 |
|
Home Calendar Current Results Standings Year-Rounder Records Training Equipment Nutrition About the UMCA Site Index |
|
From the Field: Frames
"Equipment that works well for riding five hour centuries isn't necessarily going to be the answer for riding 24-hour races, 30- to 45-hour qualifiers, or RAAM itself."
by Bernie Comeau
Bernie Comeau, a veteran of RAAM and Furnace Creek, edits "From the Field"- a series of articles on what accomplished RAAM racers (the elite of the ultra community) do and use in order to be successful.
When I competed in RAAM '98 I rode a steel-framed Ciocc and a steel-framed Bianchi. Boy, were they stiff and efficient racing bikes! One of the things that caught my attention that year was the condition of some of the road surfaces. While most roads were just fine, others were downright nasty, relentlessly pounding your hands, feet, knees, and butt as you moved over them. Bouncing along on California desert roads, the New Mexico interstate, and others, I realized that these steel-framed machines that had done me so well on various doubles, quads and qualifiers were not necessarily an advantage for RAAM. By the time I was halfway through Texas (with a dozen or so saddle sores), I promised myself that I wouldn't attempt RAAM again unless I was riding more forgiving frames. The bike you ride isn't going to be what wins or loses a race for you (many other things contributed much more fully to my downfall in 1998); however, the bike is not insignificant to your race.
What's the best bike for ultra racing?
I polled a number of accomplished RAAM riders from the 1990s to find out what bikes they like (and what they avoid), so that the rest of us can learn from their experience. RAAM is the ultimate litmus test for any bike and accessories. Equipment that works well for riding 5-hour centuries isn't necessarily going to be the answer for riding 24-hour races, 30- to 45-hour qualifiers, or RAAM itself. Long rides are not simply shorter rides writ large. The cumulative effect of time in the saddle seems to increase things like pain and exhaustion exponentially rather than linearly. Similarly, your equipment choices are going to impact you exponentially as your riding distances increase. Thus, knowledge of what works well (and what doesn't) for accomplished RAAM riders hopefully can help to enhance performances in our own ultra events, whatever the distance.
Balance comfort and efficiency!
For ultra racing, the best bike is one that maximizes energy transfer while also maximizing comfort. We'd all like a bike that weighs next to nothing, transfers power with perfect efficiency, and rides as smooth as a Cadillac, but that's just not feasible. The optimal bike will be somewhere in between ultimate efficiency and ultimate comfort. Emphasize one over the other too much, and your overall time for an event will inevitably suffer. You can have the stiffest, most efficient bike in the world, but if it's not comfortable, you're not going to be very fast for very long. On the other hand, touring bikes, with their longer wheelbases and added weight, are wonderfully comfortable for rolling over rough roads, but they're not terribly fast; you're not going to win many races with them. So what's the middle ground between comfort and efficiency for long-distance racing?
Frame Design
A better understanding of the physics of the bike and its materials will help us to understand better the principles behind why the RAAM riders have made the choices that they have.
The design and geometry of a frame determine a bike's stiffness and strength, rather than the material used. Steel in general is about twice as stiff as titanium, and three times as stiff as aluminum, but manufacturers get around these differences by varying both the thickness and diameter of the tubing. For example, a 1.5-inch diameter aluminum tube is about 5 times as stiff as a 1-inch diameter aluminum tube.(2) Practically, then, aluminum frames can be made just as stiff as (or more stiff than) a steel frame, but with less weight than a steel frame. What determines whether one bike is more stiff than another is more a factor of the geometry of the frames than the material used to build them. Manufacturers can make bikes as stiff as they wish, simply by varying geometry.
Comfort
If frame geometry is held constant, is there a difference in comfort level with different materials?
If power transfer and stiffness aren't really issues with respect to frame material, what about the materials' effects on ride comfort? This is the ability of a frame to absorb the energy that is gained from riding over a surface; energy that is experienced primarily in the form of high-frequency vibration. The more rough the road surface, the more potential vibration energy is transferred to the bike. The more a bike frame is able to absorb or dampen this vibration energy, the less this vibration will subsequently be transferred to the rider at points of contact with the bike (largely, our butts, feet, and hands). In this regard, differences in frame material seem to be pronounced.
Frame Materials
Flick your finger against a frame made of aluminum, steel, or titanium. You'll hear a high-pitched, resonating ring. Now do the same against a carbon fiber frame. You'll hear a thud. This is because the plastic epoxy in which the carbon fibers are embedded has a dampening effect. While the metal frames serve as conductors for high-frequency vibration, carbon fiber frames, by their very nature, dampen high-frequency vibration. Carbon fiber frames tend to have a much smoother ride as compared to metal frames. In fact, as Rick Denney of Triathlete magazine has found, "it turns out that the ring of metal frames is in roughly the same frequency as the texture of the road, and metal frames ring more than we realize when we ride them". Titanium appears to be the quietest of the metals here, while aluminum may be the worst culprit of all: "aluminum in a fat-tubed bike may actually transmit more road buzz than other designs... which may explain some of the perceived harshness of aluminum". (3)
If you can minimize the vibration transmitted to your hands, arms, shoulders, knees, and butt, your muscles are not going to fatigue as quickly. There will be less of a need for your muscles to be reacting constantly to "road buzz". The longer we are on the road, the more crucial this factor becomes. All else being equal, carbon fiber frames provide a distinct advantage here, because of their ability to absorb and eliminate much more road vibration.
Frame Geometry
What about actual bumps in the road (as opposed to the vibration which results from going over bumps)? Here, frame material is less of a factor. As Denney explains, "for bike frames with seat tubes, the frame is made stiff vertically by the double-diamond truss design. The truss is so inherently stiff that, for all practical purposes, it's infinitely stiff up and down. This means that the transmission of large bumps (not road buzz) to our posteriors has nothing to do with the material or tubing design. It has everything to do with the geometry of the bike". (4)
The only way to lessen the effect of road bumpiness, then, would be to lengthen the wheelbase, relax the seat tube angle, or provide suspension for the seat. The latter provides the most benefit here (because it can eliminate the problem completely), and this is where beam bikes have their particular advantages. By eliminating the seat post and suspending the rider, the rider's butt is spared from virtually all of the otherwise constant pounding that would occur from going over less than perfectly smooth roads. The additional advantage of the suspension design is that one can maintain a relatively shorter wheelbase and compact geometry with the frame (things that increase efficient power transfer) without sacrificing a more comfortable ride.
To sum up the physics of bike frames: frame material is unrelated to stiffness and strength; carbon fiber frames provide the smoothest ride (aluminum provides the harshest); and beam suspension cushions the rider best from road shock (while also allowing for the maintenance of efficient energy transfer).
RAAM Riders Experiences
Regardless of the specific manufacturer or model, though, it is overwhelmingly clear that beam bikes are the standard for accomplished RAAM riders.
Accomplished RAAM riders' choices are consistent with what we know about the physics of the bike frame. Virtually all riders came to the conclusion that, over the long haul, comfort is just as important a consideration as efficiency, and their frame selections reflected a deep understanding (either conscious or intuitive) of the physics behind frame material and set-up. Thus, carbon fiber was the frame material of choice, and beam suspension was clearly the preferred set-up.
Beam Bikes
Over 80 percent of the RAAM riders who responded to the poll were using beam bikes of some sort. Of these, the Softride Power V (a carbon fiber frame) was the most common choice. One two-time RAAM finisher rides the Power V because, in his estimation, it provides the best combination of stiffness, aerodynamics, speed, and comfort. Likewise, a two-time RAAM champion has been racing the Power V exclusively since 1994, having switched from an aluminum frame. Again, long-term comfort was a major factor in his consideration: "the beam helps out with my lower back pain a lot". Other riders consistently mentioned that it struck a nice balance between comfort and efficiency and that it was particularly formidable on flat to rolling terrain.
The Power V was not without disadvantages, though. Almost all who used it noted that it was a relatively heavy bike, and therefore not the greatest bike for climbing. Some used aluminum-framed Softrides as a lightweight alternative beam bike, but were aware of the smoother ride provided by carbon fiber. Many riders used lightweight metal bikes (either conventional or beam) for climbing, and rode the carbon fiber beam frames for all else. Others (including the two-time champion noted above) used the carbon fiber frame exclusively: "I use the same bike for all of RAAM, regardless of the terrain and wind speed". Another stated beam-alternative to the Power V was the TitanFlex, a titanium beam bike, whose beam set-up is purported to be stiffer than the carbon-beamed Softrides, and more lightweight overall.
One noteworthy comment regarding a disadvantage of beam bikes had to do with saddle sores. With the elimination of the seat post, beam bikes help to stave off some types of saddle sores. But once you do get saddle sores (typically of the chafing kind), beam bikes can be a nuisance. The rider explained, "much to my surprise, it is less comfortable with bad saddle sores. On a conventional frame, with every stroke you can get your butt off the saddle slightly and get a bit of relief. But the beam just comes up with you and keeps irritating your butt".| More Information UltraCycling Magazine Authoritative information for endurance cyclists. Each issue contains articles by experts on:
|
|
|
 Order back issues |
Conventional Bikes Two RAAM veterans have conventional bikes of all four types of frame material, and both prefer titanium. One rides a Merlin, which has "proved the most reliable", while the other prefers the Serotta Titanium: "my favorite bike; light, responsive, has a bit of flex for comfort, but not too much; just a sweet ride". Interestingly, both mentioned the comfort of their titanium bikes (which tend to vibrate less than the other metals). Both riders noted that their steel-framed bikes were "very responsive and quick climbers", but "didn't absorb road shock at all". Similar comments of responsiveness and harshness were made about aluminum frames, though with the phrase of "light weight" being added. A number of RAAM racers made mention of riding conventional carbon-framed bikes, and typically gave them quite favorable reviews. The overwhelming frame of choice in this category was the Kestrel. Common phrases that appeared when speaking of the frame were "light", "absorbed much more road shock", and "did RAAM on it almost entirely". So where does all of this lead us? Accomplished RAAM riders clearly prefer carbon fiber and titanium as the frame choices for their primary bikes; carbon fiber for its superior road-dampening abilities and comfort, and titanium for its superior responsiveness, relative comfort, and lighter weight. And beam bikes clearly win out, due to their increased comfort and (though not discussed here) aerodynamics. Regardless of whether you have aspirations to participate in RAAM, you can apply these experiences to your own ultra events, however long. The same laws of physics will apply, no matter what the course. Making the right bike selection for your particular events can go a long way both to making your ride more comfortable, and to improving your overall times. (1) A recent series of articles written by Rick Denney for Triathlete provide a nice technical synopsis regarding differences in bikes and materials. Much of my following discussion is based on his accounts and knowledge. See Rick Denney (1999) "The Truth about Frame Materials", Triathlete, nos. 183 and 184.
Accomplished RAAM riders who ride conventional frames for ultra events prefer titanium and carbon fiber.
(2) Rick Denney (1999) "The Truth about Frame Materials, Part II", Triathlete, 184, p. 82.
(3) Ibid., p. 83.
(4) Ibid., p. 83.
.