10 pounds of weight lost adds 1mph to your speed?

[fenlandpsychocyclist]

Maybe loosing 10 pounds has more effect on body size ... and hence a reduction in wind drag?

If i cycle my "usual" 30 miler on my 8.5kg trek i'll average 17mph.
If i do the same on my 13.8kg coyote avocet i'll average 14mph.

Now i'm in a very flat part of the country, so you can't say the extra 5kgs on the latter has dragged me
down 3mph.
Maybe its the wind-drag from lights, mudguards, dslr case on the handlebars, big old hi-vis coat??

 

[Sittingduck]

Weight of the bike or luggage is a different thing to weight of a person. Dropping 5kg of dead weight from the bike or a load of shopping is going to make more difference to dropping 5kg body weight, off of the rider, I think...?

Regarding the above, I would think that aerodynamics plays a considerable factor. Although this is going to be more noticable at higher speeds (20mph+), I would think...? Nevertheless it will still play quite a big part in your loss of avg speed.

 

[Nearly there]

Don't assume the thinnest guy on a bike is the fittest

 

[black'n'yellow]

Only when there is a material force (gravity) acting against you.

that would be 'all the time' then - as you are always battling either gravity (going up) and/or friction (decelleration) on the flat. Either way, improving your power/weight ratio (either by improving your power output, or reducing your weight, or both) will increase your performance.

 

[400bhp]

No, one is gravity, one is friction.

 

[black'n'yellow]

No, one is gravity, one is friction.

both of which need to be overcome in order to maintain forward motion, no?

 

[400bhp]

both of which need to be overcome in order to maintain forward motion, no?

I said:

Only when there is a material force (gravity) acting against you.

Friction + wind resistance > gravity on the flat, no?

 

[black'n'yellow]

not sure what you are arguing - my only point is that regardless of whether you are on the flat or on an incline, a bicycle must be constantly accelerated (ie pedalled), otherwise it will come to a stop. In that sense, a given effort (ie power output) will accelerate a lighter object (ie bike + rider) easier than a heavier one.

 

[400bhp]

I'm not arguing, I'm talking on an internet forum.

My point was that the overriding force on the hills is gravity, hence weight (bike plus cyclist) is generally the overriding factor. Whereas, on the flat, my understanding is that wind resistance and friction are more of an issue.

That's correct isn't it? It's a long time since I studied physics.

 

[black'n'yellow]

Decelleration is the net outcome in all of those cases. That is the only 'force' (if you want to call it that) which needs to be overcome..

 

[User6179]

 

[ColinJ]

As has been said above - weight mainly affects climbing speed.

If you really want to play with the numbers, it is is quite instructive to spend an hour or two plugging different values into this online cycling calculator!

 

[MattHB]

As has been said above - weight mainly affects climbing speed.
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And acceleration on the flat

 

[potsy]

As has been said above - weight mainly affects climbing speed.

So how come you are so fast..........downhill?

 

[ColinJ]

And acceleration on the flat

So how come you are so fast..........downhill?

"Mainly ..."

Okay, yes, heavy objects are harder to accelerate and decelerate than lighter ones, but they don't take much more energy to keep rolling atop a bicycle. They are also harder to lug up hills, but they are better at plunging downhill than lighter ones, in the presence of an atmosphere!