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power to weight and climbing math

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Old 06-28-10, 08:48 AM
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power to weight and climbing math

whats the rought math/rule of thumb on time savings over vertical distance for dropping weight and keeping power constant.

looking at my season so far, i've lost about 3 minutes to the leaders on a pair of climbs that were betwee 9-10 miles long, with 2500-2600 vertical feet of climbing.

i am a strong engine, good TT rider (beat the best climber in the 4s by about a couple of mintes on a 10 mile TT this weekend) , but at 5'10/165, i'm a bit heavy for a climber.

assuming constant power, what kind of weight cut am i looking at to hang with these guys?

i know all this is really really rough, and no i dont have power numbers, just opening it for discussion and to possibly have a rough goal.
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Old 06-28-10, 08:49 AM
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use the model on http://analyticcycling.com/
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Old 06-28-10, 09:10 AM
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or http://www.noping.net/english/ It has less ability to fine tune assumptions, but a simpler interface.
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Old 06-28-10, 09:15 AM
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hey merlin

i left on sunday after the TT cuz my ride had to get home, and didnt realize til i got home that i won some merch. (8th- i think- GC - SM4)...

did i forfeit it? was it anything cool?
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Old 06-28-10, 09:20 AM
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Roughly, over a 10km climb, you sacrifice +/- 1min for every 2kg.
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Old 06-28-10, 09:23 AM
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depends on the grade.

three pounds is good for a minute on Whiteface. that's 8 miles at 8% grade.
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Old 06-28-10, 09:33 AM
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a lot. i can't tell what you are saying (a pair of climbs totalling 10 miles, or two climbs 10 miles each). obviously, if you are losing 3 minutes over two climbs each at 10 miles, you will have less to lose than if you are losing three minutes over two climbs totalling 10 miles.

i did some basic stuff on ac.com, you are on your own if you want to change the parameters. i assumed that the total was 10 miles, that your bike weighs about 17 and that your climbing cda was .35:

initial run
cda: .350
mass: 82.55
slope: 4.92
speed: 6.26
watts: 322.2
time: 42.86

lower weight:
cda: .350
mass: 73.15
slope: 4.92
speed: 6.73
watts: 322.2
time: 39.86

145 lbs doable for you? i might have the math wrong, kinda just winged it with a calculator between other tasks i am doing right now. you should check out the ac site, and plug and chug yourself.
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Old 06-28-10, 09:54 AM
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I know it's not as fancy as the online calculators, but if you know your previous best time up a hill it's easy to see how much you'd gain (assuming same power output) by just dividing seconds / weight (lbs/kg doesn't matter).

e.g.

I pre-rode Diablo TT hill climb at 173lbs, with an 19lb bike in 31:30 (1890 seconds). so 1890seconds/192lbs. For the ride I dropped 4.5lbs off my body and maybe 4lbs off the bike (carried no food/water on TT, no cages, no seat bag, no pump, etc..)

Anyway, 1890/192 = 9.84s/lb. Race day weight of -8.5lbs 1 week after pre-ride and I turned in a time 100s faster. Pretty close to 10s/lb, with a little extra for the day-of adrenalin.
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Old 06-28-10, 09:56 AM
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sorry. two seperate races.

each climb (rist, deaddog) was between 9-10 miles and each has 2500ft gain. rist is more dynamic w steep pitches, DD is pretty steady. each resulted in me losing about 3 minutes to the lead group of 8-10 dudes.

145 isnt realist for my body type. im also new to racing (but not climbing in genrral) so i suspect i have plenty of room for power gains too.

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Old 06-28-10, 02:31 PM
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Check out http://www.amazon.com/Racing-Weight-.../dp/1934030511
changed my life
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Old 06-28-10, 02:55 PM
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Originally Posted by badhat View Post
whats the rought math/rule of thumb on time savings over vertical distance for dropping weight and keeping power constant.

looking at my season so far, i've lost about 3 minutes to the leaders on a pair of climbs that were betwee 9-10 miles long, with 2500-2600 vertical feet of climbing.
It isn't tough. Assuming that your power is constant, your speed change will be ~.8 x the weight change. For instance if your weight goes down 1% your speed will go up ~.8%. In this case I'll assume that the climb took you about 50min and you lost 3 minutes, so you need to gain 3/50 = 6% in speed, and losing 7.5% in weight will do that. That's overall weight, so if your all-up weight is 190lb that is ~14lbs... which isn't a little.

If your strategy on this climb is to hang until you pop, then I'd suggest dropping back at the beginning (unless there is a headwind), and riding your own pace. You will likely still lose time but not as much.
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Old 06-28-10, 03:07 PM
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Originally Posted by rruff View Post
It isn't tough. Assuming that your power is constant, your speed change will be ~.8 x the weight change. For instance if your weight goes down 1% your speed will go up ~.8%. In this case I'll assume that the climb took you about 50min and you lost 3 minutes, so you need to gain 3/50 = 6% in speed, and losing 7.5% in weight will do that. That's overall weight, so if your all-up weight is 190lb that is ~14lbs... which isn't a little.

If your strategy on this climb is to hang until you pop, then I'd suggest dropping back at the beginning (unless there is a headwind), and riding your own pace. You will likely still lose time but not as much.
This is what I meant, restated more clearly. So, QFT.
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Old 06-28-10, 03:20 PM
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Originally Posted by rruff View Post
It isn't tough. Assuming that your power is constant, your speed change will be ~.8 x the weight change. For instance if your weight goes down 1% your speed will go up ~.8%. In this case I'll assume that the climb took you about 50min and you lost 3 minutes, so you need to gain 3/50 = 6% in speed, and losing 7.5% in weight will do that. That's overall weight, so if your all-up weight is 190lb that is ~14lbs... which isn't a little.

If your strategy on this climb is to hang until you pop, then I'd suggest dropping back at the beginning (unless there is a headwind), and riding your own pace. You will likely still lose time but not as much.
Oh just take a big dump before the race...that's what they do in the 41.
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Old 06-28-10, 04:17 PM
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Originally Posted by El Diablo Rojo View Post
Oh just take a big dump before the race...that's what they do in the 41.
A 14 lb deuce? I am definitely not following you to the Port o Potty.
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Old 06-28-10, 04:23 PM
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Originally Posted by SpongeDad View Post
A 14 lb deuce? I am definitely not following you to the Port o Potty.
No not me...I'd be under 130lbs if that were the case..but there a quite a few geniuses on this board that will tell you that's all it takes!
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Old 06-28-10, 05:12 PM
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Originally Posted by badhat View Post
whats the rought math/rule of thumb on time savings over vertical distance for dropping weight and keeping power constant.

looking at my season so far, i've lost about 3 minutes to the leaders on a pair of climbs that were betwee 9-10 miles long, with 2500-2600 vertical feet of climbing.

i am a strong engine, good TT rider (beat the best climber in the 4s by about a couple of mintes on a 10 mile TT this weekend) , but at 5'10/165, i'm a bit heavy for a climber.

assuming constant power, what kind of weight cut am i looking at to hang with these guys?

i know all this is really really rough, and no i dont have power numbers, just opening it for discussion and to possibly have a rough goal.
The (well, my) answer is: lose weight. Don't spend too much time analyzing the problem (e.g. avoiding it), time to start tackling it.
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Old 06-28-10, 10:11 PM
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No. The answer is not "lose weight". The answer is "train harder" or better at least. The OP just said that he can't afford to lose 14 lbs. But he could probably lose 5 or 10, and gain some FTP.
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Old 06-28-10, 10:31 PM
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yeah i mean i'm not a big guy. you can see my ribs through a skinsuit. and my power is my my tree trunks, which account for a lot of the weight. brian is right, its not just weight down its weight down and power up. ive been training for bike racing since roughly last november, i'm pretty confident i can tap some more power potential, as well as probably knocking off 7-8 pounds.

other than that, i'm coming to terms with the fact that my strengths (rolling courses like morgul bismark and TTs) arent what i thought they were gonna be before i started (climbing). i'm comfortable with that for the time being.
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Old 06-28-10, 10:48 PM
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I would suggest pondering and worrying about this more after you've raced a couple of seasons. You could have just lost touch with the leaders because you weren't playing your cards right, and couldn't make up for it with raw strength.

Losing a few lbs might work, but if your diet is in order, don't bother till you have to get there. I think a lot of people could gain a couple of pounds and more than make up for it with the accompanying power increase if things are done right. I noticed that personally, so of course I have to generalize...
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Old 06-28-10, 11:14 PM
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Originally Posted by badhat View Post
i'm pretty confident i can tap some more power potential, as well as probably knocking off 7-8 pounds.
What does your bike weigh? If it isn't UCI illegal yet, there could be a couple pounds to lose there also. Don't forget the helmet and shoes either. If you are poor though, then forget about this. Probably better to play this game later in your career anyway...
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Old 06-29-10, 05:46 AM
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Originally Posted by ridethecliche View Post
I would suggest pondering and worrying about this more after you've raced a couple of seasons. You could have just lost touch with the leaders because you weren't playing your cards right, and couldn't make up for it with raw strength.

Losing a few lbs might work, but if your diet is in order, don't bother till you have to get there. I think a lot of people could gain a couple of pounds and more than make up for it with the accompanying power increase if things are done right. I noticed that personally, so of course I have to generalize...
There is a point that a rider can lose so much weight that they sacrifice power...for me that's when I get below 142. 143 seems to be the magic number. It sounds like the OP could lose some weight, 5lbs at the same FTP would be a nice gain, there is no reason to wait to lose weight if he isn't at his optimum weight now.

After I had done 3 or 4 races my coach asked me what my weight was when I graduated from highschool (135), this was important because he wanted to know approximately what my natural weight was. I also didn't do anything close to athletic in HS so this shows that I'm a naturally skinny person so it's easier for me to lose weight and get skinny. At that time I weighed 165 so we decided to shoot for 150 and he put me on a diet and within 4 months I was 146. All this time my FTP was increasing as well.

Now my 'off' season weight is around 150 my 'in' season weight is 143-145. The only thing I've sacrificed at this weight is that I suffer in the wind. I get blown around a lot where heavier riders seem to just ride through it. However when the road turns up I'm able to ride away from most guys.

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Old 06-29-10, 08:02 AM
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my wieght when i graduated HS (94) was about 190. i lived between 190 and 210 from HS though about 26ish (8 years ago), then started riding and changed up my diet (in retrospect i was starving myself cuz i was depressed over a breakup), and got to a low of about 147. i was really really skinny.

i started doing some strength training and fosucing on sustainable nutrition and weight management and found that my ideal manageable weight tends to be in the low 160s, i'm 164 as of this week. i am gonna put a little effort into trying to get below 160 for mt evans at the end of July, but not at the expense of my sanity or power.
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Old 06-29-10, 08:28 AM
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Originally Posted by brianappleby View Post
No. The answer is not "lose weight". The answer is "train harder" or better at least. The OP just said that he can't afford to lose 14 lbs.
Ok. I never said a certain amount, I just said some. 5'10" and 165# doesn't sound right for a roadie, but maybe that's just me. Everyone's different, but at that same height I weighed 165 about a year ago, now sitting at 150# with better power. Back then I thought I was ok but looking bad I had some extra baggage.

But he could probably lose 5 or 10, and gain some FTP.
Like I said, start losing some weight.. for a start at least. It's really cheap too. Not saying that's all he needs to do, but it's a part..
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Old 06-29-10, 08:47 AM
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i mean i hate to go there but lance is 5'10 and was 160-165 all through his reign
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Old 06-29-10, 08:49 AM
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then all you have to do is climb at 450 watts. problem solved.
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