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How much does weight influence performance?


xak1
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I have seen many debates on the effect of bicycle weight on performance.  But just how much can/should you spend on this issue?  I found a nice calculator attempting to model power, force and efficiency at http://rjs.org/coeff.html.  Although these types of models are highly theoretical, it does help to give broad indications.  There are so many variables and any mix of these will give you a different result.  I used this model to try and isolate bicycle weight and the effect of this on calories used, with all other factors being kept the same.  I modelled three different gradients.  The first, an off-road scenario, 13km uphill, climbing 600m (all other factors were kept the same, e.g. tyre type, clothing type, no wind, surface type, etc).  The second a perfectly flat scenario and the third, the reverse of the uphill.  As expected, weight has the biggest impact on the uphill.  The model indicated that for the same amount of work, for every 100g dropped on the bicycle, one will gain about 1-1.25 minutes of time over the 13km (around 1.5-2%).  There is, however, a bit of an exponential relationship, with improvements becoming less, the lower you go in weight.  Obviously, this is simplistic, as many other factors have an impact, and should there for example be strong wind, the weight benefit is wiped by the effect of wind.  Other issues are surface, as these can negate the effect of weight, etc.  My suspision is that the real effect is much less, where all factors come together.  What the model also shows is that on a flat there is just about no benefit - 0.08% for every 100g dropped.  Similar results on the downhill. 

Would be interested to hear views on this, and where people think the optimum point is if cost and benefit is taken into consideration.  As an example, I modelled a high-end full suspension carbon frame bike, coming in at about 11.8kg standard.  Swopping out parts for specialist light stuff, it looks like you get to a point of around 11kg where the cost benefit curve  shows an optimum.
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On a 13km climb iIt does not make a difference if you take the 100g off the rider or off the bike. At some point it becomes almost impossible to take mass off either the bike or the rider. Engineering wise I think the lightest bikes still strong enough to race is between 3 kg to 4 kg.  Losing body mass is also restricted - I dont think jou can go below 5% fat without degrading performance.

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.  Losing body mass is also restricted - I dont think jou can go below 5% fat without degrading performance.

hmmm LA @ 4%??? Wonder how he kept to that, and then he still performed?
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Im dont know very much about phisiology, 4% may be the absolute minimum then (perhaps with the right doctors Wink

 
Christie2007-08-29 03:33:01
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On a 13km climb iIt does not make a difference if you take the 100g off the rider or off the bike. At some point it becomes almost impossible to take mass off either the bike or the rider. Engineering wise I think the lightest bikes still strong enough to race is between 3 kg to 4 kg.  Losing body mass is also restricted - I dont think jou can go below 5% fat without degrading performance.

 

Just a bit of useless information: the recomended body fat % in around 6.5-7% for males and slightly higer for the Fems, however top athletes have been known to got well below this (Note not a healthy thing), this does not necesarily mean you will lose performance over the short term, but to keep at that body fat of below 6% for a longer period will cause performance loss and health problems, these concerns can lead to hospitalisation and even coma. (Previous exepriences have taught me this)

 

when Lance was below 5% , he was only in that "ZONE" for a short period ie not the whole tour. He would start the tour above 7% and after the tour would most certainly be back above 7%

 

 
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Its rather the rider's weight... you won't see a fatboy at the front of a raceBig%20smile

 

I have seen and felt the wrath of Fatty plenty of times, usually on flat or rolling courses....OuchDead

 

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Its rather the rider's weight... you won't see a fatboy at the front of a raceBig%20smile



I have seen and felt the wrath of Fatty plenty of times' date=' usually on flat or rolling courses....OuchDead
[/quote']

 

Damn right, the big boys suffer on the hilly courses and probably feel that lighter riders dont play nice with them (true and funny at times), but they love to give payback on flat courses. Nothing worse than a heavyweight on the front in a crosswind.
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Tot op 6% gradient speel aerodinamika 'n groter rol as gewig, maar daarna begin gewig al hoe groter rol speel (obviously). Dis ook nie net die gewig nie, maar ook waar dit verloor word. As jy bv 1kg op die wiele verloor, gaan dit jou baie meer baat as om 1kg op die raam te verloor. Die wiele beweeg en die raam is staties relatief tot alle dele op die fiets. Jy het baie minder energie nodig om bv 'n Zipp 202 (1050g) aan die draai te kry en aan die draai te hou as 'n Mavic Open Pro met 32 speke (1900g). Op 'n 13km klinm gaan jy definitief die verskil agterkom en in die tye sien.

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In the original example.. (assuming a smooth surface though)... 600m ascent, assume VAM of 1200m/h for a moderate athlete (meBig%20smile). Then the 13km is done in 30 minutes. If there is a minute loss for every extra 100g then I will be 10 minutes slower on a bike that is 1kg heavier - impossible.

Maybe 1 minute for evry kg?
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Tot op 6% gradient speel aerodinamika 'n groter rol as gewig' date=' maar daarna begin gewig al hoe groter rol speel (obviously). Dis ook nie net die gewig nie, maar ook waar dit verloor word. As jy bv 1kg op die wiele verloor, gaan dit jou baie meer baat as om 1kg op die raam te verloor. Die wiele beweeg en die raam is staties relatief tot alle dele op die fiets. Jy het baie minder energie nodig om bv 'n Zipp 202 (1050g) aan die draai te kry en aan die draai te hou as 'n Mavic Open Pro met 32 speke (1900g). Op 'n 13km klinm gaan jy definitief die verskil agterkom en in die tye sien.[/quote']

 

That is true for an top elite athlete, capable of VAM 1800m/h.... at 6% his speed is 30km/h and aerodynamics are starting to come into play.

 

For decent Vets, A group, B, C, D etc the speed reduces quite dramatically so even a 'shallow' hill will be a contest of weight rather than aerodynamics.
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Wat? S? jy ons Vets is stadig?

Die bronne wat ek gelees het, het 3 kategorie? getoets: Elite, gemiddeld, en ondergemiddeld en vir al drie was dit dieselfde resultate - aero wen tot by 6% en dan begin gewig 'n rol speel. Ek sal weer die bron gaan soek en seker maak... 
sias2007-08-29 06:48:06
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I lost 9kg's and can feel the difference on flat and hills!!!Smile

 

I would rather be a less heavy(climber) cyclist than a heavy(sprinter). In CPT there is so little flat races so not worth to be a pure sprinter.
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I lost 9kg's and can feel the difference on flat and hills!!!Smile

 

I would rather be a less heavy(climber) cyclist than a heavy(sprinter). In CPT there is so little flat races so not worth to be a pure sprinter.

 

To lose that much weight I'd have to have a testicle removed. Hey, maybe the saddle would be more comfortable after that too!
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