Road comfort guide: Damping, shock absorbing, and vibration reducing technologies for road bikes

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Road cycling looks like a simple job at first glance. All you have to do is pedal on tarmac roads, which can sometimes be bumpy, but your main concern is speed. So, it’s no wonder that bicycle manufacturers focus on improving aerodynamics, and the general comfort level that allows the rider to have an optimal energy output. Still, the continuously developing materials and technologies, along with the constant expansion of the road bicycle ranges, led to the appearance of the endurance road bikes. Their main attribute is their better shock absorbing and vibration reducing capability, and for this purpose, the biggest brands developed and used different systems and innovations, which we’re going to present in this article.

Stiffness vs. Comfort

The most important secret behind any successful road bike is the fine balance between comfort, stiffness, and low weight. The latter has become rather easy to achieve thanks to more performant materials, with carbon leading the charge. So, it’s down to stiffness and comfort, two notions that don’t get along very well.

But why don’t they get along? An optimal energy transfer is essential for riding your bike as fast as possible, and implies that as much of the pedaling force as possible becomes velocity via the mechanism of the bicycle. This in turn implies that the parts that are responsible for the forward motion, starting from pedals and finishing with tires, should flex as little as possible, or be as rigid as possible. On the other hand, the comfort level depends on the amount of flexing, although not necessarily of all of the earlier mentioned parts, because temporary deformation (elasticity) absorbs shocks. Hence, the importance and difficulty of reaching the ellusive balance between stiffness and comfort.

Where should a road bike be stiff, and where should it flex?

However, stiffness and comfort can live one with the other. This has to do with the fact that a quality road bike doesn’t have to be stiff in the same areas it has to be elastic, or better said, the points that significantly improve comfort don’t have to be significantly stiff. Generally speaking, this is a feat that can be reached only by using carbon.

Basicly, a manufacturer can decide where the frame will be stiff and where it will flex just by using carbon, either of the same type, either of different types, but necessarily with a different lay-up according to the requirements of the particular area.

An here sits the key to solving, at least partly, the stiffness/comfort issue. A performant frame has to be:

  • laterally stiff (not to sway sidewards when pedalling, but the energy to be transformed via the drivetrain into forward motion as efficiently as possible)
  • vertically compliant (in order to absorb the shocks, or vibrations caused by the road). Vertical compliance decreases pedalling efficiency to an extent, but not nearly as much as the lack of lateral stiffness would

A road frame should be stiff in certain points (bottom bracket shell, head tube, dropouts, chainstay), while the comfort level depends on things like seatstay flexibility, tire width, seat post flexibility, saddle or even top tube.

The bottom line is that in the quest for a more comfortable road bike, the manufacturers didn’t go for the same “recipe”, mixing the elements mentioned above. For instance, some fitted a bended top tube for better shock absorbtion, other focused on a more compliant seatstay, while most of them used a longer chainstay. So, there are a lot of similarities, and differences between models coming from the same brand, or even between models or versions of the models belonging to the same manufacturer.

It is also worth mentioning and stressing the fact that in the case of road bicycles we can’t talk about genuine damping systems like in the case of mountain bikes. The systems and technologies present on the road bicycles have the role of cancelling or reducing vibrations, and, at best, diminish the shocks caused by uneven roads, leading to an increased comfort level.

In this article we’ll reffer strictly to shock absorbing and vibration reducing technologies, without going into too much detail in what regards other features of those bicycles.

Damping, shock absorbing, and vibration reducing technologies

Specialized Zertz

If not the best known, then Specialized’s Zertz insertions are surely the most successful such technology so far, having won several Paris-Roubaix and other cobble-roads races. Basicly, they are viscoelastic dampers inserted in the seatstay and fork, having the role of reducing vibrations caused by rough roads at a faster rate than normal frames would normally do.

 

specialized_zertz

The same material was also used for the Cobl Gobl-R seat post.

specialized

Trek IsoSpeed

The guys from Trek played a different card. They didn’t weld or glue the top tube and seatstay to the seat tube, but connected them by a decoupler, that works sort of like a hinge. Hence, the seatstay-top tube body can pivot separately from the seat tube, allowing for greater movement when encountering shocks, but not altering the stiffness the bottom bracket-connected tube requires. Note also the slightly bended shape of the top tube.

2013 Trek Domane 6.9 IsoSpeed Decoupler

Bianchi Countervail

Countervail is a material seemingly developed by NASA, according to Bianchi, which, up to one point is similar with the Zertz. The manufacturer claims that the new system does much better than conventional damping, using superficial rubber inserts and isolators. To put it briefly, the advantages claimed by Bianchi are maximized handling and ride control under normal to extreme vibration loads, reduced muscle fatigue and increased energy savings in distance rides and Increased rigidity and peak power output over long distances. We rode the Infinito CV last autumn, and we dare say it was a lovely ride, but all those claims are embodied by minimal gains in real life.

bianchi_infinito_cv_2014_endurance_road_bike

Cannondale SAVE

These Americans stuck to the usual materials, but heavily tampered with the rear triangle’s shape. The SAVE technology gave the two stays an hour-glass-like shape, clearly visible when looking at the chainstay, which has been widened and flattened in the middle. Also, Cannondale released the SAVE seat post, basicly a tapered one, that is said to flex more in order to offer greater comfort.

cannondale_save

BMC TCC

The Tuned Compliance Concept (TCC) implies using different types of carbon fibers, with different lay-ups according to the demands of each particular area. So, most of the frame is made out of unidirectional carbon, while the seat post, seat stay, and about 2/3 of the fork are manufactured from woven carbon to ensure a greater amount of flexibility.

bmc_tcc

Merida Flex Stay

Merida’s technology relies on using a seatstay that uses the Flex Stay technology, which makes it more compliant by better absorbing the shocks. Also, a mix of elastic fibers contributes to this (Bio Fiber Damping Compound), along with the flat shape of the stays.

merida

 

2 COMMENTS

  1. The overview of the different approaches to the oxymoron of comfortable road bikes is really valuable …….. But has anybody,is anybody ,doing a pragmatic review and comparison between the options.
    Having suffered a double disc removal in the neck area (c4/5)
    Road riding is hugely painful but I just love it. IF only it could be true that the vibration can be significantly reduced with out reducing efficiency it would be fantastic, the British roads are not cobbles but nor can they be described as smooth .

  2. Hi Jeremy,

    I hope our article was of some use to you. Given your issues, I would dare suggest you try a cyclocross bike. Its geometry isn’t much too different from a road bike’s, but it uses larger tires that you don’t have to inflate to full pressure, subsequently damping vibrations. You can also turn to a more elastic seat post, like the Cobl-Gobl R or Merida’s S-Flex, and even a saddle that is more fluffy.

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