Is there such a thing as a truly do-it-all bicycle? Gravel bikes–which are often praised for their versatility–come pretty darn close. Despite their flexibility, however, gravel rigs still share many of the design traits and limitations associated with conventional road bikes. Last summer those limitations became abundantly clear when I began including more technical off-road sections in my mixed-terrain rides. Despite the gravel bike’s wider tires and lower gears, its road-based design placed more emphasis on aerodynamics and smooth surface efficiency than off-road capabilities.
Around the time of my existential off-road crisis, a press release from Oregon-based bike wizard Jeff Jones found its way into my inbox. The press release announced that Jones was now offering a carbon version of his popular Loop handlebar. Having previously tested—and liked–the aluminum Loop bar, I figured the new carbon version might be just what I needed to improve my gravel bike’s off-road capabilities. After a series of email exchanges, Jeff suggested that I give him a call.
In the first installment of GRAVELBIKE’s absoluteBLACK (aB) review, I covered aB’s 28T oval MTB chainring. Since then, the company began shipping their new oval CX chainrings. Available in conventional and direct-mount versions, absoluteBLACK’s CX rings feature the company’s Patent Pending narrow-wide tooth design. Because the conventional 5-bolt CX ring isn’t compatible with SRAM cranksets that have a hidden 5th bolt, I opted to test the direct-mount version. Over the past few weeks, I’ve logged 300-350 miles with the company’s 40T oval CX chainring on my Salsa Vaya gravel/commuter rig.
Despite a recent resurgence in popularity, oval chainrings are not new technology. Dating as far back as 1890, non-round chainrings have made numerous appearances in the marketplace, with the most in/famous being Shimano’s Biopace. More recently, oval rings enjoyed a boost in popularity when professional road racers Chris Froome and Sir Bradley Wiggins used non-round rings in their quests for Tour de France victories. And now, oval chainrings such as those offered by absoluteBLACK are seeing more use among off-road riders.
You’ve read GRAVELBIKE’s series of articles on 650B conversions, and now you’re thinking about converting one of your own bikes. While the process is relatively simple, every bike (and setup) is a little different, and there’s always the possibility of a gotcha lurking in the shadows. After spending countless hours testing various wheels, tires, and other components, we’ve compiled a list of tricks, tips, and lessons learned that’ll make your 650B conversion that much easier.
Mind The Gap
Tire casings relax and typically plump up a few millimeters after being inflated for 24-48 hours. Check your tires’ clearance a day or two after the initial installation to confirm that there is still adequate clearance at the frame, fork, or fenders. When in doubt, opt for a narrower tire, especially if you’ll be riding in muddy or snowy conditions.
Keep It Simple
If you plan on swapping wheels for different terrain or conditions, try to use the same components on both wheels. Having to adjust brake calipers or rear derailleurs every time you change wheels can be time consuming and frustrating. Sure, practice can make the task easier, but when both wheelsets have the same hubs, cassettes, and rotors, you can spend more time riding.
Know Thy Limits
Fat tires and low gears can take you to some exciting new places. If you haven’t ridden a particular bike off-road prior to the 650B conversion, take it easy until you’re comfortable with the new wheels’ affect on handling and braking (both on- and off-pavement). This is especially important if the different wheels affect bottom bracket height or steering geometry.
In this series’ previous installment, we covered the wheels-and-tires portion of GRAVELBIKE’s Salsa Vaya 650B conversion. For this entry, we’re going to spend some time talking about gearing.
Salsa has always spec’d the Vaya completes with sensible gearing, and my own Vaya’s gearing (36/46, 11-34) was more than adequate for pavement and gravel. For extended climbs on rocky terrain, however, that gearing simply wasn’t low enough. Drawing on my past experience with 26″-wheeled bikes, I knew that a sub-1:1 low gear would not go unused when exploring more rugged trails.
Achieving that low gear turned out to be a bit of a challenge due to the fact I was running such an eclectic mix of drivetrain components (10s Campagnolo shifters, 9s daVinci/SRAM rear derailleur, Shimano 9s cassette). Taking inspiration from Salsa’s Fargo off-road adventure bikes, I decided that a mountain-double crank would give me the low gear that I needed without having to replace any other components.
To maintain compatibility–and eek out every last bit of shifting performance–many crank manufacturers offer dedicated chainring combinations designed to work specifically with Shimano or SRAM systems. Since my hodgepodge setup contained a mix of both companies’ components, I needed a crankset that would play nicely with a non-dedicated setup. Thankfully, Full Speed Ahead designed their Afterburner double crankset to be compatible with both Shimano and SRAM drivetrains.
Installing the Afterburner crankset was a breeze, requiring only a 5mm hex key and Shimano Hollowtech II-compatible socket. During my testing, I alternated between 24/38 and 22/36 chainring setups, logging the most miles on the 22/36 combo. While it wasn’t designed for such tiny chainrings, the Campagnolo Veloce front derailleur shifted better than expected when it was positioned such that it barely cleared the chainstay.
On paved and gravel roads, the 36t chainring proved surprisingly versatile. There were a few situations where I found myself wishing for a taller top-end, but I never felt handicapped by the 36/11 high gear. When it came to navigating steep, rocky trails, the 22t chainring was invaluable. I could cruise along in the 36t ring, drop down to the 22t when the trail started to get steep, and then fine tune my cadence by shifting up or down the cassette. Thanks to the added height of the 650B knobby tires, pedal strike wasn’t an issue with the 170mm cranks when traversing rock gardens or navigating stair-type obstacles.
If you tend to divide your riding equally between pavement and dirt, consider a mountain-double crankset. For riders seeking a wider gearing range–while still maintaining the simplicity of a double-chainring system–Full Speed Ahead offers the Afterburner in 26/39 and 42/28 combinations.
Disclosure: Full Speed Ahead provided product samples for this article, but offered no other form of compensation for this review.