Wrangling club mates, meeting your friends or even just going out for a spin with your partner – all of it involves more logistics than you can shake a stick at. You need the route made, the weather checked, the ride duration agreed, the meeting point decided and all of this information needs to get to either the mobile phone or the head unit of all the participants.
It all starts in the planner. You can create groups here too. Simply hit “Add group” to create a group.
Once a group has been created, you can distribute the link to it. This will allow members to view the entire contents of the planner and each forecast.
Deciding what route to do
At the risk of sounding like an episode of “Art Attack” (an art “make along” children’s television program from the 90s) – Here’s one I made earlier…
Every group ride has its constraints and negotiations. myWindsock’s forecast dashboard will allow you to access all the information needed. In this case, if we delay the start time of the ride by 2 hours from 8am to 10am, we can catch the “warm” part of the day thanks to the panel on the left. Similarly, it can be used as a quick look for rain dodging.
On this one, we’ll imagine a member wants to ride the climbs at an exact power for some reason and that we are targeting 26kph (as many group rides aim for a particular average speed as the target). We can ask the myWindsock AI to adjust the power profile for us to check what power we need to do in order to make this achievable…
This can be used to ask questions like “how fast will the group ride be if we do the hills at” or “how can we adjust the route to hit a 3 hour target at this speed”.
After the adjustments and negotiations have been made in the Whatsapp group chat, the route can be distributed. If you share the route with a friend who also has a myWindsock account, it can be exported directly to your head unit.
The course can be exported directly to Garmin, Wahoo or downloaded as a GPX.
End the arguments in the Whatsapp chat and let myWindsock decide on the route and when to leave. You can invite your regular riding buddies to a shared planner and all check the route and adjust the forecast to see what will happen under different conditions. You can get answers along the lines of when the best time to leave is for optimal wind conditions, what happens if you do a bit of old fashioned “through and off” for 30km in the middle of the ride or how long we can stay at the cafe before we get rained on.
Use myWindsock’s group planners to organise your ride and end the arguments.
To check out the forecast we used to create this guide, click here.
With the RTTC National Hill Climb championships finishing the season and cyclocross getting underway in earnest, it’s that time of year when we start seeing cyclists go out for a run. For the past decade, myWindsock has been quantifying the headwind excuse for cyclists – but how much does difference does the wind make when we run? Running is a little bit like cycling up hill in that the speeds are relatively low (the men’s 5k world record pace, for example, is only around 24kph) and you’re pushing against both wind and gravity.
A little bit of physics
Let’s first assume that we have a rider going at a constant speed along this flat course. We can write the forces here like this, where F_drive represents the force at the pedals.
This shows the force required to ride at a constant speed is equal to the sum of the forces slowing you down. For simplicity, we’ve actually ignored forces due to drivetrain resistance. Also, if we’re going along a perfectly flat road at a constant speed, there’s no gravitational force slowing us down (there is gravity, but it’s acting perpendicular to our direction of motion so does not contribute) – so we can write that as zero too.
As well as gravity being zero, we can replace F_aero and F_roll with their actual expressions – seeing as we know the aerodynamic equation and rolling resistance equations and replace forces with power (by doing the relevant algebra) to find the power needed to ride on a flat road.
The question is, how does this change for a runner?
The first obvious thing to mention is that a runner doesn’t have rolling resistance, seeing as they step, not roll so we will need to replace the resistive force they get from each step with something else. The aerodynamic part equation is still relevant as they still have to push wind out of the way. An upright human has a cda of around 0.6 (according to a quick search). Assuming a runner is running half the speed of a cyclist but is half as aerodynamic, they’ll face around 1/4 of the air resistance a cyclist would – still quite a bit. Obviously running is slower than cycling, so the other resistive forces from not having wheels must add up to quite a lot…
The problem with running is you’re never travelling along at a constant speed. A runner is like a stone skipping across a lake, bouncing along and at each point of contact with the floor there’s a series of competing forces that are slowing you down or speeding you up. In between steps, runners fly gracefully (or otherwise) through the air in an arc with only air resistance and gravity acting on them.
Rather than go through a complicated derivation with lots of algebra to show off how clever we all are, let’s just skip to looking up measurements.
Cavagna, Thys and Zamboni’s 1976 paper, “The Sources of External Work in Level Walking and Running”, is particularly relevant here and also, oddly, explains why “super shoes” were a good idea a long time before they were created.
In order to understand what they found it helps to imagine how a runner moves. During running, the body’s centre of mass undergoes continuous acceleration and deceleration, both up and down and forwards. During propulsion, the body accelerates vertically and horizontally, while gravity subsequently decelerates its vertical movement (so you don’t just fly off the earth when you jump) and braking forces reduce its horizontal velocity during ground contact.
During the flight phase, the body continues moving horizontally, with its vertical trajectory governed by gravity and being slowed down by air resistance. The muscles must continually replenish the mechanical energy lost throughout these processes. A key finding from Cavagna’s research is that the body recovers very little mechanical energy between vertical and forward movement, meaning that much of the mechanical work performed during each stride must be actively regenerated by the muscles. Essentially, this paper found that humans are pretty inefficient when running – unlike bikes, which are extremely mechanically efficient.
The problem for us is to disentangle energy loss due to all of the factors that Cavagna researched from energy lost due to air resistance. This is a uniquely difficult problem as it will change based on the runner, their weight, their speed, their tendon stiffness, their shoes and much more. Imagine a runner with very floppy tendons but an extremely aerodynamic upper body – they might run the same speed as someone with a Spongebob Squarepants shaped torso but extremely springy achilles tendons, once of these runners will be significantly more impacted by the wind than the other.
If it’s hard to work out, is it easier to measure?
Luckily for us, it is. Many measurements were taken in the run up to the sub 2 hour marathon attempts that Eliud Kipchoge made which kicked off a branch of science focussed on running aerodynamics. A number of great papers have come out in recent years.
One of the things that came from this was the running formation. They found that the air resistance felt by Kipchoge was lowest when he had runners in front of him in a V shape that he was at the back of, then had two behind him – presumably to keep the air attached to the group so Eliud Kipchoge was sat in a small pocket of low pressure.
We know from experimental measurements made as long ago as the 70s that oxygen consumption with running increases with the cube of a runners’ air speed (the same as cycling). On a windless day during a 5k, wind resistance contributes approximately 8% of the oxygen cost at a given speed (a much lower proportion than cycling). Studies have also shown that this contribution practically goes to 0 with drafting (unlike cycling – where it is reduced but not such a great extent).
The study Biomechanics of Human Locomotion in the Wind looked into how aerodynamic forces influence human walking and running. This study was done in 2024 so its findings are pretty modern. Researchers had eight male participants and used an instrumented treadmill inside a wind tunnel to measure ground reaction forces, running biomechanics and aerodynamic loading.
Participants walked at 1.5 m/s and ran at 4 m/s (roughly 21 minute 5k pace) under different headwind and tailwind conditions, with wind speeds reaching 15 m/s. At the highest wind speed, running generated approximately 50 N of resistive force in a headwind and 55 N of forward aerodynamic assistance in a tailwind. The researchers also observed that participants adapted their posture in response to the wind, changing their cda.
Practically, how much difference does this make at Parkrun?
If you imagine a Parkrun course that’s an out and back like this one, where you spend 2.5km with a headwind and 2.5km with a tailwind.
This is a 6mph wind coming from right to left as we see it on the map here and as you can see, on this Parkrun course it’s extremely simple. It’s a block tailwind out and a block tailwind back.
We’ve made a few calculations, and this is the rough distance the wind makes due to the headwind and tailwind effects over a 5k at various speeds:
5k Time
Number of seconds slower over 5k relative to a day with no wind
25:00
55
22:30
45
20:00
43
17:30
35
15:00
30
These are quite rough estimates and do not include any provision for hiding behind other runners from the wind. They are, however, good enough for an excuse in your Strava caption when you’re doing your offseason Parkrun.
Storm Austen has already made landfall in the UK. Some damage has already been caused according to Cerys, a Barista in a Newquay coffee house speaking to the BBC, “We’ve got a very bent mop, but other than that we’re all good”. The big question is, will this impact the RTTC National Hill Climb Championships that are taking place up Porlock Toll Road on the 25th of October? For a detailed run down of the course, without an attached weather forecast, check out our course preview here. If you’re more concerned about the weather though, stick around.
Starters are slated to set off every 30s between 9:30am and 2:20pm. The wind speed shown here is in MILES PER HOUR and it’s currently looking like it’ll also be raining all morning. The big question on the lips of many is will the wind be strong enough to curtail the event and what direction is the wind blowing?
The strongest headwind ever at an RTTC National Hillclimb Championships?
Time for the big unveil. We’ve waited as long as we can for this forecast but it’s time. It’s going to be a 40mph block headwind all day.
This is the craziest hill climb forecast we’ve ever seen. 43mph headwind forecast in the morning, dropping a little bit throughout the day but will still be a 39mph wind for the late starters. Gusts will be higher. The course is very sheltered for the most part, lined with trees. Trees do have a tendency to come apart during high winds and riders should make sure to select tyres that can tolerate riding over a twig without ripping.
The shading on the map
Zooming in a little on the map above, the eagle eyed readers will have noticed a shading pattern. This demonstrates the wind’s “surface friction”. This course is a mixture between being lined with trees and open hill side. You can easily see which area is which using the key in the image, the dark shaded area is high friction (lots of stuff in the way – in this case, trees) and the lighter area is exposed with low surface friction for the wind. This course demonstrates the difference in a stark fashion.
Headwinds as hills
This headwind is like adding an extra 70m of climbing – it could be worse but the trees help out a lot!
The Wind Adjusted Elevation (WAE) plot also demonstrates the impact of the headwind. You can clearly see where the course opens up and the WAE separates from the topological elevation. The physical impact of this is equivalent to adding around 70m of elevation onto the climb. Riders can minimise this by being as aerodynamic as possible.
How to behave in a 40mph headwind
At the start, normal service goes ahead. You’re almost immediately into the shelter and you can ride how you normally do. Once the road opens up, the wind gets serious and riders will need to enter their time trial mindset.
A stationary object in 40mph wind has an air speed of 40mph and a ground speed of zero. This is important to remember. The resistance you feel on the bike from the air is not due to the ground speed. A rider going 10mph into a direct headwind of 40mph has a wind speed of 50mph, which is the same amount of air resistance as a rider going 50mph on a perfectly still day. When it gets hard, avoid the urge to stand up and double your surface area, the extra watts you gain by standing up will be lost to the wind.
TT bike or road bike?
Harry Macfarlane, of hill climb championships and Instagram fame, made waves by telling everyone that they should go “full aero” with their set up. Let’s imagine a scenario where a rider’s TT set up is 3kg heavier than their hill climb set up and their power drops 10% in the aero bars. Our imaginary rider’s system mass in 77kg and their hill climb power is 390W, this means their aero bar power is 351W. We will use a cda of 0.24 for the hill climb bike and 0.21 for the TT bike.
Hill climb bike:
The starting point – 17:14 with those numbers (slower than both the KOM and the QOM). This is a “normal” hill climb set up using good, but not nuclear, watts.
You can see from the screenshot above that the weather is worth 1:36. Let’s take a look at how the resistive forces break down to see if that gives us a clue as to whether the TT bike will be faster.
Seeing that white line even play a role in a hill climb is rare. Where the white line crosses the red line, it’s a sign that air resistance is the dominant resistive force. Acceleration forces are represented by the green line and rolling resistance by the blue line. These forces change depending on what bike you use (air resistance makes a lower contribution if you’re more aero, for example).
Let’s see how the forces break down with our new set up with a 10% reduction in power, +3kg and minus 0.03 on the cda!
There is a noticeable reduction in the air resistance measured by this simulation when we switch to the heavier, but more aero set up. There will be a trade off here though, as the forces due to gravity will increase. The key to bike selection is minimising the sum of these forces without over-indexing on any particular one.
The big question is, is it faster?
No, not even close. It’s still a hill climb after all. What if power stays the same?
Almost exactly the same. Only 4 seconds slower. Now, this does beg the question – what about a lightweight “aero” hill climb bike with clip on TT bars. Imagine a scenario where a rider might be able to achieve a cda of 0.22 but for a net gain in weight of less than 500g. Then there’s a big question to answer…
Kit selection, of course, is highly individual to your watts, cda and weight. To have the best chance of a good result, play around with your set up on the newly furnished myWindsock platform.
You may have read this expecting us to make a prediction for the men’s and women’s winning times. We have not done this as there’s obviously a huge amount of uncertainty caused by the forecast. One thing we do know is that nobody is getting remotely close to a course record with a 60kph headwind.
Forecasting the exact timing of a storm can be difficult. It’s possible that the storm will die out earlier than expected and if the forecast is wrong, it’s most likely to be in the direction of conditions being better for later starters. The easiest way to stay up to date on course specific forecasts is with us.
It is somehow already October which means only one thing, it is National Hill Climb Championships. At the time of writing, the race is 11 days away which is a bit far for an accurate forecast but close enough for a detailed course review. This year the champs course is on Porlock Toll Road in Somerset
This image, from the Porlock Weir tourist board’s website, shows a portion of the bottom of the climb. It’s a scenic climb with panoramic views across the Bristol Channel – though we can’t imagine riders will spend much time taking them in during the race.
Porlock toll road is a 4.1 mile climb – one for the long climb specialists. It’s a relatively shallow climb with a decent range of gradients that we’ll go into later, but our best guess (though it’s heavily wind dependent) is that the men’s race will be won in a time around 13:45 and the women’s in a time of around 17:00 (or, wind adjusted equivalent times). All the fastest climbs have been set on days with a strong tailwind. The shallow gradients mean the wind can impact times up here, but this is offset by the shelter most of the way up.
The map
With more than 10 corners and two hairpins, this is a twisty climb. Gabe Dellar, hill climb hitter and friend of myWindsock, told us there’s two points where he had to stop pedalling while riding up the climb when he did his course recon.
In the 1960s it was actually used as an RAC Rally stage, one of the fastest drivers at the time being the late Pat Moss, sister of Stirling Moss, who completed the 4.1 miles in 3 minutes and 56 seconds which is an average speed of over 100kph.
With more than 10 corners, some quite severe, it’s amazing the speed anyone can drive up. As the gradient is very shallow, some riders will have to stop pedalling on their way up.
The profile
This road is a shallow climb. The speeds will be high and it’s one for the lightweight aerodynamic enthusiasts. The sharp corners are sharp enough that a second or two can be gained or lost from bike handling. Tyre choice will be uniquely interesting if it’s wet on the morning of race day – which is looking possible.
A smooth climb that’s relatively sheltered. We can see from the topological elevation being extremely close to the geographical elevation the shelter along the side of the route protects riders effectively from the wind.
The red line here represents the power expended due to gravity, the white line – power due to aerodynamics. Obviously, as this is an up hill race, gravity is the primary resistive force but aerodynamics matters a lot – enough to be the difference at the end of the day.
The road surface
One report we heard back from Gabe was that the road surface on the climb is not perfect. This isn’t a surprise for a small lane in the South West of England but it’s worth bearing in mind. There is also a cattle grid on route. Our tip here is to ride a recon, of course – but with this being a toll road it will cost you a quid if you want to ride up. If you’ve spent all your money on drills to save weight on your hill climb bike but are concerned about the road surface, you can check it out on Street View.
We’ll post a detailed forecast late next week, with predicted times and pacing advice as well as physical wind features.
It’s Ironman World Championships week again and this year the men and women are back in the same place, racing on the same day – just like the good old days. Last year was the final rendition of the split competition, with the men’s race in Nice and the women in Kona but this year we are all back in Hawaii – hooray!
The race has moved around the calendar a bit in the past and the weather can change a lot depending on when it is, which is what makes this course so interesting for myWindsock users. Its usual slot of the 2nd weekend in October was ditched in 2024 – part of the reason for the fast time though the trend of the past decade in race times is clear.
The famous bike-course wind comes from the Kohala coast near Hawi, where the trade winds and the island’s terrain produce strong gusts (the “mumuku” winds).
The wind on the big island of Kona has already seen off one victim, with defending champion Casper Stornes being taken out by a big gust.
The trend in results dictate that the men’s course record almost certainly is going to have to be broken by the winner. Lucy Charles-Barclay’s over-performance of 2023 means that the women’s race could be won without necessarily breaking the record, though it’s a fast day as we’re about to see so it’ll probably go down too.
This graph shows the trend in overall finish times in the Ironman World Championships for the past 10 years. Each year improvements in aerodynamics and nutrition are causing the race to get faster and faster. Kienle’s winning time from 2014 would have only just cracked the top 30 in 2024.
The Ironman Hawaii course is really boring. It has achieved legendary status as it is pretty hot and humid which has caused some blowups and meltdowns over the years – though this is mostly down to the way people race it and not because the course itself is inherently crazy. Huge advancements in pacing, nutrition and aerodynamics have neutralised a lot of the challenges too.
The course is essentially an out and back along a coastal highway. The trade winds come from the land side and there’s a volcano which kind of shelters the riders from it. The wind can be strong, though on race day the forecast is for extremely low wind.
The only time the athletes have to really do anything other than look at their power meter is through town. They do a mini loop to get onto the main highway and a mini loop when they get back. What little wind there is forecast to be this year is sheltered from the buildings as you can see with this surface friction layer on the myWindsock map.
The elevation profile is equally simple. There’s one hill – the road up to Hawi. It’s not even steep. It’s a huge motorway drag strip. It is a point on the course where it’s possible to make a difference and split groups though so expect moves to go during this section of the course.
How to break the course record – Women
The women’s bike course record is a time of 4:26:07 set in 2018 by Daniella Ryf. This was another fast day with low air density and pretty low peak wind speeds. We will see what it would take in order to ride a 4:25 for a woman with a system mass of 70kg (including bike and kit) and a cda of 0.2 with Saturday’s conditions. The candidate most likely to break the course record is Taylor Knibb, who recently finished in the top 15 of the World TT champs and has a reported FTP of around 300W.
Conditions suggest a rider of around Knibb’s size with an average cda of about 0.2 (with some variation on the climbs and descent) will be able to ride 4:25:29 with an average power of 242W – roughly 80% of Knibb’s reported threshold. That is around the upper limit of the power professional athletes ride in Kona relative to their Critical Power but it suggests a course record is not unlikely.
How to break the course record – Men
The men’s course record was broken more recently, with Sam Laidlow riding a 3:57:22 in 2024. Laidlow is around 75kg so we will assume a system mass of 85kg (bike plus kit plus rider plus water). The question is, do Saturday’s forecasted conditions make a 3:57 or lower bike split impossible to obtain with human watts?
A 3:57 this year, as the forecast stands, will require a power of 330W. This is on the high side but not unheard of for Ironman athletes at World Championships. The men, being at the absolute front of the race, will also have more motorbikes in front of the front group – making a fast split easier to achieve with less watts than this.
If I was a betting man, I’d say every single course record will go down this year apart from the men’s swim course record. This is due to a unique combination of conditions, field strength and likely race dynamics. 2026 will probably be the fastest Kona ever!
Some of you may have noticed that myWindsock has had a bit of a new look in the past couple of months. Along with our renovation comes a number of new graphs and charts to help you analyse your rides, routes and races. Today, we’re going to go through our top 5 graphs and charts that are new, or revamped, on myWindsock.
1. Timeline view
The timeline graph allows you to view your ride as you’ll feel it on the road. It includes topographic exposure, elevation changes, power advisor, wind significance, estimated model error, CdA estimates, topographically adjusted wind speed, power settings and more. By pressing the plus bottom in the bottom left you’re able to add new values to the timeline view. The timeline view can be accessed via the arrow in the navigation bar at the bottom of the screen which expands it into what you can see here.
2. Modelled Power Components
The modelled power components graph is a revamped version of a plot on the old myWindsock platform. It tells you which component of resistive forces are slowing you down out of aerodynamics, rolling resistance, gravity and acceleration. It tells you how many watts you need in order to overcome that resistance. For example, you can see where the gravitational force goes way below 0 – this coincides with the course going down hill.
3. Conditions Evolution
This graph is visible to you in the top left hand side of your screen. It shows you how temperature, wind, rain and air density evolve throughout the day. This is good for both deciding when to leave the house for your ride, as well as checking if you’re disadvantaged with your start position in a time trial.
4. W’ Balance
This is another revamped plot from the original myWindsock platform. It tells you how much energy you have during a time trial when it comes to going over your threshold. When you go over threshold, you deplete your W’ which takes time to re-charge when you go back under threshold (for example, a period of you not pedalling on a descent).
5. Adding your own
A key feature of the new platform on myWindsock is the ability to add extensions. As part of these, you can add the output of these extensions as graphs and add them as custom data panels.
There are significantly more than 5 plots and new features on the myWindsock surface platform. If there are any there that we’ve not explained, myWindsock will explain it for you.
The “Explain This” button can be found beneath every graph, where myWindsock’s AI will explain every aspect of the graph.
In the past week, Remco Evenepoel won his fourth consecutive World Championship in the time trial. He rode the 39km course at an average speed of 52km/hour – an entire kph faster than his closest competitor. It’s looking really hard to see how someone could actually beat him in the medium term. This got us thinking, how hard actually is it? How many watts are needed at different drag coefficients to beat Evenepoel?
It’s clear that Remco is on another level to everyone else. They’ll all be scratching their heads wondering how to beat him…
How good was his performance?
Fiddling with the various values that go into myWindsock, we were able to achieve a time on the exact GPX file that he uploaded to Strava that’s just two seconds off what he actually uploaded.
Evenepoel has a reported FTP of 425W and we’ll assume a system mass (rider + kit + bike) of 72kg, not that is makes a huge difference on such a flat course. We will set CRR values and drivetrain resistance values that assume he’s on the fastest possible set up. Presumably they weren’t using slow tyres…
This is the modelled average cda of Remco, including some sitting up for cornering and more. The minimum cda is the value recorded in the wind tunnel and reported.
Using the file that Remco uploaded to Strava, we can play around with the values until we’ve matched his time. This gives us an average cda of 0.194 during the course of the TT (however, this includes all sitting up, cornering etc) so during the long flat periods of the TT his cda will be significantly lower. Evenepoel’s reported cda is 0.17 in the tunnel so this chimes with our estimate including him sitting up and cornering.
What happens to the power requirement as we change the cda from 0.194 up to 0.21? This represents a decrease in aerodynamics of just 3.5%.
cda
Power needed for 45 minutes (W)
0.194
391
0.200
401
0.204
409
0.210
419
This table of values assumes that every single other aspect of your set up is exactly the same as Evenepoel including system weight, rolling resistance and such. In reality, it’s very unlikely that these numbers would exactly match.
The performance by Evenepoel required him to do an average power of 391W which is 6.2W/kg. If Evenepoel was just 3.5% less aerodynamic the required relative power would suddenly be 6.65W/kg. While W/kg is not particularly relevant for time trials, it does showcase the vast difference that a small change in aerodynamics can make in power requirement.
What about an 83kg rider with a reported cda of 0.19? Asking for an Italian mate…
Ganna rode at an average speed of 51.3kph during the race. Adjusting all of the other values to meet this speed comes out at a required estimated average power for Ganna of 440W for his roughly 46 minute effort. This is in line with Ganna’s reported threshold values. In order to achieve the time that Evenepoel did, we can adjust the power values as Ganna is extremely aerodynamically optimised. It turns out, he’s 15-20W short.
Those of you reading this in the UK will, undoubtedly, have had multiple occasions in your life where you’ve wished it was possible for you to change the weather. Well, we have good news for you. For the low price of your annual myWindsock subscription you will now be granted this power. Here’s how…
Open up myWindsock’s Surface platform
Scroll down the panel on the left hand side of the screen
Click on the “Weather Override” drop down menu option
Input values to change the weather
Unfortunately, for legal reasons, we are only able to change the weather within the course simulation on myWindsock, we are not able to adjust the weather outside. That said, it’s still interesting…
You go faster when it’s hot
The human body doesn’t love hot temperatures, especially a British one. That said, there’s an offset – as the air resistance of a bicycle decreases when it warms up so you need to produce less power to go the same speed. Bare with us while we do a little bit of maths.
This expression tells us about the power needed (P_aero) to ride at a given velocity (v). You’ll notice there’s a little symbol that looks like the letter p, that’s a Greek letter called rho and in this equation it represents air density. What this tells us is the power required to ride at a specific speed, v, is directly proportional to the density of the air.
Now, air is made up of tiny little particles, mostly:
Nitrogen molecules ((N_2)) — 78%
Oxygen molecules ((O_2)) — 21%
Argon atoms ((Ar)) — 0.9%
Carbon dioxide molecules ((CO_2)) — 0.04%
Water vapour molecules ((H_2O)) — variable
When it gets really hot, all of these particles whizz around quite a bit faster which means in every cubic meter of air, there’s actually less particles than when they’re moving slowly. When you’re cycling, you have to push each of these particles out of the way – that pushing is the force we feel from the wind and we call it “air resistance”.
Air density is proportional to atmospheric pressure (P – not power this time) and inversely proportional to temperature. When temperature goes up, air density goes down (if all other things are fixed).
This is why you go faster when it’s hot. In real life, the temperature does impact your ability to produce power. But on myWindsock – we can just pretend that isn’t the case…
How hot does it need to be for me to break the Poggio KOM?
The Poggio di San Remo segment on Strava is held by Tadej Pogacar and Filippo Ganna who some how managed to ride up it at 39kph. Neither of them share their power data on Strava but presumably they did quite a lot of watts.
As we’ve already discussed, air resistance decreases when the temperature goes up. That means, you ride faster for the same watts. Imagine a 76kg rider on a 6.8kg bike doing 500W on this climb in a relatively aerodynamic road bike position, with a cda of 0.23 on a windless day that’s 30 degrees. This is 6.5W/kg for around 6 minutes, so pretty good but not alien level world tour numbers.
This gives us a prediction of 6 minutes and 16 seconds. A pretty good time on this segment. But what happens if we change the weather?
Getting the perfect day
We are now going to calculate the conditions required for our imaginary rider to get the KOM on this climb. We will start with the wind…
The Poggio di San Remo segment is twisty enough that if we turn the wind up too much, the headwind section slows us down more than the tailwind speeds us up…
Wind Speed (m/s)
Segment Time (min:sec)
0
6:16
5
6:09
10
6:07
15
6:12
As it turns out, 10m/s is the optimal wind speed (at 30 degrees with this cda) on this climb. Any faster, and the headwind section slows us down more than the tailwind speeds us up.
We need to find 37 seconds to get that time down to 5:30. We will use our optimised wind direction and wind speed to increase the temperature until we find that extra 37 seconds.
Temp (degrees C)
Segment Time (min:sec)
30
6:07
40
6:05
100
6:00
Well, looks like we aren’t getting that KOM then…
It turns out, a regular human has absolutely no chance competing on the Poggio with Ganna or Pogacar. Ah well, we tried.
Every grand tour used to contain a long flat time trial but these days they’re becoming more and more rare. Truthfully, we miss them and the organisers of the Vuelta must have been reading our minds because they’ve bought it back, though we’d prefer for it to be 50km like the good old days.
After making their way out of El Puerto de Santa María, riders will sette into their pace for a prolonged high-speed effort. There are a few twists and turns in Lomopardo and Estella del Marqués, where there’s also a time check. The route is tailor-made for pure time trial specialists so look out for big performances from Küng and Hayter.
The course map
The course is pretty simple, there are around 10 corners that will cause the riders to have to take some kind of action, be that get off their aero bars or slam the anchors on, but in general it’s a flat TT that goes from one town to another – the kind we’ve seen a million times.
The wind map and surface friction
Anyone who’s ridden their bike in coastal European towns will be familiar with the wind. We’ve all left a town into the open areas and found ourselves suddenly being thrown around by the wind between hedgerows and buildings. That’s why we developed the surface friction mapping at myWindsock.
The myWindsock surface friction plot displays the area’s topology. Shaded areas are where the wind will move slower than forecasted due to buildings, trees or other physical features of the landscape. As it happens, for this particular time trial the wind is relative mild but we can still see areas of the course where buildings slow the wind down around the start and finish towns. The wind is forecasted to be around 5m/s (18kph) for the time around which the GC riders set off.
The race is forecasted to be majority tailwind which means that the windiest part of the day is actually the fastest.
As you can see, the wind adjusted elevation plot shows the course to be effectively net down hill, despite finishing at a higher altitude (slightly). Essentially, riding the course will feel “down hill” as riders are pushed along by the wind. Especially in the middle section between the two towns.
Riders will be setting off between roughly 2pm and 5pm for this time trial. Broadly speaking, conditions get slower throughout the afternoon giving the time trial specialists who are a long way down on GC even more of an advantage against the GC riders. The only GC rider who has a track record of beating the TT purists is Roglic, who will be setting off during the slowest part of the window.
There’s a ten second difference between setting off at 15:00 compared to 17:00, so there’s not a lot in it but we’ve seen world tour time trials of this distance won by smaller margins.
How hard is it to gain two minutes?
To have any chance of winning this Vuelta, Roglic will have to ride this TT about 2 minutes faster than Mas. Given this will be the target, how good a performance is actually needed to pick up two minutes on a “bad” time trialist?
A bad time trialist in the Vuelta is a pretty good time trialist:
Enric Mas will probably not mind us saying that, relative to other riders at his level, he’s never been the best time trialist. Reportedly, he weighs about 61kg and has a sustained 40 minute power of around 370W. Let’s say he’s about 4% lower power on the TT bike than the road bike (this is the upper end of “average”) then we can guess he will ride around 355W for this TT. We’ll assume his cda is 0.2, it’ll likely be a little lower but as he’s not a TT specialist he will also sit up a bit, so that’ll drag his average cda up slightly. We will assume his mechanics have him on fast tyres and a fast drive-train.
Plugging all of these assumptions into myWindsock gives Mas a predicted (but large error bars here as this estimate really was a bit of a guess for things like power and cda) of 40:29.
In order to challenge on GC, a top GC rider will need to produce a time of 38 minutes and 30 seconds. What kind of performance does this require? Let’s go back over some of our assumptions and put them into “peak TT Roglic” mode.
Back in the day, Roglic wasn’t just a ‘good for a GC guy’ time trialist, he was great. He’s reported to be at a weight of 65kg, which is a couple of kg heavier than Mas. During this Vuelta, he’s been climbing at a similar, but slightly slower, rate as Mas. Based on his track record though, we can estimate him to be slightly more aerodynamic as well as have a slightly lower power loss in the TT position.
We will assume his sustained 40 minute relative power is 1% lower than Mas at the moment, based on their climbing performances so far during this race. This gives him an estimated 390W to play with, but we’ll assume he loses only 2% of this relative to Mas in the TT bars instead of Enric’s 4% drop off. That means our estimated TT power for Roglic during this TT is 383W. We will also assume a cda of 0.19, we could be more aggressive with this estimate but he’s currently struggling from the impacts of a crash in training before the Vuelta started.
All of these assumptions lead to a time of 38:56, about a minute and a half faster than Mas.
Now, in order to get that two minute gap back, he will have to take some risks on pacing. Let’s now assume he’s magically slightly more aero at 0.18 and loses no power in the TT bars. This is essentially the best possible day that Roglic could conceivably have…
This would give Roglic just over 2 minutes back. He needs a generational day, but it’s within the bounds of possibility.
This blog scratches the surface of how World Tour Cycling Teams use myWindsock to prepare for time trials. If you want a detailed look at Stage 18 of the Vuelta – you can check out the forecast here.
myWindsock’s new version, surface, allows you to customise the information panel on the right hand side of the user interface. While, of course, your account comes pre-installed with a large array of pre built panels focussing on many aspects of cycling including weather, aerodynamics, terrain and more – each rider is different and this blog will focus on how to go about setting up your own panels.
Panel Basics
This is a screengrab of the right hand side of the screen on desktop with the Ironman 70.3 World Championships course pre loaded into myWindsock. By clicking the three dots on the right hand side you’re able to see a drop down menu which contains the panel you’re in, the ability to edit it and an option for panel library. Next to the three dots, there’s a a star, which allows you to input a text based description of what you want and myWindsock will automatically adjust the panel based on what you want.
The pre loaded Panel Library comes with six options…
Default – A broad overview of the course.
Performance Deep Dive – Focussing on effort and power delivery.
Wind Analysis – This is self explanatory.
Course and Terrain – Focusing on the elevation and physical aspects of the course.
Race Plan – A panel designed for race preparation
Aerodynamics and CdA – Focussed on aerodynamic analysis
Users are also able to update the pre loaded panels, as well as design their own from scratch. Today, we’ll focus on editing the Race Plan panel to go from the default panel to one more focussed on triathlon.
Editing a Panel
There are two ways to edit a panel, the option from the drop down menu or the text input option.
The data panel can be customised with a prompt.
In order to decide what to prompt the panel we need to decide what we want to know in order to prepare for the race. Preparing for a triathlon is a unique challenge as we need to carry a lot, it’s not actually a maximal effort and we need to get the gearing correct. It’s also, in the case of professional racing, a “semi drafting” race where some advantage is to be gained by being among a group of riders even if they must stay 20m apart. This means that energy investment is less linear than during a pure time trial as energy applied at seemingly non optimal points in the course might actually make sense in the context of non-draft triathlon.
We can use the Panel Index to see what’s currently contained in the Race Plan. With this, we can see what’s currently contained in the plan and decide what we want to delete or add. The first thing we’ll do is prompt the text box to delete the “W’ Balance Risk” plot as I don’t have up to date critical power information for this race – just a rough idea of the power I could hold, so we’ll delete this as it provides a false precision for the pacing plan in my specific case.
We can ask myWindsock to delete the panel for us in natural language like this. The new panel index now contains four charts.
How many charts is too many?
For a course that’s 90km with mountains, it’s possible to summarise all the pacing and race preparation information between 5 and 10 charts. The exact charts you feel you need prepared is left for the user.
The first thing we will do is add two charts, one which has an elevation profile and a second which shows us the distribution of gradients during the ride.
Our new Panel Index looks like this. We can now go onto looking at the Pacing Strategy Section.
UK Time Trial Events
