Category: Discussion

Highlighting and discussing events in cycling and using myWindsock to improve performance.

How does your CdA compare?

Everyone knows that aerodynamics are extremely important for cyclists – even more so for cyclists concerned with their speed. myWindsock have analysed thousands of files from time trials in the UK and looked into the distribution of CdA values and what speeds result from this.

This graph is an analysis of how the average CdA required for various speeds during a time trial. The black line represents the average and the faded orange bars represent the variance of values. You’ll notice a much wider range of cda values for speeds under 40kph as it’s much more possible to muscle your way into these speeds with a lower CdA. At 50kph, we seldom see a rider with a cda of more than 0.2 which shows just how aero British riders are!

Why is cda important for cyclists?

The term ‘cda’ actually stands for two things, how slippery you are (cd) and your frontal area (a) – CdA is the product of these values. It is used by engineers as one term because practically, it’s often difficult to separate the effect of the two with measurements. Generally speaking, CdA is a measure of how aero you are.

Why are aerodynamics important for cyclists?

Aerodynamics play a crucial role in the sport of cycling, as they can significantly impact a cyclist’s performance and speed. When a cyclist rides, they face resistance from the air around them, on a flat road this takes up roughly 80% of total resistance. The faster a rider travels, the greater the air resistance they experience. By optimising their aerodynamics, a cyclist can reduce the drag they face and improve their speed and efficiency. This can be achieved through various means, such as selecting the right gear, maintaining a good position and using aerodynamic wheels, helmets and skinsuits. Even small gains in aerodynamic efficiency can make a significant difference in their overall performance and race results.

myWindsock allows you to analyse your aerodynamics, with a number of CdA measuring features available calculated with a combination of your power data and the weather where you’re riding.

myWindsock premium features

myWindsock premium will measure your CdA on every ride! For around two pounds a month you will get…

  • Unlimited Athlete Profiles 
  • Unlimited Uploads
  • Design Optimum Power Plans
  • Aerodynamic Analysis & Testing**
  • Advanced Charts & Analysis
  • Weather Trends
  • Unlimited Virtual Athlete Profiles
  • 15 Strava Segment Windsocks
  • Unlimited Daily Activity Uploads (fair use)
  • Strava Segment Filtering
  • Strava Leaderboard Effort Weather*
  • Advance Cycling Weather Metrics
  • Download Virtual Partner
  • Annotate the race or training plan with Course Notes

This huge array of features will cost you $2.50 (£2) a month – sign up here.

Power and aerodynamics – how can you strike a balance?

Time trials are an interesting discipline and all of you reading this will likely have found yourself in a position where you’ve done one of the following… 

  1. Gone way too aggressive with your position and lost huge amounts of power 
  2. Not gone aggressive enough and been beaten by riders doing much lower watts 

Both of these two options are sub optimal and the best way to address them is a good bike fit, to convince you of its importance though we have decided to take a look at the consequences of getting it wrong on a CTT time trials course by using myWindsock to help us make sense of the data.

CTT and myWindsock

Before we do that though, a little interlude on how you can check a CTT event in the myWindsock app. 

All time trials in the UK are available on myWindsock, head to myWindsock and click planner where you’ll be able to click on the UK Time Trials option.


You can select between open and club events and see race conditions by hitting the ‘view event’ tab. From here you’ll be presented with a forecast that has race day (and time) conditions that you can adjust to match your own power, cda and event start time. We will now use one of these forecasts to see what happens when we get the balance between power and aero a little wrong…



What happens when we get the balance wrong?

So, armed with this new information on how we can view CTT events in myWindsock – let’s check out Reading CC’s club 10 for the 4th of April as an example. Clicking ‘view event’ we are presented with the following forecast… 

Let’s imagine our test rider can do 350W for 20-ish minutes with a moderately aggressive position. The cda we might see for this sort of position will be around 0.250±0.2 for a 70-80 kg male rider, the cda for a female would be a tad lower as women tend to be smaller so have a lower frontal area. This gives us a time of 22:32 for this 10 mile course, pretty handy. 

Our rider then makes some adjustments, goes super narrow and drops his saddle down to get as aero as possible – throwing comfort and power production out the window. Due to this, he’s suddenly limited at his maximal aerobic power, which for a rider who has a 20 minute critical power might be around 275W, but his cda is now 0.19 – let’s see what happens to the time… 

We see that our rider is suddenly 30s slower over 10 miles. Now let’s imagine our rider does the opposite and suddenly veers the other way – raising their stack really high, going wider and moving the saddle back up high to maximise power production. Imagine they achieve a 20 minute power of 370W in this scenario but suddenly have a more typical road bike cda of 0.350, what happens to the previous time of 23:03? 

Suddenly we are faced with a scenario where our rider is doing 100W more than the aggressive position yet going much slower! 

These numbers are exaggerated slightly to illustrate a point but the fact remains that a balance must be struck between aerodynamics and comfort. 

Key takeaways

  1. Time trial positioning is a 3-dimensional problem. The time you’re able to complete a course is a function of power and cda – finding the minimum of this function is essentially the art of time trialling boiled down to mathematics!
  2. 3D calculus is relatively hard in the scheme of maths, luckily myWindsock does this for you as it calculates a predicted time based on power and cda, all you need to do is play with the numbers to find the best option for you.
  3. Usually, when striking a balance between aerodynamics and power production – lean towards aero but don’t overdo it. This way you can get quite close to the optimum without being overly aggressive and risking injury.
  4. Get a bike fit… 

If you want to perform to the best of your ability at your next cycling time trial open or club event, use myWindsock to check the forecast and plan your ride accordingly. Turn data into information and race with confidence. 

4 vital charts for time trialists

1. The Map

The Wind Lines on the myWindsock map give you an intuitive view of the course and the prevailing wind direction. The Wind Lines are colour coded blue for tailwind, red for headwinds. See the wind arrows, they show the wind direction and the wind speed for all locations on the route. See wind arrow icons for more details.

2. Feels Like Elevation

Knowing what to expect is a crucial part of your pre race preparation. The Feels Like Elevation chart is the perfect chart to describe how the road will feel when the elevation has been adjusted for the wind resistance. You now know just how the road will feel.

3. Where power matters most

Knowing where to focus your precious energy is a crucial part of time trialing. This is where the chart “Where Power Matters Most” is a vital tool in your pre race preparation. The orange sections on this chart show where power has the greatest affect on your time. The deeper the orange the more important those Watts are!

4. Rolling Average Speed

Now this one is for your Chimp, you know that voice that is saying, “you’re going too slow!”. This chart shows how you can expect your average speed to change during the event. For example, an uphill or headwind start will keep your average speed lower than your target average speed. The better way is to understand how your average speed will evolve from the start to finish so you can stick to your plan.

Now to check out your time trial. View you event from the Cycling Time Trials page.

CiCLE Classic Women’s Preview

This is an exclusive myWindsock overview for FTP Racing, ahead of the CiCLE classic 2023 race.

Current forecast: CiCLE 26th March 2023 14:00

Weather Overview

Light isolated showers possible throughout race.

Wind Report

Moderate Breeze from the North East, with maximum gusts of 32mph. Wind expected to gradually slow throughout the event.

Charts > Wind Speed

Key Moments

Crosswinds

0-5.5km

95km – To Finish

Breakaway opportunity/risk

The following orange sections indicate areas where a break could be successful.

View this graph within the app by clicking ‘charts > Where power matters most’

More analysis…

We recommend working through the myWindsock guide for latest forecast highlights. Go to forecast: CiCLE 26th March 2023 14:00

Have a great race!
Ben

How much power do I actually need?

Time trials are a weird sport as aerodynamics shapes a lot of it. The strongest rider doesn’t always win! It’s important to have a solid training plan in place. This should include a mix of endurance rides, interval training, and strength work to improve both your aerobic and anaerobic capacity. Ideally, you should be training at least 4-5 days per week, with a combination of longer rides (2-4 hours) and shorter, higher intensity efforts.

In addition to your training, it’s important to focus on your nutrition and recovery. This means fueling your body with high-quality, nutrient-dense foods to support your training, and making sure to get adequate rest and recovery between workouts. Proper hydration is also key, especially in the days leading up to your time trial.

When it comes to the day of the time trial, there are several factors to consider. One of the most important is pacing – it’s critical to start strong but not overdo it in the first few miles, as you’ll need to maintain a high intensity for the full duration. A good rule of thumb is to aim for an even effort throughout the ride, with a slight increase in intensity towards the end if you still have some energy left in the tank.

With all of that said though, once training and pacing is dialled there’s the question of how many watts we actually need?

Are you a UK Time Trialist?
All UK Time Trial Events forecasted here.

How many Watts?

We decided to sift through the data to see what it would tell us. This graph is taken from around 13,000 time trials in the UK and shows us how much power we need to achieve various speeds. The vertical orange bars show us the range in power that we saw in our data.

How aero?

Exactly how aero riders were also varied. Past 43kph ‘average’ was a cda of 0.2 – this is seriously slippery! It also shows us that the pointy end of the field in UK time trials are also extremely aero, look how small the range in cda is! No wonder that the sharp end of championship races is so closely contested.

If you want data like this to accompany your training, check out myWindsock here!

Are you a UK Time Trialist?
All UK Time Trial Event analysis here.

How to analyse time trial performance with myWindsock

Time trials are a strange kind of race. Figuring out whether or not you’ve done well isn’t as simple as it is in a criterium, road race or cyclocross race where you can simply see how you’ve done against the rest of the field. Time trials aren’t that simple, where conditions on the day and equipment can make for wildly unfair comparisons between the rest of the field. Sure, you can look at power data but as we know – watts aren’t everything and aero is. Without a device measuring how aerodynamic you are, how can you tell how you performed? 

Recently, I took part in a road bike time trial and found myself kind of underwhelmed with my performance. On paper it was fine, I averaged 40 kph on a relatively grippy course but my power was low and I felt rubbish with a high heart rate. The race was on Saturday and on Monday I woke up ill – which explains some of it but how can we look at performance?

The aims of a time trial 

Time trials are a quest for efficiency. You’ve got two factors, the efficiency of your body in producing power at the legs (biochemical efficiency) and then your mechanical efficiency which dictates how much of your leg power is converted to speed. The beauty of time trials is that we are really only racing ourselves and an improvement could mean that the answer is yes to any of the following questions… 

  • Did I produce more power?
  • Was I able to push myself harder than before? 
  • Was I more efficient? (More power for a lower heart rate, more speed for the same power etc…)

The thing is, working these out does require a little bit of post race analysis. For this, I use Training Peaks and myWindsock, this blog will show you how… 

Did I produce more power?

Shortly put, not really. I did my third best power of 2023 but I hadn’t really done a maximal ten minute effort and, as you can see, my power from ten to twenty minutes declined horribly. The strange thing was that I am quite fit but didn’t even get close to my previous best efforts. I woke up quite ill on the following Monday which explains this.

Was I able to push myself harder than before?

At the time, I felt like I was going full gas. Burning lungs, legs and the copper taste in my mouth. It turns out I should have been a little more suspicious of the post race cough which basically continues to this day!

My heart rate was pretty high and quite stable during the race, usually I’d expect it to come down on descents and it wasn’t doing this. I did push myself hard, but I suspect this was achieved as a result of illness more than anything else. 

Was I more efficient?

Hopefully, this part will allow me to salvage some kind of positive from the time trial. We can use myWindsock’s Strava report to have a look at this! My average cda for this, according to myWindsock, was 0.308! This is shockingly high for me. Usually, in a road bike time trial myWindsock has me around 0.25±0.02.

We can also see a low weather impact of 3.9% and ideal temperatures with no rain. The road surface was not perfect but I’m not sure that explains the woeful performance from me.

When is a bad day simply a bad day?

The neat thing about myWindsock is that, for me here, it was the final piece in the puzzle to solidify the fact that I was just rubbish. Sometimes, that happens. My power was low, my heart rate was high, I wasn’t very aero yet it was a relatively fast day. A weather impact of less than 5% is minimal and definitely not enough to be an excuse. 


If you want to analyse your performances in the context of the conditions – check out myWindsock here.

How much slower is +5Kg (11 lbs)

Due to a very serious spinal injury, myWindsock founder Ben, had 12 months without cycling. He returns to cycling 5Kg (11 lbs) heavier. How much slower can he expect to be? See the Instagram post below.

A bit more detail

We are all about real world riding, so we picked a very typical 25 mile course, on an average UK spring day. This course has some small ups and downs but would be categorised as flat. You can try the course yourself here, J4/8.

Our experiment was acrross 3 power ranges, 100, 200 and 300 Watts. Look at the chart below to see the differences between the powers. The differences are considerable. Remember, the time affect of a resistance compounds the slower you are moving. Less power, greater cost. No more, “I’m too slow for that upgrade” 😉

Often cyclists are surprised by how little time weight costs on a flat course. We are told lighter is always better and to upgrade to the lightest components. As you can see losing weight will have an affect on your speed, but we hope this will keep everything in perspective when making lifestyle and financial choices.

How to try your own experiments

The beauty of myWindsock is that all the variables are accounted for, Physics, Weather & Performance. This allows you to get real world test results in a virtual environment.

  1. Simply pick any route from your “Activities & Routes” menu.
  2. Set the date and time of your experiment for the most accurate cycling weather.
  3. Make changes to your Virtual Athlete profile.

Have a try yourself here.

Preparing for my time trial

Hello readers of the myWindsock blog, lately you’ll have noticed we’ve been a little quiet here. This is because we have been working on partner content with CTT and NoPinz but we are back today and I (Tom) have signed up for a TT this coming weekend! I thought it might be a good opportunity to do a mini series on how I will use myWindsock to get ready for this TT, predict my performance and plan my ride. 

The race is a road bike time trial – this means I’ll not be allowed a TT specific bike or helmet – as well as restrictions on the kind of wheels I can use. It’s a 15 mile time trial on the H15/10 near Maidenhead. 

Luckily, I’ve done a few road bike time trials so I have plenty of previous data to help me prepare.

Predicting the race duration

The first step is to figure out roughly how long the race is going to take me. For this, I’ll need a cda value to plug into myWindsock. Using a time trial I did in August last year on my road bike I can get a value for my cda which will be relatively accurate. The stats from the race are below…

I didn’t have a great day averaging a lower power than I wanted, but the race has come in handy as I can use it to hopefully have a better day in future! A good example of why getting out to race is rarely a bad shout! From this race we can use my live cda plot to predict performance at another TT.

This plot shows us how cda develops with time and generally there’s a couple of key takeaways from it… 

  1. My cda on descents doesn’t vary a huge amount, but does get slightly lower as I go down hill. 
  2. I sit up way too much on faster climbs – this is something to avoid in my coming race. 
  3. My flat cda is around .253, descent cda around .247 and climb cda around .270.

The second step is to figure out how much power I can do at my race. The previous race we used to calculate my cda wasn’t representative of my abilities at the moment but recently I’ve done a critical power test. The outcome of this test put my critical power at 360W bang on – this is the power I’ll aim to average during the course of my TT at first and make micro-adjustments based on predicted race duration.

Plugging these numbers gives me a time of 34:39, or a speed of 43.2km/h… Stay tuned for tomorrow’s blog on my power plan, with a weather impact of 4.5% predicted, he who rides the smartest in the wind will prevail! 

How will a ride feel?

Take a look at the below graphic for this week’s Manchester District 10 mile. If you subscribe to myWindsock Strava Activity emails you may have already seen a similar graphic for your own rides. If not, activate your emails here.

https://mywindsock.com/modules/shareables/map.php?source=strava_segment&id=22428508&time=1677938400

56.4% headwind isn’t good news! However it is only through viewing the Feels Like Elevation graph beneath that we begin to see what affect the wind will have on the course.

Relating the wind to it’s equivalent elevation gain is one of the ways we are helping to describe the weather for cyclists. Learn more about Feels Like Elevation.

So what does this tell us? Initially we see an easing of the course profile due to the tailwind start. Then, once the headwind begins, the road begins to feel harder than the traditional elevation profile would suggest.

Graphs like Feels Like Elevation can be found for any past activity and any future ride forecast. Simply select the route from you Activities & Routes menu to begin.

If you haven’t already signed up for myWindsock Weather & Analysis, start here.

How much time does a skinsuit save?

If you’re reading the myWindsock blog, or came across this from our friends over at NoPinz it’s likely you already know what a skinsuit is and you might even be sold on the virtues of their number pocket that saves you watts. If you attend a local time trial, it’s likely the pointy end of the field will be in a skinsuit and these days, most people wear one for all forms of racing. The uninitiated, or even those of you that only take part in the skinsuit wearing because everyone else does, might be left wondering why people wear these? Surely a jersey and shorts is more comfortable? It certainly makes using the bathroom a little easier. We know a skinsuit is faster, but how much difference will it really make on race day? 

With great partners like NoPinz, we are able to get a hold of some data that tells us how many watts a skinsuit saves a rider and this can be converted into a change in cda. That’s all fine and good – but still doesn’t mean much on race day. What we really want to know is how much time will this save us today, or on the day of our race? During his hour record attempt, GCN’s Ollie Bridgewood used a NoPinz skinsuit to save himself a whopping 20W. These numbers are seen across the board and a ten percent reduction in drag due to a well fitted skinsuit is commonly seen.

Here at myWindsock, we specialize in turning data into information giving you confidence on race morning. Cycling is an uncertain sport and anything that can reduce the noise in the information that drives your decision making is valuable. By making use of our physics engine, we can calculate how much time a skinsuit will save you on a particular course.

A worked example – the Perfs TT

For our simulation, we will use two runs of myWindsock on Sunday’s open time trial which is being held on the Portsdown Hill circuit. We have fixed the cda at 0.220 for the first run and, while keeping all other variables fixed, we will reduce the cda to 0.198 for the second run. This is roughly the proportion of savings a skinsuit will achieve – worth around the 20W that Ollie was able to save with his Flow skinsuit from NoPinz. For this, our test rider is pretty handy – being able to maintain 325W for the duration of the TT with a system weight (bike, rider and equipment) of 80kg.

Test run 1: cda = 0.220

Our rider is coming in at a shade under 39 minutes with an average speed of 41.1kph – not bad! Let’s improve his wardrobe choice slightly and pop him in a NoPinz skinsuit and drop that cda.

Test run 2: cda = 0.198

The savings are huge, more than a minute! This is just the skinsuit too, imagine the cumulative savings from pacing, optimised position and other equipment choices. Slower riders will also achieve greater time savings for the same proportional saving in aerodynamics. As we can see, a skinsuit is worth it.

If you want to see how the watt savings touted by brands turn into time savings on your local TT course, they’re all available in myWindsock pre-loaded. Just hit Activities & Routes, UK Time Trials, and then scroll until you find your open TT! Or simply go here UK Open & Club Time Trials. On top of this, you’ll be able to see what kind of power is required for whatever performance level you are targeting.