Being in the rumor business here, occasionally we stir up a few bees nests. Some of hearsay surrounding the Continental belt drive system introduced at Eurobike did just that, which included a rumor that Gates Carbon Belt Drive was considering Aramid to replace the carbon. We’ve heard from several folks with hands on experience that if handled improperly -mainly if its crimped or folded to severely- the Gates system can weaken and snap. We haven’t experienced this since our only test bikes with the Gates system have come prebuilt. That said, Gates has replied that they are absolutely not considering Aramid. Here are the combined comments from Todd Sellden, director of Gates Carbon Drive Systems, and their PR agent:

It is incorrect to say that Gates is considering using Aramid.

Gates used Aramid 30 years ago in a similar industrial belt. A decade ago Gates phased out Aramid and introduced its patented carbon fiber tensile cord technology for industrial belts because it provides superior power density. The years of R&D that Gates has with carbon tensile cord in industrial belt applications made carbon fiber the most sensible and durable material for bicycling, which is why Gates made carbon fiber the backbone of the Carbon Drive. Unlike industrial belts that are being marketed for bicycling applications, Gates Carbon Drive is the result of years of R&D on a bike-market-specific application and it is truly the premium product in the bicycle marketplace—and the only system designed from the ground up with bicycling in mind.

Regarding tooth size: Gates experimented with various tooth profiles (from 8mm to 14mm) before the launch of Carbon Drive. Gates found the larger teeth required larger sprocket sizes that are heavy and impractical for bicycling applications, where weight is a major consideration. The 11mm tooth size on Carbon Drive was chosen specifically because Gates found it to be the best combination of light weight and strength.


  1. there is no doubt that Aramid(kevlar) has several times higher tensile strength than carbon fiber. and also performs better when kinked, twisted and bent. but they would know what works best in their application.

  2. had one, broke one, not sure why it snapped, came on a pre-built spot. my knee still hurts. loved it while it was working, but i have no clue why it broke, at least a chain will show so stretch and impending doom.

  3. Nick C,

    No, your wrong:

    Material: Tensile strength
    Kevlar 49 (Aramid) 3000 MPa
    (just picked a random carbon fiber)
    Zoltek Panex 35® 50k Continuous Tow Commercial Carbon Fiber for Industrial Applications, 4137 MPa

    info from, and too many years of material science and engineering classes

  4. I have a CTS gates system on my bike. Its fine but its not without fault. first is the bigger chainring required does not fit in the middle position on my crankset because ti would hit the frame. Not a huge issue but i dont like it. Second is the noise. My belt creaks and generally sounds like a cricket if i start pedaling hard. On SS that is a hard thing to avoid. Cleaning the belt does get rid of the noise but it comes back within a few miles of dusty trail. Perhaps if gates invented a vacuum that I could ride in then all would be well. I have broken one belt but it could have been my fault and either way gates replaced it no questions. I do not hate the belt system but I would not waste money on it again. Chains work really well…

  5. I had creaking from my belt until I switched out to the newer CenterTrack parts. After that I was able to significantly reduce tension and avoid creaking. I think the CenterTrack feature is a significant improvement to the original Gates Carbon Belt Drive system.

  6. I agree with Aaron. I upgraded the original CDX system on my Trek District to a Center Track. It is nearly silent when adjusted properly in any surface or weather condition. I frequently startle people on trails because with no gears or chain they don’t hear me coming. The CTS system is very sensitive to belt alignment and tension. Using a Cricket gauge and a small picture hanging laser and I can dial in a CTS in a few minutes. I have also worked on other riders belt drive systems where the complaint was excessive noise or grinding. In every case, the belt was either too tight, or was not aligned properly. In some cases the alignment needed spacers, in others merely flipping the cog did the trick. The CTS cogs have a 2mm offset. I recently changed my wheelset to Ultegra WH-6700 tubeless using the single speed conversion kit from Gates. At this point, I would challenge anyone to hear ANY noise coming from my bike when pedaling in an outdoor environment. The Hutchinson Intensive tires mounted tubeless at 100 PSI made the bike even quieter.

  7. Sorry, I said CTS. I thought that was the center track system. Mine is the center track system. I checked the alignment using my frame table and it is not too tight. Still sounds like a mob of crickets are chasing my on the trail. When I have a chain on the same bike there is zero noise.

  8. Back when I was riding SS, I thought a belt drive would be cool. Until I saw a dude standing halfway up a hill with a broken belt in his hands. At least with chains you can carry a few extra links so you can ride (not walk) home.

  9. A perfect PR answer to the question. Which equals no answer. It is true carbon is stiffer and stronger, so it allows for a smaller and slightly more efficient belt. But aramid is definitely more bastardproof than carbon. And not just a bit more. It is the very reason my velomobile has carbon integrated frame for stiffness, but an aramid shell because that is were idiots will hit it. Carbon bullet proof vests aren’t a big succes either. I’d never trust a belt drive with carbon fiber instead of aramid.

  10. aramid has a lot more stretch in it than carbon. just try mounting a tubeless road tire over a standard folding road tire to feel the difference. belt elasticity hurts efficiency, ends up loading fewer teeth at any one time, requires more tension to avoid skipping, etc.
    unless it’s made of one of the UHM aramid fibers i’ve heard about somwhere.

What do you think?