Scientific question?

[PrinceVlad]

Hi Guys

 

I have a question for the scientific minded folk amongst us.

 

I currently weigh in at a fairly lightweight 122kg's. You can imagine climbs to be a nightmare.

 

In the estate I ride in I average about 20km/h. On the open road I think it would be more, but for purposes of the question lets work at an average of 20km/h.

 

Now lets say I lose the extra pounds and go down to about 90kg's, what would the average speed (or speed in general) increase with accepting that the power output stays the same.

 

Answers please...for interest sake....and maybe a bit of motivation.

 

Cheers

[Stretch]

its irrelevant as speed gain on uphill > speed loss on downhill.......and i dont feel like working it out

[DIPSLICK]

i am lower grade maths/science, but i can tell you it will be a lot

[jaxtun]

i am lower grade maths/science, but i can tell you it will be a lot

lower grade?? don't be so hard on yourself Dipsy

[DIPSLICK]

lower grade?? don't be so hard on yourself Dipsy

aunty i got matric on lower grade with a warning not to come back, i think they passed me just to get rid of me STRUE STORY

[F111]

The basic formula is P = MV

you will go faster with the same watts in perfect conditions.

 

P M V

2440 122KG 20K/h

2440 90Kg 27K/h

 

Here is a good page where you can find all the answers.

http://www.cyclingpowerlab.com/PowerSpeedScenarios.aspx

Edited November 27, 2013 by F111

[slowashell]

I really have no scientific knowledge, but maybe a bit of common sense.

 

Loosing weight can only benefit you, health wise definitely. Speed will improve, based on you having less kilos to drag over every km, plus I am sure you will find it easier climbing hills.

 

Bottom line, no matter what your weight is, there is no substitute for training. Set yourself small, attainable goals, either based on your weight, or your average speed and stick to them.

 

Now, all I have to do is follow my own advice.

[@ndy]

Slight hi jack alert!

 

I have often thought about the weight factor but from a different angle. Because my bike and I weigh close to 100 kg it is easy to consider losing 1 kg as 1% of my all up weight. I would like to know how much a loss of 1 kg makes towards lowering climbing effort. I assume this would be a relatively easy calculation if one can take out some variables like surface and wind resistance but I'm not sure how to calculate it.

 

I have lost nearly 10 kgs in the last two years and it has made a big difference for sure. For motivation I try and tell myself that 1 kg = 1% easier climbing but I know it can't be that simple.

[NotSoBigBen]

its irrelevant as speed gain on uphill > speed loss on downhill.......and i dont feel like working it out

 

I reckon speed gain on uphill is greater and translates to all of the rest of the ride so considering how little time is spent going 'downhill' that overall you will be much faster?

[dracs]

Slight hi jack alert!

 

I have often thought about the weight factor but from a different angle. Because my bike and I weigh close to 100 kg it is easy to consider losing 1 kg as 1% of my all up weight. I would like to know how much a loss of 1 kg makes towards lowering climbing effort. I assume this would be a relatively easy calculation if one can take out some variables like surface and wind resistance but I'm not sure how to calculate it.

 

I have lost nearly 10 kgs in the last two years and it has made a big difference for sure. For motivation I try and tell myself that 1 kg = 1% easier climbing but I know it can't be that simple.

the steaper the hill - the closer to correct your 1% gets.... (as road and air resistance be relatively insignificant) Edited November 27, 2013 by dracs

[Lucky Fish]

http://www.bikeraceinfo.com/tech/weight.html

[Stretch]

I reckon speed gain on uphill is greater and translates to all of the rest of the ride so considering how little time is spent going 'downhill' that overall you will be much faster?

 

yip - if you can climb you will be faster

[Memnon]

It's a slow day so this question forced me to try to remember those long forgotten days of physics. If on the uphills we assume that wind resistance etc has no impact (i.e. very steep uphills) and that power remains the same then an inverse relation to speed and mass would apply: halve your mass = double your speed.

 

On the flats though, your power is only there to overcome resistance. If you have a super bike then this is mostly wind resistance (drag) - not strictly true but I can't remember all the other complicated bits and pieces. If one uses a sphere to represent a person (also not true but it is the easiest one to calculate the drag coefficient for) and then adjusts its diameter to represent a change in mass then (if I got the excel part right) a change in mass from 120 to 90kg would allow an increase in speed from 20 to 22km/h.

 

The 2 things i take from this: 1.) I am having a very SLOW day, 2.) if you lose weight then make sure you ride BIG hills to show off to your mates how much faster you have become.

[porqui]

Simple exercise to work out gain.

 

Take rucksack

Fill with mass equivalent to weight you want to lose

Now put that on back and go cycle usual course.

Note difference in average speed.

 

Add difference to present average speed and ........voila!

Solved

 

 

 

Flame suite on!

[Robrider]

The basic formula is P = MV

you will go faster with the same watts in perfect conditions.

 

P M V

2440 122KG 20K/h

2440 90Kg 27K/h

 

 

 

 

Er... No.

That is wrong on so many levels.

[90 Inch]

You don't need maths for this, you need some common sense.

 

No scientist can answer that question without knowing all the variables, on a flat course your weight has little effect especially at 20Km/h, but loosing weight will improve your climbing speed dramatically and almost proportionally with the weight loss, if this was the only change. The climbs are where your average speed would have been dragged down the most.

 

But the process of loosing the 32Kg would increase your fitness level significantly as well, so your speed gain would benefit from this as well.