Thursday, July 9, 2009

The Fit

Last November, at Clearwater, I was stronger on the bikel; had a lighter, more aerodynamic, faster bicycle; felt more focused and stable in my training environment; usually feel stronger than everyone else on the bike. The result? I was two-and-a-half minutes slower than the previous year. My watts were high (around 320 for 2 hours and 8 minutes), so something with position was wrong. I called Dean Phillips, at Fitwerx in Peabody, MA, for help.

Here's Dean, riding a very similar set-up to my current bike (Cervelo P3, HED Aerobar, Zipp 808 front and 900 disc rear). Dean is a wildly strong cyclist, but for all his power he's gotten faster over the past few years, as he's added some years, while his watt numbers have remained mostly the same. How? Well, he's a nutcase about refining his position, and he's had a lot of success using some very complicated aerodynamic protocols for testing that you can use on the open road. Like any good scientist, he's deliberate, exact, and controlled, and he uses the same techniques when you go to him for a fit. This below information may be boring as hell to the non-triathlete/time trial crowd, so I urge you to go and read Brandon Stafford's post on his excellent blog pingswept about leveling the floor in his partner's office. It's much easier to understand.

I'm posting this information not only to give a shout to Dean and Fitwerx's excellent program, but to dispel some myths about bike positioning. We've been conditioned to believe some truths:

  1. Lower in front is better. We're triathletes, not cyclists, but we look at Fabian Cancellara's 17 cm drop (that's the difference in height from the saddle to the aero bar arm rests, distance "I" in the figure above and table below) and think "I better go lower in front."
  2. Narrower in front is better. A narrow shape cuts through the wind with greater alacrity, right? Well, maybe not. We've got to remember that we're dynamic shapes as we move through the air, and things such as how the air moves around our upper arms and across our (literally!) cycling thighs change with different body shapes.
  3. Compact is better. A brief perusal of Slowtwitch's accounting of bike positions at Kona last year seemed to make the point that more compact will get you onto the podium. Again, that's probably true if you've got a body type like Craig Alexander or Normann Stadler. That kind of position might not work for Bryan Rhodes, Mike Lovato, or me.
OK, now look at the numbers that Dean found for me in an incredibly useful bike fitting session this past January. Numbers in regular font are my old position (Clearwater '08). Numbers in bold signify my new position. I've put in italics the three items I outlined above: saddle-to-armrest drop (I), armrest width (G), and length of cockpit (C).

Existing TT Position
Recommended Baseline TT Position

A Saddle Height over BB 79.8 cm
A Saddle Height over BB 80.3 cm
B Crank Arm Length 175 mm
B Crank Arm Length 175 mm
C Tip of Saddle to end of Aero Bars 77.0 cm
C Tip of Saddle to end of Aero Bars 85.0 cm
D Nose of saddle to BB +2.4 cm
D Nose of saddle to BB +2.3 cm
E Aerobar Angle 4 degrees
E Aerobar Angle 0 degrees
F Saddle Horizontal Tilt -2.5 degrees
F Saddle Horizontal Tilt -3 degrees
G Aero Bar Pad Width (Center) 21.25 cm
G Aero Bar Pad Width (Center) 22.0 cm
H Aerobar Size/Extension 35.0 cm
H Aerobar Size/Extension 37.0 cm
I Top of Saddle to Top of Armpad -14.5 cm
I Top of Saddle to Top of Armpad -13.3 cm

Let's talk about saddle-to-armpad drop first. Instead of getting lower in front, Dean raised my front end by 1.2 cm. That might not sound like a lot, but raising the front end opens up the angle between your torso and your thighs, and can improve your power output. Tradeoff? Well, you're higher in front. What do you do to go faster on your road bike? That's right, ride in the drops, lowering your front end. So, in order to counterbalance that move upward, Dean moved me outward, as in statistic C, distance from tip of saddle to tip of aerobar extensions, or, in shorter terms, the length of my cockpit. Dean moved my hands a full 8 cm forward. If 1.2 cm is significant in bike fitting, 8 cm is a galaxy of distance. Part of that number comes from the new HED aerobar Dean installed, the extensions of which are 2 cm longer than my previous bodily torture Profile Design standard-bend devices. But even accounting for that equipment stretching, I'm 6 cm farther out in front. Dan Empfield at ST is probably smacking his forehead as I write this, but here's what Dean has to say about it:

"For larger cyclists and triathletes, extending the front end of the cockpit can make air flow more easily under the arms and across the thighs."

Dean lengthened my cockpit, and then counseled me to keep my wrists twisted in, so my shoulders would shrug and come in closer to my body. This wouldn't have been possible in my old position, as my back would have arched up into the air. An arched back? I'll agree with Empfield that an arched back is the key to a slow bike split. So, if you're a big cyclist, maybe everything you've heard about being low and compact might not work for you.

The third myth I'm going to dispute is the "narrower is better" myth. Dean moved my armpads out 3/4 of a cm, again to facilitate airflow between my arms and out the space created between my arms and thighs. The slightly wider position also gives me a greater power platform against which to push.

The result of all this? Let's compare my bike split at Clearwater (2:08:29) with the winner's, Terrenzo Bozzone (2:01:29), exactly seven minutes. Remember, Clearwater is a perfectly flat course, supposedly my powergel and clifbar. Now let's look at the numbers from Boise.

Christopher Bagg: 2:10:40
Craig Alexander (winner): 2:10:09.

Not bad, I say. If I can bike in Craig's company, I'm sold. I believe Dean's fit is the difference, as my bike training hasn't been too different this past spring. Go and see Dean. Or at least remember that you are a unique athlete, and may not benefit from a riding style of what you see on the streets of Monaco.

1 comment:

kilidogs said...

I'm handicapping Chris Bagg vs. Brandon Stafford in a Geek-Off. Borrowing a hybridized Auntie Dukes/Chris bagg subjective (squishy) methodology, I'll be using four categories:



Head Size


Brandon Stafford:

Pointlessness (8). Strong score here for Brandon. The plane kind of helped, but so would have some 2x4's sawzalled into big shims.

Rigor (9.5): Solved multidimensional least squared equations, and coded it in python so now everyone can do it. To tip the scale to ten, he'd have to do it in R.

Head Size: (9) Not quite a Papa Urquhart planet, but certainly capable of sustaining orbital bodies.

Mancrush: (5) Still staying in good shape, but going a little grey. A hand-shake kind of guy. The spark isn't there.

Chris "Ogre" Bagg

Pointlessness: (3) Once you accept that athletics is a legitimate endeavor, then improving performance through technology is pretty legit. I guess anything that doesn't involve even more hours on the bike is especially good.

Rigor: (4) Tossing out a post hoc ergo prop argument isn't going to win any geek offs. Props for the precise measures, but at least support your causal assertions by validating your premise... can we get some evidence that you can improve as much as you did through wind resistance alone? Can a brother get some equations up in here?

Head Size: (7) Some months ago, it probably would have been a 6, but the slim, fit Bagg makes the noggin look bigger.

Mancrush: (10) What can I say? Always a perfect ten in this category...