How the OSPW System Turns More of Your Power into Speed
Our signature Oversized Pulley Wheel System gives you maximum efficiency. But how? Science and real-world testing proves that larger rear derailleur pulley wheels, made of the right materials and by the right hands, cut friction, save watts and boost speed. Here’s how it works...
The derailleur, invented in the early part of the 20th century, is credited with transforming cycling, providing a range of gears to climb the steepest mountain and maximise speed and mileage from riders’ leg power on the flat and descents. They’re unheralded, workmanlike, and have remained largely unaltered in fundamental design. But in recent years the derailleur has become more proficient and efficient, saving you more watts and giving you increased performance thanks to the introduction of CeramicSpeed’s Oversized Pulley Wheel System.
The Oversized Pulley Wheel System – OSPW System – is an aftermarket item specifically designed to replace your bike’s rear derailleur's two pulley wheels and the cage they live in.
There are CeramicSpeed OSPW Systems compatible with Shimano, SRAM and Campagnolo drivetrain systems which all work on the same principles but are designed and machined to work perfectly with the other host drivetrain components from those brands. It’s the combination of the design and size of the pulley wheels (sometimes known as jockey wheels), the quality of the bearings they run on and the materials in the complete unit that combine to make the difference. As a standalone upgrade, they deliver a significant efficiency saving for your drivetrain, and this can be enhanced by pairing with other CeramicSpeed products. Here’s how...
How watts and time savings work
There are many variables to calculate exactly how watt savings manifests itself in time but, as a general rule, a saving of 5 watts means you’ll ride 0.5sec/km faster. Working with the conservative figure of 2.4 watts saved using CeramicSpeed OSPW System compared to a stock Dura-Ace 9000 system, that adds up. When it comes to triathlon – specifically Ironman – on the 180km bike leg, by using an OSPW System, you’ll be looking at saving 43 seconds: that’s a huge advantage and it can also mean energy conserved for the run.
The principle also translates directly to other cycling disciplines. With all other factors equal, a sportive rider equipped with CeramicSpeed OSPW System will ride their 100km event 24 seconds faster than a standard setup.
Putting the OSPW System to test
Are bigger pulleys better? The Friction Facts division of our R&D lab looked at the benefits larger pulleys bring as well as the several factors that make for an efficient oversized pulley wheel system.
Optimum number of teeth
Even the most diligent cycling aficionado – be it road, cross-country mountain biking, touring, cyclocross or triathlon – might struggle to number the teeth on their derailleur pulleys: chapeau if you who knew that 11 has been standard for years. But what if that number was increased to, say, 16 or 19?
One expectation could be that the increased surface area of the pulley wheel would increase friction, which would lower, not raise, efficiency and so leach watts. It’s a seemingly logical answer, but in the case of the oversized pulley wheel, incorrect.
Not all oversized systems are created equal. In fact, an inefficient larger pulley system can even generate more friction than the stock set it’s replacing.
The greatest cause of friction as your chain moves through the pulley wheel is the tight angles it must negotiate. The development team behind the product calculated that an 11-tooth pulley causes each link to articulate 33 degrees as it enters and exits each pulley wheel; whereas a 19-tooth pulley wheel drops this to 19 degrees. Opening up these angles reduces chain tension at the pivot point of the chain links and, in turn, lowers friction and ultimately has you riding smoother and faster for the same wattage input.
That’s not all. Larger pulley wheels spin at a lower RPM than smaller, stock equipment – in the same way a 50-tooth chainring can rotate slower than a 34-tooth chainring moving the same amount of chain links. So the pulley wheel bearings spin at the same slower revolutions, and with the friction generated by a bearing’s resistance being directly related to rotational speed, a slower-spinning bearing produces less friction, delivering increased drivetrain efficiency.
Not all are created equal
Using CeramicSpeed high-quality ceramic bearings, German brand Berner was the first to produce larger aftermarket pulley wheels, although it was not designed and tested to the same extent as our Oversized Pulley Wheel System (OSPW System) whose development followed soon after.
Back in 2014, independent test lab, Friction Facts (now a division of our R&D lab) performed in-depth testing of the soon-to-be-launched CeramicSpeed OSPW System and the data that revealed showed our system to be far superior to the alternatives.
Friction Facts discovered that in its lowest cage-tension setting, the CeramicSpeed OSPW System created friction of just 0.83 watts, and in the highest cage setting, it measured only 1.43 watts. This compared with the Berner system which produced almost double the friction in the low setting: 1.49 watts, and 1.96 watts in its higher setting. Both systems were benchmarked against a stock Dura-Ace system tested in the same conditions. It measured 3.25 watts on the lower setting and 3.80 watts on the higher setting.
The numbers demonstrate that an oversized system has the advantage, but there is more to it: not all oversized systems are created equal. In fact, an inefficient larger pulley system can even generate more friction than the stock set it’s replacing.
The first important factor is bearing choice.
Our bearings – also seen on wheel hubs, bottom brackets and headsets – are not only renowned for durability (lasting up to 20 times longer than some steel bearings), but also offer impressive power savings of between 10-12 watts (total savings cumulated depending on the upgraded setup). Our OSPW Systems come fitted with standard or coated CeramicSpeed Bearings that are significantly more efficient than stock alternatives. Friction Facts, for example, showed a difference of 0.35 watts when using CeramicSpeed’s pulley bearings compared to a top-end Dura-Ace alternative of the same size. This is all very important as inefficient bearings outweigh the efficiency gains from larger pulley wheels.
Cage tension is also important – and this is a balancing act. Lower cage tension is a generally good principle for efficiency, but not so low that a thrust in power can result in the chain leaping off the pulley wheel. Cage tension that’s too high results in high friction and this can be commonly found in some poorly designed oversized systems to compensate for their poor shifting performance. CeramicSpeed’s engineers have spent years researching and testing in this area to hit the sweet spot. But we also know that all riders, and their complete bike setups, are different – so our OSPW System comes with up to four settings for watts saving of 30-45%+ compared to stock pulley arrangements.
Materials matter – other structural factors at play affecting efficiency, are the pulley wheel and derailleur cage material. CeramicSpeed offers two options of pulley wheel materials, both with high durability and low weight. These are aluminium and titanium, with an innovative and alluring 3D printed hollow titanium option, which naturally costs more to produce. Whichever wheel material you choose, the cage is made from carbon fibre and polyamide, for the optimum balance of durability over many miles without sacrificing weight.
It’s clear that a CeramicSpeed OSPW System can save you significant time and energy. And that friction-cutting benefit is enhanced even further when combined with the CeramicSpeed UFO Chain. We took the decision to invest in a dedicated lube development laboratory and it’s paid off with a chain that’s proven to slash chain friction by a significant margin. The improvement in the clean-wax-treatment method not only delivers more speed but also greater durability. While previous models called for a new wax treatment after 320km, the current UFO Chain doesn’t require a new treatment until 600km. The UFO Chain is proven both in the lab, and the real world of top-level professional racing with many professional WorldTour road teams and triathletes, taking advantage of this efficient performance, along with cyclocross, gravel and cross-country mountain bikers.
Our Oversized Pulley Wheel System has been tested and proven on the harshest testing grounds in every weather condition. The CeramicSpeed OSPW Systems chosen by everyday road riders, triathletes and cyclocross racers are the same that are used at the Tour de France, Paris-Roubaix, Kona Ironman World Championships, the Cyclocross World Championships, Dirty Kanza and many other events around the world. Many races and championships have been won and records have been set on bikes running OSPW Systems, right across the disciplines, but the benefits apply to everyone, whatever you ride!