cycling
22. Februar, 09:37 Uhr
Full article with graphs at http://cyclingtipshq.com/how-much-difference-does-a-headwind-make-when-cycling
I was out on a 100km route today, which I had planned perfectly. First half out into the wind, and second half with a tailwind taking me home.
As I was battling through the first 50km I couldn’t help but wonder how much of a difference the headwind was actually making (anything to distract me from the task at hand!). So when I got home I had a go at working it out.
Disclaimer: I need to stress this is not some kind of scientific investigation. It is a bit of fun aimed at answering some questions about the difference a headwind can make when cycling. I have no background in science (this will become clear very soon!) and have used tools available to be on the internet to crunch some data which you might find interesting.
Tools:
In order to get to my results I am going to be using the fantastic Bike Calculator created by Curt Austin. Curt has been helping riders for years, early on through spreadsheets and since 2008 has had a website dedicated to his amazing calculator. It is also available on an iPhone App.
If you want more information on the inner workings off the calculator you can get some here.
For this experiment I felt this was the best way to get accurate results without hiring a wind tunnel for the evening! As an amateur you have to trust the best information available to you. So here we go, one man, one spreadsheet and alot of numbers!
Assumptions:
For these results I am going to keep a number of elements constant, so we can focus primarily on headwind, power and rider position.
Therefore the following things are going to remain constant through the examples:
Bike Weight: 8.3kg
This is the average weight of the top 10 bikes in this year’s road.cc bike of the year
Rider Weight: 84kg
This is the average weight of a man of in the UK given by a BBC survey conducted in 2010.
Tyres: Clinchers
I felt these were more common than tubeless tyres.
Elevation:
The elevation has been kept at a constant 100m above sea level to avoid air pressure changing the results.
The Scenarios….
Riding In The Hoods
For the first scenario, we are riding along on the flat in the Hoods when we turn to face a headwind. Our power output is 180w which given the variables above means we are riding at 30.14 km/h. As we turn into the wind we maintain our power output.
For each 5km/h of additional headwind you can see we are losing about 10% of speed.
At a head wind of 30.48 km/h we would have lost half of our initial speed slowing down to 15.07 km/h.
I was shocked at quite how much speed the headwind costs us, and whilst it does feel hard out on the road I thought as much of this was in my head as reality, but this proves not to be the case.
Riding In The Drops:
The drops give a more aerodynamic position, bringing your body downwards and meaning less area for the wind to take effect on.
This table compares riding in the hoods vs the drops.
As you would expect with less frontal area hitting the wind your speed is naturally improved with the same power by riding in the drops.
With our variables above at 180w on the flat with no headwind you are giving yourself a boost of just under 2.5km/h which was more significant than I expected.
What’s interesting is how much greater the percentage benefit is of cycling in the drops the stronger the wind.
You can see from the chart ‘Improvement vs Hoods %’ the difference this makes with no headwind the speed improvement at 180w is 7.49%, but take that up to 25km/h and you are saving yourself 12.05%. Into a 50 km/h headwind the drops are going to save you 16.58%.
Now for some the drops are just too uncomfortable, so the speed saving is not worth the discomfort level, but if you are on an out and back route, it would seem saving any time you can spend in the drops for the worst of the headwind is going to be the most beneficial.
Whilst this may seem like an obvious statement, I hadn’t realised quite how much difference it could make to my speed.
How Much Additional Power Do We Need To Account For A Headwind?
If you’re like me then you’re not going to let mother nature defeat you this easily, so naturally we’re going to put a bit of extra power through the cranks.
But how much extra do we need to account for those headwinds?
Well you’ll be pleased to know I’ve looked into that too!
Assuming you stick in the hoods as you turn into the wind and want to maintain your flat 180w non headwind speed of 30.14 km/h you are going to have to find some serious power to make up for the headwind.
Into a 5 km/h headwind this equates to an additional 50w meaning you need to push out 230w. Unfortunately this does not ramp up in a linear way as by the time you hit 20km/h (4x the headwind) you need to push out an additional 248w (nearly 5x the wattage at 5km/h)
This makes a headwind really unsustainable for maintaining a constant speed, especially when riding by yourself. On a group ride it gets a bit easier as studies have shown riding in a group can save up to 40% of a rider’s energy, meaning by taking turns maintaining a faster speed should be easier.
Saving Power By Changing To The Drops When We Hit A Headwind
So now moving onto a bit more of a real world situation. We are cycling along on the flat, hands on the hoods, when we hit a headwind. We immediately change into the drops knowing it is going to save us power and make our ride into the wind easier.
Once again the aim is to keep our speed constant at 30.14 km/h.
You can see from the table what a power saving changing to the drops gives us. In a 5 km/h headwind, if we’d stayed in the hoods we would have had to put in 230w to maintain our speed, but by changing to the drops we only need 187w, which is only 7w more than our starting power.
The saving initial is 18.7% by changing to the drops, but this rises as high as a 22% saving if you head into a 50 km/h headwind (and if you can find an extra 626w from somewhere!)
You can start to see from this data the tangible difference you can make to your speed by getting into a more aerodynamic position when you hit a headwind.
How Does Riding Into A Headwind Compare To Riding Uphill?
This is another question often debated when we’re out riding.
We’ve all been there “That headwind was awful today, like riding up a 10% hill”.
But was it though?
Each 5 km/h increase in headwind is equivalent to a gradient increase of around 0.57%.
This is measured by keeping the power at 180w and reviewing the speed lost by the headwind/gradient variables.
Once again you can see how much effort it takes to ride into a headwind. Whilst I thought the equivalent gradient might be a bit more than this, it does bring home the point of how hard you are working.
How Does This Translate To The Real World?
Well the reality is that it doesn’t. There are so many variables in the above data it would be impossible to match any scenario perfectly.
Take the air resistance generated by the headwind. This alone would throw up a number of questions:
- Was the wind directly towards us?
- Did it remain at a constant km/h?
- Were we sheltered at any point by cars/trees/other riders etc?
- Did we hold our shape perfectly on the bike?
What I hope I’ve done in this article is given you some idea how much additional effort it takes when cycling into a headwind and reinforced how important aerodynamics are to cycling, especially when the conditions are bad.
Tips For Cycling In The Wind
Here are some tips for making the best of a bad situation when cycling into the wind:
- Try to make your self as aerodynamic as possible. As you can see from the information above, riding in the drops will help but there are also other things you can do. Tucking your elbows in, wearing less baggy clothing, keeping your head still will all help your cut through the wind more easily.
- Try and keep your cadence high. Just like cycling uphill, drop down gears to keep your cadence above 80RPM. Don’t be embarrassed to change into the smaller front ring if needed. A high cadence keeps your legs fresher so don’t be a hero!
- Plan your route. I always prefer to head out into the wind so you’ve got something to look forward to on the way back. Check the weather forecast the night before and plan a route based on the main wind direction.
- Remember the benefits. Whilst riding into a headwind never looks pretty on Strava, the reality is you’re working harder. This is all going to help your fitness, and make you a faster rider come the calmer days.
- Get out earlier. If you do want to avoid the worst of the wind you will generally find the day to be calmer the earlier you head out. You may find you can time it so you head out into less of a wind than brings you back!
- Be careful with cross winds. Wind is rarely constant, and on a strong, blustery day it can easily knock you off course. Be aware of the direction the wind is coming from, and look for potential hazards that could cause the wind to send you sideways. Gaps in the hedgeline for gates, and passing lorries can be enough to send you out into the middle of the road if you’re not concentrating.
- Ride in a group. You can save alot of effort by sheltering in a bunch. This is especially handy on a windy day. Make the most of a local group ride to help your through a windy day, just make sure you do your fair share of time on the front!
- LEARN TO LOVE IT! Ok, so I’m an optimist, but even I won’t pretend I’ve got a big smile plastered on my face when it’s really bad. However, the more you can improve your attitude to bad conditions the better it will feel. I don’t know about you, but one of the reasons I ride is because I want to become a better cyclist. Faster, stronger, leaner. A tough, uncomfortable training session is going to help me achieve those goals quicker than an easy jaunt. If I just pretend the wind is actually doing my a favour, like some kind of sadistic coach, I can almost convince myself it’s for the best. Well almost…..!
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