Cycling UK Forum

thirdcrank wrote:

Ayesha wrote:....Weight inside you will be advantageous when you lift your bum off the saddle, cus that 500g of water is applying 4900 Newtons on the downward pedal, ...

But you have to lift it all again before the next down stroke.

Thirdcrank is right, carrying weight on the body (rucksack or large proportions) does mean you press down with more weight, but you have to lift it up. This makes each complete stroke much harder for the same effective work.

If you want to see it in action go to a spin class. The lithe spinners find it much easier standing than us "amply proportioned" blokes, but the difference vanishes returning to the saddle. If you want to prove it to yourself use a weighted rucksack and compare sitting to standing.

In response to the OP, you carry water to replace lost fluids. Loss of fluids impairs performance. If it didn't then you could simply sweat fluid on a ride & get lighter. And of course you the total weight is the same inside you, but of course compared to starting weight, you are lighter through the fluid lost in sweat.

Ayesha wrote:

slacker wrote:If anything your total weight is now slightly more. Assuming you drank all the water and didn't spill any on top of the original weight you're now also carrying a bottle's worth of air

True, 1 liter of air is 1.28g....

probably not true, assuming you "expand" due to the water, you will displace air, so there will be a compensating increase in bouyancy

[XAP]Bob wrote:But the bike is now lighter Mick

Mick F wrote:We come onto the age-old argument of suspended vs dead weight.

As I said, it's an argument!

I like a lighter bike, no matter how heavy I am. It seems more lively and quick.
However, physics would say that low down weight is less of a hindrance to efficiency than high up weight because of the swaying motion.

As I said, it's an argument ....

bigfoot wrote:
Thirdcrank is right, carrying weight on the body (rucksack or large proportions) does mean you press down with more weight

Could you explain why?
I'd have thought it is all to do with effort put through abdominal, back & leg muscles than anything to do with actual weight(or mass) and seeing as the extra 'weight' is carried in the stomach for a fair while I'd ascertain that it has no impact on the downward 'force' applied to the pedals.

Mick F wrote:

[XAP]Bob wrote:But the bike is now lighter Mick

Mick F wrote:We come onto the age-old argument of suspended vs dead weight.

As I said, it's an argument!

I like a lighter bike, no matter how heavy I am. It seems more lively and quick.
However, physics would say that low down weight is less of a hindrance to efficiency than high up weight because of the swaying motion.

As I said, it's an argument ....

More of an amused discussion. Arguement implies fractured tempers.

Tonyf33 wrote:

bigfoot wrote:
Thirdcrank is right, carrying weight on the body (rucksack or large proportions) does mean you press down with more weight

Could you explain why?
I'd have thought it is all to do with effort put through abdominal, back & leg muscles than anything to do with actual weight(or mass) and seeing as the extra 'weight' is carried in the stomach for a fair while I'd ascertain that it has no impact on the downward 'force' applied to the pedals.

A couple of reasons I can think of
-You are supporting your full weight in tension on the muscle, as well as pushing down
-You don't move perfectly when pedalling, there is significant work "bobbing up and down"

Have a look at

http://www.cptips.com/climb.htm

If the weight wasn't lifted up again after each pedal stroke, to "benefit" from the extra weight in the way implied by ayesha, the rider's body would have to drop an additional approx 170mm with every pedal stoke. We've discussed this before in a different context and I'm pretty sure the conclusion* was that standing on the pedals allowed a rider to get a short-term extra output, especially when over-geared (eg when on the point of stalling in lowest gear on a steep hill) at the expense of tiring quickly.

* If it wasn't the conclusion, it will have been what I posted and it convinced me.

Back to the OP, if I drink a bottle of water, my kidneys typically start working much better. That usually results in a loss of gross weight.

Now don't spoil it all by going back to the OP! The OP is watching closely and is highly entertained in exactly the way he'd hoped!!

OP

The best way to keep liquid weights down is to...

1/ Don't take a bottle and get drinks at shops and cafes.
2/ Go to the lavvy immediately after having a drink at the cafe.
3/ Be hard and accept a bit of dehydration for a few hours.

mrsbloomsburybarton wrote:Now don't spoil it all by going back to the OP! The OP is watching closely and is highly entertained in exactly the way he'd hoped!!

OP

I feel used

What would you prefer?

180 lb on the pedal of a 20lb bike, or
179 lb on the pedal of a 21lb bike?

Ayesha wrote:What would you prefer?

180 lb on the pedal of a 20lb bike, or
179 lb on the pedal of a 21lb bike?

i doubt i'd be able to tell the difference. other than in either case, i would wonder where half my bike went

160lb on the pedal of a 19lb bike.

[XAP]Bob wrote:More of an amused discussion. Arguement implies fractured tempers.

Is this the Five Minute Argument, or the Full Half Hour?

mrsbloomsburybarton wrote:That's what I thought. Somebody is trying to convince me I save weight by drinking the water, I think I only do that by sweating it out!!

not until it evaporates from your clothes!