If you ride a mountain bike, chances are you are familiar with having some form of suspension – at least on the fork legs. Traditionally, however, road bikes with drop handlebars rarely use suspension at all. Short of double-wrapping bar tape and fitting wider tires, how do manufacturers bake comfort into their road bikes?
FRAME MATERIAL
Up to the mid-1980s, almost all road bicycles were made of steel, and for good reason. Despite its weight and susceptibility to corrosion, steel delivers a characteristic springiness to its ride quality that helps absorb bumps and keeps a rider fresh over long distances, which is why it’s still a favorite of bicycle tourers.
The later introduction of titanium addresses the corrosion and cuts weight, but is otherwise essentially a “twin” frame material to steel. It has never seen widespread adoption, though, because of its reputation for being hard on its tooling and finicky with welding…both factors driving up its price.
Due to the expense of titanium and professional cycling’s desire to drop the weight of steel, aluminum came into prominence. Early frames, however, were infamous for a harsh ride. Manufacturers later learned to manipulate it into frame tubes vastly different from the simple round ones of steel bicycles using a couple of favored tricks. Double- or triple-butted aluminum frame tubes have multiple wall thicknesses along their length, allowing comfort to be tuned and weight reduced, while hydroforming shapes the tubes during manufacture to maximize the material’s more meager strength. While current aluminum frames ride better than ever, very few bicycles use the material on fork blades.
The concept of “tuning” the frame material peaked with carbon fiber composites. In addition to tube shaping and butting, the properties of a carbon fiber frame are dictated by the types of carbon fiber ply used, and their subsequent layup. High modulus carbon fiber is good for stiffness per unit weight, but bad for comfort; lower modulus carbon fiber is usually applied to places where either greater flex or a lower price point are desired. With these layups a closely guarded secret, the scope of tuning a bicycle frame is much wider.
GAPS AND GIVE
Manipulating the material itself to create a suspension effect can only get you so far, though, as competitors of the annual cobblestoned cycling races Paris-Roubaix and the Tour of Flanders can attest to.
Specialized tore out the rule book with its Roubaix endurance road bike. In early iterations, the Roubaix introduced gaps cut into its seat stays and fork blades, filled with elastomer inserts. In a clever bit of marketing, Specialized called the system “Zertz,” making it look like the elastomers doing the job. In reality, the subtle flex created by the gaps they sat in did the lion’s share of the work.
Other manufacturers have taken notice. Notably, Italian manufacturer Wilier injected elastomers into a linkage built into the rear triangle of its new Cento10NDR endurance road bike, which can be swapped for a different density to tune the ride. Another Italian maker, Pinarello, made a damper out of the elastomers themselves with their Dogma K8-S.
MECHANICAL FLEX
Trek went about introducing comfort a different way via the so-called “IsoSpeed Decoupler” on their Domane road bikes. A bearing pivot helps isolate the seat tube from the rest of the bike, helping it flex more freely and making it act like a leaf spring. It was so successful that they even engineered it into the Madone, their aero bike, in a novel “nested seat post” implementation.
Later incarnations of the Domane introduce the IsoSpeed Decoupler tech up front, which is a pivot at the steerer tube and headset area, in order to balance the front end with the bike’s plush-riding rear.
SHORT-TRAVEL SUSPENSION
Somewhere along the way, the engineers at Cannondale must have thought “why not try something from the mountain bike world?” when they set about designing their gravel bike, the Slate, released in 2015. Coupling with larger-volume 650B tires was a modified version of their Lefty suspension fork, dubbed the Oliver.
Beyond the funny looks, the Slate stoked the adoption of suspension for an otherwise rigid cyclocross or gravel bike. Fox retooled one of its forks into a short-travel “AX” unit, while Lauf got into the game with its Grit fork as well, using glass-fiber leaf springs that shed weight over a traditional damper unit.
Where your typical mountain bike will yield anywhere from 100 to 160 mm of suspension travel up front, those adopted by road and gravel cyclists are typically limited to 30 mm.
One downside to this design is it’s susceptible to a phenomenon called “pedal bob.” Under high pedaling loads, the suspension can squish with each pedal stroke, sapping power. On mountain bike forks and similar, this is dealt with by actuating a mechanical suspension lockout, but this also adds a layer of complexity.
SUSPENSION UP TOP?
With the Roubaix refreshed for 2017, Specialized retired the Zertz system and dabbled with suspension of its own. They went their own way and put it higher up, above the head tube.
The result is a needle-bearing suspension cartridge within the fork’s hollow steerer tube, dubbed “FutureShock.” A couple of springs provides the 20 mm of suspension, and Specialized gives you three options of upper spring for tuning firmness. Because this design suspends only the weight of the handlebars and nothing else, the company says it is resistant to pedal bob and other undesired effects.
FutureShock isn’t without its problems, either. As the cartridge occupies the space where a star-fangled nut or a compression plug would sit for headset adjustment, that procedure is done via a couple of grub screws, which some reviews say don’t like to keep their tightness.
the accidental randonneur 