body weight & bike performance correlation
BY: duder5189 on 2012-06-14 11:21 AM

So in my head, if one were to drop 10 pounds overnight, he or she should automatically pick up some speed on the bike.  You've simply got less mass to push around.  This would seem to be especially true on inclines.  I guess another way to look at it is, put on a 10-pound backpack or giant water bottle and you're going to slow down a certain amount.

First...is this true?  Second...anyone seen studies, articles or the actual science behind it?  Is there any way we can say...if you weigh 200 pounds and drop 10 you will almost automatically gain X mph on the bike?  I'm sure there are other mitigating factors that would not make that type of statement totally reliable, but I'm sure there's been some thought put into this and some conclusions drawn.  I'm wondering that they are.  Thanks.

RE: body weight & bike performance correlation
BY: ThomasGerlach ProTri on 2012-06-14 11:25 AM

I think you are really going to be disappointed by the amount of speed you get with 10 pound reduction.  I will dig around as I have good comparison, but really the sport is all about how many watts you can put out.

Edited by ThomasGerlach ProTri 2012-06-14 11:49 AM

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RE: body weight & bike performance correlation
BY: JohnnyKay on 2012-06-14 11:26 AM

On steep hills, this would be very true and fairly easy to estimate.  On flat ground, less so on both counts.  Weight plays a very small role in the speed of a bike on level ground.  Aerodynamics play a large role.  10 pounds could mean marginally less ar resistance and perhaps an ability to hold a more aero body position but the lower weight, by itself, wouldn't change the bike speed much.
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RE: body weight & bike performance correlation
BY: the bear on 2012-06-14 11:31 AM

There are calculators out ther (e.g., analytic cycling) that will do what you ask but the bottom lone is that weight (rider, bike, rotational) is nearly irrelevant in triathlon. Certainly aerodynamics trump weight by a significant margin. If you're a really big guy then losing frontal area will make you faster.
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RE: body weight & bike performance correlation
BY: spudone on 2012-06-14 11:40 AM

Running, on the other hand... might get a noticeable benefit.

RE: body weight & bike performance correlation
BY: duder5189 on 2012-06-14 11:41 AM

No, I wouldn't be disappointed at all!  If there's nothing to gain, then I don't need to lose the weight!

RE: body weight & bike performance correlation
BY: SevenZulu on 2012-06-14 11:44 AM

Running will likely see some improvement more so than cycling.  However, if you can crank out the same watts at 135 pounds vs. 190 pounds, then I suspect that you'll notice a difference.

RE: body weight & bike performance correlation
BY: duder5189 on 2012-06-14 11:45 AM

Considering all this, it's fairly amazing how much people will pay to shed like 6oz. off their bike, no?  I know for a fact people literally count ounces when picking out components for their bikes...is that all just a big waste of time and money?  Or is bike weight more relevant than body weight?

RE: body weight & bike performance correlation
BY: gsmacleod on 2012-06-14 11:47 AM



For triathlon, yes. If you are doing a number of uphill TT's, then it might be worth it.

Shane
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RE: body weight & bike performance correlation
BY: TriBoilermaker on 2012-06-14 11:48 AM

Aero is the key on the bike not weight.
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RE: body weight & bike performance correlation
BY: TriBoilermaker on 2012-06-14 11:49 AM

I should have added, for triathlons. As others have stated if you are doing other types of riding then weight can be a bigger factor.
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Triathlons are a test you get to take and grade for yourself
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RE: body weight & bike performance correlation
BY: buck1400 on 2012-06-14 11:56 AM

Duct tape two bags of sugar to your bike, ride one of your typical training rides and let us know the reuslts!  Don't have a clue what you might find out, but I am almost thinking about trying myself!

On a related subject, my wife and I were discussing my weight loss (45#) and its effect on some lower back problems I had been having.  She didn't think it really would make much difference.  I said, well, think about if you had to carry around a 40# bag of softener salt all day.  She then decided the weight loss prolly made a big difference.

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RE: body weight & bike performance correlation
BY: MUL98 on 2012-06-14 12:12 PM



Doesn't this depend on the type of course you're preparing for? If you are racing a hilly course like IM Wisconsin or LP, I think weight reduction helps quite a bit. At least that's been my admittedly unscientific experience.

RE: body weight & bike performance correlation
BY: gsmacleod on 2012-06-14 12:24 PM



That's actually the key to this; it seems sensible that a heavy bike would be a much larger penalty than it actually is; if you crunch the numbers, the time losses while climbing are mostly recovered when descending and the end result is very close to a wash.

shane
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RE: body weight & bike performance correlation
BY: Goosedog on 2012-06-14 12:31 PM

Race results are great, but what you really need to impress your friends is a staggering W/kg.  So, lose the weight.

 

RE: body weight & bike performance correlation
BY: JohnnyKay on 2012-06-14 12:39 PM

You will be slower, but not primarily due to the weight.  Those two bags of sugar are like to wreck havoc on your aerodynamics.  If you filled your water bottles (that you would carry normally) with something like coins, instead of water, that might make a good test.  Let us know how it goes. 

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RE: body weight & bike performance correlation
BY: wgraves7582 on 2012-06-14 1:00 PM

I agree with this and the mostly is probably covered in length of climb vs length of descent.  I ride with a buddy and he is 40+lbs heavier than me - I smoke him on the climbs and if long enough he would never catch me on the descent but if it is a short climb or we are chatting and climbing - he thoroughly smokes me on the descent and I catch him on the flats/next climb.

I think some of it is bike type as well.  Some frames are stiffer and handle power transfer better instead of losing it to frame flexing (I hope this is correct but I believe I have read that somewhere) but then again that is all dependent on length of climb as well and your original power output.

I ride a lot and can keep up on my steel 12 speed with the carbon guys but that is all engine not bike.  Would I be a lot faster on carbon or Ti?  I don't know, someone buy me one and I will let you know

RE: body weight & bike performance correlation
BY: MUL98 on 2012-06-14 1:06 PM



Interesting. I haven't seen the data, but if this is true, I question why pro cyclists focus on eliminating every ounce of fat. Particularly good climbers. I always assumed it was to create a positive weight to power ratio in order to climb faster/better. (Actually I'm pretty sure I read articles about this)

It appears you are saying that regardless of weight, descending allows for sufficent recovery. Why the obsession with weight then? Or does the nature of triathlon (as opposed to cycling) change this in some way?

I will say I feel like a better climber when I'm lean, and my times seem to reflect that. Of course that is - as stated above - not very scientific. It may just be that leanness is a natural side effect of getting more fit and the fitness is what allows for better climbing. Or maybe it's just the pacebo effect.

RE: body weight & bike performance correlation
BY: shepherdsflock on 2012-06-14 1:12 PM

I commute back and forth to work on my road bike with about 10 lbs worth of gear (when you include my work clothes, shower stuff, lunch, bike lock, panniers etc.). One Saturday I decided to strip my bike and ride my normal route to work to see how much difference it made. It made about .4 mph difference in average speed. I will say, however, that it climbed hills and accelerated much faster. Though .4 mph IS a difference, it's not a huge difference; and I attribute much of that small difference to the aerodynamic improvement of not having my panniers and stuff hanging out in the wind.