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If weight makes such a big different on the hills(19 posts)

If weight makes such a big different on the hillsKristin
May 19, 2003 11:03 AM
Then why don't the women blow away all the men on all climbs?
Power-to-weight ratioPseuZQ
May 19, 2003 11:13 AM
Sometimes the guys are heavier, but they're also usually stronger, or at least strong enough to compensate for the extra weight. At least that's the theory I have for being smoked by really big dudes....
Some of them do...Fez
May 19, 2003 11:13 AM
But the idea behind losing weight is the dead weight... fat, excess weight on bike, upper body bulk that does not help climbing.

I think the pro men have a little power advantage over the pro women that far overcomes the excess weight the pro men carry.
It's the Power/Weight ratio that counts.MR_GRUMPY
May 19, 2003 11:15 AM
If you have two riders. One of them weighs 100 pounds and can put out 200 watts on a climb. The other weighs 200 pounds, but can put out 300 watts. The lighter rider has a higher power to weight ratio, and will kill the other rider.
There are other factors, but power is the #1
True, and on the flats, the 200lb/300 watt rider will be pullingrwbadley
May 19, 2003 11:47 AM
the 100lb/200 watt rider as the extra weight/wind resistance will not be as much a factor.
Okay, now this is the part that dazzles meKristin
May 19, 2003 11:54 AM
I don't get how that works. I get dropped on the hills all the time, yet when on flats I can hang on no trouble. I might even take a turn out front. I can understand why I go faster on flats than on hills, but I don't understand why people who are fast climbers seem to slow down on flats. Technically, I shouldn't be able to hang at any given point in the ride--well, currently, I can't--but I can do something closer to hanging on the flats.
Okay, now this is the part that dazzles mefrankamo
May 19, 2003 12:12 PM
On the flats, what you're working against is wind resistance. There's not much of difference between a large rider and a smaller one when it comes to the drag that they create. So the climbers have roughly the same amount of resistance, but less power to work against it.
Put another way...vindicator
May 19, 2003 1:34 PM
It's all a matter of how much power you can generate vs. what forces are slowing you down.

Up a hill, there is some wind resistance but mostly it's your weight that's working against you.

On a flat, there is some drag from your weight but mostly it's wind resistance that's working against you.

So, take two riders. A weighs 125 pounds and can put out 200 watts. B weighs 200 pounds and can put out 300 watts.

Up a given hill, based on weight, steepness, and wind resistance, the forces working against A equal 130 "pounds" of resistance, while those working against heavier B equal 205 "pounds" of resistance.

Their power to resistance ratios are thus 1.538 for A and 1.463 for B. A will outclimb B.

Yet, on the flats, weight becomes so much less of a resistance force, and wind resistance is barely higher for the heavier rider. Of course wind resistance is higher because they're going faster. So let's call A's resistance 50 "pounds" and B's 60 "pounds". Here, the power to resistance ratios are 4 for A and 5 for B, so B will handily outsprint A.

Think of A as Fredy Gonzalez and B as Mario Cippolini.
Okay, now this is the part that dazzles meThe Human G-Nome
May 19, 2003 1:49 PM
well, all groups are different, but in mine the riders will always purposely slow down for the flats. in the Bay Area we have so many climbs and so many hills that the flats are just a place to warm up, catch your breath and rest your heart rate a little before the next big climb. in this way, the bigger guys are almost always at a disadvantage. we have up to 60 people on our ride and the pace is always dictated by the smaller guys. also, you can draft much more effectively on the flats going 25mph then you can on the climbs going 10mph. better still for smaller riders, big riders tend to want to pull more on the flats and spend a little time out front which makes it even easier for the goats to grab a wheel and rest up even more.
And the big guy...CHRoadie
May 19, 2003 2:37 PM
...will absolutely leave the little guy in the dust on a descent.
This is what I don't understand.JonnyHu
May 19, 2003 2:52 PM
I know from real-life experience that big guys win on descents, but why? Newton showed us that if you drop a marble and a basketball from the same height, assuming minimal differences in air resistance, that they hit the ground at the same time. Since air resistance is not a differentiating factor on descents based on rider size (and if anything I guess the smaller rider has the advantage), why do the big guys win? Obviously "power to weight" isn't the answer here because again the smaller rider, if he has an advantage on the ascents, still has the advantage on the descent. Or are descents simply exaggerating the affects that account for the advantage of the big guys (guys with more power) on the flats? I'm getting very confused....
roll two objects down a hillcollinsc
May 19, 2003 4:09 PM
the heavier one accelerates faster. F = ma still applies and the bigger the m the bigger the F.

top speed (coasting) should be very nearly the same, but the big guy will get there a lot faster.
air resistance IS the differentiating factor, Physics for Poets:KSC
May 19, 2003 5:44 PM
F=ma is only a partial explanation. Air resistance is, simplistically, a function of the cross-sectional area and the speed of the object. Falling objects like to reach terminal velocity: a point when the force resulting from the air resistance is equal the force due to gravity and therefore acceleration equals 0. Terminal velocity of the more massive object is higher than that of the lighter one because more air resistance (which ramps up as you go faster and faster down the hill) is required to equal the force due gravity.

Of course if you're like me, your speed downhill is more a function of how poorly your brakes work than how much you weigh.
Hmmm. Thanks.Kristin
May 19, 2003 11:49 AM
Of course I have both working against me at the moment. :)
Riding postion and muscle groups.Ian
May 19, 2003 1:27 PM
Some people are more efficient in one postion or another. I am a big guy, 220lbs and 5'11". I do not have the prototypical riders build. But, while I hang with many guys on the flats that weigh 75lbs less than I do, I also hang and sometimes pass them on the climbs. Once I get into an upright posture and start to pull with my hamstrings as much as I push with my quads, I become a much stronger rider. I suppose I should attempt to adopt use of those muscle groups all the time, but when in the drops, it just does not feel as natural as it does when sitting upright and climbing a hill.

Ian
you're luckyThe Human G-Nome
May 19, 2003 1:53 PM
it's a rare rider who weighs on the plus side of 200 but still feels comfortable and in command on the climbs. i don't know if you're doing this to lose weight, but if you are you're going to be one hell of a goat once the wait comes off. there's a guy in my club who's lost almost 40 pounds since December and increased his speed on climbs by an average of 3-4mph. you're going to be unstopable!
awesome...funknuggets
May 19, 2003 2:45 PM
As a man of shrinking waistline... I want to say a few things quickly here, losing weight does not necesarily mean you will suddenly become a much better climber, although the less weight can't hurt. When I rode A-LOT back in college (some 10 years ago), I was racing to upgrade to cat 2. I weighed about 156. After college, I lost interest for a while and got caught up in life stuff...house, wife, kid...etc. And just got back on the bike two years ago after a 7 year hiatus. In my off the bike period (call it the dark ages), I took a stint at body building and beefed up to 192. When I hopped on the bike, I was a turd. I rode last year with marginal results... went down to 183, and this year am down to 172... but despite miles and miles and a fantastic base and much more structured training schedule... I cannot lose any more weight. However, I am a MUCH stronger climber than I was at 156.

So, what is my point? Structured training and mileage and effort will do help increase your strength to weight ratio by eliminating mass and increasing power, but do not discount the power of training to increase your proficiency of pedal stroke, breathing technique and positioning.

Yes, there are specific "physics" advantages or disadvantages to weight. However, you give me two riders with the exact same base, training, equipment and wattage output... EXCEPT that one is 20 lbs heavier. However, the heavier guy is more educated and seasoned as to the other technical aspects of climbing... I would put my money on the 'fat' guy every time.

So, my basic point is... just because someone is bigger or smaller, does not immediately directly correlate into climbing advantages or disadvantages. Often bike skills, positioning, equipment, and strategy play a far more important role in who gets to the top first.

so sayeth the funk
ExperienceIan
May 19, 2003 5:35 PM
Yes, you are very correct that experience plays a big part in bike riding as a whole. I rode Six Gap (a century in GA with 10,700 feet of climbing) 3 years ago, and finished. Then last year when I went again, I trained all summer, climbing, climbing, climbing as much as I could. That summer really got me in touch with my body; how I felt when I climbed, how I felt at 40 miles, 60 miles, when I could stand, sit, how to pace myself, etc. Although my time was not much better last year, I felt much better and was much more comfortable and controled on the bike. I look forward to doing it again this year and seeing how I feel.

Ian
A little late to join this posting but...KeeponTrekkin
May 20, 2003 6:07 AM
A few misunderstandings have been posted.

Those that are correct illustrate that the differences in any situation (assuming equal technique) relate to the energy supplied (watts of power) vs. the energy required to do the task (e.g. climb a hill at a certain rate or achieve a certain speed on the flats).

The energy required to climb a hill is directly proportional to mass and therefore, weight. A heavy rider needs energy output directly proportional to the weight difference from a lighter rider. The examples cited are illustrative.

Speed on the flats, as others have stated, is primarily a function of energy (power) and wind resistance.

Wind resistance is related to your cross sectional area. Weight is related to the volume of your body. Being a volume and a cubic function, (e.g. l x w x h), weight rises faster than frontal area (w x h). Power tends to rise with body size but I think in the flats, technique and conditioning are greater factors than simple physics and generalizations.

Going downhill is another matter. Power and energy are proportional to weight and the force to be overcome is wind resistance. Power of all coasters is provided by the force of gravity. The power of a heavy coaster is proportionately greater than that of a light coaster (due to greater mass). The wind resistance of both increases by the SQUARE of the velocity. Therefore, it is highly likely that the heavier rider will reach equilibrium (power provided = power required) at a higher velocity than the lighter rider even though the heavier rider has a larger frontal area.