Head wind lighter or heavier?

BMKN

Just curious about head winds, I'm pretty light for my height, 5ft 10" 10st 7lbs I can fly up hills until my fitness stops me, I am a great sprinter usually hold 45-50kph for 1km sometimes more depending on wind direction, I suck at head winds I don't seem to have the power in my legs, some guys on aluminum frames in casual clothes pass me out, not that often but it happens, they look bigger than me in terms of weight, but they fly into a head wind no bother to them, I sometimes even have to give up and turn home, So my question is, is a heavier person better at battling a head wind than a lighter person if they were the same fitness and same bike same course?

freddiegrubb

If they were the same level of fitness I'd say the heavier rider because h/winds aren't always so, roads twist & wind direction will vary. Side winds are my bugbear as they seem to blow me all over the place so much so that I don't take my hands off the bars ( to wave cars through etc.) It's not too bad if the wind is constant you can compensate for that, it's the gusts that seem to be my danger.

bernithebiker

BMKN wrote:

Just curious about head winds, I'm pretty light for my height, 5ft 10" 10st 7lbs I can fly up hills until my fitness stops me, I am a great sprinter usually hold 45-50kph for 1km sometimes more depending on wind direction, I suck at head winds I don't seem to have the power in my legs, some guys on aluminum frames in casual clothes pass me out, not that often but it happens, they look bigger than me in terms of weight, but they fly into a head wind no bother to them, I sometimes even have to give up and turn home, So my question is, is a heavier person better at battling a head wind than a lighter person if they were the same fitness and same bike same course?

Yes.

I'm similar to you in that I struggle with head winds, and I'm light, 63kg, I think the sameish as you.

Our advantage is our power to weight ratio,which comes into play when climbing and sprinting. But it ain't worth jack diddly when you're on the flat fighting a headwind. Then you just want power and lots of it= big bloke.

Also, a wind of say 30km/h acting on 70kg is going to have more of an effect than if it's acting on 100kg.

There is an argument to say that bigger blokes have a bigger frontal area then us, which slows them, but I think this is marginal compared to the above 2 points.

BMKN

That's a bit more ego friendly than their better than me I do notice that I tend to fly past heavy guys on hills but they can hold a fast pace better than me on the flats which is very frustrating, I suppose it's down to the whole science of mass and momentum also, you would wonder is it worth being lighter then, it's the consistent winds and gusts was nearly blows. Off my bike waiting a a traffic light the other day managed to clip out in time, does anyone find ur bike front wheel lifting off the ground when u sprint off from a stop or slow speed?

jibberjim

A headwind increases the apparent wind speed such that your watts per CdA become more and more important, if you're struggling in relation to other riders then your w/CdA is simply worse than those riders, it doesn't particularly matter at all about your weight unless the wind is gusting significantly then the more momentum might make a tiny, tiny difference, however those would need to be significant gusts to have any meaningful impact.

So don't blame the weight, blame your poorer aerodynamics.

bernithebiker

jibberjim wrote:

A headwind increases the apparent wind speed such that your watts per CdA become more and more important, if you're struggling in relation to other riders then your w/CdA is simply worse than those riders, it doesn't particularly matter at all about your weight unless the wind is gusting significantly then the more momentum might make a tiny, tiny difference, however those would need to be significant gusts to have any meaningful impact.

So don't blame the weight, blame your poorer aerodynamics.

Surely an 80kg rider, compared to a 60kg one, assuming = fitness, will be putting out more power. He has longer, bigger legs, more muscle mass.

So the question the is, is this extra power offset by his slightly worse CdA. I don't think so.

jibberjim

bernithebiker wrote:

So don't blame the weight, blame your poorer aerodynamics.

Surely an 80kg rider, compared to a 60kg one, assuming = fitness, will be putting out more power. He has longer, bigger legs, more muscle mass.

So the question the is, is this extra power offset by his slightly worse CdA. I don't think so.[/quote]

Well you've just said "assuming equal fitness" but that's meaningless - equal w/kg does not mean equal fitness, because the smaller framed rider does better for various other reasons meaning they should have higher w/kg (it's why the 90kg guys aren't winning hill climbs, they have a disadvantage in w/kg. So there's no such thing as assuming equal fitness.

In any case, the advantage is absolute watts, not weight - adding weight to your body won't do anything to help you into a headwind.

dynamicbrick

I understand Cd - which is Drag Co-efficient, but what's CdA?

Headwinds are a constant thing down here on the coast, and you learn to adopt a TT-esque position, even when pottering along at 10mph. Console yourself that people in casual clothes are probably just popping to the shops.

Unless you happen to experience the guy I did one evening along Brighton seafront - on my back wheel for 3 miles into an absolute howler of a headwind. So ferocious that I was elbows on the flats, knees in, elbows in, head down, and still on the small ring. Towards the end of the cycle lane he eventually decided to take his turn on the front and blasted past... on a bloody great Dutch style step-through... with child seat on the back... wearing a huge parka... and smoking a joint... I tried to get in his tow, but he dropped me like my chain had fallen off. If I ever see him again and his bike isn't electric I'm packing it all in for golf.

bernithebiker

dynamicbrick wrote:

I understand Cd - which is Drag Co-efficient, but what's CdA?

.

You frontal area ( in m2)

bernithebiker

jibberjim wrote:

bernithebiker wrote:

So don't blame the weight, blame your poorer aerodynamics.

Surely an 80kg rider, compared to a 60kg one, assuming = fitness, will be putting out more power. He has longer, bigger legs, more muscle mass.

So the question the is, is this extra power offset by his slightly worse CdA. I don't think so.

Well you've just said "assuming equal fitness" but that's meaningless - equal w/kg does not mean equal fitness, because the smaller framed rider does better for various other reasons meaning they should have higher w/kg (it's why the 90kg guys aren't winning hill climbs, they have a disadvantage in w/kg. So there's no such thing as assuming equal fitness.

In any case, the advantage is absolute watts, not weight - adding weight to your body won't do anything to help you into a headwind.[/quote]

I still think that a big framed rider will tend to put out more power than a small framed rider, be they both Cat 1, or both pros, whatever.....

nickyboy zz

To oversimplify;

Wind resistance is proportional to your frontal surface area

Power delivered is proportional to your volume

A 10% increase in frontal area produces a greater % increase in volume and therefore power delivered. So a smaller, lighter rider may have 10% less surface area but, assuming same levels of training, his ability to deliver power will be reduced by more than 10%. Therefore in circumstances where it is total watts output that matters (such as on a level road) the stockier rider has an advantage.

BMKN

Also surely a lighter rider will be blown back more than a heavier rider so the heavier rider will not have much more ground to make up compared to a lighter person, if u take an example of throwing a bottle into a wind, the lighter bottle will be tossed back by the wind more than the heavier one will be, assuming the same force were applied, and therefore will have to make more of an effort on the lighter bottle/Rider to get to the same point as the heavier rider, so more of the lighter riders energy is wasted on getting to the same speed as the heavier rider and will fatigue more.

rolf_f

jibberjim wrote:

A headwind increases the apparent wind speed such that your watts per CdA become more and more important, if you're struggling in relation to other riders then your w/CdA is simply worse than those riders, it doesn't particularly matter at all about your weight unless the wind is gusting significantly then the more momentum might make a tiny, tiny difference, however those would need to be significant gusts to have any meaningful impact.

So don't blame the weight, blame your poorer aerodynamics.

I don't think that explanation fully explains observation. Big blokes are not particularly likely to be more aerodynamic than us skinnies and adopting a more aero position helps but doesn't exactly transform our performance against the wind! The point is that light riders are potentially fast without being particularly powerful - like the difference between a Lotus Elise and a Bentley. It's complicated. I can outclimb most riders but on the Fred it was me walking up bits of Hardknott and the big blokes still pedalling up on standards. When the gradients eased and I got back on the bike I was able to claw the time back but I simply didn't have the power at that stage to keep pushing up. A similar effect I daresay applies to the headwinds.

BMKN wrote:

Also surely a lighter rider will be blown back more than a heavier rider so the heavier rider will not have much more ground to make up compared to a lighter person, if u take an example of throwing a bottle into a wind, the lighter bottle will be tossed back by the wind more than the heavier one will be, assuming the same force were applied, and therefore will have to make more of an effort on the lighter bottle/Rider to get to the same point as the heavier rider, so more of the lighter riders energy is wasted on getting to the same speed as the heavier rider and will fatigue more.

I think it is more that the light rider will have a harder time maintaining speed - he's got less kinetic energy for a given speed. However, if both riders are blown to a slow pace, the lighter rider should find it easier to get back up to speed.

More weight = easier to maintain speed, less weight = easier to change speed.

BMKN

I think Im going to put some muscle on next winter then

ballysmate

I'm sure someone will point out I'm talking shite but here's my take on it.
If you take it to an extreme. Object A has mass 1Kg, Object B has mass 10 kg. Both have the same surface area, say 1m sq. Similar to 2 wheelie bins if you like, one empty, one full.
A strong wind is able to blow A down the street. Object B remains stable.
A force has to be applied to A for it to remain in position.
Therefore, in the case of 2 riders of differing weight, would the lighter one not need to expend energy just to remain his position.

BMKN

Ballysmate wrote:

I'm sure someone will point out I'm talking shite but here's my take on it.
If you take it to an extreme. Object A has mass 1Kg, Object B has mass 10 kg. Both have the same surface area, say 1m sq. Similar to 2 wheelie bins if you like, one empty, one full.
A strong wind is able to blow A down the street. Object B remains stable.
A force has to be applied to A for it to remain in position.
Therefore, in the case of 2 riders of differing weight, would the lighter one not need to expend energy just to remain his position.

Thats what I think also

bernithebiker

Ballysmate wrote:

I'm sure someone will point out I'm talking shite but here's my take on it.
If you take it to an extreme. Object A has mass 1Kg, Object B has mass 10 kg. Both have the same surface area, say 1m sq. Similar to 2 wheelie bins if you like, one empty, one full.
A strong wind is able to blow A down the street. Object B remains stable.
A force has to be applied to A for it to remain in position.
Therefore, in the case of 2 riders of differing weight, would the lighter one not need to expend energy just to remain his position.

Sounds good to me!

jibberjim

Ballysmate wrote:

I'm sure someone will point out I'm talking shite but here's my take on it.
If you take it to an extreme. Object A has mass 1Kg, Object B has mass 10 kg. Both have the same surface area, say 1m sq. Similar to 2 wheelie bins if you like, one empty, one full.
A strong wind is able to blow A down the street. Object B remains stable.
A force has to be applied to A for it to remain in position.
Therefore, in the case of 2 riders of differing weight, would the lighter one not need to expend energy just to remain his position.

No, this is garbage, your first idea is to do with the friction of the wheelie bin to the ground, the heavier one has higher friction so the wind forces are not sufficient to overcome it. So it remains still. In the case of a bicycle, the heavier rider does indeed have higher friction (ie the rolling resistence through the tyres is more) but since the rider is moving forward, they're already overcoming this.

Big Blokes are more likely to be more aerodynamic in proportion to their power (The A part in particular of CdA doesn't scale with weight that much, so while it will rise, it won't rise as much necessarily as the lighter rider..) nickyboy zz said it all above.

bernithebiker

This for me, explains why a light rider has the most to gain from aero and weight savings.

Because proportionally these factors affect him more.

A 300w rider into a 100W headwind is using a third of his power to overcome drag. Whereas for a 400w rider its 25%.

Low power eco cars make big efforts to reduce drag, rolling resistance and weight, as it helps them compete with larger engine vehicles.

ballysmate

jibberjim wrote:

Ballysmate wrote:

I'm sure someone will point out I'm talking shite but here's my take on it.
If you take it to an extreme. Object A has mass 1Kg, Object B has mass 10 kg. Both have the same surface area, say 1m sq. Similar to 2 wheelie bins if you like, one empty, one full.
A strong wind is able to blow A down the street. Object B remains stable.
A force has to be applied to A for it to remain in position.
Therefore, in the case of 2 riders of differing weight, would the lighter one not need to expend energy just to remain his position.

No, this is garbage, your first idea is to do with the friction of the wheelie bin to the ground, the heavier one has higher friction so the wind forces are not sufficient to overcome it. So it remains still. In the case of a bicycle, the heavier rider does indeed have higher friction (ie the rolling resistence through the tyres is more) but since the rider is moving forward, they're already overcoming this.

Big Blokes are more likely to be more aerodynamic in proportion to their power (The A part in particular of CdA doesn't scale with weight that much, so while it will rise, it won't rise as much necessarily as the lighter rider..) nickyboy zz said it all above.

Not arguing with you, I genuinely don't know. But do two sailing ships with a weight disparity need different sized sails to move at the same speed? Therefore needing differing power inputs.

gavbarron

Naval architecture and hydrodynamics are whole different subjects and equally if not more confusing, you'd have to consider hull form, draft, even the paint used and its condition and so on. Lets keep it to bikes.

I think peoples ability in wind is to a large extent, mental. I have friends who equal me on hills and TTs but give us a strong headwind and they buckle every time, I think not being able to 'see' the end of it destroys some peoples will.
I think this may be the case with the OP, who can by his own admission hold 50kph for 1km, which is good enough to be coping with even the strongest of winds.
Most people think they struggle in wind but its because they expect to be riding faster on the flat for a given effort that they feel worse for it. If you are strong on hills and can complete 1km 'sprints' then in a race you'll be fine, just sit in and let everyone take a turn in the wind before jumping off the front near the end.

bernithebiker

jibberjim wrote:

Ballysmate wrote:

No, this is garbage, your first idea is to do with the friction of the wheelie bin to the ground, the heavier one has higher friction so the wind forces are not sufficient to overcome it. So it remains still. In the case of a bicycle, the heavier rider does indeed have higher friction (ie the rolling resistence through the tyres is more) but since the rider is moving forward, they're already overcoming this.
.

So lets take friction out of the equation and say the bins are on ice. Then we come back to F=ma, so for a given wind force, the light bin will accelerate backwards quicker than the heavy one.

sungod

unlike wheelie bins, people riding bikes are powered systems

for constant windspeed/angle on a flat road, the system's (rider + bike) mass has no relevance (leaving aside minor stuff like drivetrain resistance and the limiting case where the wind overcomes tyre friction and just blows it all away), speed is all about power and aerodynamics

when there is a change in windspeed/angle there will be a change in force on the system, the system will then undergo acceleration inversely proportional to it's mass, a = Δf/m, the rider compensates if necessary (for instance by leaning slightly more) and the system returns to the case where weight is again irrelevant

when the windspeed/angle keeps changing significantly, the light rider will get blown all over the place, especially if they're on deep rims

bernithebiker

sungod wrote:

unlike wheelie bins, people riding bikes are powered systems

for constant windspeed/angle on a flat road, the system's (rider + bike) mass has no relevance (leaving aside minor stuff like drivetrain resistance and the limiting case where the wind overcomes tyre friction and just blows it all away), speed is all about power and aerodynamics

when there is a change in windspeed/angle there will be a change in force on the system, the system will then undergo acceleration inversely proportional to it's mass, a = Δf/m, the rider compensates if necessary (for instance by leaning slightly more) and the system returns to the case where weight is again irrelevant

when the windspeed/angle keeps changing significantly, the light rider will get blown all over the place, especially if they're on deep rims

Firstly, it doesn't changea great deal that the bike is a 'powered' system. You are simply applying a force to move the bike forward which is being counteracted by the headwind.

Assuming constant wind speed and a constant bike speed/power is too simplistic. In reality, the wind speed and direction are changing all the time, creating lots of force imbalances and therefore accelerations. The mass of the bike/ rider then comes into play, i.e. almost all the time.

Imagine a test rig bike propelled along the flat with a 100w motor, into a wind tunnel making a constant 10km/h. Here the forces will balance and the bike will settle at a speed of say 25km/h. Now rapidly increase wind speed to 30km/h, the bike will now suffer a deceleration proportional to it's mass.

Now repeat but with lead in the bike's frame to triple its weight. This bike will declerate slower than the light one.

pinno

Wots u need is:

On the flat - good power to drag ratio
On the hills - good power to weight ratio

Two different things unless you are Phillipe Gilbert but he can't climb the big cols fast only the rolling roads of the Ardennes.

The 'pure' climbers of the Cafe de Colombia era (almost gone now) like Lucho Herrera were like dieting racing snakes weighing in at less than 60kg, Richard Virenque, Marco Pantani etc. Sprinters/super domestiques were/are big and strong but heavy; Magnus Backstedt, Gilbert Duclos Lassalle, Thor Hushovd, Cipo and even on the track - Chris Hoy.

In the last 35 years, how many 'pure' climbers have won the TdF? Only Pedro Delgado and Marco Pantani. the only exceptions are the complete all rounders who could mix it in a sprint and fly like birds were Bernard Hinault or Eddy Merckx and perhaps Big Mig.

sungod

bernithebiker wrote:

Firstly, it doesn't changea great deal that the bike is a 'powered' system. You are simply applying a force to move the bike forward which is being counteracted by the headwind.

Assuming constant wind speed and a constant bike speed/power is too simplistic. In reality, the wind speed and direction are changing all the time, creating lots of force imbalances and therefore accelerations. The mass of the bike/ rider then comes into play, i.e. almost all the time.

Imagine a test rig bike propelled along the flat with a 100w motor, into a wind tunnel making a constant 10km/h. Here the forces will balance and the bike will settle at a speed of say 25km/h. Now rapidly increase wind speed to 30km/h, the bike will now suffer a deceleration proportional to it's mass.

Now repeat but with lead in the bike's frame to triple its weight. This bike will declerate slower than the light one.

er, you seem not to understand what i posted, you've simply restated what i said

bernithebiker

sungod wrote:

bernithebiker wrote:

Firstly, it doesn't changea great deal that the bike is a 'powered' system. You are simply applying a force to move the bike forward which is being counteracted by the headwind.

Assuming constant wind speed and a constant bike speed/power is too simplistic. In reality, the wind speed and direction are changing all the time, creating lots of force imbalances and therefore accelerations. The mass of the bike/ rider then comes into play, i.e. almost all the time.

Imagine a test rig bike propelled along the flat with a 100w motor, into a wind tunnel making a constant 10km/h. Here the forces will balance and the bike will settle at a speed of say 25km/h. Now rapidly increase wind speed to 30km/h, the bike will now suffer a deceleration proportional to it's mass.

Now repeat but with lead in the bike's frame to triple its weight. This bike will declerate slower than the light one.

er, you seem not to understand what i posted, you've simply restated what i said

OK, yeah, I guess we pretty much agree.

When you say the rider has to compensate by leaning, then yes, but also, by pedaling a bit harder if he wants to maintain his speed. (assuming a wind angle of say 45'). (And the lighter the rider, the more exaggerated this effect).

bernithebiker

So would it be fair to summarize by saying;

a) lighter riders are more affected by the wind (or to be more precise changes in wind speed and direction, which is happening almost constantly)

b) drag force increases with the square of your speed, and the power required must be cubed to increase speed. Therefore, power is king when fighting a headwind. To go faster you have to either find more power or improve your Cd. Generally speaking (and there will always be exceptions) the bigger built you are, the easier it is to produce extra power. So once again the light rider is penalised.

Rigged

As someone who weighs 54kg, this thread made depressing reading

rolf_f

Rigged wrote:

As someone who weighs 54kg, this thread made depressing reading

Cheer yourself up with some tailwindy hill repeats in the company of big blokes!

ddraver

I think its way more simple that you re making out - You just need power in winds, how much you weigh or your frontal area is pretty much irrelevant. If you want to get better then ride into headwinds on the flat, there is no secret to it, it sucks for everyone, you can make it suck less (by reaching the turnaround point faster) by working on your power.

Bigger guys may naturally have more power, but that's it

Cycling is 99% about Power to Weight ratio (Dr Ferrari got that bit right). I'm a big guy, I was a decent rugby player, I will never be a good cyclist (possibly a track sprinter)