15 January 2019

Independent Fabrication Independence Touring Bike w/ Rohloff SPEEDHUB 500/14



This beautiful Independent Fabrication touring bike went to a customer in Toronto, Canada. The rider had a solid vision for his bike, and came to us with very specific requests for the frame, custom paint, and components. Rohloff's SPEEDHUB 500/14 internal gear hub was the starting point for the build. As a previous SPEEDHUB owner who'd completed an extended tour with the hub, the rider was familiar with Rohloff's unparalleled reliability and wide gear range.

The rider's fondness for Independent Fabrication made them the obvious choice for the frame. Looking for a utilitarian and comfortable setup, he requested a dynamo front hub (which contains a small generator that powers the bike's lights and an on-board USB charger), upright seating position, and striking silver components to complement frame's unique paint job, which features sun-kissed orange crystallance with cream highlights. Cycle Monkey coordinated with IF to get the details worked out, and we couldn't wait to assemble the bike once the frame and fork arrived.


Independent Fabrication builds a variety of frames (steel, titanium, carbon, and titanium mixed with carbon) and forks (steel only) in-house at their facility in Newmarket, New Hampshire. They have built a reputation for both top quality frames and the extraordinary abilities of their in-house paint shop. IF builds frames on an exclusively custom basis, and they are no strangers to building bikes around the Rohloff SPEEDHUB. We have showcased several on our blog over the years, and have worked with shops and IF directly on many more.

IF's extensive custom frame program made it easy to accommodate the rider's requests and ensure compatibility with the SPEEDHUB and Schmidt SON SL dynamo hub. The fork required a special conducting plate inside the dropout to enable the use of the SL (connector-less) version of Schmidt's hub, which passes the current generated by the hub through the dropout up to the headlight and USB charger through wires hidden in the fork leg. The electrical connection between the fork and hub is automatic, eliminating the need for the manually-connected wires typically required with dynamo hubs. The fork also received mounts for a Pass and Stow front rack (not shown in photos) for future installation.

No wires needed here.
Cycle Monkey generally completes builds around custom frames that employ adjustable dropouts or an eccentric bottom bracket to tension the chain or belt. In this case, the rider was more comfortable with a chain and opted to keep the frame as simple as possible by using a Rohloff chain tensioner. While we generally prefers the use of adjustable frames with the Rohloff hub, the tensioner option does offer two distinct advantages when running a chain on long-distance self-supported adventures:

1) The spring loaded jockey wheels automatically adjust for wear in the chain and maintain consistent tension.

2) The tensioner holds the chain in place when the wheel is removed,  just like with a rear derailleur, instead of having it fall to the ground.

Without a rear disc brake mount or a dedicated Rohloff dropout, this bike required an alternate method to secure the hub axle to the frame. One option would have been to to use the Rohloff torque arm, but that was not the preferred method.  Adding an eyelet to the left dropout to accept a bolt compatible with the Rohloff OEM2 axle plate was a cleaner solution that was fitting for a custom frame.

This customer opted for the use of a chain tensioner for this particular build to keep the frame as simple as possible
Cable routing was set up to run the Rohloff shift cables along the down tube and left chainstay to feed into the cable box of the external shift mech on the SPEEDHUB. Taillight wires run piggybacked onto the shifter cables, then up the rear rack to the light. The rear brake cable runs under the top tube in a standard cantilever setup, and rack and fender mounts are included for additional utility.


The custom paint job was the finishing touch on this beauty. At a distance, it looks fairly straightforward, with just a bit of masking to create the panels and stripes. However, crystallance paint requires three layers, one of which includes glass flake that can be difficult to top with an additional layer. Naturally, the expert painter at IF worked enough magic to apply the cream color over the orange base layer and make everything come out looking top notch.

This paint job shines nearly as bright as the dynamo headlight

With the one-off frame shining in all its glory, our Wheel House got to work prepping a shiny silver set of wheels. Silver anodized Rohloff and Schmidt hubs were laced into polished Velocity Cliffhanger rims with Sapim Race spokes and brass nipples. The Cliffhanger is Velocity's burliest touring rim, making it well suited for this aggressive touring build. Cream-colored Schwalbe Big Apple tires wrapped around the hoops to complement the frame's unique colorway while adding comfort to the ride thanks to their large air volume.

Cushy tires, sparklin' rims
At Cycle Monkey, we constantly promote the durability of the Rohloff drivetrain for a variety builds, including touring setups like this rig. With a 526% gear range and long-term reliability that's been proven with over 20 years on the market, SPEEDHUB is the drivetrain of choice for long distance touring.

Gebla's Rohbox is a ratcheting shift box that allows for the use of SRAM or Campagnolo shifters with the SPEEDHUB
Despite the SPEEDHUB's many benefits, some riders don't mesh with the feel of Rohloff's twist shifter. Luckily, we have an alternate option for these riders. Gebla's Rohbox allows the use of SRAM MTB shifters (among other options) to shift the hub instead of the traditional grip shifter. The Rohbox was just one of many high end parts included on this build to provide ultimate comfort and durability.

This rider approached us with a very specific vision of his ideal bike, and we worked with him to source the components and build up the bike of his dreams. But you don't need to have it all figured out to get started on your dream build. Whether you have a detailed plan or a rough outline for your next bike, get in touch and we'll figure out the best way to make it happen.


Build details

• Frame: Independent Fabrication Independence custom steel
• Fork: Independent Fabrication custom steel with Schmidt SL dropout
• Headset: Chris King Steelset NoThreadset
• Stem: Velo Orange
• Handlebar: Nitto Bosco
• Shifter: SRAM X9 triggers, modified with Gebla Rohbox
• Grips: Ergon GP1 BioKork
• Seat post: Kalloy Pillar
• Saddle: Brooks B66
• Front Hub: Schhmidt SON28 SL
• Rear hub: Rohloff SPEEDHUB 500/14
• Spokes: Sapim Race
• Nipples: Sapim Brass
• Rims: Velocity Cliffhanger
• Tires: Schwalbe Big Apple
• Cranks: White Industries VBC
• Pedals: Velo Orange Sabot
• Bottom Bracket: SKS
• Chainring: White Industries Direct Mount
• Rear Sprocket: Rohloff
• Chain: Wippermann 8sX
• Chain Tensioner: Rohloff
• Brakes & Levers: Velo Orange Crand Cru
• Skewers: Pitlock anti-theft
• Headlight: Busch & Müller Lumotec Classic T Senso Plus
• Taillight: Busch & Müller Toplight Line Brake Plu
• USB Charger: Sinewave Reactor
• Fenders: Velo Orange stainless steel
• Rear Rack: Tubus Cosmo stainless steel

11 January 2019

Soma Wolverine Adventure Bike with Rohloff SPEEDHUB 500/14, Gates Carbon Drive Belt, and Schmidt Dynamo Hub



This decked-out Soma Wolverine was built for a customer in San Jose, CA. The rider was looking for a rugged commuter bike that would be efficient on his daily trips to work, but would also offer the versatility to enjoy longer tours on the weekend and even a few cycling-oriented vacations. Soma’s Wolverine frame fit the bill as a sturdy option that is affordable, works well with a Rohloff hub, and is belt-ready.

Like many of our customers, the rider was drawn to the simplicity and hassle-free nature of the Rohloff SPEEDHUB 500/14 internal gear hub and Gates Carbon Drive belt drivetrain. Shifting duties are handled by a set of Campagnolo Veloce shifters driving a Gebla Rohbox. A dynamo hub and lights from Schmidt, which are self-powered, were also high on the list of requirements for daily utilitarian use. From there, Cycle Monkey rounded out the build with a variety of high end parts to create a top quality commuter that isn’t afraid to stray off the beaten path.


Soma Fabrications, whose South San Francisco headquarters are located a stone’s throw from Cycle Monkey, offers affordable steel frames that are often considered an alternative to Surly. Price, intended use, and many features are similar, but the sliding dropouts and belt drive compatibility of certain Soma models, like the Wolverine, easily check the boxes for many of the build requests we see at Cycle Monkey.


Compared to the horizontal dropouts used by Surly, sliding vertical dropouts allow you to swap wheels more easily. The Wolverine also features a handy split in the right seatstay, which allows a belt to be installed without the frame modifications required with Surly frames.

Look closely, and you'll see a split in the right seatstay, which allows for easy installation of the Gates Carbon Drive belt. 
Soma says the original intention for the Wolverine was to build a monster cross bike—basically a drop bar bike with cyclocross geometry and cross country mountain bike wheels. The idea was to create a fully-capable off-road touring rig that would also be sporty enough for commuting through the city and all-around adventure riding.

The Wolverine is capable of running a wide variety of drivetrains, including the ultra low maintenance setup included with this build. Rohloff’s SPEEDHUB 500/14 is an internal gearing system with 14 evenly-indexed speeds entirely encased in the rear hub. In addition to the benefits of such a wide gear range, the internal nature of the gearing makes it virtually impervious to the elements, making it an ideal option for both off-road use and year-round riding. Even for daily commuters like this rider, the only service required is an annual oil change, which can be completed at home or by Cycle Monkey.

Rohloff's SPEEDHUB and the Gates Carbon Drive belt system are an easy fit with the Wolverine's sliding vertical dropouts.
Looking for the ultimate in reliability and lack of maintenance, this rider paired the Gates Carbon Drive belt system with his Rohloff hub. Belt drive systems don’t rust in inclement weather and they don’t require lubrication. Simply wipe ‘em down after a particularly dirty ride, and you’re good to go again. We also see Gates Carbon Drive belts lasting 5-10x longer than your average chain and they do not stretch—meaning you won’t have to readjust the dropouts to maintain belt tension.

Rohloff SPEEDHUBs are typically activated with a twist shifter, which can be mounted to the end of drop bars with an adapter. Many riders, like the owner of this Wolverine, prefer the feel of traditional road bike brake lever shifters (brifters) on their drop bar bikes. Gebla’s Rohbox allows you to run the SPEEDHUB in tandem with brifters from SRAM or Campagnolo, making it an easy choice for this build.

The Gebla Rohbox ratchet box pairs with modified Campagnolo or SRAM shifters, making it a great choice for drop bar riders who find the Rohloff twist shifter unappealing.
Naturally, we took full advantage of the included braze-ons for this utilitarian machine, with front and rear racks from Tubus capable of hauling the groceries as well as bikepacking gear. Front and rear lights on this build are courtesy of Schmidt, and are powered by a SON dynamo front hub. Dynamo hubs contain a small electric generator that self-powers lights and other electronics as you ride. They’re an ideal solution for commuters and bikepackers, because they keep your lights running both day and night with no need to charge.

Dynamo lights from Schmidt can be mounted at the fork crown or to the front rack, as on this Wolverine
Wolverines are known to be vicious, but we wanted to ensure the bike provided a friendly ride with all the mileage it’d be getting. High volume Schwalbe Marathon Plus tires provide a cushy ride without sacrificing efficiency, while hydraulic disc brakes provide ample stopping power with lots of modulation.

Comfort at the most important touchpoint comes thanks to an all-leather Brooks Saddle mounted to Cane Creek’s Thudbuster seatpost. As the name implies, the Thudbuster mitigates the jarring effects of rough roads by isolating the rider’s seating position from the frame with 76mm of travel right in the seatpost. Paired with a high-end saddle like those from Brooks, the Thudbuster adds a significant amount of comfort to any bike with a rigid rear end, and it might just save yours.

Isolation at its finest
With a low-maintenance, belt-driven internal drivetrain from Rohloff and Gates, an always-on lighting system from Schmidt, and ergonomic touchpoints for comfort over the long haul, this Soma Wolverine is just one example of how these versatile steel frames can be built up. They’re a perfect building block for the worry-free bike we love to put together at Cycle Monkey. Order yours today, and drop us a line so that we can bring it to life with a custom build kit perfect for the way you ride.

Frame: Soma Wolverine
Fork: Soma Wolverine
Headset: Chris King NoThreadset
Stem: Thomson X4
Bar: Salsa Cowchipper
Shifter: Campagnolo Veloce with Gebla Rohbox
Bar Tape: Lizard Skins
Seatpost: Cane Creek Thudbuster LT
Saddle: Brooks B17
Front Hub: Schmidt SON28
Rear Hub: Rohloff SPEEDHUB 500/14
Spokes: Sapim Race
Nipples: Sapim Brass
Rims: Velocity Dyad
Tires: Schwalbe Marathon Plus
Cranks: Shimano XT
Pedals: Shimano XT Trail
Bottom Bracket: Chris King
Sprockets: Gates Carbon Drive
Belt: Gates Carbon Drive
Front Light: Schmidt Edelux
Rear Light: Schmidt SON Taillight
Front Rack: Tubus Tara
Rear Rack: Tubus Logo EVO
Bottle Cages: King Cage Stainless






28 December 2018

Tech Talk: Rohloff's "Through-Axle" A12 Hubs


In 2016, Rohloff introduced a new version of their renowned SPEEDHUB 500/14 14-speed internal gear hub that works with through axle frames. Dubbed the SPEEDHUB A12, Rohloff offers versions to fit frames with 12x142, 12x148, 12x177, and 12x197mm spacing. The SPEEDHUB A12 is nearly identical to the standard Rohloff SPEEDHUB 500/14, with the exception of how the hub connects to the frame.

A12 hubs mount to the frame with frame-specific adapters and custom bolts, so Rohloff requires that frames be verified for compatibility before they make the hub available for purchase. As a result, A12 hubs are always special order items, and delivery takes anywhere from a few weeks to a couple months.

This tech talk covers the details of the A12 system and provides instructions to guide you through the ordering process.

A12 hubs are NOT through-axle hubs!

With through axle frames, the defining interface dimensions for a rear hub are usually based around 2 measurements—the distance between the dropouts and the outer diameter of the axle. The combination of these two measurements provides a standard used by hub makers to ensure that hubs are easily interchangeable between different frames with the same dropout spacing. Most through axles on the market today feature a 12mm outer diameter, so hubs must include a 12mm hole through the center in order to accept the axles.

When riders first encounter Rohloff A12 hubs, most assume the hub is a true through axle version of the SPEEDHUB with a 12mm hole through the center. In reality, A12 hubs do not include a 12mm hole through the center but instead use a pair of 7mm bolts to secure the hub to the frame. These bolts are combined with a pair of adapters that reduce the openings in the frame dropouts from 12mm to 7mm.

The pieces of the A12 system are shown in the image below. The red and blue pieces are inserts that reduce the openings in the dropouts from 12mm diameter to 7mm, and they will be sized specifically for compatibility with your dropouts and type of through axle. The green pieces are custom M7 bolts that hold the wheel into the frame, and the grey pieces are locking washers that keep the bolts from loosening. The ends of the hub are threaded to receive the M7 bolts, but the rest of the internals are identical to the original, quick-release or threaded axle SPEEDHUBs.


A12 versions use the same proven 14-speed gearbox that has transported riders to and from work, round-the-world tours, trail rides, and other self-powered (and increasingly motor-assisted) adventures for the past 20 years.

Why hasn’t Rohloff created a true through-axle version of the SPEEDHUB?


When Rohloff designed the SPEEDHUB in the mid-1990s, 5mm quick-release skewers were standard across the bike industry. The SPEEDHUB was designed around this standard and does not have space for a 12mm shaft to pass through the center.

It should be noted that at the time, it was revolutionary for an internal gear hub to have a quick release axle, and the SPEEDHUB remains the only internal gear hub on the market to offer this option (all others use a threaded axle with axle nuts). In order to fit a larger 12mm axle, the entire hub would need to be redesigned, which to-date Rohloff has been unwilling to entertain for a variety of reasons. Most importantly, creating space for a 12mm axle would likely lead to a larger and heavier hub because everything would need to scale in size around the axle increase, which is counter to the desire of most riders for a smaller, lighter hub.

A12 ordering process

Ordering an A12 hub is not a simple matter of placing the order and having it arrive a few days later.

First, dropout thicknesses need to be determined to ensure the parts will work together. Insertion depth of the mounting bolts is critical to proper functioning of the A12 system and must be standardized across all frames. Because dropouts vary in shape, thickness, axle capture method, and thread pitch between manufacturers—or even between models from the same manufacturer—Rohloff produces a variety of adapters to fit most frames.

Rohloff has devised a testing method to determine both whether a given frame’s dropouts are compatible with the A12 mounting bolts and which specific frame adapters will be required. Rohloff’s testing procedure measures thickness in two distinct ways and then compares the results to provide a double check. Cycle Monkey can complete this process in-house if dropouts or frames are sent to us, or send the Rohloff testing kit to dealers.

Once the dropouts have been measured, the results are submitted to Rohloff for review and approval, along with the frame's serial number. Upon approval, the hub can be added to our next bulk shipment, which occurs approximately every 2 months. We are also happy to ship hubs separately with an additional international shipping fee.

Note that each hub will be registered to an individual frame, and the warranty will be tied to exclusive use with that frame. Additional paperwork can be submitted for use with an additional frame(s).

Does your frame have Paragon sliding dropouts? Check out Paragon Inserts for A12 Hubs


For riders whose frames feature sliding dropouts that are compatible with Paragon’s inserts, Cycle Monkey has developed a solution that eliminates the need for the red and blue adapters shown above and allows you to slide the hub directly into the dropouts and secure it with just the A12 fixing bolts. These inserts have IS brake tabs for use in combination with our Monkey Bone and an OEM2 axle plate. Check them out over at Paragon (part #s DR4055, B4055, DR4056, B4056).

Ready to get started?

Despite the somewhat complicated ordering process, Cycle Monkey has helped multitudes of riders with through axle frames successfully enjoy the wide-ranging benefits of Rohloff’s SPEEDHUB. 

If you’d like to get started with the ordering process or have additional questions about the A12 system, please don’t hesitate to drop us a line or place an order.

Additional notes on A12 Hub drivelines and wheels:

- The driveline of the 12x142mm hubs is the same as the standard 135mm hubs.
- The driveline of the 12x148mm hubs is 3mm narrower than the 12x142mm or standard hubs and the wheel is dished 3mm towards the drive side. The entire 6mm of additional width between 142mm and 148mm hub spacing is located on the drive side of the hub to accommodate the SPEEDHUB shifting mechanism. This biases the hub 3mm the left of the bike’s centerline. As a result, the flange offset values are 33mm left side and 27mm right side.
- The driveline of all SPEEDHUB XL and XXL fat bike hubs is the same, so 10x170mm QR, 12x177mm A12, 10x190mm QR, and 12x197mm A12 have the same sprocket position. 190/197mm hubs have 10mm of extra axle length on either end compared to 170/177mm hubs.

13 December 2018

Classic Commuter: Rohloff-Equipped Rivendell Sam Hillborne



This classically-styled commuter belongs to a local Bay Area customer who was looking for the convenience and reliability of modern components like dynamo lighting and internal gearing for his vintage-inspired Rivendell Sam Hillborne frame. 


The project began with the desire for a Schmidt SON28 dynamo hub and Rohloff SPEEDHUB 500/14 internal gear hub. As a daily commuter, reliability, lack of maintenance, and ease of use were absolute requirements for every component of this build. Dynamo lighting from Schmidt fit the bill with its self-generating, no-charge-required illumination, and Rohloff’s SPEEDHUB was the clear choice for a wide-range drivetrain that would perform reliably day after day in any weather conditions. 
 
Built as a high-end commuter, the build was completed with top quality components in polished silver and brown leather to complement the nostalgic design of the lugged steel frame.





Rivendell is a Bay Area company located in Walnut Creek, just down the road from Cycle Monkey. Their calling card is lugged steel frames, and they offer a variety of platforms for daily commuting, road riding, trail riding, and touring. Rivendell is a small company, and they pride themselves on taking a different approach to frame materials and construction than most contemporary builders:

All of our bikes have lugged steel frames. We believe it's the best and most beautiful way to make bicycle frames, and trends won't sway us. We don't sell bikes for racing, and rather than apologize for that, we'd like to point out that since we are unburdened by racing values, we're free to design better-than-racing bikes. Bikes that fit better, ride better, and are more comfortable. Bikes that let you carry a load, whether that load is a tent and camping gear, a computer and files, or groceries. Our bikes are safe, comfortable, practical, and beautiful. Racing bikes might be lighter, but they are less comfortable, less useful, and for the most part, harder to like the looks of - Rivendell Bicycles

Rivendell's aesthetic and design choices might fall outside the norm, but their commitment to this unique approach is unwavering, and their execution of classic steel frames is second-to-none.

Rivendell presents the Sam Hillborne an all-rounder road bike packed with style and value. Clearance for 40mm tires provides the flexibility to comfortably take on dirt road adventures, while rack and fender mounts provide easy set up for commuting and errands. Add the Rohloff SPEEDHUB 500/14 and self-powered lights, and the Sam Hillborne is quickly transformed into the ultimate commuter.




Cycle Monkey's Wheel House assembled a pair of eye-catching wheels with polished-silver hubs, Pacenti PL23 rims, and double butted Sapim Race spokes with brass nipples. The highlight, of course, is the Schmidt SON28 dynamo hub. Providing self-powered lighting of both the front and rear lights that help riders stand out in traffic and light the road ahead, dynamo lights are a no-brainer for commuters like this customer.



The Rohloff SPEEDHUB 500/14 internal gear hub is an excellent option for any commuter because of its durable, hardened steel internal gear wheels, wide gear range, and sealed shifting system, which protects shifting components from everyday wear and tear. The SPEEDHUB provides long-term dependability in all riding conditions, making it the perfect drivetrain choice for a bike that is relied on for daily transport. 




Rivendell does not design frames with Rohloff-specific or disc brake compatibility, so this build required an aftermarket SPEEDHUB setup that will work with virtually any standard frame.  

The torque arm connected to the left chainstay fixes the hub axle to the frame and prevents it from spinning while the rider is pedaling. Chain tension comes courtesy of Phil Wood's Philcentric thread-in eccentric bottom bracket, which also allows for a small range of tension adjustment. In the end, this setup functions the same as bikes designed specifically around the SPEEDHUB.


Cycle Monkey completed the classic commuter build with high-end components from Chris King, Nitto, Paul Components, Gilles Berthoud, and Brooks, all of which contributed to the desired aesthetic. 


This build demonstrates the possibilities when you take a beloved frame designed for traditional drivetrain components and build it up around a Rohloff SPEEDHUB 500/14. Cycle Monkey relished the opportunity to put together a build kit that inspired this customer ride his Rivendell and brought more enjoyment to his daily commute.

If you have a stock frame and want to run a Rohloff SPEEDHUB or make you frame belt drive compatible, just give us a call.  We'd be thrilled to talk it through and help you get the process rolling.

Build details

• Frame: Rivendell Sam Hillborne
• Fork: Rivendell Sam Hillborne
• Headset: Chris King Threaded
• Stem: Nitto Technomic
• Handlebar: Nitto Albatross
• Shifter: Gilles Berthoud for Rohloff SPEEDHUB 
• Grips: Brooks
• Seat post: Nitto Dynamic
• Saddle: Brooks B67
• Seat Clamp: Seat binder 
• Front Hub: Schmidt SON28
• Rear hub: Rohloff SPEEDHUB 500/14
• Spokes: Sapim Race
• Nipples: Sapim Brass
• Rims: Pacenti PL23
• Tires: Surly Knard 700 x 41c
• Cranks: Middleburn RS8
• Pedals: MKS Sylvan
• Bottom Bracket: Phil Woods Philcentric
• Chain ring: Middleburn RS7
• Rear Sprocket: Shimano 39T single speed ring
• Chain: Wippermann 8sX
• Brakes & Levers: Paul Racer
• Torque Arm: Rohloff
• Front Light: Schmidt Edelux II
• Rear Light: Schmidt SON Taillight
• Fenders: SKS Longboard  
• Rear Rack: Tubus Logo Evo 

07 December 2018

Gates Carbon Drive: There's an app for that...

Not sure what size belts or sprockets you need for Gates Carbon Drive? Their handy app can help...
Belt drive systems from Gates Carbon Drive offer a multitude of advantages over traditional, chain-driven drivetrains: Belts do not rust or require lubrication, offering year-round reliability with minimal mess and virtually no upkeep. You can simply wipe ‘em down after a messy ride and immediately be ready to roll again—no chain cleaner or removal necessary. Belts also last 5-10x longer than most chains and don’t stretch. As a result, belts and sprockets tend to wear at the same (significantly slower) rate. The lack of belt stretch also means that belt tension typically does not require adjustment over the entire life of the belt. Set and forget!

So, what do you need to know to run one yourself?

Gates Carbon Drive systems contain three essential components: a front sprocket, rear sprocket, and the belt itself. There’s a huge range of sprocket interfaces and belt lengths available, and here at Cycle Monkey, we often field questions from riders wondering about compatibility with their current bike or the best choices for a custom build project. Many of these questions relate to sprocket sizes and belt length.



Luckily, Gates has created a handy app for mobile and web that’s incredibly helpful in answering these types of questions. To get started, all you need to know is your desired gear ratio and the minimum and maximum effective chainstay lengths for the frame you’ll be working with.

Gear ratio is the final drive ratio you’d like to achieve, and is calculated as front sprocket size divided by rear sprocket size, so that a drivetrain with equally sized front and rear sprockets has a ratio of 1 (ex. 32 Tooth Front / 32 Tooth Rear = 1 / 1 = Gear Ratio of 1. Smaller gear ratios make it easier to climb hills, while larger gear ratios offer a higher top speed and prevent you from spinning out at too high a cadence once you get up to speed. If you live in a hilly area or are a mountain biker, you’ll want to consider a smaller ratio. Stronger riders or those primarily riding on flat ground will benefit from a larger one.

Riders accustomed to calculating gear ratios with their chain-driven setups will be pleased to hear that this ratio calculation is the same. The number of teeth on belt sprockets will typically be greater, but gearing will be the same as long as the ratio is maintained.

Effective chainstay length refers to the distance from the center of the bottom bracket to the center of the rear axle. Belt-driven bicycles require this length to be adjustable in to apply proper belt tension and account for different gear ratios. As a result, belt-compatible frames have a range of chainstay length, rather than a single value like that you’d typically see on a manufacturer’s geometry chart. This adjustability is achieved with adjustable rear dropouts, an eccentric bottom bracket, or horizontal dropout slot lengths.

Sliding rear dropouts are one way to achieve the flexibility in chainstay length that's required by belt systems 
Once you’ve determined these two values, you can use the Gates calculator tool to determine which sprocket sizes will provide your desired gear ratio, along with the correct belt length. If you get stuck, feel free to drop us a line at info@cyclemonkey.com, and we’ll be happy to give you a hand.

The interface differs slightly between the mobile and web apps. Generally speaking, the web app is easier to use if you’re trying to determine which components are compatible with your bike, while the mobile app allows you to explore the gear ratio and compatible chainstay lengths of the various sprocket/belt combinations more quickly.

On the web: Enter your desired gear ratio (or front and rear sprocket sizes) along with your chainstay length (in mm), and select the “Find Solutions” box. From there, you’ll receive a complete list of sprocket and belt combinations that will fit your needs. They’re organized from top-to-bottom in terms of compatibility.

On mobile: You’ll see three columns on the mobile app which allow you to scroll between various sizes for the front sprocket, rear sprocket, and belt. The “center distance” (chainstay length) and gear ratio will be displayed below for any given combination. From there, you can select the “catalog” tab in the bottom navigation to find sprockets and belts in the sizes you’re looking for. The mobile app also features a nifty belt tension meter that measures sound waves with your phone’s microphone to evaluate belt tension!



If you’d like to further refine your search based on desired wheel/tire size and crank length, the “advanced options” selection on both interfaces will allow you to do so.

There are a few additional considerations when it comes to building your ideal Gates Carbon Drive system, As mentioned above, belt systems require some degree of flexibility when it comes to chainstay length or “center distance” in order to properly install and tension the belt. If you plan on only running one gear ratio throughout the life of your bike, you’ll need a 12mm range of movement at a minimum. If you want to experiment with different sized sprockets and gear ratios, Gates recommends a 25mm range of movement. 

You’ll also need to make sure that the front sprocket you select is small enough to clear the frame/chainstay. Note that belt sprockets are wider than chain sprockets, and that you’ll need at least 2mm of clearance between the sprocket and chainstay. Some crafty guesswork with a ruler can go a long way in determining whether or not the sprocket size you’ve selected will clear your frame.

Of course, you’ll need to select sprockets with the correct interface for your bottom bracket and rear hub. Unless you plan to go singlespeed, you’ll need to run an internal gearing system, such as Rohloff’s SPEEDHUB 500/14 internal gear hub or Pinion’s gearbox. These systems share many benefits with Gates Carbon Drive, including a low maintenance burden, ease-of-use, and incredible durability.

Of course, adding multiple gears into the equation with an internal gearing system means that you’ll have more than one gear ratio to consider when selecting sprockets. If you’re interested in a more detailed comparison of gearing between derailleurs and these internal systems, check out our posts on Calculating Gear Ratios with Rohloff Hubs and Calculating Gear Ratios with Pinion Gearboxes. If you’d like to compare systems, check out this helpful online bicycle gear calculator.

At Cycle Monkey, we love to help riders navigate the process of retrofitting an existing bike or bring their vision to life with a custom build. If you’re curious about running a Gates Carbon Drive system yourself, don’t hesitate to give us a shout!

Find the web app here
Download the mobile app from the Apple and Android App Store.