We’re willing to bet that standard metal chains for bicycle drivetrains are unlikely to disappear any time soon. Especially at the elite level, belt-driven drivetrains have a long way to go if they aspire to the gearing range and light weight attainable even with moderately priced, standard parts groupsets.
That being said, if Gates Carbon Drive keeps improving their belt systems, it’s quite possible that a growing majority of urban, commuter, and mountain bikes could be belt-driven in the not too distant future. For 2011, the company is showing a new belt and pulley system called CDX-CT. The CT stands for Center Track, and with the new design the belts are wider and stronger while the cogs are narrower. The net result is that belt systems will fit more bikes and more rear hubs, once again growing their potential to gain even more ground on everyday bikes.
Belts for More 2011 Bikes
On day-one of the Interbike Outdoor Demo, we stopped in at the Gates tent to get the download on their new system. Sponsored singlespeeder Jake Kirkpatrick, winner of the recent Dakota 5-0 mountain bike race, greeted us. He rides Black Sheep rigid titanium bikes with Gates belts.
Although Kirkpatrick left his 2010 race bike at home, he pointed us toward a wide array of new bikes powered by Gates Carbon Drive belts. For 2011, the company is making belts and pulleys (their new nomenclature for the chainrings and cogs, a.k.a. sprockets that the belt engages) for a whopping 90 models built by 24 different brands. While the most eye-catching belt bikes are exotic singlespeed mountain bikes and of course Trek’s carbon District, a 12-pound singlespeed carbon fiber commuter, the majority of belt bikes are actually urban, utility, and commuter bikes.
“Of course, being in Colorado we love the mountain bikes,” said Gates’ global director Todd Sellden, who acknowledged that Gates’s biggest opportunity is in the world of urban bikes that see heavy use, sometimes harsh conditions, and little maintenance. “We use mountain bikes as a test bed. Singlespeeders love the responsive feel of belts.”
The main advantage of belts is their light weight, strength, and long term durability. They’re silent, virtually impervious to mud, grime, and weather. Plus, they’ve got great resistance to stretch and wear. On the down side, belts do require proper alignment and tension on installation so they don’t jump off their pulleys. They also tend to be expensive, and their wide profile limits how many bikes they can fit.
Since introducing their original CDX belt system, Gates has lowered the price with the newer CDC system. It’s aimed at urban and pavement bikes. The CDC belt kit uses wear-resistant hard anodizing on the front ring instead of the more expensive carbide coating used for the CDX chainring. The CDC system also uses a steel rear cog instead of the lighter aluminum cog found on the lighter weight, but more expensive CDX kit.
As a result, the Gates CDC system is priced competitively enough to be spec’ed on bikes with retail prices as low as $800. At this price point, belts become attainable for a wide range of bikes built for the rigors of daily commuting and utility use. Even better, many of these bikes are not one-gear singlespeeds. Most are built with multi-speed rear hubs like the Shimano Alfine11-speed unit. Just like that, a virtually zero-maintenance drivetrain has become available for everyday, around-town bikes.
Center Track Takes Center Stage
While it’s not yet in final production, the new CDX-CT system promises fitment for even more bikes. Instead of flanges on the pulleys to keep the belt in place, the center track kit uses just that — a track or spine down the center of the pulleys that fits into a groove in the center of the belt. The system is essentially self-aligning.
Even better, without the flanges on the pulleys, the system is 20-percent narrower and doesn’t require as much clearance between the front ring and frame, or between rear cog and back wheel. Put simply, it will fit more bikes without requiring them to be built especially for belt compatibility.
At the same time, the belt itself is made wider and therefore stronger. It can handle higher tension and as such, can be stretched across smaller pulleys. With smaller pulleys and no flanges, a CDX-CT system is about 50 grams lighter than the current CDX kit. Its total drivetrain weight including belt and both pulleys is just 190 grams.
While the CDX-CT system is not yet scaled up for full production, look for Gates to keep cinching belts on bikes that benefit from their simple and efficient drivetrains.