Are belts the future of cycling? Well yes and no. Like any system they have advantages and disadvantages, but after selling them now for a few years we are more and more convinced that for many purposes they make an ideal solution.
They are without doubt cleaner, quieter and longer lasting than a chain so they are perfect for people that want to do high milages with the minimum of maintenance. They don’t need to be lubricated and they run almost silently. A belt drivetrain is considerably lighter than a chain and sprocket.
We offer these bikes with the Gates Carbon Drive
Belts last up to 4x the life of a chain because they don’t ‘stretch’ and wear in the same way. This is because belts have no moving components like a chain, they’re constructed with continuous loops of carbon cord inside a nylon/polyurethane jacket. Chains lengthen over time as their components wear (pins, bushing, rollers) until eventually chains will no longer mesh well with the sprocket teeth. A belt causes some wear on the sprocket which will eventually cause excess noice and eventually some slippage but reports of over 30 000 km usage suggest that this takes a long time.
Obviously there are some disadvantages:
- Belt drivetrains require a lot of tension resulting in a slightly less efficient drivetrain than with a chain. This tension is also said to damage bottom bracket and rear hub bearings but it is our experience that your bearings will wear at the same rate.
- To fit a belt drive you need a special frame. Belt compatible frames have a ‘belt splitter’ in their rear triangle. You also need some means of tensioning the belt. usually 'rocker' dropouts or an eccentric bottom bracket.
- Carbon drivetrains are expensive, but could be considered good value if you take into account the kilometres you can expect to get out of a belt.
- Belts can only be used with an internally geared hub, or as a singlespeed (not for derailleurs). This is primarily why the product is not mainstream.
- Belt lengths are fixed and only certain lengths are available, limiting the drivetrain ratio options available. If you want to fit one to an existing frame, or build a frame for a belt drive, you have to use an online calculator which gives a range of possibilities, in order of suitability.
- Belts can be mishandled; users should be careful not to twist or bend the belt.
- Its much more complicated if you want to change your gear ratios as only exact combinations of sprocket size, chainring and belt will work. To calculate what combinations you can use with your chainstay length you will need to download the Gates Carbon Drive Calculator
The Carbon Drive runs at quite a high tension. This tension varies between whether you use a singlespeed or internally geared hub and how powerful you are as a rider. Tension variation (tight spots) may occur when the crank is rotated. Gates therefore recommends taking several tension measurements at different crank arm locations to find an average. Around a 10lb or 15Hz variation is considered acceptable . If significantly more variation exists, Gates recommended centring the chainring on the crank spider.
The Centertrack system solves some of the problems of the CDC/CDX system, namely belts slipping on cogs under low belt tension and high-load. The biggest difference to the CDC/CDX system is that Centertrack will allow for more lateral intolerance: This means that when your frame flexes slightly, the belt is still able to run efficiently without the chance of slipping even though tension is reduced. Because the Centertrack belt runs at a lower tension it will allow for more lateral intolerance and it reduces stress on your drivetrain, namely bottom bracket bearings, hub bearings and chainring/cogs. The Centertrack belt is quieter and clears debris better from the cog and chainring: The open cog design of the Centertrack system actually repels dirt and mud better than the older flanged cog system on the CDC/CDX. With the Centertrack design, the chainline tolerance is reduced. The Centertrack rear cog is stainless steel and should outlast a few belts.