Will there be a day when the majority of top-flight downhillers are on air sprung bikes regardless of the course?
As it is right now, most suspension companies manufacture both an air-sprung fork and shock intended for downhill use, with strong rumors of others about to debut their own new platforms to the world. That isn't surprising, of course, given that the general perception among many consumers being that air springs mean premier suspension, and pricing and nomenclature also supports this. What is odd, though, is that this train of thought persists despite many sponsored World Cup downhillers preferring to use coil-sprung alternatives on their race bikes. There is no hiding this fact when talking about the back of the bike as it is pretty easy to spot a coil or air-sprung shock, but it gets a little murky when it comes to forks - it's no secret that some riders who's forks not only have the decals of the air-sprung version but also the corresponding air cap, are actually running a coil inside. The world's fastest racers are a particular bunch and if some of them feel more comfortable with a coil-sprung fork, that is what they will run come race day. I believe that we will see a shift away from coil springs in the future, though, with air becoming the predominant method of holding up a World Cup downhill race bike within the next five years.
Devinci's Steve Smith on his RockShox BoXXer at the Fort William World Cup. Is his works BlackBox fork fitted with a coil spring, or an air system?
KHS's logan Binggeli on his air-sprung Manitou Dorado.
Why it will happen
Air springs offer both lighter weight and limitless spring rate options that, at first glance, should make them the obvious choice for a racer, but there is far more to the equation than just those two facts. On the other side of the coin there is increased friction caused by the seals required by the air spring and the increased seal surface area, increases in spring rate as temps go up under hard use (remember that air expands as its warms up), and fluctuating damping levels due to both the air spring's rate changing and heat build-up. Admittedly, those sound like some serious issues that any rider would want to avoid, but some top racers currently choose to run springs on less demanding courses. The last few years have seen engineers make up ground in those battles: look at RockShox's 'Hot Rod' damper needle that is claimed to compensate for heat build-up with its "thermoplastic resin core" that is said to allow it to change shape slightly as temps rise, the slippery stanchion treatments (Kashima from FOX, BlackGold from RockShox, and Gold Slick Ano from X-Fusion) that have become de rigueur, and internal trickery like the just released 'Counter Measure' negative spring that RockShox has been using in their BlackBox Vivid shocks and is now putting into production. FOX's Dual Rate Control Valve shocks have even allowed engineers to tune the shock's air spring rate and curve like never before, although that technology was developed largely by Trek's suspension lab in partnership with FOX and won't likely be employed on another brand's bikes.
One trait of an air spring that no amount of smart engineers locked together in a room can solve is their inherent rising rate. A coil spring that is labelled as having a 400lb/in rate (meaning it takes 400lb to compress it one inch
) will compress in a linear fashion, but an air spring will ramp up in rate as it is compressed. This fact can be used by engineers who design their bike around the characteristics of an air shock, but it also means that certain bikes will never meet their potential if their stock coil-sprung shock is swapped out for an air unit (the opposite can also be true
FOX's Justin Frey working on Aaron Gwin's RAD 40 fork. Is Gwin's works fork air-sprung?
|The spring system is unlike anything out there in the gravity suspension world. It is a 100% FOX design that has several different adjustments for individual riders' weight and riding style. It is not a hybrid system. The Trek World Racing team races on FOX designed spring systems. - Mark Fitzsimmons, FOX's Race Program Director|
The worlds of motocross and supercross are often looked at as the leading edge of suspension technology, and the 2013 season has seen nearly all of the top 450 riders make the move to either the Showa or KYB air forks, with the majority of them reportedly very happy with the performance. Word is that it isn't just the 2 - 3lb weight loss, but also the improved overall feel that the riders are fans of. Yes, the terrain that they race on is markedly different from a World Cup downhill track, but it is probably fair to say that the average supercross racer is far more demanding and in-tune with their suspension than most World Cup downhillers. It is only after extensive testing on private tracks and with their own private suspension technicians that those riders will run an air fork when it counts, and that is exactly what we've seen happen. Granted, massive resources in the sport allow Showa and KYB to manufacture expensive one-off internal parts that have first-rate tolerances, as well as include insanely expensive stanchion and damper rod coatings that take suppleness to the next level, but it is a clear sign that air is better, even if it takes more money to make it so. It is only a matter of time until we see less expensive methods and lighter weight parts used within the works-level forks of the world's fastest downhillers. KTM's Ryan Dungey even used a air-sprung rear shock for a few supercross rounds before a seal failure saw his bike sag to bottom out as the gates dropped (reportedly due to the harmonics of the bike as he brought the revs up to start the moto