The imprortance of weight-When and how?

Crow92

Something that I've been wondering about for a long time is what is the effect of weight reduction on a bike in terms of performance?

Is there a ratio of losing weight on the bike being comparable to losing body weight. (I'd assume it isn't the same losing 2 kg on the bike and 2kg body fat?)

And finally what components on the bike that'd benefit the most from a reduction in weight.

SWL

Crow92 wrote: »

Something that I've been wondering about for a long time is what is the effect of weight reduction on a bike in terms of performance?

Is there a ratio of losing weight on the bike being comparable to losing body weight. (I'd assume it isn't the same losing 2 kg on the bike and 2kg body fat?)

And finally what components on the bike that'd benefit the most from a reduction in weight.

A reduction in the total sum of a combination of body weight and bike weight makes a difference in my opinion.

It don’t matter which one you sees a reduction performance will increase. In fact I would argue that a reduction in bodyweight or fat is more beneficial that a reduction in bike weight, a lot cheaper too.

The weight of a bike is not that important, the transfer of power through the material of the bike frame and its aerodynamics is more important; both of these areas will see significant developments in the coming years especially with official weight limits.

morana

A reduction in body weight will save you money but a reduction in bike weight will cost you...quite a bit.

I would say the best bits to reduce weight are the wheels. A simple change of tyres and tubes and the correct pressure can have a dramatic impact on performance.

Crow92

morana wrote: »

A reduction in body weight will save you money but a reduction in bike weight will cost you...quite a bit.

I would say the best bits to reduce weight are the wheels. A simple change of tyres and tubes and the correct pressure can have a dramatic impact on performance.

Very true, I'm not personally looking to shed weight of myself, only weight abour 63kg or the bike, just wondering on a slightly more scientific way just about weight. Not aerodynamics or rolling resistance. *Edit* But that is a nice diagram lumen

How would a reduction in wheel weight benefit?

Lumen

morana

That seems to be at odds (iirc) with some of the cervelo stuff. They were of the opinion that a gradient of 8% was the tipping point regrading aerodynamics v weight so I would have expected they contribution of Air resistance to be bigger at 8%. Maybe I am not recalling correctly...

Lumen

morana wrote: »

That seems to be at odds (iirc) with some of the cervelo stuff. They were of the opinion that a gradient of 8% was the tipping point regrading aerodynamics v weight so I would have expected they contribution of Air resistance to be bigger at 8%. Maybe I am not recalling correctly...

I'm sure Cervelo's models demonstrate whatever they want them to.

When I ride up an 8% slope the only air resistance I can feel is in my lungs.

ROK ON

Lumen wrote: »

I'm sure Cervelo's models demonstrate whatever they want them to.

When I ride up an 8% slope the only air resistance I can feel is in my lungs.

Lumen,

DO you have any source or similar chart type stuff that inidcates how various weight profiles affect energy needed on differing gradients.

I am over 90kg. Lets say I want to get to 85kg. For a 7% climb, how much less energy is required to go at same speed (or for the same effort how much faster would the lighter cyclist go) cet.par.

Beasty

I worked out using the bike calculator (and it's pretty much borne out by my times), that on the Ardgillan Hill climb (1.8km, 4.5% average slope), that each kg is worth just over 2 seconds, and every 2 watts is worth 1 second on my time (of around 5m 20s), based on a weight of bike + rider of just under 100kg

ROK ON

Beasty wrote: »

I worked out using the bike calculator (and it's pretty much borne out by my times), that on the Ardgillan Hill climb (1.8km, 4.5% average slope), that each kg is worth just over 2 seconds, and every 2 watts is worth 1 second on my time (of around 5m 20s), based on a weight of bike + rider of just under 100kg

Hi.

Thanks Beasty, but I'm looking for some sort of simulation as to what say 10kg would save on a 15km climb averaging 6%.
I find it hard to believe that it would only save me 2secs over 1.8km with a lower gradient.

Lumen

ROK ON wrote: »

DO you have any source or similar chart type stuff that inidcates how various weight profiles affect energy needed on differing gradients.

I am over 90kg. Lets say I want to get to 85kg. For a 7% climb, how much less energy is required to go at same speed (or for the same effort how much faster would the lighter cyclist go) cet.par.

http://bikecalculator.com/wattsMetric.html

12kph @ 7%
= 263W @ 90kg
= 250W @ 85kg (5.6% less weight, 4.9% less power)
= 237W @ 80kg (11.1% less weight, 9.9% less power)
= 224W @ 75kg (16.7% less weight, 14.8% less power)
= 211W @ 70kg (22.2% less weight, 19.7% less power)

It's only a model, but perhaps not far off.

The opposite way of looking at it is that the 80kg cyclist putting out 263W is doing an extra 1.2kph, which would cost the 90kg cyclist almost 20W extra up that 7% hill.

20W can be the difference between holding on and getting dropped, or talking and grunting incoherently.

ROK ON

Lumen wrote: »

http://bikecalculator.com/wattsMetric.html

12kph @ 7%
= 263W @ 90kg
= 250W @ 85kg (5.6% less weight, 4.9% less power)
= 237W @ 80kg (11.1% less weight, 9.9% less power)
= 224W @ 75kg (16.7% less weight, 14.8% less power)
= 211W @ 70kg (22.2% less weight, 19.7% less power)

It's only a model, but perhaps not far off.

The opposite way of looking at it is that the 80kg cyclist putting out 263W is doing an extra 1.2kph, which would cost the 90kg cyclist almost 20W extra up that 7% hill.

20W can be the difference between holding on and getting dropped, or talking and grunting incoherently.

Thanks.

Thats closer to what I am looking for.

I want to be able to climb for 10km (during the summer) at a certain speed. So I am trying to figure out what weight I need to aim for to be in with a shout of doing that all other things being equal (which they are not of course).

Beasty - apologies. I have had a quick fiddle with the bike calc thing. 15km climb @7%.
One rider 85kg and one rider 95kg.

If both were putting out 248watts on the climb there would be a 7 minute differential in their climbing time according to the calc (which is actually close enough to the calc that yo provided).

Diarmuid

ROK ON wrote: »

Hi.

Thanks Beasty, but I'm looking for some sort of simulation as to what say 10kg would save on a 15km climb averaging 6%.
I find it hard to believe that it would only save me 2secs over 1.8km with a lower gradient.

If you knocked out 250W average over that 15km 6% slope, you'd be 340sec faster if you went from 90 to 80kgs

Benefit From Less Weight
This Much Less Weight 10 kg
Over This Distance 15000 meters
On Hill of Slope 0.06 Decimal
Faster by 340.05 s
Ahead by 1435.60 m
Frontal Area 0.5 m^2
Coefficient Wind Drag 0.5 Dimensionless
Air Density 1.226 kg/m^3
Weight Rider & Bike 90 kg
Rolling Coefficient 0.004 Dimensionless
Power 250 watts

Source

AstraMonti

Lumen wrote: »

http://bikecalculator.com/wattsMetric.html

12kph @ 7%
= 263W @ 90kg
= 250W @ 85kg (5.6% less weight, 4.9% less power)
= 237W @ 80kg (11.1% less weight, 9.9% less power)
= 224W @ 75kg (16.7% less weight, 14.8% less power)
= 211W @ 70kg (22.2% less weight, 19.7% less power)

It's only a model, but perhaps not far off.

The opposite way of looking at it is that the 80kg cyclist putting out 263W is doing an extra 1.2kph, which would cost the 90kg cyclist almost 20W extra up that 7% hill.

20W can be the difference between holding on and getting dropped, or talking and grunting incoherently.

Explain me something here (you or anyone who can). If you lose 10kilos you will potentially lose some power as well. At which percentage would you start noticing negative effects? Or to rephrase the question, how much weight can you lose without comprising your power output?

Diarmuid

AstraMonti wrote: »

Explain me something here (you or anyone who can). If you lose 10kilos you will potentially lose some power as well. At which percentage would you start noticing negative effects? Or to rephrase the question, how much weight can you lose without comprising your power output?

I doubt there's a rule of thumb on that. It depends on how much "excess" weight you are already carrying.

Lumen

Diarmuid wrote: »

I doubt there's a rule of thumb on that. It depends on how much "excess" weight you are already carrying.

Stop losing weight somewhere after flat stomach and before the point at which people begin to smile kindly and let you skip queues.

Dubba

AstraMonti wrote: »

Explain me something here (you or anyone who can). If you lose 10kilos you will potentially lose some power as well. At which percentage would you start noticing negative effects? Or to rephrase the question, how much weight can you lose without comprising your power output?

Duno, but best bet is to lose wight gradually while minimizing muscle loss by upping protein in diet & maybe adding a bit of weight training. That's my plan anyway, I would like to get from 80kg down to 75kgs while not losing too much power.

AstraMonti

Dubba wrote: »

Duno, but best bet is to lose wight gradually while minimizing muscle loss by upping protein in diet & maybe adding a bit of weight training. That's my plan anyway, I would like to get from 80kg down to 75kgs while not losing too much power.

That's exactly where I am. Start of November I was 80kgs with 15.5% of fat. Now I am 76,3kgs with 14% of fat. I also lost some % of muscle. I can get down to 70 by july if I want, but I am not sure if that would make any sense or if I should stay around 75kgs and improve power.

Dubba

That's a good drop of weight alright. Do you notice the hills getting easier and do you think you've lost some power on the flats?

seve65

Some of you may have seen this:

www.training4cyclists.com/how-much-time-does-extra-weight-cost-on-alpe-dhuez/

Summary from the article:
"1. Normal bike + 1.8L extra water in tyres(!)
This setup was quite interesting and got quite a lot of attention the day before when he had a puncture..! It was possible to fill 900ml into each tyre. Reducing weights on wheels is more important than reducing weight on non-rolling equipment e.g. bike saddle.
2. Normal bike + 1,8L extra water on bike.
This setup also got some serious attention because he rode a relative fast pace compared to most riders visiting Alpe d’Huez. Thus, when he performed the trial, well-trained riders were trying to keep up with his pace because this setup looked so extreme.
3. Normal bike
This setup was a completely normal bike.
4. Normal bike, reduced tyre pressure only 3 bars.
The last setup was ridden with reduced tyre pressure to 3bars. This was a tough finish on the last ride up Alpe d’Huez this day.
Results:
1. 52.01, 275w
2. 51.34, 277w
3. 49.40, 278w
4. 50.38, 273w"


Comments are fascinating.

lalorm

stripping 1kg of body fat is better than stripping 1kg off the bike. As far as I understand it, fat costs oxygen. So if your bike is 1kg lighter, you still need to fuel the fat you are carrying with oxygen when you are climbing that hill. So if you strip 1kg of fat, you have the same weight loss overall and are more fuel efficient since oxygen rich blood isn't going to the excess fat.

Wheely GR8

I would have thought inertia has a lot to do with it aswell ,the lighter the bike the greater the push.

Morrisseeee

Here's another link that might be of interest..........
2Peak

You can see that for a 76kg person to do this climb (2km climb, 125m elevation, 10kg bike) in 7min, you would produce just under 300W (3.89 Watt/kg).
But for a 90kg person, it goes up to ~340W and 3.8Watt/kg.

Now if that 90kg person can do that climb in 7min (@ 340W), and if they then loose 10kg, can they still put out 340W, and if so they would see a dramatic increase, ie. they could then do the climb in ~6min 25sec.

I suppose the Q I'm asking there is: does a person's threshold power or max sustained effort (on a climb) vary due to weight loss ?

I'm thinking if a person is starting off and loosing 5/10kg for the 1st time then it's a shock to the system & power will be reduced, but if it's a person who has been on that weight before then it's not so much of a shock & less power reduction ??!! (<< confused.com )

I'd imagine the above figures rely on 'everything else being equal', ie. same bike, conditions, and your body(due to a drop of 10kg): breathing, leg strength, fitness, power etc.

Nwm2

Lumen wrote: »

I'm sure Cervelo's models demonstrate whatever they want them to.

When I ride up an 8% slope the only air resistance I can feel is in my lungs.

Col De La Tipping Point (Select Aero vs Weight)

Tipping point (ie weight trumps aero) at 8% for 'good pro', 5% for average weight 250W rider.

No info on the model used...

DirkVoodoo

AstraMonti wrote: »

That's exactly where I am. Start of November I was 80kgs with 15.5% of fat. Now I am 76,3kgs with 14% of fat. I also lost some % of muscle. I can get down to 70 by july if I want, but I am not sure if that would make any sense or if I should stay around 75kgs and improve power.

I think with Lumen's chart, it is important to realise that you are seeing absolute power to propel a given weight at a certain speed up an incline, it has no bearing on threshold power or other physiological factors. I'm guessing the negative effects you speak of are probably going too far into the red. But it depends on where exactly your red lies. Have you done any testing yet? That would be a good place to start, identify your strengths and take it from there.

Any of those cyclists listed could be riding well below, at or far above threshold. The only thing for certain is that as you decrease weight, your power required to overcome gravity decreases. Heck, the heavier guy could be far more comfortable than the lighter guy.

Eat better, train more and properly, you should see improvements.

Lumen

Morrisseeee wrote: »

I'm thinking if a person is starting off and loosing 5/10kg for the 1st time then it's a shock to the system & power will be reduced, but if it's a person who has been on that weight before then it's not so much of a shock & less power reduction ??!! (<< confused.com )

You're overthinking it. If you have 10kg to lose, losing it steadily will make you faster. If you don't, losing 10kg will make you seriously ill. It's easy enough for practical purposes to find out how much fat you have, and although (DXA tests aside, possibly) the accuracy isn't great you'll know to within a kg or so.

"I don't want to lose power" is certainly a handy excuse for staying on the pies and beer. :pac:

DirkVoodoo

Wheely GR8 wrote: »

I would have thought inertia has a lot to do with it aswell ,the lighter the bike the greater the push.

Correct me if I'm wrong, but when climbing up a steep gradient, gravity is the main source of inertia, no?

Lumen

DirkVoodoo wrote: »

Correct me if I'm wrong, but when climbing up a steep gradient, gravity is the main source of inertia, no?

Technically, gravity is a strong source of ertia. If that's not a real word it damn well should be.

Anyway, inertia is fairly irrelevant on a bike, except in extreme cases e.g. 14kg race bikes which no-one would use in a race. A heavy bike acts like a big flywheel going up hill. The effects of rotating mass are also massively overstated.

blorg

Lumen wrote: »

Technically, gravity is a strong source of ertia. If that's not a real word it damn well should be.

Anyway, inertia is fairly irrelevant on a bike, except in extreme cases e.g. 14kg race bikes which no-one would use in a race. A heavy bike acts like a big flywheel going up hill. The effects of rotating mass are also massively overstated.

I wouldn't say inertia is irrelevant. If it didn't exist, your bike would stop dead the second you stop pedalling.

@Dirk- gravity, air resistance and rolling resistance are forces acting against the rider's propulsive efforts and the bike+rider's inertia.

smacl

blorg wrote: »

I wouldn't say inertia is irrelevant. If it didn't exist, your bike would stop dead the second you stop pedalling

There's also the case of a downhill directly followed by an uphill, where if you gather as much momentum as possible on the former you reduce the effort required on the latter. Makes a big difference on the smaller rolling hills. Put another way, you can benefit in the potential energy gathered by gaining altitude.