By Stephen Haynes, photo by Justin Steiner
Gates is a Denver-based company that has been manufacturing belts for automotive, agricultural, and industrial applications for more than 100 years. The company partnered with Spot Brand, located in nearby Golden, Colorado, to develop a belt-driven drivetrain for bicycles in 2007. Gates’ Carbon Drive System uses a high-strength belt that has carbon fiber cords embedded in a rubberized belt. The sprockets are machined from aluminum.
Early versions of the Carbon Drive System occasionally suffered from alignment issues; the forces generated by pedaling and braking could lead to misalignment of the sprockets, causing the belt to “walk” off the sprockets. In 2009, founder of Avid and owner of Spot Wayne Lumpkin developed Center Track technology in conjunction with Gates. The center ridge on the sprockets helps to mitigate alignment issues.
There has been some controversy over the validity of belt-driven bikes in the mountain bike community. Initial hiccups with my test bike seemed to validate many people’s suspicions of the Carbon Drive system for off-road use. Dropping the belt on a few different occasions—and potentially damaging the fragile carbon fiber cords by walking it back onto the cogs, as you would a chain—compelled Spot and Gates to insist I put a new belt on. I was sent a new belt and we set about installing it.
Here I come to my first hiccup with belt drive. The bike (a Spot Rocker SS. You can read the full review here.) came set up for a rider 40lbs. lighter than I am. I was assured this wouldn’t have been an issue for most consumers, as the shop you purchase the bike from would dial in the belt for you. Fair enough.
My second hiccup with the belt drive occurred when I had to tension the new belt. Installation is a delicate matter. The belt must be handed with kid gloves, as the belt’s carbon fibers can be damaged if kinked. Tensioning the belt was a different story. I was told to download the free Gates Carbon Drive Bicycle Calculator (GCDBC) app for the iPhone. The iPhone 4 and 4s to be exact. (Dumbphone users, those with older iPhones or Driods are S.O.L.) I enlisted the help of some co-workers with the required technology to assist in “tuning” the belt.
An adjustment that seemed like it should have taken five minutes ended up taking the three of us over an hour. The GCDBC app takes a hertz measurement, via the iPhone’s microphone, when the belt is plucked. The app then spits out a reading. You take this measurement and tighten or loosen the belt accordingly. Ambient noise often skewed the results and tightening and loosening of the dropout and tension bolts began to wear on us.
The hour spent toiling over the proper tension was worth it. After four months of abuse I have not had a single issue with the system. I’ll even admit that in the last few weeks of my test period I was trying to break the thing. Leaning back and mashing with everything my 225-pound ass could muster, only to have the damn thing spite me and continue to work perfectly. I’ve done no maintenance since it was installed; no scrubbing, wiping, or hosing down, and it continues to perform flawlessly.
I think this could make a great drive train for singlespeed racers. The Carbon Drive System is very light and, despite the finicky setup, has proven reliable in a multitude of sloppy conditions. For weekend warriors interested in the Carbon Drive System, I still say go for it, but be aware of the prep that has to be done beforehand, and the precautions you have to take when setting it up. The system has a two-year warranty against defects. Gates is also com- mitted to making customers happy and is willing to assess inquiries regarding belt problems on a case–by-case basis.
Belt drive pros and cons
- Belts perform well in harsh environments: Belt drives are less susceptible to mud, sand, and, unlike a chain, a belt will never rust.
- Exceptionally light: Weight weenies and racers take note: an entire belt-driven drivetrain can weigh as little as 250g (belt and both sprockets). A singlespeed chain weighs approximately 280g.
- Very quiet: My belt ran silent even when full of mud and muck.
- Goes the distance: Belts have excellent longevity and they won’t stretch. A single belt can outlast many chains.
- Low maintenance: No need to lube. I never so much as washed my belt off and it performed flawlessly.
- Not field serviceable: Other than carrying a spare with you, there is no fix for a busted belt.
- Belts are fragile: You must be careful not to damage the carbon strands embedded in the belt when installing or removing it. Once damaged, the belt must be replaced.
- Finicky installation: Having to handle the belt with kid gloves is one thing, having to tune it with the assistance of an iPhone app is another. Patience Grasshopper.
- Aglinement issues: Belts are much more sensitive to misalignment than chains.
- Frame-specific: Belt drive presents frame builders with several design considerations: chainstays must be within a certain length and the drive-side chainstay be dimpled or use a yoke to accommodate a much larger, and wider sprocket. The frame must have a break on the drive-side seat- or chainstay for the belt to be installed and removed.