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One ring to rule them all? Single-chainring setup tips

With cyclocross nationals behind us, ’cross season is definitely over (unless your name is Compton or Hyde). So what will you do with that bike? Does your cyclocross rig end up sitting in the garage for much of the road season? Well, it shouldn’t.

All of us in the VeloNews office favor single-chainring bikes for cyclocross. Maybe you’re still on a double, but more and more ’cross bikes are now built with SRAM one-by (Force, Rival, or Apex) drivetrains, or an equivalent Shimano set-up. This poses a bit of a challenge if you want your ’cross bike to do double-duty in the summer. Here are our tips to making a single-ring bike more versatile.

1. Start with the chainring

Well, perhaps we should rephrase that: Start with how fast you want to go. The majority of ’cross bikes come with 40-tooth chainrings. If you’re the type of rider who hates getting spun-out in an easy gear, you might want to bump up to a 42-tooth ring. This might be a good move if you live somewhere flat as well. On the other hand, if you plan on riding a lot of steep climbs and you like to spin, the 40 should be good, provided your cassette range is wide enough (more on that later).

Photo: Brad Kaminski | VeloNews.com
Photo: Brad Kaminski | VeloNews.com

2. Compare gear ratios

Gear inches is a common unit of measurement for bicycles. Essentially, if you’re in a given chainring/cog combination, it measures the distance traveled by one rotation of the crank, under drive by that gearing. The late Sheldon Brown’s gear calculator is a great resource to tinker with your options. If we take a semi-compact ring setup (36/52T) with a common road cassette range, 11-28T, the gearing ranges from 34.7 inches (easiest) to 127.6 inches (hardest). Your ’cross bike, with a 40T ring and the same cassette, has a range of 38.6 to 98.2 inches. And now (hopefully) you see our single-ring quandary.

3. Consider your cassette

Naturally, those living in places with flat terrain might not be too bothered by a limited gear range. If you kept that 11-28T cassette and grabbed a 42T chainring, your gear inches would be 103.1; it would be 108 inches with a 44T. In more tangible terms, if you pedaled 100rpm, you’d go 32.1mph with a 44/11T combo.

If that won’t work, you’ll need to get a cassette with wider range.

Photo: Brad Kaminski | VeloNews.com
Photo: Brad Kaminski | VeloNews.com

SRAM drivetrains

– Can you swap your wheels from a standard 11-speed cassette body to an XD driver? If so, you’ve got a bunch of options. The ultimate, limitless budget approach is to swap the cassette driver and get a $308 10-42 Force 1 cassette. This one-piece alloy cluster is amazingly light (315g). Run it with a 42T ring and your range is 27-113.4 inches, or 8-33.7mph at 100rpm.

– Can’t swap that driver, or don’t want to spend $451 on the upgrade (cassette, driver, and chain)? All is not lost. You could get an 11-36 PG-1170 cassette; you might not even need a longer chain. (But make sure you check.) That sets you back $110. With a 42T chainring, your gears are 31.5-103.1 inches/9.4-30.7mph at 100rpm. If you want an easier climbing gear, you can opt for the $79 Apex 1 cassette, 11-42T. However, that cassette weighs 538g.

Shimano drivetrains

Shimano drivetrains can also accommodate a range of gearing options as 1x setups. Using an Ultegra (mechanical or Di2) GS rear derailleur, you can pair your 42T chainring with an 11-36T cassette for the same 31.5-103.1 inch range as SRAM. Dura-Ace derailleurs only accommodate an 11-30T cassette, so you’re better off going with the less-expensive and more versatile Ultegra option.

Want a wider gear range? If you’re running a Shimano Dura-Ace Di2 or Ultegra Di2 drivetrain, you can swap out the rear derailleur for an XTR Di2 mountain bike derailleur (289g) and 11-40T cassette. Shimano’s road shifters will play nicely with the mountain bike derailleur as long as you’re running a 1x setup and don’t have a road front derailleur connected to the system. Unfortunately, the derailleur alone costs about $400; the XT model is a little less pricey at $300.

On the other hand, Wolf Tooth Components offers a simple solution for expanding your Shimano drivetrain’s gear range without the hefty price of a new derailleur. The company’s $22 RoadLink (17g) hanger extension offsets your bike’s rear derailleur making it compatible with mountain bike cassettes. This allows you to run up to an 11-40T cassette with your 40T (27.0-98.2 inches) or 42T (28.4-103.1 inches) chainring. However, be aware that none of Shimano’s road derailleurs have clutch mechanisms, like the XTR, XT, or SRAM’s 1x units, so chain security might be a concern on rough terrain.

Caveats

Make sure your rear derailleur is compatible with larger cassettes. Short-cage (like a road bike) derailleurs rarely accommodate more than a 32T cog in the back. Medium cages max out at 36T. The least-expensive SRAM derailleur that accommodates a 42T cog is the $74 Apex 1. Some bikes are coming with long-cage derailleurs that work with big cassettes, like the Jamis Supernova recently reviewed. SRAM says about 60 percent of Rival rear derailleurs sold in 2016 were long cage, and 35 percent of Force 1 derailleurs sold had long cages.

Check your chain length — you might need a longer one to accommodate a bigger chainring/cassette combination.

Don’t expect it to feel quite like a road drivetrain. A wider-range cassette has bigger jumps between cogs, so it’s a little harder to maintain that smooth, steady road cadence. For instance, the largest jump on an 11-28 cassette is 10.6 gear inches, or 3.2mph at 100rpm. A 42T ring with a 10-42 cassette has a much bigger maximum jump, 18.9 inches, or 5.6mph at 100rpm.

If you have a double-ring drivetrain, don’t let that stop you! Most ’cross bikes have compact chainring bolt patterns, which means you can put a 34/50T combination on the front, or a 36/52T. That, however, will definitely require a longer chain.

Gear ratio chart

Gear Inches Chart.xlsx

(Gear inches shown)