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 has a place for bike tourers who want a no-fuss drivetrain which is lighter, easier to maintain and has an exceptional wear life.
Gates Carbon Drive system is slightly limited for the touring market, as it only really has a use for those with either a Rohloff or Shimano Alfine internally geared hub. But we can’t think of an application better than road touring that belts could be used for. The simplicity, silence and wear life are perfect for long distance riding as a handful have already shown.
We’ve been running Gates Carbon Drive for over two years now. Our full review is HERE. We briefly used the CDC kit before upgrading to the CDX Centertrack kit on our Surly Long Haul Trucker‘s and more recently our Co-Motion tandem.
- Belts require little to no drivetrain maintenance (no greasy hands!)
- Belts last more than twice the life of a chain (so far we have travelled somewhere between 15000km and 20000km on one Centertrack belt without problems – 16/08/2013)
- Belts are impervious to road grime and weather
- Belts do not rust
- Belts do not require lubrication
- Belt drivetrains are silent all the time on the road
- Belts are considerably lighter than chains
- Gates have helped us out with warranty assistance when we’ve needed it
The Why Not:
- You need a belt compatible frame to run a belt drivetrain
- After some time, the belt makes a lot of noise on sandy, dry roads – we recommend using belts for primarily road touring. (Stopping the squeak is an easy fix, a squirt of water and a rub with your finger, but it will have to be done every 20-100km depending on the fineness and annoyingness of the grit.)
- Belts can only be used with an internally geared hub, or as a singlespeed (not for derailleurs)
- Belt lengths are fixed and only five lengths are available, limiting the drivetrain ratio options available
- You must be careful not to inappropriately twist or bend the belt
- Getting a spare belt in remote areas is difficult (we carry a spare each @ 74g)
- If the chainring or cog get damaged, it is difficult to obtain spares (we will have to wait for spares)
- Carbon drivetrains aren’t cheap
What do we think of our Drivetrain?
Gates Centertrack is perfect for road touring. You can read our full review of the the Centertrack Drivetrain HERE.
Given that 90% of our about-the-world-trip is on sealed roads, the silence, durability and maintenance-free nature of the Centertrack kit outweighs the annoying squeaking we might get every 50km on a sandy road.
We recommend belt drive to people who ride the majority of their tours on sealed roads; people who spend more time off-road than us should stick with a chain.
Gates Offer Two Belt Options
New for 2011 was the Centertrack system. It offers many advantages over the older CDC/CDX system which I will outline below. The main difference between the systems is the use of a central “fin” that runs in a “track” molded into the center of the belt, rather than the use of “flanged cogs”. If you’re considering belt drive – make sure you get Centertrack!
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
We Recommend Using Centertrack over CDC/CDX
The Centertrack system is a vast improvement over the CDC/CDX system. 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 differences to the CDC/CDX system are 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.
The Centertrack belt is even quieter: I thought the CDC/CDX system was quiet, but I’m finding that the Centertrack system is 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: I found that with the standard belt you could put it on with a slightly out chainline and it would still run ok. Some riders have run slightly-out chainlines with the standard belt, and their belts have worn prematurely as you’d expect. With the Centertrack design, I have found that the tolerance is reduced further so 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 CNCd 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 or hose, and rinsing the belt/cogs down with water. No degreaser, no chain cleaner. No dirty hands. Just like a chain, the cleaner the drivetrain is, the better 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.
Your Frame Must Have a Split to Run Belt Drive
Not all frames can run belt drive. A belt frame will have a few essential characteristics that make it suitable. The first is a split in the seatstay, chainstay or dropout. A carbon belt is one piece, so it is necessary to have a split. Various companies offer different splitting styles. We love our Fixie Inc stainless steel piece!
The next characteristic is an adjustable chainstay length. This is done through sliding dropouts, eccentric bottom brackets or horizontal dropouts (more below).
Another characteristic is the use of a stiff rear frame triangle. The less flex, the smoother the belt can operate. Touring bikes already have very stiff rear triangles as they need to carry heavy loads on their pannier racks.
Do not get someone without an understanding of belt drive to modify your frame
It is essential that a frame modification is done correctly. Not any frame can be modified to run a Shimano internally geared hub – it has to have adequate chainstay clearance. If anyone pulls out a 40lb rubber mallet to flatten you chainstay to allow a belt cog to clear it – punch them in the face!
If you’re going to get this modification made, see a reputable frame builder. We used Ewen Gellie for our work. It will often cost between $400-$800 AUD to modify a frame including paint.
Chainline 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 is available for your frame
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.
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 Carbon Drive on both the drive and non-drive side of your tandem.
We believe tandem touring with belt drive is best left to sealed roads (especially for the tandem belt and chainrings, less so for the drive-side belt and cog), as we’ve experienced noise on the tandem 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 4000km. 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 one cog size available (20t). 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.
Dropouts for Belt drive
Sliding vertical dropouts: Sliding dropouts are the best option for belt systems. Why? 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 into the perfect tension.
EBB: Eccentric bottom brackets allow your wheel to slot in an out at perfect tension. My only concern is that it would be quite difficult to get the appropriate tension for a belt. Not only getting the tension would be hard, but making small adjustments to tension is quite a task on EBBs!
Horizontal track dropouts: You have to be really careful with belts in horizontal dropouts. 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.
- CDX Centertrack
Chainring: $190 AUD
Alfine Cogs: $190 AUD
Rohloff Cogs: $190 AUD
Belts: $120 AUD
Centertrack Kit Total: $500 AUD
Chainrings: $190 AUD
Alfine Cogs: $190 AUD
Phil Wood Rohloff Cogs: $320 AUD
Belts: $120 AUD
CDC/CDX Total: $500-$630 AUD
Australian shoppers – contact Black Mountain Sports for a list of stockists.
We love our belt drivetrain! After 15000km+ it 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.
In our opinion, the significant advantages of Centertrack over CDC (outlined above) make it the only belt drivetrain to use.
Anyone who is keen for getting a system and has a question can email us, or can contact Black Mountain Sports, the importer of Gates for Australia, with any further questions. Black Mountain Sports will be able to put you into contact with a local bike shop that can order everything in and set it all up for you!