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Old 01-05-07, 02:01 PM   #1
hiromian
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Using combined weight to get power to weight ratio.

Is that the way it should be done? Power devided by (The weight of the bike + the weight of the engine) I'm 149 lb + 24 lb bike so I need to develop a wopping R600Durace 400 watts to have a power ratio of just 2.3. Without the bike it would be 2.7.
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Old 01-05-07, 02:13 PM   #2
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No.

It's your weight, in kg. At 149lbs, you weigh 68kg (67.72). If you were to produce 400w, you would have a power to weight ratio of 5.88w/kg, as 400w/68kg = 5.88. And then, of course, you have to get into how long you can hold that for, for it to actually mean something. Most (untrained) people have trouble putting that out for even a minute.
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Old 01-05-07, 02:13 PM   #3
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power to weight is usually done as power (at whatever time frame or intensity you want) : weight of rider in kg

so yours would be X watts / ~68 kg

adding in the bike is an interesting idea, but it is not how it is traditionally done. I also think it lacks relevance at the highest level of the sports where comparisons of atheltes need not include bike weight, becuase all pro bikes can pretty much be assummed to be at the UCI weight limit.
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Old 01-05-07, 04:22 PM   #4
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Got it, Thanks
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Old 01-05-07, 05:17 PM   #5
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Quote:
Originally Posted by hiromian
Is that the way it should be done? Power devided by (The weight of the bike + the weight of the engine) I'm 149 lb + 24 lb bike so I need to develop a wopping R600Durace 400 watts to have a power ratio of just 2.3. Without the bike it would be 2.7.
I know the figures are always reported as watts/rider weight in kg, but I've always thought that it would make more sense to use rider + bike weight.

There was an interesting article in Velo News last month about the UCI weight limit on bikes being unfair to lighter riders since the same 15 pound bike is a much higher percentage of a small rider's body weight.

I know a 230 pound rider who races on a 15 pound Scott, so that's only 6.5% of his weight.
If I had a bike that was 6.5% of my weight it would be 9 pounds!
Maybe someday.
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Old 01-05-07, 06:36 PM   #6
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Using power-to-weight ratio might be a good indicator for hillclimb or sprinting-acceleration performance. But for flat-line and TT performance, you want to use power-to-AeroDrag ratios. You want to pack as much power into as small of a package as possible for straightaway speed. That's why time-trialers have such cramped and inefficient positions that doesn't generate the most power. However, even at producing 95% of possible max-power, triming down aero-drag to 90% will give you much faster speeds than producing 100% power at 100% aero-drag.
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Old 01-05-07, 07:24 PM   #7
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What is a good bench-mark power to weight ratio?
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Old 01-05-07, 07:32 PM   #8
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What is a good bench-mark power to weight ratio?
http://www.cyclingpeakssoftware.com/...11/profile.asp
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Old 01-05-07, 09:10 PM   #9
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http://cyclingforums.com/attachment....achmentid=7616

20 minute power, for those who haven't done an hour FT test.
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Old 01-10-07, 10:15 AM   #10
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i wonder how accurate that power profile benchmark really is. i just started riding a little over 6 months ago (havnt raced yet) and according to that chart my 20 minute power is apparently upper cat3 level. something is off.
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Old 01-10-07, 10:19 AM   #11
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Quote:
Originally Posted by DannoXYZ
Using power-to-weight ratio might be a good indicator for hillclimb or sprinting-acceleration performance. But for flat-line and TT performance, you want to use power-to-AeroDrag ratios. You want to pack as much power into as small of a package as possible for straightaway speed. That's why time-trialers have such cramped and inefficient positions that doesn't generate the most power. However, even at producing 95% of possible max-power, triming down aero-drag to 90% will give you much faster speeds than producing 100% power at 100% aero-drag.
So the best TTers are the big guys? If power increases linearly with mass, but surface area doesn't, shouldn't large guys have the highest power/drag ratios?
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Old 01-10-07, 10:38 AM   #12
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Originally Posted by stea1thviper
i wonder how accurate that power profile benchmark really is. i just started riding a little over 6 months ago (havnt raced yet) and according to that chart my 20 minute power is apparently upper cat3 level. something is off.
What are you using to measure power?
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Old 01-10-07, 10:44 AM   #13
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I think that particular chart is very innaccurate. I think the one from NYVelocity is a bit better: http://www.nyvelocity.com/content.php?id=112.

Though, they are all very hazy estimates. But given that one chart tells me I'm a cat 2 and the other tells me I'm a pro, I think niether are too accurate.
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Old 01-10-07, 11:03 AM   #14
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Originally Posted by Squint
What are you using to measure power?
powertap pro i recently bought last week. ill be doing 5s, 30s, 1min, and 5min benchmarks as soon as my next interval day comes up.
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Old 01-10-07, 11:48 AM   #15
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Originally Posted by stea1thviper
i wonder how accurate that power profile benchmark really is. i just started riding a little over 6 months ago (havnt raced yet) and according to that chart my 20 minute power is apparently upper cat3 level. something is off.
You don't have to be a Cat 3 to produce Cat 3 power. If your numbers are correct, and you choose to race, and your bike handleing skills and tactics are good you should be able to move up to Cat 3 within a season.

I had my power tested after riding for 4 months and my 30 minute power was at Cat 2 level even though I was a Cat 5 with 1 race under my belt.
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Old 01-10-07, 11:53 AM   #16
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Originally Posted by stea1thviper
i wonder how accurate that power profile benchmark really is. i just started riding a little over 6 months ago (havnt raced yet) and according to that chart my 20 minute power is apparently upper cat3 level. something is off.
I think the key to success is to also have good power to weight in the other categories. That is, 20 minute power will get you to the finish line, but it would also be useful to have good short term power for the sprints.

And as others have mentioned, tactics and skills end up playing a big role. Of course, if you are producing upper cat-3 power, you should find it fairly easy to move up, all other things equal.
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Old 01-10-07, 12:06 PM   #17
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[QUOTE=grebletie]I think the key to success is to also have good power to weight in the other categories. That is, 20 minute power will get you to the finish line, but it would also be useful to have good short term power for the sprints.

QUOTE]

I think I'm still at Cat 5 in the 5s and 30s power measurements.
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Old 01-10-07, 12:09 PM   #18
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Yeah, one reason I hate those charts is that I gradually change from a cat. 5 to a cat. 2 as the time frame gets longer. Yay for more lifting and sprint training, but all I want to do is TT and climb a lot.
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Old 01-10-07, 12:10 PM   #19
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Originally Posted by VosBike
I think that particular chart is very innaccurate. I think the one from NYVelocity is a bit better: http://www.nyvelocity.com/content.php?id=112.

Though, they are all very hazy estimates. But given that one chart tells me I'm a cat 2 and the other tells me I'm a pro, I think niether are too accurate.
Both charts you reference rely on the same data gathered by Coggan. There are different versions of that chart floating around, though, as it has been updated with new data.

It's important to note that the category assignments are merely examples. From what I understand, Coggan assigned the upper and lower values of the chart using real-world data, and then extrapolated the data points in between.

Given the increased use of power meters, I wouldn't be surprised to see the power estimates become more accurate, as more and more data is gathered.
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Old 01-10-07, 02:33 PM   #20
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Quote:
Originally Posted by Pizza Man

There was an interesting article in Velo News last month about the UCI weight limit on bikes being unfair to lighter riders since the same 15 pound bike is a much higher percentage of a small rider's body weight.

I know a 230 pound rider who races on a 15 pound Scott, so that's only 6.5% of his weight.
If I had a bike that was 6.5% of my weight it would be 9 pounds!
Maybe someday.
Not only should the weight limit be the same, they should put weights on you light guys, like they do to make the jockey weights even in some horse races.
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Old 01-12-07, 03:35 AM   #21
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Originally Posted by branman1986
So the best TTers are the big guys? If power increases linearly with mass, but surface area doesn't, shouldn't large guys have the highest power/drag ratios?
Yeah on perfectly flat TTs, the big guys are usually fastest. However, add rolling terrain and hills and it really mixes things up. Also power actually doesn't increase linearly with mass due to VO2-max & lung-capacity not going up linearly. Steady-state power produced at LT/VO2-max therefore doesn't go up linearly.

What I was pointing out is to not overlook the aero part of the equation. It starts playing a bigger part of the equation once you get over a certain speed. I'd say 23-25mph. After that, you have to add HUGE amounts of power for each 1mph gain. It's easier to get that 1mph through aerodynamic optimization.
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Old 01-12-07, 06:39 PM   #22
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Quote:
Originally Posted by DannoXYZ
Yeah on perfectly flat TTs, the big guys are usually fastest. However, add rolling terrain and hills and it really mixes things up. Also power actually doesn't increase linearly with mass due to VO2-max & lung-capacity not going up linearly. Steady-state power produced at LT/VO2-max therefore doesn't go up linearly.

What I was pointing out is to not overlook the aero part of the equation. It starts playing a bigger part of the equation once you get over a certain speed. I'd say 23-25mph. After that, you have to add HUGE amounts of power for each 1mph gain. It's easier to get that 1mph through aerodynamic optimization.
This is why a power tap is so good.
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