10-42t cassette Add a 44t chainring and the range is almost identical to 2x11
Above Top right The Stig loves a bit of rough Narrow-wide chainring teeth secure the chain
Top Above Single ringing loses lefthand shifter complications Clutch mech and bigger cassette evens out weight with 2x11