Friday, November 30, 2007

Cycling Frontal Area

I found this photo and thought it was interesting:

I guess whoever created this didn't have a TT bike? My guess is that TT position would be somewhere between the two recumbent photos in frontal area.

Tuesday, November 27, 2007

The Power-Equipment-Speed Relationships

I spend and awful lot of time and energy measuring my power on the bike. But power doesn't win races, speed does. For the foreseeable future, power will be the best way to track changes in fitness; and it will be the best method of structuring a training program.

But in order to step back and see the big picture or to run through various equipment scenarios, I think it's important to know:

  1. how much faster will I be on a flat TT if I increase my FTP by 20 watts, or

  2. how much time will I cut off a climb if I lose 5 pounds, or

  3. how much time will I cut off a climb if I buy a bike that's 2 pounds lighter, or

  4. how much energy (power) will I save sitting in a 25-mph paceline if I swap my Ksyriums for Zipp 404s, or

  5. if I do a solo break away with one lap to go on the rolling Augusta road race course would I go faster with my lighter box section rims or heavier but more aero deep section rims, or

  6. what will the winning gap be if I sprint with 800 watts over 150 meters against a 180-pound guy putting out 970 watts? And more importantly, who will win? And if it's not me, how many more watts do I need to win?

There are many variables involved in answering those questions, but almost all of them are measurable to a fairly high degree if you have the time, equipment, patience, and desire. I've already answered many of them for myself, but I've used different spreadsheets or methods or web sites for almost every question and situation. And those spreadsheets, methods, or web sites often make assumptions that I don't agree with or simplifications that don't apply to what I'm doing. So it's hard to be consistent across the board with answering the questions and be confident in the answers.

So I decided to create a spreadsheet that ties all the physics together to the best of my abilities. I'm well aware that I'm probably the 10,000th person to attempt this task and that it's been done by folks with a lot more knowledge that I have. My spreadsheet might be better than some and will not be as good as others you might have seen. I hope it is accurate from a physics and math standpoint, but I'm not 100% sure. If you find errors, please let me know so I can make corrections and minimize the embarrassment factor.

But if nothing else, going through the tedious process has helped me understand the physics behind the above questions better than I did before, and that's reason enough to do it.

I've named the spreadsheet Badger because all the other names I thought of were about a mile long and sounded like the title of someone's masters thesis. This is bike racing, not study hall. It's a work in progress, but if you assume a rolling resistance coefficient, you can calculate almost anything else (use Crr=0.005 if you aren't sure. There are field tests to measure Crr, and I'll work on those later).

My spreadsheet is available here: Badger

In a nut shell, this is how it works:

  • The first sheet, "CdA calc", uses your input data (weight, weather data, distance, time, slope, and assumed rolling resistance) to calculate the forces against the rider (rolling resistance, air resistance, and slope resistance). Start and finish speeds should be entered so momentum can be accounted for, but results are best when start and finish speeds are equal. All the forces against the rider are set equal to the wattage you put out (to satisfy conservation of energy), and the equation is set up to solve for your drag coefficient CdA. For coast down tests, use wattage equal 0.
  • On the second sheet, input your weight, weather data, and the CdA that you calculated from the first sheet (you have to manipulate Cd and A to get the right CdA). Use 0.40 for A if you aren't sure - as long as CdA is correct it really doesn't matter). Assume a rolling resistance coefficient (Crr). Then you can set up each segment of any course to see how changing variables such as wattage, weight, rolling resistance, and CdA will change your finish time for the entire course. If the totals on the left side of the spreadsheet show errors, just delete any cells on the right side of the spreadsheet that aren't being used and that should solve the problem.

Friday, November 23, 2007

Strange Time for New Sprint Records

My sprint power:

Old Records: ------Peak-1042w; 1s-1062w; 5s-979w; 10s-880w
Today's numbers: Peak-1149w; 1s-1119w; 5s-1061w; 10s-919w

Either the Thursday 8x15s intervals are having an effect or I have a fresher anaerobic system this time of year because I'm doing mostly aerobic work. Maybe some of both.

Thank you Otter and Badger for serving as carrots on the 1/5 second and 10 second records, respectively. I lost both sprints, but maybe I was close enough for you to hear me breathing for a change.

Wednesday, November 21, 2007

Time Trial Pacing

I've always read how important it is to pace properly in TTs. My last two FTP tests on the Cervelo are hard evidence of that fact.

Two weeks ago, I started out too hard. My first 5 minutes I averaged almost 300 watts. I ended up averaging 251 watts over 45 minutes and was completely exhausted at the end - I didn't even have a good finishing kick.

Last night I started out correctly. My first 5 minutes I averaged 263 watts. I ended up averaging 265 watts over 45 minutes. I felt better throughout the test and had a very strong finishing 5 minute push.

My motivation was pretty low last night, so I attribute the entire wattage increase to proper pacing.

Wednesday, November 14, 2007

Orbea FTP Test

Last Tuesday was a 45-min FTP test on the Cervelo in TT position on the computrainer -- average 251 watts.

This Tuesday was a 45-min FTP test on the Orbea in road position on the computrainer -- average 274 watts.

That's a 9% difference and realistically probably 10% becasue I was fresher for the TT ride. That's about the difference that I expected between the two bikes/positions. The Orbea ride was also paced much better and I felt much more powerful throughout the test. It wouldn't surprise me if my TT ride wattage next Tuesday is higher due to better pacing alone.

The unexpected part of the whole deal was finding out that my computrainer wattage is 10% higher than the wattage measured by my Ergomo (mounted on my Orbea). I'm confident that my Ergomo is accurate, and this confirms a 10% difference between the two that I found last week when testing a teammate. I thought maybe his left leg was weaker due to a prior injury (which would result in an Ergomo/CT discrepancy), but I guess not. You'd expect the computrainer number to be a little less than the Ergomo number (maybe 2-4%) because of drivetrain losses between the crank and the road, but not 10% different.

All of my Tuesday night FTP tests will be on the computrainer but not always with the Ergomo, so I'll use CT numbers in my winter-training tracking charts. Measuring change is the important part, not measuring accurate wattage. Plus using the CT numbers will make me look stronger than I actually am, which is always a bonus!

Bottom line: My road FTP is about 265 now. Hopefully when I test in early January it will be at least 280.

Wednesday, November 07, 2007

Cervelo FTP test

My winter training season officially kicked off this week, and Tuesday is my FTP test day. I plan to alternate each Tuesday between my Cervelo P2K and my Orbea Orca. (winter plan is posted at Two reasons to alternate: 1. I'll get good L4 workouts in TT position and road position and 2. I'll find out how much power I sacrifice in the TT position.

Last night's FTP test was 45 mintues long. I started out much too hard, although I didn't realize it at the time. My first 20 minutes average was 265 watts, but my total test average was 251 watts.

I'm not sure exactly how to interpret the numbers. This summer I developed a theory that 20-minute ave power on a computrainer is equal to FTP (for more infor on that theory, see So the 265 watt 20-minute average is what I would expect this time of year on my Orbea. The 251 watt 45-minute average should be multiplied by probably 1.03 to account for trainer vs. race motivation factor, which would give me 258w for FTP. That seems about right for TT position. I hope to find that my road bike FTP is 10-20 watts higher than my TT bike FTP.

It'll be interesting to see what the Orbea numbers look like next Tuesday. Maybe with better pacing I can yeild a FTP in the 275 range with the Orca. If so, then my February target FTP might be in the 290 to 295 watt range (4.4 watts/kg). That would be a very good platform from which to begin higher intensity training for 2008.