Lightening the load

[Manc33]

You know how they say "a pound off the frame is worth two off the wheels"... what about your own body fat?

Is there some ratio to it or is "1Lb off the frame 1Lb off your body"

I used to ride a bike that was about 23lb and I weighed 180lb. Total weight: 202lb.

Now I am on a bike thats about 35lb but I only weigh about 160lb. Total weight: 195lb.

I am only 7lb lighter now on the heavier bike than I was heavier on the lighter bike (sounds like nonsense but might be right) but on hill climbs is there any more advantage to the bike (disregarding wheels) being light as opposed to you?

This is without the complication that if you're thinner you're probably fitter and thus more capable anyway so will find it easier.

[NATURAL ANKLING]

Hi,
Spent the last 3 years riding a bike that is 40 - 50 Ibs.

I cant wait to get on my road bike even if its 21 Ibs.
I am 30 Ibs lighter than I used to be at my heaviest.

I would say that I am stronger and fitter.
I started out five years ago after a rest of 10 years off bike.
And first mini excursion was all up at 275 Ibs, bike at 75 Ibs on off road, when I got home I realised well on the way home is that the rear tyre only had about 30 - 40 psi, I didn't even put air in it

For comfort, then weight on bike is better, more comfort so better performance.

But how would you test unless your fitness was similar at different weights
Perception is a very powerful thing which just might tip the balance.

[Manc33]

Thats true, there's a hill I used to get up in one go all the time I tried the other night and had to stop for a breather twice.

Once you're biking every day I think overcoming a bike thats got 10lb more weight isn't really that big of a deal.

Plus you go faster downhill.

[seph]

surely the saying is ''an ounce off the wheels is worth a pound off the frame'' highlighting the effect that less rotating mass helps a bike to accelerate more easily..

[gaz]

So loosing an ounce off your feet is better than loosing a pound off your tummy . I shall give up my diet immediately and cut my toe-nails instead .

[seph]

well If you can lose an ounce off your toenails I think a trim maybe overdue..

I hadnt thought about in relation to pedalling, but yes, I suppose saving a few grams off shoes would save more on the effort required to accelerate compared to saving the same mass on, say, a jacket.
Not sure how you'd test it though

[Samuel D]

While rotating mass does have a greater effect than non-rotating mass on acceleration, it only takes a small experiment to see that the difference is usually not worth worrying about.

That experiment is this: hold the bicycle off the ground and spin the front wheel with your hand. If you have a speedometer, adjust your effort to get the wheel spinning (from stopped) at about 30 km/h. It doesn’t take much effort, does it? A single push with one arm is enough to do the job in a fraction of a second.

This is the additional energy needed to accelerate the rotating mass of your front wheel to 30 km/h. The rear wheel is similar. When your large leg muscles are working hard for several seconds, that additional work is usually negligible.

Having said that, it is surprising how small differences can nonetheless be felt or otherwise noticed, especially if you’re riding with someone else. If you tend to be dropped by a meter or two after each red light, those metres are very noticeable. They are nothing compared to the vastly larger energy-expenditure differences between almost any two riders over many kilometres, but they may be more visible.

As for weight on the bicycle versus your body, I don’t think it matters, there being no way to transfer weight between the two.

[cycleruk]

This is the additional energy needed to accelerate the rotating mass of your front wheel to 30 km/h. The rear wheel is similar. When your large leg muscles are working hard for several seconds, that additional work is usually negligible.

With regard to your rear wheel example you are not just accelerating the wheel, you are accelerating the weight of your body and bike as well.
My special light weight wheels are not just lighter but are stiffer and I think it is also this that makes a difference with acceleration.
Less weight will help with hill climbing of course be it off the bike or off the body.
There used to be a famous racer (can't remember his name ) who liked to remove his bottle off the bike and put it in his back pocket when climbing.
It's all about power to weight ratio. decrease the weight or increase the power.

[[XAP]Bob]

Moving the bottle might help you throw the frame side to side if you are honking, but it might just be to stop it falling out as well...


Mass on wheels rather than frame has an effect on acceleration, but not on steady state motion.
Mass on body should always be reduced

At least when cycling some of the energy you "waste" whilst running by lifting the body can be brought back onto the pedals.

[tykeboy2003]

Plus you go faster downhill.

No you don't, you have more momentum but the acceleration due to gravity is the same whatever your weight.

[Mistik-ka]

Plus you go faster downhill.

No you don't, you have more momentum but the acceleration due to gravity is the same whatever your weight.

However if you slim down you'll experience less wind resistance.

[Manc33]

Don't talk to me about gravity.

[[XAP]Bob]

Plus you go faster downhill.

No you don't, you have more momentum but the acceleration due to gravity is the same whatever your weight.

The force due to gravity is proportional to mass (meaning that the i impeded gravitational acceleration would be the same), but the wind resistance doesn't scale with mass - and if the same resistance acts on a larger mass then it will have less effect...

So a heavier bike/cyclist, with the same aero characteristics, will go faster down a hill

[pwa]

Plus you go faster downhill.

No you don't, you have more momentum but the acceleration due to gravity is the same whatever your weight.

I'm too heavy and have to work hard going uphill, but I do pass lighter riders (including family members) going down the other side. Being lardy does make you faster on descents where you are not using your brakes. Being big must increase wind resistance, but this seems to be more than countered by the effect of increased mass. Even so, I would rather be lighter.

[Mick F]

As for weight on the bicycle versus your body, I don’t think it matters, there being no way to transfer weight between the two.

I don't think it's as simple as that.
Strength has to come into it, plus torque and technique.
Extra weight (within reason!) can have no affect at all. It all depends on how much power/torque/technique/stamina you have.

Also, if the weight is high up versus low down, it can change the dynamics of riding and balancing. Higher up weight is more difficult than lower down weight.

Outright speed is more dependent on air resistance than weight.