Gates Carbon Belt Drive has been developed over the last 25 years for applications on 6000hp drag racing cars, 150hp motorbikes and more recently, bicycle drivetrains. Although Carbon Drive isn’t for everyone, it certainly has a place for bike tourers and city riders who are after a no-fuss drivetrain which is lighter, easier to maintain and offers an exceptional wear life.
Gates Carbon Drive system is slightly limited for the bicycle touring market, as it is only able to be used with internally geared hubs such as the 14 speed Rohloff or 8/11 speed Shimano Alfine.
My extensive experience with a belt drivetrain includes a two year, 31,000km bike ride between Europe and Australia, lots of multi-month tours around Australia/NZ/Asia and my current bike trip from Argentina to Alaska. I started playing with belts on my modified Surly Long Haul Trucker in 2010, then bought a dual-belt Co-Motion tandem and am currently on a Koga WorldTraveller-S.
Belt Drive Thumbs Up
1. Belt drivetrains last up to 4x the life of a chain because they don’t wear in the same way. While chains lengthen over time and eventually no longer ‘mesh’ well (pins, bushings, rollers, teeth), belts are constructed with a few continuous loops of carbon cord inside a nylon/polyurethane jacket, and therefore, have no moving parts. My first belt lasted 31,000km!
2. Belts require little to no drivetrain maintenance and don’t need to be lubricated (no greasy hands). The most maintenance you’ll have to do is get a toothbrush and give the belt a scrub from time to time.
3. Belts are mostly impervious to road grime and weather, and will not rust if you leave them in the rain.
4. Belt drivetrains are almost silent on the road.
5. Belts are considerably lighter than chains, in fact, a sprocket/cog/belt is lighter than a chain alone.
Belt Drive Thumbs Down
1. You need a belt compatible frame with a built-in tensioner to run a belt drivetrain. Belt compatible frames have a ‘belt splitter’ in their rear triangle and should also be ‘stiffness test approved’ – more below.
2. Belts can make a lot of noise in dusty conditions. Stopping the squeak is an easy fix; a squirt of water will normally do it. But if the dust is constant it’s good to have a Hanseline Belt Drive Care Stick on hand to keep everything running smooth. If you don’t have access to this wax product, silicone spray (with no added solvents) or a biodegradable chain lubricant is said to work fine too.
3. Finding a replacement belt in a bike shop is virtually impossible. That said, on a long distance bike trip, you need to ship in most high-quality bike components anyway. It’s prudent to carry a spare belt (74 grams) to get you out of trouble, they fold up nice and small. I’ve never carried a spare chainring or cog as they’re very unlikely to be damaged on a bike trip.
4. Belt drivetrains require a lot of tension resulting in a slightly less efficient drivetrain than a perfectly lubed chain drivetrain.
5. Belt components are expensive initially, but they’re very good value if you work out their cost-per-mile.
6. Belts can only be used with internally geared hubs, a Pinion gearbox or as a singlespeed.
Why Aren’t Belts Common?
Chains are compatible with mainstream bikes, or more specifically, bikes designed around derailleur gearing systems. To get the same gearing options, belts must be used with internally geared hubs. Although internally geared hubs are brilliant for what we do, derailleur setups fit onto almost any bike frame type, plus they’re cheap, reliable, simple and lightweight.
The CDX High-Performance belt drivetrain is the most well-proven belt option. You’ll find this on almost all touring and adventure bikes. This system now has 16 belt lengths, 7 front sprocket sizes and 8 rear cog sizes to give you the most drive ratio options.
Gates recently released an oversized version of the CDX drivetrain which is designed to get an even better range and durability. These sprockets and cogs have 25% more surface area which allows you to run a lower belt tension and therefore reduce the wear on the system. There are currently 4 front sprocket and 4 rear cog sizes available.
The budget belt drivetrain from Gates is the CDN Urban. The idea is to bring belt drive to city bikes in the 500€ complete price range. These products are only designed for light-duty use, so try and avoid them if you do a lot of commuting or are planning on travelling with a belt drivetrain.
Cleaning a Belt Drivetrain
Cleaning is as simple as getting a water bottle and an old toothbrush, and rinsing the belt/cogs down with water. No degreaser. No chain cleaner. No dirty hands. The cleaner the drivetrain is, the more silent and efficient it will run! Apply your Hanseline Belt Drive Care Stick for an even smoother ride.
Handle Belts Carefully
You have to be really careful with how you handle carbon belts, as misuse can lead to internal fibre damage, compromising the strength of the belt. They are sensitive to crimping (1&6), twisting(2), back-bending (3), inverting (4) or zip tie’ing (5).
Belt alignment is essential. With the CDC/CDX, make sure that the belt is sitting perfectly on the chainring and cog. At full tension, it should be silent. You will be able to see if the belt is rubbing on either of the ‘windows’ on the chainring or cog. With the Centertrack system, you will know when it is misaligned – it will make lots of noise at full tension.
When you put the belt on, it is essential that you do not ‘crank it on’ like you may with a chain. You must essentially put the belt onto the chainring and cog before setting the tension. Simple for sliding dropouts and EBB, slightly harder for horizontal dropouts. Use the image below as a guide.
If you’re folding a belt, or unfolding a belt, you must be careful you do this in the correct manner. The belt should naturally sit in a loop which folds three times. See the below picture for an example.
Belt Drive Bike Frames
Not all frames can run belt drive. A belt frame has a few essential features that make it suitable.
– The first is that there must be a split in the seatstay, chainstay or dropout. Belts are one piece, so a frame split is essential.
– Next, there must be an adjustable chainstay length. This is commonly made possible through sliding dropouts, eccentric bottom brackets or horizontal dropouts (more below).
– Another essential frame feature is a stiff rear triangle. The less flex, the smoother the belt can operate under load and corners. Touring bikes generally have very stiff rear triangles as they need to carry heavy loads on their pannier racks.
Dropouts for Belt Drive
Sliding vertical dropouts: Sliding dropouts are the best option for belt systems because they are easy to adjust to get the high tension that belts require. You also do not need to tension your belt every time you take your wheel out; it simply drops out and goes slots back in to the perfect tension.
EBB: Eccentric bottom brackets allow your wheel to slot in and out at perfect tension. EBBs require a bit more work than sliding dropouts to get the appropriate belt tension. Making small adjustments to tension is also a bit of a pain.
Horizontal track dropouts: You have to be really careful with belts in horizontal dropouts. If you are using belts and horizontal dropouts, you must have a minimum of 10mm left in the dropout before the belt is tensioned. This space is required to get the belt onto the chainring. Eg. If your chainstay is adjustable between 420-440mm, you must have your belt taut between 430-440mm.
It is essential that a frame modification is done correctly. Not any old frame can be modified to run a belt drive, especially if you want to use it with a Shimano internally geared hub. Shimano IGHs have quite a narrow chainline and this often results in chainrings rubbing on the chainstay. If anyone pulls out a 40lb rubber mallet to flatten your chainstay… have a few words with them!
If you’re going to get this modification made, make sure to see a reputable frame builder. It will often cost around $500 USD to modify a frame including paint. We used Ewen Gellie for our work in Australia. Cycle Monkey in Northern California (USA) also does frame mods.
Chainline, Tyre and Frame Clearance Issues
One of the biggest challenges facing frame manufacturers and the use of belt kits has been frame clearance of the front chainring. This is seen mostly on bikes using belt drive with Shimano internally geared hubs. The gear selector on Shimano hubs is external and on the drive side, resulting in a really narrow chainline.
This is more of a problem for belt-bikes than chain-bikes as:
– Belts and belt cogs are wider than chains and chainrings
– Belt cogs do not get as small as chain cogs
– 46t or bigger is most likely required
– Belt drivetrains are fussy
– They must be perfectly aligned
Chainlines of various internally geared hubs:
– Alfine 8 or 11: 44.85mm
– Nexus 8: 44.35mm
– Nexus 7: 43.05mm
– Rohloff with Phil Wood Cog CDC: 52, 54 or 56mm
– Rohloff with Gates Centertrack: 54mm
Working Out Your Belt Ratio
You will need to use the Gates Calculator in order to work out what chainrings and cogs are available for your frame. It all depends on your chainstay length.
As mentioned above, if you are using the Centertrack kit and horizontal dropouts, you must have a minimum of 10mm left in the dropout before the Belt is tensioned. This space is required to get the belt onto the chainring. Eg. If your chainstay is adjustable between 420-440mm, you must have your belt taut between 430-440mm.
Belt Drive and Tandems
It is possible to use Gates Carbon Drive as a timing belt. This will save you about 250g over a chain and chainrings. In order for Carbon Drive to work on your tandem, the frames boom tube must be 724mm between bottom brackets and you will need to use 130bcd cranks. It is possible to run belts on both the drive and non-drive side of your tandem.
We believe tandem touring with belt drive is best left to sealed roads, as we’ve experienced noise on the timing side on both sandy, and dirt roads with fine dust. If you ride only a small percentage of your travels on dirt, then cleaning the belt with a bit of water every 50-100km won’t bother you too much and certainly doesn’t outweigh the positives of this system on sealed roads.
We used the CDC timing kit initially, but were quite disappointed by it – it only lasted 2000km (review HERE). Our Centertrack timing belt is going strong with little signs of wear after about 19,000km. You can read the Centertrack timing belt review HERE.
Belt Drive and Rohloff Hubs
You can run belt drive with a Rohloff hub if you adhere to their rules. Not adhering will result in the chance that Rohloff will not be able to honour warranty replacement down the road.
Firstly, your frame must be built for the purpose of the belt drive. In Rohloffs words, it must be ‘stiffness test approved’. A belt drive production bike or custom frame manufacturer will be able to use the appropriate tools in order to make it ‘stiffness test approved’.
Secondly, your Rohloff hub must be belt-converted. This ‘belt-conversion’ adds a Rohloff machined adapter to the hub to allow the use of third party belt components. Rohloff records the serial numbers of belt converted hubs and without this conversion, you risk the chance of not being honoured the warranty. If you already have a Rohloff hub, you can get it converted to belt drive for a fee.
A belt ‘snubber’ is required for all Rohloff users. Belt snubbers prevent the belt from walking off the cog. The reason that these measures must be taken is due to the fact that Rohloff cogs actually incorporate a seal surface for the hub. With a ‘belt conversion’, the hub is sealed and ready for aftermarket components.
You are slightly limited in terms of ratios with a Rohloff, as there is only three cog size available (19t, 20t, 22t). This, in addition to the fact that you are limited with your chainstay length, means that there are only a few ratio options available. Manufacturers who produce belt-specific frame are generally aware of this fact and will produce frames with ideal chainstay lengths for their application.
Gates Centertrack: Gates offer the full kit for Rohloff, including a stainless steel cog.
Gates CDC/CDX: There are a few Rohloff aftermarket cogs available.
Tensioning the Belt
Gates 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.
Measuring Belt Tension
iPhone app: If you have an iPhone, you are able to download an app which will measure how much tension your belt has! Simply hold the phone next to the belt and give it a few plucks. It will quickly give you an average frequency rating. We’ve also heard of people using a bass guitar and digital tuner to work out the frequency!
Gates tools (sonic tension meter, krikit gauge): You are able to use the uber fancy sonic tension meter, or cheaper krikit gauge if you are iPhoneless. The Krikit gauge is not as accurate as other measuring tools, but essentially you put your finger in the loop on the tool and apply pressure until the tool clicks. It will give you a rough estimate on whether to increase or decrease your tension.
Chainring: US $70-110
Alfine Cogs: US $110
Rohloff Cogs: US $110
Belts: US $90-110
Centertrack Kit Total: US $300
The Low Down
I love belt drivetrains!
The simplicity, silence, long wear life and maintenance-free design of the Centertrack kit makes it the perfect for bike touring. The Gates Centertrack drivetrain on my tandem has proven itself and it’s durability with its 31,000km ride from Europe to Australia.