Belt drive systems are used in cars, industrial equipment and motorcycles, why not bicycles?
I consider the bicycle to be one of man's greatest inventions of all time. Why? Because in more than a century of its existence, the bicycle is essentially still powered by a chain and cog. If there were a better, more efficient way to power a bicycle, companies like Shimano would have already figured it out.
But the folks at Gates aren't convinced a chain is the best way to drive a bicycle. Although a patent was filed in 1890 for a belt driven bicycle, since then, the challenge of making the belt stiff enough to not flex or break while staying on its track has proven elusive.
Gates updated the original belt drive to include a keyed center track to keep the belt from migrating off. It works flawlessly.
That is until industrial belt drive pioneers Gates Corporation developed the original Carbon Drive System in 2007. Although plenty stiff, the original Carbon Drive System still had issues with alignment and staying on its track. In 2011, Gates released the CenterTrack and CDX systems, featuring a groove down the center of the belt which lines up with machined fins between each chainring and cog tooth, keeping the belt perfectly aligned while requiring less system tension.
An automotive strap wrench makes a good chainwhip for Gates cogs.
The Gates Carbon Drive belt is made of stretch-free carbon fiber tensile cords covered by a weather-resistant polyurethane outer. Although the belt is remarkably strong, bending, crimping, and/or twisting it the wrong way can bring it to a premature end. Even transporting it improperly can do damage--Gates prescribes a particular coiling of the belt to prevent damage to the carbon fiber cords should you need to carry one.
And though you may be tempted to use the belt as a chainwhip to remove a Gates cog, don't. This too is belt killer. Use a strap-type automotive oil filter wrench instead. It works perfectly.
Like any new kind of technology, the Gates Carbon Drive system takes some getting used to. First off, all the gear inch calculations you're already used to with chain driven systems get thrown out the window. Instead of familiar gear ratios like 32:21 and 34:19, you're dealing with oddball numbers like 46:28 or 39:26.
The Gates system made the feathery Ibis Tranny even lighter-it weighs in at about half that of a traditional chain and cog drive system.
And because you can't cut and adjust the length of a belt like you can a chain, once you figure out the proper gear ratio, you'll need to order the correct belt length. Measured in number of teeth, the CDX belt comes in eight different lengths.
Because each gear might potentially use a different belt length or at least require an adjustment in the frame tensioning system, easily running a "dingle"speed option - two different gears that run the same chain tension-is pretty much out of the question. Not a deal breaker for most buyers, but something to consider nonetheless.
The Gates Carbon Belt Drive is clean looking and performing.
Another minor annoyance with the belt is figuring out how much tension to run. There's two ways to properly measure the tension-a Gates tension meter or the Gates smartphone app. Because the app is free and with me whenever I have my phone, I downloaded it and gave it a try. The app works by listening to the tensioned amplitude of the belt when you pluck it like a bass guitar string. It shows the recommended Hertz range and tells you at what frequency your belt is vibrating.
Although a pretty slick idea, I could never seem to get three consecutive accurate readings from the app. And further, my belt tension always seemed lower than what the recommended tension was. Because I was running the Gates system on my Ibis Tranny 29, the frame tensions by telescoping behind the bottom bracket. I literally sat my entire body weight on the bike to tension the rear triangle, cinched down the Slot Machine bolt on the Tranny 29, and I was still below the recommended tension.
After that I gave up and simply took a rather unscientific "tight enough" approach. It's worked fine for me with no slippage at all, so I'll just stick with it. The app does have a few other handy features though, including a complete product catalog of all cogs, rings and belts as well as a calculator to figure out specific gear setup so you know exactly what ring, cog and belt to use.
Continue to Page 2 for more on the Gates Carbon Belt Drive System and full photo gallery »
By replacing a chain made of several hundred parts with a one-piece belt, even the humble singlespeed becomes simpler.
On-trail performance
Of course this is the most frequently asked question of everyone who sees the belt drive setup on my Tranny 29. Is it really silent? Yes…most of the time. Is it lighter than a chain setup? Yes. Do you feel a difference in stiffness? Absolutely. In fact, for me the most noticeable attribute of the Gates Carbon Drive system is how damn stiff the system is. While titanium, steel and even some alloy cogs and chainrings flex under power, the 12mm wide Gates Carbon Drive Belt feels noticeably stiffer when putting down donkey strength on steep climbs.
Another huge advantage of the Gates Carbon Drive over a traditional chain is with travel convenience. Because the Tranny 29 has a rear triangle that completely separates from the front, I can fit my bike into a Ritchey Breakaway suitcase and fly charge-free on airlines. Having the belt in this situation is extra nice because there is zero grease, grime or grit to deal with when breaking down and reassembling the bike. If you plan to travel with your singlespeed, and specifically with an Ibis Tranny 29, I highly recommend the Gates Carbon Drive system.
At 274 grams for an entire setup (118t belt, 46t ring and 28t cog), the Gates Carbon Drive system is just north of 100 grams lighter than my chain driven setup, with some chains like the SRAM PC-1 weighing more than an entire Gates drivetrain all together. So if you're a weight weenie, you're going to love the Gates system.
Beauty is in the eye of the beholder, but we think the Gates system looks pretty cool.
Now onto the topic most people ask about; is it really silent? When properly maintained, yes, the Gates Carbon Drive system is whisper quiet. There's no squeaking, no creaking and no chain slapping off the chainstay over bumps. All that's required is a quick hose down with water after each ride to keep it properly "lubricated".
However, in dry, dusty conditions, the belt can develop a characteristic squeak that gets rather irritating. A quick squirt of a water bottle will silence the belt for a little while, but on hot days, you want to be putting that water into your body, not wasting it on your drivetrain. The folks at Gates told me if the belt starts to squeak on rides, simply shoot the belt with some silicone-based spray lubricant. I took their advice, and sure enough, the belt was quiet for several dry, dusty rides in a row.
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| A straight chainline is crucial but easy to attain with the Gates system. |
Does the belt skip, pop or jump at all? Absolutely not. Since July I have put the Gates Carbon Drive system through the ringer, literally track standing on trail obstacles trying to muster all the German/Scottish power and anger I could to make the drivetrain falter. It never did.
The only environment I haven't been able to test the Gates Carbon Drive system in is paralyzing mud. But based on the prevalence of the Gates in areas like the Pacific Northwest, I can only conclude that it works reasonably well. Gates claims that after 192 hours of salt spray testing, zero rust or corrosion built up on the Carbon Drive system. Most traditional chain drivetrains would be completely seized by then. My only question is how fast does the belt deteriorate under muddy, grimy and gritty conditions. Perhaps some readers with experience can chime in.
Potential Drawbacks
So what are the drawbacks? Well, perhaps the most noticeable one is cost. An eight-speed chain, decent alloy cog and chainring might set you back $100 total. By comparison, the Gates Carbon Drive system costs double to triple that depending on configuration. Does the Gates Carbon Drive system last twice as long? Gates claims it does, but seriously, it would take me years to confirm that claim. I'm still running the same titanium chainring and cog I bought four years ago, and I've put thousands of miles on them.
Because the belt is continuous and cannot be broken and re-fixed like a traditional chain, a bike with a chainstay or seat stay slot is required to install the Gates drive.
Another drawback for many is that in order to run the Gates Carbon Drive system, you must have a frame that is compatible with a belt drive system, meaning your frame needs to have a slot in the rear triangle somewhere in order to fit the belt through. Therefore, the Gates Carbon Drive system might not even be an option for a vast majority of singlespeeders who already have a bike.
A third potential, albeit minor, drawback is the potential requirement of carrying a spare belt everywhere you go. Although the belt weighs practically nothing at less than 100 grams, still, with its extremely fragile handling requirements, you can't just stuff it into a jersey pocket. And since I avoid hydration packs like the plague, finding a place to put the spare belt is kind of a PITA. But as the old saying goes, when there's a will, there's a way.
The Gates system accentuates the smoothness of trails like the Flume Trail above Lake Tahoe.
Who should buy it?
The Gates Carbon Drive system is a viable singlespeed option for those who want the absolute lightest and quietest drivetrain setup possible, those who travel a lot and don't want to deal with greasy griminess, those who want flex-free performance for the absolute best power transfer and those who don't mind spending more than double the amount of money over a traditional drivetrain.
But for those who have already invested a bunch of money into different color anodized chainrings and cogs, have a frame that is non-belt compatible, occasionally like to run a dinglespeed setup and have a rather tight budget, the traditional chain setup is always a viable choice.
In the end, would I buy a Gates Carbon Drive system for another bike? Absolutely. I like running the highest performance equipment on my bikes, and in my experience, the Gates system outperforms the traditional chain and cog when it comes to power transfer, stiffness and weight. As a bonus, it's quite a conversation piece to those who've never seen a belt drive bicycle before. Provided you have the budget, the Gates Carbon Drive is well worth the added expense.
MSRP: $220-280 depending on configuration
For more information visit gatescarbondrive.com.
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