Can a more compliant bike allow you to ride faster?

Compliance is one of those buzzwords you often hear brands mention whenever they release a new bike. Essentially, it is a term used to characterise flex in a frame in an axis that will increase comfort.

Adding compliance to the frame commonly removes some of the harshness out of the ride increasing comfort and helping to battle fatigue, and some people will say that means it allows the bike – and you – to perform better. But how true is that?

In a recent trip to the cobbles of Paris-Roubaix, GCN's Hank and Conor decided to take a look at whether an increase in compliance actually translates to a faster bike, or if it is all just marketing hype.

How is compliance designed into a bike frame?

There are a number of ways that bike manufacturers can incorporate compliance into their frames. Firstly, there is the geometry of the tubing used in the frame construction, especially in the fork and the seat tube that directly support the rider's weight. There are also the materials that are used with variable wall thickness on metal bikes to help give a more compliant ride.

Read more: What do bike geometry terms really mean?

On carbon fibre bikes, a different lay-up or weave can be used to retain the frame's strength in one axis whilst allowing it to flex in another. The shapes and profiles of the tubes can also have a big influence on the compliance of the frame.

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Carbon fibre allows manufacturers to tune specific areas of the frame to have tailored properties

The difficulty with making road bikes compliant is that they also need to retain their rigidity in the horizontal axis to allow for efficient power transfer without precious energy being lost to flex in the frame.

Do different materials have different amounts of compliance?

The short answer to this question is yes. Compliance alone shouldn’t be the only reason to buy a bike made out of a specific material but it should at least be a consideration. Things such as the price, where and how you want to use it and a whole range of other factors should make up the end decision.

It is worth noting that aluminium, steel, titanium and carbon all have different properties and different ways in which compliance can be incorporated into their design. On a scientific level, it is Young’s modulus that defines the flexibility of a material and therefore how much compliance it can provide. The more resistant a material is to bending the less compliance it will offer.

Read more: Should your next superbike be made from stainless steel?

Steel and aluminium will have the same strength and rigidity in all axis with the tube shape being the main way that compliance can be added. These metals have a fixed material property meaning that they cannot be tailored across the different sections of the bike to provide specific characteristics.

Carbon fibre on the other hand can be tailored by using different weaves and different thicknesses of the material to provide compliance in specific areas and axis. This is why carbon fibre is such a loved material by designers as it allows a lot more creative freedom than other materials.

Can you add compliance to your bike?

The compliance of a frame is fixed and cannot be modified, however there are other ways that you can increase the compliance of the bike as a system. Fitting wide, higher-volume tyres will provide more vertical compliance as the tyres deform and act as suspension cushioning the rider from the road surface below.

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Fitting wider tyres will increase a bikes compliance

There is also the potential to look for specific seat posts or stems to increase compliance on the bike too. Some manufacturers make endurance-spec components that have more flex than standard helping to increase comfort and some bikes can even be fitted with small suspension units to help isolate the rider from the road.

Read more: What tyre width do pro cyclists use on the cobbles?

Does compliance translate to a faster bike?

This really does depend. There certainly is a fine balance between having enough compliance to keep you comfortable and having too much and making the ride feel sloppy. As a general rule, the rougher the surface that you intend to ride the more compliance it needs. This is one of the reasons why mountain bikes have suspension forks and shocks, and why we went to test our theory on the Roubaix cobbles.

If adding compliance helps to keep you comfortable so that you can keep pushing on the pedals then it certainly will help you ride faster. It has been shown multiple times that an increase in comfort does translate to riding at least more powerfully, if not faster.

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The rougher the surface is that you are riding the more impact compliance will have on the ride quality

Having not enough compliance is not just going to affect your comfort, it will also mean that you and the bike get bounced around on rougher surfaces. This will not only mean that it is harsher on your body but also the tyres are not on the road surface all the time meaning that valuable watts are lost.

Read more: Should the pros use suspensions at Paris-Roubaix?

If on the other hand, you tend to ride smooth tarmac roads then adding compliance will do very little to increase your speed. If you are unsure if making some changes to your bike to increase compliance is worth it, start by thinking about the surfaces you ride on.

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