Position, position, position

Embed from Getty ImagesThe adverts in bike magazines try to convince you that their components are more “aero” than somebody elses, the tech time trial geeks in your club are obsessed with “aero”, aero wheels, aero frames, aero handlebars, aero seatpins, aero chainrings, even aero pedals, the list goes on. This is all well & good, aerodynamic kit does make a difference, especially in a time trial, but if you’re concentrating on having the most aerodynamic bike, you’re maybe spending vast sums of money on vanity, rather than first dealing with the real issue, you.

The ‘You’ Issue

A quick study shows that somewhere between 65 to 85% of aerodynamic drag is reported to be caused by the rider, the rest by the bike. The massive 20% variance across riders is caused by many factors. For example, take two riders with the same limb & body lengths, but one carries lots of weight in muscle or fat (or both), while the other is running at ‘pro-level’ body fat. The two riders would therefore fit exactly the same size bike, which has the same drag for both. Where it varies is that the large rider’s forward motion is affected by his size much more than the smaller rider, so of his overall greater drag, his bike’s percentage share is smaller. There is no standard percentage drag apportioned to your bike, it’s different in everybody, it’s even different depending on what clothes you’re wearing. So any figures you see on ‘time saved over 40km’ for any particular component, are based on many assumptions. We can safely assume the marketing information is going to be at the more generous end of possible savings, while not being untrue, only a very small number of people may get this maximum benefit.

Bits n Pieces

This brings us back to component choice (I include the big items like frames in this, but not wheels, see later for that). If you’ve not got your optimum position, or something reasonably close to it, buying all the aero kit in the world may not to help you at all, it may even hinder you. Bad equipment choice, from a ‘fit’ aspect, can lock you into a less than perfect position by not allowing your body to get as aerodynamic as possible. It’s all too common, when I see time trial pictures posted, there is a strange draw to have a look at the bike-cost versus position, quite often it’s incredible that so much is spent without ever going for a proper bike fit or taking good advice.

As a start, a fully adjustable set of aero-bars & an adjustable stem are very cheap options considering the cost you’re intending to spend. That should allow you to set up a position correctly on your current bike, which, may not make your bike look pretty, it may save you a lot of money in the long-term. Then you have the opportunity to know exactly where your saddle & handlebars should be in relation to the bottom bracket, a quick check with a tape & a spirit level on your desired frame (with wheels in) should indicate which size it is you’ll require. Not going along this route may result in you buying what would be your normal road bike size. Often, riders will require a different size, with a longer or shorter top tube, or a lower stack height. You’ll need to get your body to fit this new fast-looking bike without compromising your ideal position, while using available kit. So if you buy one with too short a top tube, you may not find a stem long enough, time trial bike fit is not simply a case of ordering a medium, if you normally ride an off-the-peg medium road frame. It requires a bit more work, you may require something different to what you expected.

The Wheel Question

This is another vastly complicated subject, in this instance it comes under a completely separate topic, as wheel choice has zero impact on position. So you can probably buy your wheels first, use them on the new bike, especially as wheels have a relatively large impact on your speed. But as with other components, there’s no hard & fast rule as to which wheels are best for you. Weather conditions, a rider’s weight & ability to buffer cross winds also come into play here, so trying wheels before you buy could be another valuable piece of testing before you reach for the bank card.

The Gist Of It

Spending some time really looking at your position, or getting somebody with some knowledge to look at it, probably doesn’t give you that instant gratification of buying a shiny new component, or a flash time trial bike. It’s maybe the non-sexy option, maybe it’s difficult, maybe you’ve “not got the time” or maybe you believe the adverts to the letter. The fact is that you could buy ‘the fastest frame in the world’, but if you buy a size you can’t replicate your ideal aero position on, then you’re going to be catching a lot more wind.

The golden rule should be to sort your position first, then (and only then) find the aero frame & components that allow you to replicate that position. This is where buying your new TT frame from a local bike shop really helps, they should be able to let you ride a bike of similar geometry & give some valuable advice on the matter, before you spend your hard-earned cash.

Time trial bikes look great, having one makes people feel ‘a bit Formula 1’, they’re a desirable addition to your stable. But always bear in mind the advantages you get from components are minimal compared to your body position. Be sure you can transfer your highly efficient position across to the geometry of a new time trial frame.

Don’t get carried away by a bit of shiny aerofoil bling, choose the correct bike by spending some time getting your aero set-up dialled in on another bike first.

 

 

 

 

Breaking Wind

I’m often irritated by reading some very uninformed & aggressive forum trolls ideas on what makes riders fast in a time trial, the bit that bothers me most is the complete lack of understanding of aerodynamic theory. This isn’t too hard to grasp, at it’s most basic, something small creates less drag, while something big creates more. But it gets complicated when we start looking at cross-sectional area & body lengths, here’s some busted myths…

I don’t go fast enough to use any aero kit.

Aye you do, even if you’re ground speed is low, you most likely race in winds blowing faster than you can ride, so you’re combined air speed is at a significant level where small aero advantages will make a big difference. It’s all too often you see riders off their aero bars while riding into a headwind, this is the worst thing you can do, this is precisely the point that you need to be the most aerodynamic, regardless of your overall average speed.

Get aero in a headwind, think about air speed rather than road speed for aerodynamics.

Why are pro riders going faster in time trials when they lose weight?

It’s not hard to understand, a smaller object requires less power to travel through air at the same speed as a larger object. A larger object has more wind resistance. So if we take one ‘sample rider’ weighing 80kg, then reduce his weight to 75kg, will he be faster on the flat? The answer is undoubtably yes. But you’re now thinking that it only counts if a rider reduces that weight as fat content, incorrect. The rider can reduce the weight as a mixture of fat & muscle, making their limb & torso cross sections smaller, while not reducing their overall fat percentage, here’s how.

Lets say this ‘sample rider’ is pushing 400 watts during a time trial at 80kg, 400W isn’t too much in muscular terms, but it’s a lot in aerobic terms. Your average skinny youth rider is perfectly capable of producing a wattage much greater than this in a sprint, so that in itself displays the required muscular physique to produce over 400W. So if our ‘sample rider’ reduces their weight to 75kg (for example if they were already at a very low body fat percentage), then they have lost 5kg but still have plenty of muscular power left to produce the required wattage.

Aerobic power output does not require big muscles, smaller muscles have less drag, an endurance rider can lose muscle and still go just as fast aerobically. Similarly, if you’re a chubby cyclist, you could record some much better results from eating less cakes & drinking less lemonade.

If I go as low as possible, I’ll be quicker?

Also not true.  As the hip to torso angle decreases, so does power generated, so a rider who’s front end is crouched as low as possible is losing power in that position. This results in a play off between power & aerodynamics, something that is going to be very hard to replicate unless you have access to the measurement resources of a pro rider, so you’re going to have to estimate it yourself. There’s also going to be physical limitations here, Jonathan Vaughters has said that his pro rider, Dan Martin, has bad hip flexion, so will be unable to attain a very aerodynamic time trial position, potentially ruling him out of winning grand tours with a large amount of time trialling in the future. There’s also the physical limitations involved here, get too low and your thighs will start to hit your ribcage. It’s all about finding a ‘sweet spot’ that is correct for you as an individual, a compromise between aerodynamics & power generation.

Low isn’t always best, everybody is different, so it’ll take a bit of work for each person to find their optimum position, don’t try to copy somebody else exactly, but certainly take some tips from photo’s & videos of pro’s with a similar body type to yourself who have access to wind tunnels.

I can go just as fast as somebody else who weighs the same as me with the same power output.

Maybe you can & maybe you can’t, some things are just down to genetics. If you are the same weight & height as somebody else, but possess a longer back & shorter legs, you may have a lower aerodynamic drag. A simple rule is that longer objects along the direction of movement through air cause less turbulence, so a rider with a long body like Wiggins for example has a genetic aerodynamic advantage, he has short arms relative to his size and can also tuck those away easier as everybody has to conform to the UCI positional rules which advantage & disadvantage certain body types. So if you have access to a power meter, you may be able to find your optimum position by doing some field testing, but it has to be very closely controlled, likely impossible to do the estimates on different days, or even different conditions on the same day, a very subjective & complicated area to step into.

A time-trial bike is quicker than a road bike.

Again, this statement isn’t true in itself. The statement should be, ‘a correct position on a time trial bike is faster than a correct position on drop bars.’ I’ve been really shocked by the awful positions of some riders on tri-bars from early season Scottish race photos, some actually assuming worse positions on tri-bars than holding the tops of the bars, yet they assume they are ‘aero’ as they are using aero kit. What people forget is that aero kit in itself isn’t aerodynamic as such, it is used as a tool to get YOU more aerodynamic. You can spend all the money you like and bolt on all sorts of stuff, but without some thought & correct positioning, you could be better off without it.

Spend some time to get your position correct, don’t just bolt on kit & hope for the best.

A constant heart rate gives the fastest time.

As far as heart rate goes, it’s a historic measurement, it measures the effect on your body of what you did to it a few minutes ago, so in short time trials it is virtually useless for the first few minutes until you reach a plateau. At that point, if you encounter a headwind and you maintain the same speed, your heart rate monitor will tell you all about it, just a bit too late. Another effect is something called cardiac-drift, where your heart rate rises over time with a constant power output, so if you maintain a constant heart rate over a time trial, your will be producing less & less wattage as time goes on.

Heart rate isn’t an ideal guide to riding a time trial, but can be used wisely if you’re aware of its limitations.

A constant power output gives the fastest time.

You’ll not be happy about this if you’ve just bought a power meter & you think that if you find your FTP (Functional Threshold Power) and ride at exactly that then you’ll produce the fastest time possible, that’s not what will happen.

Every race will have slightly different gradients, slightly different wind conditions, different weather, traffic etc, there’s plenty of variables. It’s been shown that if there is a small hill with a subsequent small descent, then it’s best to power over that slightly and recover on the downhill (you’ll always find it much harder to maintain high wattage downhill, so it’s almost an enforced rest). It’s also been shown that the differences in power outputs when riding in a tailwind are much smaller relative to the difference in speed you gain, so shoving out a load of watts in a tailwind won’t necessarily gain you that much time. The opposite is true in a headwind, where large time gains can be gained through smaller changes in wattage.

So for those using power meters there are some very specific strategies you could use to achieve the fastest time possible by varying your wattage throughout your ride depending on gradient & wind conditions. An absolutely constant power output is never likely to give you the best result, it’s worth experimenting to see what works best for you.

Aerodynamics is irrelevant when climbing.

Take the Tour of the Campsies time trial as an example, the fastest riders can be seen climbing ‘The Crow’ on the tri-bars, Arthur Doyle is a prime example of this, look over some recent photo’s if you don’t believe me. If you require heavier aero kit for the rest of the ride, you may as well use it on the inclines. We can also see that pro riders like Richie Porte used tri-bars during Paris-Nice to win the Col d’Eze time trial. Porte opted for this setup over the lightest possible bike he could use, he did this because it proved faster, I trust Sky’s boffins to be able to calculate this kind of thing correctly.

Again, there’s more to this than meets the eye, pro riders are climbing significantly quicker than amateur riders, so there will be a larger effect the faster the climbing speed. Any rider will gain an advantage from using tri-bars & aero kit on anything but a straight out hill climb.

Conclusion

Hopefully I’ve given some riders something to think about, I really hope I don’t see those kinds of photos from early season again, with riders who look like they’ve not even spent 20 minutes setting up their TT bikes correctly. Put you bike on a turbo trainer, set up a mirror so you can see your position and aim to get ‘in the tube’, i.e. everything apart from your legs into an imaginary horizontal tube. The smaller the imaginary tube you can fit your body head & arms into, will generally prove to be the most aerodynamic, but remember not to go too extreme or you’ll reduce your power output too much. It will take some time to perfect, but it’s worth much more time to you than buying the next very expensive bit of aerodynamic kit and not using it optimally, or even worse, it slowing you down through poor setup.

Subsonic Flow

There’s been a lot of chat about Gorilla Greipel’s new chrome dome helmet, but lets look at the facts and come to the understanding that these are here to stay, especially in the northern classics & more generally in colder climates like ours.

A bit of History

Proper polystyrene protective helmets began appearing the very late 80’s in Scottish racing, they became part of the rules in about 1991 & the old foam & leather ‘bunch of bananas’ or ‘hairnet helmet’ became confined to history forever. The very early helmets were a little bulky, but then Giro, Specialized and a few others developed some good looking (at the time) lids and things moved on from there. Greg Lemond was an early pioneer and trailblazer of everything aero, likely prompted by sponsor pressure too, he promoted Giro helmets and used a very early closed vent version of the ‘Air Attack’ model called the ‘Giro Track Attack’ which reputedly had a 5% aero advantage over a bare head, although nobody was listening back then (things have gone full circle now and a new ‘Air Attack’ now exists along with a development ‘Track Attack’). Meanwhile the pro’s were regularly sitting at the side of the road protesting about having to wear the things, while us amateurs were just getting on with it. Things changed, the pro ranks were allowed to discard the lids on the last mountain of a stage race, then eventually they had to wear them all the time, that’s where we are right now.

Some Technicalities

You can understand to some extent what the pro’s were annoyed about, early helmet technology had resulted in some not particularly well vented examples, they had to wear what their sponsor gave them, so helmet choice/luck became part of the game. Helmets then became increasingly vented to keep the top riders happy, those riders needed them to have enough airflow over their head for 50 minute climbs in 30 degrees heat a low speeds. All the adverts were stating the amount of vents, as if it was the key selling point to ‘normal’ cyclists.

Now consider your average Scottish race, you’re unlikely to be climbing many hills over 5 minutes, at most it’ll be 10 minutes climbing, temperatures on the warmest day are 25 degrees one day a year, but likely you’re racing in an average of 15 degrees, punching over small hills at a reasonable speed. Do you really need as much airflow as the 50 minute, low-speed, 30 degree heat boys? Of course not, don’t kid yourself on.

This brings us to ventless aero helmets for road racing. They currently look ridiculous to us, but so did all helmets when we first saw them, maybe we’re just not used to them yet. The Sky team have been using them for a couple of seasons with their Kask helmets. Although these ones show the vents and retain the look of a vented helmet to some degree, although the yellow ones were ridiculous. So we have a half way house here, some manufacturers are trying to retain a vented look, while others like Lazer are going full aero, which is the likely outcome over the next couple of years. The vague vents will slowly disappear in order to become more aero, the UCI will change the rules and stop everything becoming too aero and un-Merckx like. So we have a hidden race, between an acceptable look and the desired function, to go faster. Greipel’s claimed sprint max speed was 74km/h in one of the Tour down Under stages, so how much advantage did this aero hat give himself and his team, with Henderson dropping him off into the final sprint at his claimed 70km/h? There’s obviously no data out yet, but Cavendish’s worlds helmet cover on his Specialized lid will explain that it’s a measured ‘marginal gain’ and worth enough watts to encourage manufacturers to develop products. You’ll hear terms like ‘subsonic flow’ ‘boundary layers’ & ‘turbulence’ being banded about in marketing material, it’ll all become very technical, they’ll all claim to be the fastest.

Helmets for Scotland (or anywhere cold)

Do we need all these vents, as explained above, we don’t. So as you’ll see in the northern classics from now on, non vented helmets will become prolific, even more so in cold markets like our country. If pro’s can wear non vented helmets in stages of le Tour, if we’re honest with ourselves, we could wear them all year round. Especially in winter, they would probably make a significant difference with reduced airflow and nice warm head. We’re currently wearing helmets with 20 something vents in minus temperatures, there’s no logic to that. It comes down to aesthetics, vented helmets look correct right now, only because since 1991 we’ve got used to them, previous to that anything other than a hairnet, a bare head or a cap looked right. Times change and in 5 to 10 years time, once there’s plenty of pro photos out there of top riders saluting the crowd in an aero road race helmet, you’ll think aero road helmets are the thing to wear in the bunch or training ride.

The future of headwear

Expect Assos & Rapha to ‘develop’ breathable under-aero-caps to complement your new fast lid, where there’s a marketing opportunity, there’s the momentum to make anything stick. Aero, ventless road race helmets, you’d better get used to them, they’re not going away, in fact, they’re probably a good idea in Scotland, you’ll get used to how they look.