Gates has been offering belt drive systems for bicycles for several years now. We’ve seen them on the timing side of tandems, as the primary drive for OEM applications like Trek’s District single speeds, and more and more companies are building frames to accommodate a single speed belt drive, or even pairing them with an internal geared hub from Shimano or Rohloff.
Switching to a belt drive has numerous benefits. One is lighter weight compared to a chain and sprockets, which is a plus in every application. No one has ever complained of weight savings, unless it compromised strength, but a typical belt will last more than twice as long as a bicycle chain, so they have certainly proven their durability. Quieter performance is not necessarily the goal of every rider, but that’s another area where the belt excels. Finally, the belt drive requires no lubrication, and therefore runs much cleaner than a chain. This has a lot of appeal not just to casual cyclists that would like to avoid the maintenance and messiness of a lubricated chain, but it’s been a huge hit with the cyclocross crowd. Careful design has lead to sprockets that shed mud, snow and debris so well that more and more single speed racers are choosing the Gates Carbon Drive to take them to the podium.
Gates offers some different setups, for different applications. The original CDX™sprockets have a raised guard on the outside face, protecting the belt. This line currently has the widest application, and can be found on mountain bikes as well as those mostly limited to pavement, such as touring and trekking. The CDC™utilizes a similar design, and is ideal for commuter bikes. For off road, poor conditions, and high performance, the CDX™CenterTrack™is the leader. They’ve slimmed down the profile, increased the strength, and added a groove down the center of the belt that matches the new sprocket design. This lends strength while eliminating the outer guard, resulting in the ability to brush off whatever the road or trail throws at it.
Skeptical about strength? Think you’re going to break one with your massive calves and quads? Gates offers 10mm and 12mm belts. Both of those belts are under 1/2 inch, and you’re wondering how strong could they possibly be, right? Well, Harley owners typically run belts from 1-1/8 inch to 1-1/2 inch, with anywhere from 50 to 100 horsepower. You’re not going to break one, even if it’s only about 1/4 the width. And when you look at the success they’re having in the terrible conditions found in cyclocross racing, it’s safe to say that it will hold up well under normal day to day use.
The Gates Carbon Drive system isn’t perfect though. You can’t just retrofit it to your current ride. Since the belt is one piece, unlike a chain that you can split, the frame needs to be designed around it. This usually means a bit of extra hardware at the drive side rear dropout, that allows the frame to be split so the belt can be installed. Swapping gear ratios also means a new belt with your new sprockets, since it can’t be cut to fit like a chain. That can be an expensive proposition. Setting up the belt with proper tension can be a little tricky, but they’ve released an iPhone app to make that easier. From what I saw, it’s similar to a guitar tuner. “Pluck” your belt, and measure the frequency to verify correct tension. One other consideration is that there are finite combinations at this time – you’ll need to find a combination of front and rear cogs for the desired gear ratio, plus a belt length that will allow for proper tension give your chainstay length. None of these issues are completely insurmountable, as evidenced by the rapidly growing popularity (and success) of the belt drive, but I’ve included them to clear up some questions we’ve seen on the forums and elsewhere.
For more info, check out carbondrivesystems.com, then head to your favorite bike dealer to test ride this technology.
– Brian