'Praxis'

How to Decide Whether to Use a Single Chainring for Cyclocross

Single chainring fever is sweeping the bicycle industry. If you’ve been paying even an iota of attention to the cycling media over the last couple years, you’ll have noted that narrow-wide single chainrings have rather rapidly become the default specification on mountain bike, fat bikes, and many cyclocross bikes. Meanwhile, we’ve seen a few examples of road bikes built around a single chainring, such as Specialized’s lunch race bike, which fill a niche, suited to criteriums and other fast riding where speeds remain high or relatively high at all times.

On the mountain bike side, eliminating front derailleurs has allowed frame designers to more easily fit suspension assemblies into the space around the chainrings, and most importantly, shorten chainstays by curving seat-tubes. This was surely a relief to many, as 29ers were previously plagued by their necessarily long chainstays and associated slow handling. One might say the single ring saved the 29er from being relegated to the pile of technological blunders the created by the bicycle industry over the decades.

English Cycles Mountain bike
Here’s a beautiful example of an English Cycles MTB that uses a curved and flattened seat-tube, made possible by omitting the front derailleur.

 

As we so often see in Western culture, once people get onto a good thing, they often feel compelled to try it everywhere possible. Perhaps it’s hope for an improvement on the status quo enabled by newtechnology that clouds our collective judgment and sees us try to shoehorn technologies onto platforms where they don’t make good sense. The narrow-wide single ring is such a technology. The fact is, there is no one technological solution for all riders, everywhere. There is no ‘universal’ bike set-up for off-road riding, let alone racing. Instead, just as regional trail systems vary widely, so do the requirements for the bike that traverse them.

On the one hand, one might say: ‘No, one could surely ride anywhere with one set-up.’ I’d actually agree, one could ‘ride’ anywhere in the world with one set-up. However, some of that ‘riding’ would be walking, either/both up and down. Some of it would be really fun. Some of it would really suck. Sometimes it would be scary. Very little of the riding would fall into the Goldilocks zone: just right. The fact remains that some regions have such polarized riding that double chainrings continue to make more sense than single chainrings. If you are going to climb for three hours, then descend for 2 hours, you are probably better off with a double chainring than a single. Yes, SRAM’s Eagle group (mtb shifter only) will get it all done, but with absolutely enormous gaps between gears. If riding with buddies, that might not matter. If racing up and down, it might.

For a lot of riders, however, a single ring set-up has become a great option for off-road riding, particularly if the majority of their riding is done in the same region, with a constrained range of gearing requirements. Racers, on the other hand, will likely be challenged to arrive at each race with the chainring they need for the course, and could spend a lot of time and energy trying to figure out what it should be. Is there a simpler option?

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In this piece, I’d like to focus on the single ring option for cyclocross. Many riders will find themselves using the same bike for both cyclocross and gravel, so I’d like to help those thinking about whether to go from two rings to one sift through the pertinent ins and outs. We’ll go through a process of evaluating riding requirements in order to narrow down whether a single will work for you on cyclocross tracks. A lot of this will also apply to the gravel side. In that case, it’s pretty much a matter of looking at gravel rides as you would cyclocross courses: what is the easiest gear required, and what is the hardest gear required for the riding? With 11-42 cassettes now available for drop-bar bikes (11 speed), a rider happy with a 42 tooth chainring could be content with a 42 / 42 climbing gear, 1:1. I personally require gearing lower than 1:1, so I will use a double for the spring and summer gravel rides and races.

Let’s get into the key questions you might want to consider when trying to suss out whether to switch to a single ring for cyclocross:

Do I shift my double chainring during CX races I’ve done?

I’m pretty confident most people will answer ‘No’ to this one. In Europe, many of the races have paved, fast starts and finishes, which the pros use their big rings for. This is not common in North America. Instead, shifting is a common cause of chain derailment and complicates gearing decisions during races.

Are my courses generally hilly? Importantly, are any of the climbs longer than a minute?

I’ve yet to meet a cyclocross course that required a smaller ring for climbing that couldn’t be covered by a larger cassette. However, I’ve heard of long climbs on courses that require low gears. If you ride courses like that you can either run a double or a single with a wide range cassette. There are trade-offs on both sides, but I’d personally lean toward one ring, and have been very happy with one for the last 8 years. An 11-36 cassette would likely cover the extremes one would face, and many riders actually prefer significant jumps between gears in cyclocross so that they don’t need to shift as much as with a tightly spaced cassette.

Which ring do I use when I race a double?

If the answer is ‘the small one,’ consider getting a narrow-wide of similar size. If the answer is ‘both,’ check out your cassette and think about whether a broader range would allow you to use just one ring. 11-28 is a typical cassette for cyclocross, but going with an 11-32, 34, or 36 would likely be pretty simple. An even lower climbing gear is also possible.

Do I need to use the same bike for training rides during cyclocross season where I’ll need a double?

Be careful with this one. A 42t chainring gets you going pretty darn fast with an 11t cog. I’ve done group rides with just a 42 and fared well. If you ride alone most of the time, you might need a bigger ring even less during CX season.

Do I have budget for a single ring?

This one is pretty straightforward. Switching to a single ring would likely require a clutch rear derailleur (for keeping the chain tight), perhaps a new chain (worn down chains won’t stay on well, and will only accelerate wear on your new ring and cassette), and perhaps a new cassette with a broader range. All this depends on the type and state of components on your bike.

Do I have time and tools or budget to change between single and double set-up (assuming the double is required at other parts of the year)?

Tools are fairly standard, and the job should take the average home mechanic about 2 hours max to remove extra bits, and perhaps 3 to put it all back on. But you have the whole winter for that!

What sort of ring works well?

Riders used to run single rings without shifting ramps and pins with various chain guides and  plates designed to retain the chain. I used a guide/plate combo for a few seasons, and it worked well while the guide was adjusted properly, but if it came out of adjustment I had jamming issues. Grass and mud also ended up getting  packed into it, which was problematic. I had more than one race ‘ruined’ by a mechanical issue with the setup. For 2015 I swapped to an Absolute Black narrow-wide ring with a SRAM XO clutch mountain bike derailleur. (Disclosure: Absolute Black provided me my rings at no charge, and has supported our club’s events with prizes over the last two years).

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Absolute Black Mud Narrow-wide
Absolute Black’s attention to detail is what drew me to them. Their machining effectively allows mud to evacuate, while some other rings have a step that traps mud, forcing the chain off the ring as it builds up.

 

The clutch style derailleurs have very tight spring tension on the lower pulley, which keeps the chain snug on the chainring. Some of the rings out there use really deep teeth, rather than alternating narrow / wide teeth, which I imagine works well too. A narrow-wide ring fills up the narrow and wide links in the chain more fully than a ‘flat’ ring, which helps the chain track straight and stay in place.

SRAM Clutch XO
SRAM’s derailleurs are impressive. This is a 10 speed XO mountain bike derailleur, and it works perfectly with any of SRAM’s 10 speed road shifters. It handles a 36-tooth large cog with a double chainring too, for the summer’s gravel riding.
Kogel Bearings Narrow Wide
Thanks to Kogel Bearings’ support, I was able to run their excellent narrow-wide derailleur pulleys on my cyclocross bike this year. The ceramic bearing pulleys were flawless, making shifting more precise, and helping keep the chain aligned with their narrow-wide design. After all the bike washing, they are still spinning as-new.

 

I’ve used the same Absolute Black round 42 tooth ring now for two seasons, with some snirt road riding in the mix. I’ve dropped my chain while riding exactly twice. The first was in the early spring, when I pedaled through a compression (a rounded hole of sorts) as I was turning. This flexed my steel bike enough to allow me to pedal the chain off the ring. The second time was at the Calabogie CX race this fall, when I rode through a similar compression, again pedaling the chain off the ring. Unfortunately, this cost me a podium spot. I’ve learned to not pedal while turning through compressions. This is a bit of an uncommon scenario, so it doesn’t bother me.

Shirt Kogel Absolute Black SRAM
I normally switch to an 11-36 cassette for the winter’s shirt rides, but made do during the 2016/17 season’s first ride on an 11-28 over hilly terrain.

 

Beside the two derailments I experienced there have been many, many rides, races, and crashes on the narrow-wide with nary an issue. Perhaps most spectacular, I didn’t unclip in time for a high speed barrier in Cornwall, smashed into it, flipped, sent my bike flying, and my chain was still on. I sent my bike across the course in the first 45 seconds of CX nationals in Sherbrooke and a racer rode over it; no dropped chain. I rode through insane mud at the same race: no issue. Perhaps most epic, last year at Upper Canada Village we had freezing mud conditions, and my bike was totally covered. No issue. The last weekend of racing this season in Almonte was the same, though a little less freezing, and my drivetrain worked without a single issue. To me, this is amazing, and the best endorsement of a narrow-wide set-up I can imagine. I am 100% sold on the narrow-wide format, and can’t imagine going back to my old format.

Cyclocross narrow-wide Absolute Black mud
Almonte was a snowy, muddy battle. My chain stayed on, I got to win.

 

Ok, so let’s say you’re convinced, and you want to give this a go. What is required? In my opinion, a clutch rear derailleur is essential. Yes, you can and many do use a regular rear derailleur with a narrow-wide ring. These folks will say it’s great until they have one or two issues, then they will say it’s crap and they’ll get a clutch derailleur. My first try with a narrow-wide, borrowed from Iain Radford, was a total fail in some hideous mud at Almonte, and I had a regular derailleur. I learned my lesson.

For SRAM, this is easy to accomplish with ten or eleven speed drivetrains, because both 10 and 11 speed shifters from them have the same indexing, meaning you can mix and match shifters and derailleurs across their model ranges. For example, if you want to run an 11 speed derailleur with your 10 speed shifters or vice versa, you can, provided you use a 10 speed cassette and chain / 11 speed cassette and chain. If you want to run 10 speed road shifters with their MTB derailleurs, you can. In fact, this is the way you’ll accomplish a set-up for either 10 or 11 speed shifters that can handle both a double chainring setup for summer and single for winter. This is because SRAM’s CX-1 style derailleurs do not work with double chainrings. So if you are converting your bike, you’ll want to use a SRAM MTB derailleur to retain both chainring set-ups. If, on the other hand, you want to run a single for all the riding you’ll do on your bike, you’ll be better off with their CX-1 style derailleur, which shifts better than their MTB derailleur (it is really impressive).

A concrete example of a typical situation is my plan for 2017. I currently have 10 speed SRAM with the XO MTB derailleur discussed above. I will be building one if not two new bikes for gravel and cyclocross, and will need to run one of the bikes as a double in the spring and summer, then a single for fall. I plan to use SRAM’s Force 22 shifters and brakes, combined with my existing SRAM XO 10 speed rear derailleur. This will save me having to buy another MTB derailleur. Come fall, I will take the double spider and rings off the crank, replacing it with a narrow-wide ring. I’ll swap to a Force 1 rear derailleur, which will give me the best shifting performance.

For Shimano, you’ll similarly need to use a MTB derailleur with their road shifters if you want a clutch. Unfortunately, at present Shimano’s MTB derailleur has a different cable-pull-to-derailleur-actuation ration than their road derailleur, meaning you’ll need a cable pull converter to make such a pairing work. Check out this link for info on that, along with good material on wide range gear options.

Regardless of derailleur and shifters, it’s worth noting that some cranks – notably SRAM’s – allow you to remove your chainring spider and directly mount a narrow-wide ring to the crank. This is a good idea, because it allows you to drop weight and potentially improve chain-line on your bike. Not only the newer CX-1 cranks can do this, all of SRAM’s cranks with a removable spider will work. Sweet! Check out how rad this Absolute Black direct mount ring looks! In addition, this is an oval ring, which I will post about separately.

absoluteblack-sram-direct-mount-cx1-oval-chainring-cyclocross-chainring

 

I hope this helps you think through whether switching to a single ring for cyclocross will work for you. If there’s any aspect of the issue I’ve missed, please let me know in the comments below, or on one of the other social media platforms you find me on. I’m more than happy to address questions, and will update content I’ve missed. Speaking of which, yes, chain guides are available for single ring setups, and some of the pros are using them. However, I didn’t get into them here because my experience (with MTBs and CX bikes) has been that guides can cause more problems than they solve. When dropping a chain from a simple ring, placing it back on is easy. However, when something goes wrong with a guide, it goes really wrong. Given my excellent performance experience with a good narrow-wide alone with a clutch derailleur, I feel it is best to continue guide-free. Perhaps stronger riders will need more protection, and I recommend taking a look at Absolute Black’s guide if you fall into that category.

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