MTB Gearing Options - 1X, 2X or Triple
Triple chainrings, doubles and now single ring drivechains; we’ve never had so much choice in MTB gearing, but which is the best for you?Along with fat tyres, triple chainrings used to be a defining feature of a mountain bike. Now with the advent of double and single chainrings, the triple has become somewhat unfashionable. The first major chink in the armour for the triple came when SRAM introduced the 2x10 drivechain. With a wide range 11/36 cassette, the double ring system came close to matching the total gear range of a triple with one ring less up front. More recently, simplistic single-ring drivechains have been thrust into the spotlight, helped greatly by SRAM’s chain guide free XX1 and X01 systems.
So here’s our take on the relative merits of each system and how they compare…
Doubles vs Triples
First off we’ll look at doubles versus triples—the two most common setups that you’ll encounter on new bikes. After decades as the dominant system, it’s pretty clear that triples are on the back foot, with most mid-to-upper end mountain bikes now coming spec’d with a 2x10 drivechain.
Double ring drivechains can be divided into two basic groups; there’s the all-mountain/trail oriented double and the XC race double. The former is similar to the two smaller chainrings on a triple but the big ring is exchanged for a bash guard. With this setup you still have a true ‘granny gear’ (with a 22 or 24 teeth) and the other ring is only slightly bigger than your regular middle ring—usually it will be a 34 or a 36.
With an XC double you get a small ring that is between the granny and middle of a triple while the bigger cog is slightly smaller than a regular big ring—it’s typically a 26/39 or 28/40 combination.
In either case you get a slight simplification of the drivechain when compared to a triple chainring system. I say ‘slight’ as both still have two derailleurs, two shifters and two cables. You often hear about how much lighter a double is but in most cases you only drop 30g by eliminating one chainring plus a few extra grams with a shorter chain and a mid-cage rear derailleur. On average you’ll lose 50-60g all up, so going with a double won’t turn a tank into a featherweight XC racer.
You’ll generally gain some extra ground clearance with a double—especially if it’s an all-mountain style setup with a smaller chainring and a bashguard. The difference is less pronounced with an XC double but you’ll still gain a slightly broader margin for error when hopping logs or rolling down drops.
Overall, the potential range in chain angles is reduced when compared to a triple. Ideally you want the chain to be as straight and direct as possible (when viewed from above) in its path from the chainring to the cassette. Pronounced chain angles are inefficient and increase drivechain wear. Run a triple in the big/big chainring combination or even somewhere close to it and you’ll get a terrible chainline. The same will apply in the small/small combo; you typically get lots of chain rub and a horribly inefficient feel through the pedals in these crossover gears. With a two-by drivechain there are fewer unusable or inefficient gear combinations. So even though you have fewer gears in total, less of them are rendered unusable due to chain line issues. That said, the extreme crossover gear combinations on a double are still less than ideal and should be avoided if possible.
As well as having fewer unusable gear combinations, there also tends to be less gear overlap with a double chainring combo. Have a look at the triple drivechain in the gear charts; the granny ring only offers two gears that are lower than what you get in the middle ring. Likewise, the big ring only provides two ratios that are higher than the top gear in the middle ring. All the other ratios overlap, so in some ways you’re carrying three chainrings for very little gain. You still get this overlap with a double but it isn’t as pronounced, so once again you get a total range that’s very similar to a triple, with the same gaps between shifts on the cassette, but with fewer overlapping and unusable gears.
Combine all of these things with the cleaner looks of a two-by drivechain and it’s pretty easy to see why the tide is changing. So what’s the retort; is there any point to a triple or should we all get with the new school?
Well the first and most obvious comeback for the triple-team is the wider gear spread. Sure, a two-by drivechain can come close to the gear range of a triple but it won’t match it. An all-mountain/trail double may give you the same low-end gearing but the 34 or 36-tooth big ring can see you run out of steam pretty quickly on open fire road descents or on the road.
An XC double may offer sufficient top-end gearing but the lower gears will be compromised. The 26x36 first gear on a typical XC setup is roughly the same as your second-lowest 3x10 gear, so you only gain one easier ratio on a triple. Is it worth going a triple to gain one lower gear? Well if you ask me on a 30% pinch part-way up a 5km long climb, I’d say there’s no way you’re taking my granny away!
Some say that if you’re going slow enough to need a gear that low, you may as well walk. Sure, you may be going at walking pace in a 24x36 gear but that’s not the point. I bought my MTB to ride, not push, and if the super low granny gear gets me up that extra steep trail without unclipping then I’m a happy man. It all depends on your perspective but for me, part of the challenge is riding not walking. Being able to control your low-speed balance and clamber up technical climbs without resorting to higher gears and momentum is a skill that’s worth developing. Of course your local trails mightn’t have steep and sustained climbs, or maybe you’ve got the engine of a World Cup racer, in which case an XC two-by drivechain will work just fine.
I’ve read it plenty of times on the forums; ‘Triple chainrings are pointless; I don’t need 30 gears!’ Sure, 30 gears is excessive, especially if you obsess over the gearing charts and focus on the duplicate gear ratios. However, getting 30 gears isn’t the aim of a triple. The thing that makes a triple good for some riders and some trails is the middle chainring. The 32-tooth middle ring tends to be a sweet spot that gives you all the right gears for technical singletrack riding in hilly terrain.
With an 11/36 cassette on the back, the middle ring will allow you to pedal up some pretty steep hills as well as letting you maintain some speed on the flatter parts. Large chunks of a ride can be tackled in the middle ring and you’ll hardly ever shift between chainrings—in practice it’s like having a one-by drivechain, but you’ve still got a big ring for the road and a bail out granny gear for those times when your legs give in. In the same situation an XC double may have you hunting for an appropriate chainring, with the big ring being too hard for the ups and the smaller chainring too easy. Also remember that cross-chaining isn’t good on any multi-ring drivechain. So trying to ride everywhere in the big ring on a 2x10 system may increase drivechain wear if you’re often resorting to the big/big gear combo. The crossover gears may be worse on a triple, but if you stay in the middle ring the chain line is actually quite good.
Young & Single
Wide range 10-speed cassettes helped to make single ring drivechains a viable option for general trail riding. When combined with an appropriately sized chainring, an 11/36 gear spread will take you many places. However, the single ring concept became even more appealing when SRAM launched their 1x11 drivechain. The massive range offered by the 10/42 cassette comes ever so close to matching the gear spread of a multi-ring drivechain.
There’s much to like about going single. Swapping from a triple to a double only saves a handful of grams but going to a single ring can make a substantial difference. You’ll eliminate two chainrings, one cable, a shift lever and the front derailleur. Expect to drop 150-300g when compared to a multi-ring drivechain.
If you combine a clutch style derailleur with one of the new ‘wide-narrow’ style chainrings, you should be able to forgo a chain guide. This keeps the bike looking tidy and running silently, as there’s no front guide or derailleur for the chain to rattle against. The clean and simple looks continue up at the handlebar, as you’ll only have a shifter on the right hand side. The vacant space on the left side allows you greater freedom when mounting remote levers for dropper post or suspension controls. Some bikes wind up with a bird’s nest of cables at the handlebar; at least going one-by helps you de-clutter a little.
The teeth on regular chainrings are designed to aid shifting—that means they’ll have shallower teeth and release points that actually help the chain fall off. A dedicated single ring will have deep-cut teeth and no release points. Not only does this help with chain retention; it also creates a more durable drivechain, although this is offset to a small extent as the wear isn’t distributed between multiple chainrings. There’s very little compromise in the chain line when compared with a triple or double.
The chain can run a relatively straight line between the cassette and the chainring, and this further improves both durability and efficiency. You’ll be able to use every gear on the cassette with no chain-rub and obviously there are no overlapping ratios—what you see is what you get.
Of course the limitation of a single ring setup comes with the narrower total gear range. A typical 2x10 system provides a 470% range in gear ratios while a triple gives a massive 530% range. By comparison, a 1x10 setup with an 11/36 cassette offers a 330% range and even the massive 10/42 SRAM 11-speed cassette still only garners a 420% spread. Yes, that gear range will be plenty for some riders, but much hinges on your strength/fitness and the trails that you like to tackle.
The gear range may be a limiting factor for some but at least you can select the size of the front ring to suit the trails. Going to tackle a really hilly ride? Fit a smaller chainring. You can collect an assortment of different chainrings and swap them at will. With the appropriate chainring choice you should have a gear spread that’s optimised for most of your trails—like the sweet-spot that you get with the middle chainring on a triple drivechain.
One for All?
Hopefully all of this information gets the message across; there is no ‘one true drivechain solution’ for all mountain bikers. Some may consider the triple chainring dead and buried but for certain riders it is the only way to travel.
Much will come down to personal preference and the type of trails that you ride. If your trails are flowing, fast and you never face any ridiculously tough long climbs, then an XC double will suit just fine. If your trails are slower and more technical with the occasional steep 20-minute climb plus a road ride to the trailhead, a triple will be the most comfortable option. A lower geared trail two-by drivechain could also work here if you don’t mind spinning a lot on the road. If you are willing to forgo some gear range for simplicity and improved chain retention, sign yourself up for a new-school single ring setup. If you still can’t decide, earn yourself some legs of steel get a single speed—there are no rights and wrongs when it comes to MTB gearing options!