Wednesday, March 26, 2008
Monday, March 17, 2008
The last post covered the bad and the ugly from Perry, so now I'll allow a little space for the good. I had a good TT in Perry and took 2nd. I've been working hard on my position on the bike, I upgraded some equipment, and I've made it a point to do at least one hard ride per week on the TT bike. It's paid off. I'm faster now in TTs than I was last year. This weekend my average speed was 25.9 mph for about 10 miles.
In July 2007, my coast-down testing showed me having a CdA = 0.265 with an assumed 0.005 Crr (rolling resistance coefficient). Last week, after lots of tinkering with my position, adding a rear disc wheel, and installing Veloflex Record tubular tires, I reduced my assumed Crr to 0.045, which - if all else was equal - should have resulted in a higher CdA measurement. But I found that my CdA had dropped consierably to CdA=0.233.
To put that in perspective, a drop in CdA from 0.265 to 0.233 would result in a savings of 56 seconds on a pan-flat 10-mile TT course holding a constant 300 watts.
Using a very rough approximation of the segment lengths and slopes encountered in Perry this weekend, I modeled my ride with known CdA, distance, and time to calculate wattage. I normally put out more wattage while climbing, so that was considered for each segment. The model shows that my average power was about 299 watts. If I'm putting out about the same wattage now on my TT bike as on my road bike, and if my 60-min power is about 95% of my 20-min power, then that relates to a FTP of 299 x 0.95 = 284 watts, which is exactly what I recently tested it to be.
Here's a snapshot of the model. You can find the spreadsheet at Badger 3 if you'd like to use it.
A little moisture made Firetower Road easier to ride this year, but the dirt and wind were still more than I could handle. My power output was much higher than last year, but evidently so was everyone else's.
Here's some 2007-2008 comparison data for those who are interested. This is for the Competitive 35 and under field (I weigh 149 lbs):
My NP for the first 45 minutes of the race in 2007 was 224 watts; in 2008 it was 270 watts. My NP for last 8 minutes prior to losing the group in 2007 was 204 watts (remarkably low, even considering that my FTP was only 235 or 240 at the time). In 2008 my NP for the last 8 minutes before catching the autobus was 301 watts, which makes more sense - that's about 15 watts above my current FTP. I can only hold 4.44 watts/kg for a while before popping.
The climbs were tougher this year, too. Here are my average power numbers (with watts/kg) for the two short climbs on the front part of the course for the first two laps (L is lap, C is climb):