Mountain biking is still a relatively young sport in the grand scheme of things, with dedicated ‘mountain bikes’ only really becoming widely available in the late 80s/early 90s. We’ve come a long way since those days, and the rate of innovation in mountain bike design has been truly staggering. The bikes we ride these days are pretty unrecognizable compared to those old Klunkers, and honestly it’s pretty crazy looking at what we were riding even just a decade ago.
There have been a number of key innovations in the last decade or so that have truly changed the game, such as dropper posts, the use of carbon in various components and a bunch more, but I want to make the case that the 1x drivetrain is among the most important, if not the most important. I want to pose this idea not necessarily as fact, but more to open a discourse and to understand what it’s allowed frame designers to do.
Not wanting to simply make such a bold statement and hope it sticks, I turned to four engineers from some well-known bike brands to get their take on the subject. But first, some history.
History of the 1x drivetrain
There’s a lot to unpack with the advent of the 1x drivetrain, and it’s not quite as simple as just ditching a chainring or two from the crankset. Downhill riders had been running single chainring setups for years, albeit with full chain guides which could be tricky to set up, and God help you if you ever managed to drop a chain. Personally I started running a 1x drivetrain on my trail bikes back around 2010 with a 9sp derailleur, and I immediately recognized how much more reliable it could be. Michael Buell, Sales Manager and President at Banshee, came to a similar realization early on.
“I believe I started running all my bikes 1x all the way back to 2009/2010. Coming from a DH racing mindset at the time, it seemed like a no brainer to put a single ring and chain guide on all bikes,” he said.
Then the clutch derailleur entered the scene, with a friction clutch that reduced chain drops by preventing excess derailleur cage movement. This definitely helped with chain retention, though most 1x users were still running full chain guides at this point, or more commonly a front derailleur and either no guide or a lower guide.
In 2012 SRAM totally changed the game when they released their 11sp XX1 groupset that utilized a clutch derailleur and a chainring with a narrow-wide tooth profile that they called X-Sync that gripped the chain and •gasp• had zero option for a front derailleur. With a 10-42t cassette the range was good, and a lot of people adopted this system, but the range was not great. So front derailleurs didn’t go away, with both Shimano and SRAM offering double chainring setups for some time. Shimano released several 1×11 groupsets with a 46t cassette that gave riders a more useable low gear, another nail in the coffin for the front derailleur.
In 2016 SRAM launched their 12sp Eagle groupsets with a 10-50t cassette, and that was it for the front derailleur; the brand has not developed or produced another mountain front derailleur since then. With a useable low gear, great shifting, and quick roll-out to lower price points, SRAM had the market sewn up.
Up until this point frame designers were still designing around front derailleurs, but with a widely available 1x drivetrain this provision stopped featuring on new frames. Today both of the big players have a solid range of 1×12 drivetrains, and despite Shimano insisting on producing a 2×12 system for who knows what reason, the mountain bike front derailleur is all but dead.
This leads us to the benefits of the 1x system, and the design innovations it unlocked for bike engineers.
Anyone who has come into mountain biking in the last five years and doesn’t know the frustration of stopping several times in one descent to put right a dropped chain, or untangle the dreaded chain suck, should count themselves lucky. While front derailleurs have their place on road/touring bikes, for the mountain biker a 1x drivetrain means increased chain retention to the point of almost zero drops, decreased complexity in terms of drivetrain setup, and simplicity of use while on the trail.
Buell said “there is a large percentage of like-minded people like myself who see a ‘less is more’ benefit here. Why have 27 gears with redundancy when you can achieve all that is needed with 7-12 options, especially when it means lower profile components and more durable and reliable drivetrains under severe and aggressive use.”
Over the years mountain bikes have become increasingly complex in terms of design, with complicated suspension linkages and parts that never even existed before such as dropper posts. But at the same time, bikes are also more refined, with tube shapes that flow better, internal cable routing, and other things that require space within the frame. Getting rid of that one derailleur cable made a big difference in terms of cable management and general aesthetics.
Rocky Mountain Bikes Product Manager Ken Perras said, “removing the need to have a front derailleur cable installed made it much easier to manage things at the front end of the frame. Internal dropper posts were just becoming more widely available and things were getting crowded at the front of the frame. Removing one piece of housing made optimizing integrated routing much easier.”
Dropper Post Real Estate
While more simplicity and fewer dropped chains is great and gives us a couple less things to worry about on the trail, it’s paved the way for one more thing — the dropper post. That prime real estate underneath the left hand side of the bars was swiftly taken up by the dropper post remote, transforming it from something clunky and kind of useful into an absolute necessary game changer.
While dropper posts and front derailleurs have coexisted, being able to run the remote under the bar makes posts a lot easier to control, and while Scott doesn’t necessarily agree that one led to the other, he says that “in the last decade I would suggest that the biggest innovation has been the dropper post. It went from an obscure gadget to a must-have piece of kit.”
On the other hand, Noel Buckley, Owner of the Knolly brand and product engineer, thinks that the development of the modern dropper post is one of the most important things to come from widespread acceptance of the 1x drivetrain.
“The first time I ever saw a dropper post at Interbike about 20 years ago I thought, ‘what the heck, that is the dumbest thing I’ve ever seen,'” he said. “I think having the space for dropper posts is really big, if you’re my height (I’m 6ft 1″), you need at least six, seven, even eight inches of adjustment, and dropper posts have only recently gotten into that range with that mass market adoption, and a lot of frame designs couldn’t handle that until recently either.”
The front derailleur occupied a large amount of space in a crucial location where the bottom bracket, crank and chainring, tire, and often a suspension pivot or two come together, creating a myriad of clearance issues. Getting rid of that one element meant being able to do a ton of different things with that space, one of which is simplifying and further optimizing frame design for strength, weight, and stiffness.
Perras says, “from Rocky’s frame development perspective, removing front derailleurs was mostly significant in that it allowed us to widen the main pivot and also optimize its placement relative to the chainring size used. Widening the main pivot improved rear triangle stiffness, which is a benefit up to a certain point.”
Josh Kissner, Director of Product at Santa Cruz, said that “in the short term [getting rid of the front derailleur] allowed us to add a second upright tube to the swingarm, making it symmetrical and a more efficient structure. Front derailleurs take up a ton of room in the frame and also require the seat tube to be in a very specific spot.”
Anyone who has tried to run high volume tires on an older bike with a front derailleur might have run into clearance issues, with the tire rubbing on the tip of the derailleur when in the small chainring, and this became more common with increasing wheel diameters and tire widths. The only real way to solve this was to run the FD at an angle and fudge the limit screws, both of which meant sub-par shifting. Or, it meant going back to a smaller tire size. Getting rid of the derailleur entirely meant that finally, wider tires could be used in combination with shorter chainstays on bigger wheeled bikes.
According to Scott, “it just cleaned things up and opened up a much greater space to design into for things like tire clearance.” Buckley agreed, saying “there’s an argument for sure that tire clearance was an issue, and tires did get bigger, but then they stopped.”
OEM Spec and Maintenance
Front derailleurs have always had a reputation for being somewhat finicky; the scourge of the home mechanic. They’re not always easy to set up, tricky to keep that way, and even when one does work well enough, you might break it and then have to figure out what the hell you were going to replace it with. Scott told me that at one point SRAM alone offered more than 70 different variations of their front derailleurs.
Buckley points out that getting rid of front derailleurs eliminated a major source of complication. “I think the biggest advantage is simplicity — simplicity for the vendor in terms of parts sourcing because that’s two less parts to source being the FD and the shifter, and simplicity for the user.”
Perhaps even bigger than inclusion of the dropper remote or anything else is what the 1x drivetrain has done for suspension performance. Bike design is as much about angles as it is about squeezing suspension pivots into tight spots, and freeing up that bit of space around the bottom bracket/crank area meant that many brands could move suspension pivots into places previously unavailable, notably on short-link floating pivot bikes from brands like Santa Cruz, Ibis, Pivot, Banshee, and many others. This freedom meant that bike designers could do what they’d been wanting to do with their suspension for years, and led to the amazing pedaling and descending performance we now know and love.
For Santa Cruz Bicycles, freeing up that space was absolutely instrumental in the design of their current bikes.
“Eliminating the front derailleur gave us the freedom to completely re-imagine how we could configure VPP, which led to the lower-link mounted shock that we have today,” said Kissner. “This helped us massively improve our suspension kinematics compared to the previous frames and is the design we’re still tweaking and improving today.”
Banshee Bikes, running a similar short-link floating pivot design faced similar issues. Scott said removing the front derailleur opened up space around lower links and chainstays.
“It was always a battle to fit around full range of motion of the possible FDs from both SRAM and Shimano to ensure compatibility. This was especially problematic for short link four-bar designs like I use, as the lower link needed to occupy the same space as the FD, and both had significant ranges of motion through their respective travel.”
Clearly getting rid of the front derailleur gave manufacturers a lot more freedom in terms of suspension design, as evidenced by the fact that both Santa Cruz and Banshee now run their suspension components and linkages much tighter in the bottom bracket area than before.
Another important suspension characteristic is anti-squat. Anti-squat describes the way a suspension linkage resists compression while pedaling. Low anti-squat tends to result in a design that bobs a lot while pedaling, and high anti-squat usually is very efficient under pedaling load.
Kissner describes the relationship between drivetrain choice and anti-squat as “one of the most important improvements.” He explains, “anti-squat (the amount of influence your pedaling has on the suspension) varies drastically with chainring size. On a 2x or 3x drivetrain we had huge changes in the size of chainrings, making it impossible to make a bike that pedaled well in both the small and large chainrings. I think most companies optimized the pedaling for the ~32t middle ring, which meant the bike would probably extend the suspension (excessive anti-squat) in the small ring, and compress the suspension (squat) in the big ring. There’s no way around this. But now that we’re able to design around a single ring, performance is infinitely better in the real world.”
Perras agreed, saying “in the past, on full-suspension platforms, you had to compromise the anti-squat curve between two or three chainring sizes which meant that the extremes didn’t feel that great, with either too much or too little anti-squat in a given chain ring. Designing with one chainring further optimizes the design.”
I think one of the biggest takeaways from this for me is that there’s no “one big innovation,” and that we’ve come a long way over the last couple of decades through experimentation and refinement. Clearly the dropper post is one of the biggest changes we’ve seen, and while the 1x drivetrain made room for the modern dropper remote, it’s hardly completely dependent upon that. Yes, 1x drivetrains helped enable numerous mountain bike innovations, but the fact is 1x systems have been around forever in various forms.
The other big takeaway from this is that maybe the biggest real improvement to the way a bike rides that the 1x drivetrain unlocked is anti-squat. The subject of anti-squat is one that I hadn’t thought about in terms of running multiple chainrings, and totally makes sense as to why we have bikes that pedal so great these days. Can we claim that the 1x drivetrain is completely responsible for this? Probably not, but it certainly helped.
Clearly the removal of the front derailleur was more important for some brands than others, mostly based on their chosen suspension design. But all agree that it was absolutely a great thing and instrumental in the development of the modern mountain bike, but for different reasons.
Given that truly innovative bike ideas are often stifled because they’re too weird or radical, a lot of ‘innovations’ don’t really really feel all that innovative in the end.
“Weirdly, I don’t think that there has really been much true innovation in the industry,” said Scott. “Yes, things have evolved a lot… from geometry, to materials, but most ‘innovative’ things this industry sees are gimmicky, or solving a problem that doesn’t exist.”
Buckley seemed to agree.
“The biggest thing for us as a business that we’ve learned is that the mountain bike industry is much more of a fashion industry than [we] initially thought. Everybody talks about performance and engineering but to be honest certainly in the frame side of things, that’s all secondary to industrial design.”