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.
Our extensive experience with Carbon Drive has been on a two year, 31,000km trip between Europe and Australia. We started with belts on both our modified Surly Long Haul Trucker‘s and 10,000km later used dual belts on our Co-Motion tandem.
- 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. It actually took until 31,000km until we snapped our first belt!
- Belts require little to no drivetrain maintenance and don’t need to be lubricated (no greasy hands). The most maintenance we did was a clean our belts with a tooth brush whenever we got a lot of dirt on the drivetrain.
- Belts are essentially impervious to road grime and weather, and will not rust if you leave them in the rain!
- Belt drivetrains are almost silent on the road; they have a pretty cool humming sound.
- Belt drivetrains are considerably lighter than chains, in fact a cog/ring/belt is lighter than a chain alone.
The Why Not
- Belts can make a lot of noise on sandy, dry roads. We came across this problem in less than 10 short sections of our trip. Stopping the squeak is an easy fix, a squirt of water and a rub with your finger, but it sometimes needs to be done every 20-100km depending on the fineness of the grit. Silicone spray or Rohloff biodegradable chain lube is said to keep them silent for longer, but we never had access to these products when we needed them!
- Getting a spare belt at any old bike shop is virtually impossible. It’s a send-in job. But that said, most high-end bike components need to be shipped to you. We always carried spare belts because they are the most likely part to break, and really don’t weigh much, just 74g. We never carried spare chainrings or cogs as we had a low chance of damaging or wearing out those components.
- 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.
- 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.
- Carbon drivetrains are expensive, but we think they’re pretty good value if you consider the kilometres you’ll get per dollar invested.
- 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 five lengths are available, limiting the drivetrain ratio options available.
- Belts can be mishandled; users should be careful not to twist or bend the belt – see below.
What do we think?
Gates Centertrack is perfect for road touring.
Given that 90% of our across-the-world-trip was on sealed roads, the silence, durability and maintenance-free nature of Centertrack outweighs the annoying squeaking we might get on sandy roads. That said, we generally recommend belt drive to people who ride the majority of their tours on sealed roads. Those who spend more time on dirt than us should stick with a chain, or risk having a squeeky belt drivetrain!
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, are cheap, reliable, simple, and lightweight.
First available in 2011, Centertrack is Gates second go at the bicycle drivetrain and it offers many advantages over CDC/CDX. The main difference is that Centertrack uses a central fin that runs along a molded track on the belt, rather than employing flanged cogs like on CDC/CDX. We’ve had much more success with longevity on the Centertrack kit.
CDX Centertrack weight:
Chainring (Gates 50t x 130bcd): 97g
Rohloff cog (Gates 20t): 94g
Belt (Gates 118t): 74g
Introduced in the mid-2000’s, the CDC/CDX kit was Gates first go at carbon drivetrains. It uses flanges on opposite sides of the front chainring and rear cog to make sure the belt tracks straight.
Chainring (Gates 50t x 130bcd): 71g
Cog (Phil Wood 20t): 181g
CDX Centertrack > CDC/CDX
The Centertrack system is a vast improvement over CDC/CDX. It 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.
The Centertrack belt runs at a lower tension: This reduces stress on your drivetrain, namely bottom bracket bearings, hub bearings and chainring/cogs, and improves efficiency.
The Centertrack belt is even quieter: I thought the CDC/CDX system was quiet, but I’ve found the Centertrack system even more silent.
The Centertrack system 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.
The Centertrack belt is very picky in terms of chainline: The CDC/CDX belt can be installed with a slightly out chainline, and as a result, people found their belts wore prematurely. With the Centertrack design, the tolerance is reduced. If your belt is slightly out, you know about it straight away as you can hear the rear cog making lots of unhappy sounds.
The Centertrack rear cog is stainless steel: There were problems with the CDC/CDX cogs which saw them wear out quicker than the belt itself! The new CNC’d stainless steel cogs should outlast a few belts.
The Centertrack system is roughly 3mm wider than the CDC/CDX system: This solves some issues for frame clearance as the front chainring sits out further from the spider.
The Centertrack system is cheaper, especially for Rohloff users: Previously Rohloff owners had to use a Phil Wood stainless steel cog to run the CDC/CDX system. Now Gates make a far cheaper alternative which is also stainless steel for Rohloff hubs.
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!
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 what belt ratio to use
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 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 conversation you risk the chance of not being honoured 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 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: $70-110 USD
Alfine Cogs: $110 USD
Rohloff Cogs: $110 USD
Belts: $90-110 USD
Centertrack Kit Total: $300 USD
Australian Shoppers: Contact Black Mountain Sports for a list of stockists.
We love our belt drivetrains! After 31,000km our Centertrack tandem drivetrain has proven itself and it’s durability. The simplicity, silence, long wear life and maintenance free design of the Centertrack kit makes it the perfect for bike touring. The significant advantages of Centertrack over CDC/CDX definitely make Centertrack our recommendation.