Carbon Frame Tech Explained

Ribble has been synonymous with producing top quality, high-performance carbon road bicycles since they first hit the market back in the early noughties. Every frameset is designed in house, by our R&D team based in Lancashire and is custom made for us and us alone.

Every Ribble frameset manufactured far exceeds the relevant safety standards required. In fact, Ribble goes above and beyond by developing class-leading framesets using the very latest cutting-edge construction techniques and design features. Before any frame is permitted to leave the factory it is must first be tested to ensure it exceeds the most stringent quality control and safety measures.

The flagship Ultra SL R carbon aero frameset is by far one of the most advanced of its type on the market today. It shares many of the design cues and class-leading features as that of our endurance carbon range of bikes. However it pushes the boundaries of aerodynamic integration to the limit in the pursuit of speed. Here, we delve deeper into the latest manufacturing innovations and technologies that make up the very DNA of every Ribble carbon frameset.

This may be a slight oversimplification, but there are essentially two types of carbon frames - carbon monocoque and tube-to-tube. What's the difference? Let us explain.

Carbon Monocoque

A carbon monocoque frame is formed from individual strands of carbon fibre, which are then woven together to form one single construct of carbon. Creating what amounts to a single piece of carbon helps to distribute dynamic stress over a wider proportion of the tubing. Because the best way to avoid weak spots, especially at the joints, is to have no joints at all. This one-piece construction is far superior in terms of strength and stiffness to that of separate pieces of carbon that are bonded together.

Tube-to-Tube

Instead of layering individual strands of carbon together to form one complete structure, each portion of frame is layered up in separate pieces. The head tube, top-tube, downtube, bottom bracket assembly, and rear triangle are then bonded together to form one complete frame. This process is far less labour-intensive than the monocoque method described above, making a tube-to-tube frame more cost-effective to manufacture and consequently cheaper to buy.

How does this affect ride quality?

A monocoque frameset is deemed to be superior to a tube-to-tube version in every way possible. Being a 'one-piece' construction imbues the frame with a stiffness that is unmatched, making it exceptionally resistant to torsional and lateral flex. This means the frame better resists the twisting forces placed on it during the normal act of pedalling, especially when sprinting or standing on the pedals during steep ascents. The more resistant to flex the frame is, the more of the power generated by the rider is transferred into forward motion, making the monocoque frame vastly more efficient.

Image: A partially constructed Endurance SL frame. The eagle-eyed may spot the plastic at the top of the shot, which forms part of the EPS mould process outlined below.

As well as being of monocoque construction, the Ultra and Endurance SL R/SL series of framesets also benefit from an advanced manufacturing process known as a Full EPS Inner Core System or expanded polystyrene system if you like the techy stuff.

EPS is a process whereby an expanded polystyrene internal mould is covered in latex. Individual strands of carbon fibre are then ‘layered up’ to an exacting specification over this internal construct. The whole mould is then heated to 130°, inflated and then cured. When the latex is removed it produces a perfectly smooth finish, with none of the excess material you tend to find on the inside of less advanced frames. But what difference does this EPS core make to the overall construction of a frame?

• Unlike other methods of manufacturing, the EPS process results in a frame that exhibits zero excess carbon material on the inside of the tubing. Why should this matter we hear you ask? Well, not only is the inside of the frame completely smooth to the touch, but it also eliminates any imperfections, which in turn enhances the structural integrity of each carbon fibre to create a stronger frame.
• It enables the frame to be constructed as one complete section of carbon. A monocoque frame is stronger, lighter, and stiffer than a comparable bonded frame.
• It eliminates the imperfections in the carbon layup that earlier production methods were susceptible to. Zero imperfections result in exceptional strength and reliability.

Using the highest quality carbon tubing is essential to achieving the holy grail of strength, durability, and weight. To achieve this, we utilise a bespoke mixture of Toray T1000/T800 carbon fibres. Using high-quality carbon fibre and the EPS construction technique allows us to build carbon frames using less material, without compromisng strength or the overall ride quality. And just as importantly, it results in a much lighter frame overall.

The graphic above demonstrates how various frame shapes affect airflow differently. From left to right: Round, Aerofoil, and Truncated Aerofoil tube profiles.

Aerodynamics played a key role in the development of the Ultra SL R, Endurance SL R and SL framesets. With every tube shape being analysed, dissected, and perfected in the wind tunnel and during real-world testing to enhance the aero gains experienced at speeds achievable by riders of all experience levels as well as seasoned pros. The Endurance range, for instance, significantly reduced drag by up to 28.5% compared to the previous generation of frames. However, the Ultra SL R/SL framesets take this one step further. Extensive wind tunnel and real-world testing resulted in the most aerodynamically advanced and slipperiest aero road framesets Ribble has ever produced.

• **Truncated aerofoil tube profiles **- Previous generations of aero frames featured teardrop tubes which were extremely aero but less stable in crosswinds. The truncated aerofoil reduces these effects whilst providing beneficial aero drag savings.
• **Enhanced lateral stiffness **- When you stomp on the pedals, the power generated will cause a frame with reduced lateral stiffness to 'flex'. Thereby reducing the amount of power generated being transferred to forward motion. This is inefficient, so a frame that exhibits a high degree of lateral stiffness is more advantageous to overall speed and pedalling efficiency.
• It's lighter as there is less material - A monocoque frame can be manufactured to be lighter for the same amount of strength
• Provides better vertical compliance. The dropped seat stay design of the frame and profile of the tubes work mutually to absorb vibration transmitted through the frame.
• **Internal cable routing **- Cables create drag as well as looking untidy. Routing the cables through the frame removes the drag effects of the cables whilst giving the bike a super clean look.
• Internal wedge seat clamp- Instead of an external seat clamp, there is now an internal wedge mounted within the junction of seat tube/top tube.*

Above image: The Ultra SL R's tube profiles are designed to minimise the effect the rider plays on the overall aerodynamic efficiency of bike and rider combined.

Image: The distinctive dropped seat stays that are the trademark of all Ribble's carbon frames.

Each Ribble frame feature dropped seat stays which are far from being a cosmetic affectation. Dropping the stays down the seat tube introduces vertical compliance for enhanced comfort through vibration absorption and more efficient power transfer.

Every Ribble frame incorporates several cutting-edge design features to make them faster, lighter and more comfortable.

• Precision steering- An oversized (tapered) fork steerer, headtube and fork blades stiffen up the front end for pinpoint handling during out of the saddle efforts.
• Dropped seat stays- Enhanced shock absorption helps filter out the fatigue-inducing effects of 'road buzz', keeping you fresher for longer.
• Boxed section chainstays- They ensure that the bike remains stiff for better power transfer.

Our current range of high-performance carbon road disc bikes offers more than sufficient clearance to fit the modern tyre widths that are better suited to the rigours and demands of today's road surfaces.

Tyre clearance has undergone somewhat of a revolution over the past few years and consequently, most bikes are now optimised for wider tyres that enhance ride comfort, speed and grip. Our road disc bike range embraces this new dynamic, with rim brake versions now offering clearance for 28mm tyres or 25 mm with mudguards. However, with the limitations of rim brakes removed the clearance increases to 32mm on our disc brake models or 25mm with mudguards.

For those who wish to sample the delights of riding off-road, there's the option to choose gravel, hybrid, or all-road bikes. These framesets are designed to accommodate a vast selection of tyres to suit all types of terrain/surfaces, offering compatibility with chunky gravel tyres as wide as 45mm.

The Endurance SL R Series frameset is currently the lightest frameset in the Ribble lineup, tipping the scales some 300g lighter than its Endurance SL sibling at just 850g. Part of this weight difference comes from Ribble's decision to eschew the aluminium normally found bonded into the bottom bracket shell of most frames in favour of a press-fit BB. The Endurance SL R features a BB86 press-fit bottom bracket shell that offers cyclist a high-performance solution for optimising power transfer and enhancing their overall ride experience.

Other bikes in the Ribble lineup (excluding electric models) use the traditional threaded bottom bracket system, which requires an alloy insert in the frame shell to accept the threaded BB. Of course, this adds weight. However, the advantage of a threaded BB system is it is easier to service and maintain as it can easily be unscrewed from the frame.

In summary, we can say that our carbon framesets are manufactured from the best carbon that money can buy. Not only are they light and stiff but they also absorb more of the vibrations from uneven surfaces than any other carbon frame that have come before. In practical terms, this ensures you feel less fatigued when riding longer distances and on rougher surfaces. Plus, they can be built up come in under the UCI's weight limit to create a bike that will literally float up the climbs.