I felt today was a good day to do some testing. When I did my last test back in December I skewed the results some by doing all the time trial tests in one day. A 1, 6, 12 and 30 minute in one day plus graduated exercise test. The last test was the 30 minute TT. Well, can you imagine how depleted I was when I got to that test? Rune Duke correctly observed that the TT tests should be spread out over several days! This is why these people don't pay me. I have so much to learn.
My 30 minute power on that first test was 240 watts giving me an FTP of 230 watts. Today was different by a fairly large degree. I warmed up for a half hour or so riding over to a development here call "Stonebridge". This is a nice place to do TT work because:
A. It is close by...only 3 miles from my house
B. It has a circular drive with two three way stops and very little traffic
C. The course length is about 2.75 miles.
The results:
Power-Tap #1:
Duration: 29:57
Work: 491 kJ
TSS: 54.8 (intensity factor 1.048)
Norm Power: 275
VI: 1
Distance: 11.834 mi
Min Max Avg
Power: 178 460 273 watts
Heart rate: 147 200 176 bpm
Cadence: 79 103 89 rpm
Speed: 20.2 27.5 23.7 mph
Pace 2:11 2:58 2:32 min/mi
Looks like I zeroed in on 275 watts. The improvement over December is hard to measure because of the flawed testing. I think there has been some improvement though. I did another 20 minute TT after some recovery and here's how it looked:
Power-Tap #4:
Duration: 20:00
Work: 298 kJ
TSS: 30.6 (intensity factor 0.959)
Norm Power: 251
VI: 1.01
Distance: 7.703 mi
Min Max Avg
Power: 0 698 248 watts
Heart rate: 130 192 172 bpm
Cadence: 72 100 90 rpm
Speed: 18.1 27.3 23.1 mph
There was some fall off suggesting again that doing the testing the way I did in December fouled up the test data. Check out how much speed I lost by averaging 25 less watts.... .6 mph. Interesting stuff. I wasn't paying any attention to these speeds because my set up was definitely not for max speed. I used my standard road bike set up with my heavy rear wheel and power tap. A fun experiment might be to slap on the aerobars and see what kind of difference they make. Could I develop more power by moving forward on the bike? How much speed improvement would I see. What if I pumped my tires up to 140 psi like I do for TT's?
Tuesday, April 03, 2007
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4 comments:
Well it sounds like youve improved. I would say that you would gain some speed if you moved up a little, it engags more muscles. And for pumping the tires to 140, thats less rolling resistance, so naturaly its faster
Yes, I think you're correct.
Very cool analysis!!
Impressive numbers. I should look into
investing in a powertap since it sounds like a great training tool.
Oh, and higher tire pressure does not
always mean you go faster. Unless the road surface is perfectly smooth, too high of a tire pressure can actually can slow you down. As the tire pressure goes up, the tire deforms less as you roll on it which is good, but this also means that it's less able to soak up bumps in the road. Each time you hit
one, there's a small force backwards that slows you down. The higher your
tire pressure, the larger this force is.
Somewhere in the middle there's an optimal happy medium. Depending on your weight and the quality of the road surface, I've heard that this is usually in the range of 100-120psi. For cross and mountain racing, the bumpiness effect wins out and pressures down around 35-40psi often end up being fastest.
In fact, you could test this out for
yourself by trying different tire
pressures while riding at a constant
power and comparing your average speed
over a fixed course. Maybe something like 100,120,140 psi at a constant 200W? You would probably have to repeat the test a bunch of times to cancel out external effects like wind and stray rocks, but I think it could work.
Sorry for the long message, but I get excited by this physics stuff!
David
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