[music] Ollie: Drafting, it's is one of the features
of cycling that makes it so interesting and fascinating tactically. By sitting behind
other riders and sheltering in their slipstream, you can save a lot of energy. You can ride
at the same speed as them, but for less effort and it's most noticeable at high speed. It's
why we see riders performing through and off taking turns on the front. It's why we see
sprinters bursting out from behind their lead out trains at the last possible moment. It's
why in the team pursuit, we see riders constantly rotating around and sheltering in the wheels.
What about when you're climbing? I mean, when you're climbing, you're typically riding at
a lower speed. Is drafting still important then? Or is there a cut-off when drafting
ceases to become important because you're not going sufficiently fast?
Well, we're hopefully going to answer that question by first listening to what a world-class
climber and Tour de France rider has to say, talking to a world-class cycling aerodynamicist
and expert, and getting Hank to ride up a hill, as a sort of practical experiment. First
up, we're going to hear from Team Sunweb rider Nico Roche. When it comes to riding bikes
as fast as you can humanly go up mountains, Nico is one of the best in the world. He's
a two-time stage winner of the Vuelta a España, and has also come 12th overall in the Tour
de France. He's ridden for several teams over the years,
but notably, he rode for Team Sky. I say that's notable because Team Sky - well, you know,
now Ineos - have been famous for having a lead-out train of domestiques behind which
sits the team leader when they're going up mountains. Here is what Nico had to say, while
riding on his home roads near Monaco. Nico: I'm just going up the back side of [unintelligible
00:01:59]. I'm going to talk to you a little bit about drafting. How important is drafting
on a climb? Well, it really depends on what type of climb. Obviously, the steeper the
climb is and the lower the speed is, the less important the drag counts. On those kinds
of flattish fast lines, obviously, depending on the wind as well, drafting is a lot more
important than some of the really, really steeper climbs.
Does drafting impact, just say the tactics of a race? Well, it definitely does. It's
very often you hear especially on the Ventoux, for example, which is probably one of the
biggest examples where it's very renowned to have this strong wind. If you had a headwind
the Ventoux, or the same goes a little bit with the [unintelligible 00:02:53]. Those
climbs, it's very important not to isolate yourself. It's all about tactics of knowing
if you need to fight to stay with the group, or on the opposite, if you're feeling strong,
wait for the right moment because the group will have a severe advantage on you. Especially
if there's a headwind with those flatter or more exposed bits. [unintelligible 00:03:23]
I will stay behind his teammates. Well, once again, there's also a psychological side,
showing that all your teammates are there. That's you're outnumbering most of the other
teams. Also obviously from the performance side,
you are dictating the speed of the race, the speed you want to be, you feel comfortable
with, and making the most of having that draft. Like I said, then, when his last man goes,
usually, shortly after that, it's time to make the difference. It's basically to impose
his tactics or the team tactics on the race, and like I said, also for the aerodynamics
or drafting advantage by using every single unit he's got in front of him.
Ollie: We're now going to look at the maths and physics of drafting while climbing by
talking to an expert. We're going to chat to Dr. Xavier Disley from AeroCoach who routinely
mathematically models climbs to help elite riders go up them as fast as possible. He
has a detailed understanding of the aerodynamics of cycling. Using this, combined with mathematical
modeling, he's been able to help riders win the National Hill Climb Championships in the
UK, notably, Hayley Simmonds last year taking the women's title and Richard Bussell, who
came second in the men's competition. Good to see you Xav. Thanks for doing the
call. Can you quantify how important drafting is? When you're climbing?
Xavier Disley: There's obviously a number of things that are going to affect how important
drafting is when you're climbing. The amount of-- Obviously, everyone knows that drafting
reduces your aerodynamic drag. You can see this, you sit behind another rider and you
know that if you power-up it will decrease for the same speed, but the amount of reduction
in aerodynamic drag that you'll see will differ depending on a number of different factors,
how big the rider is in front of you, how close you are to them, things like the wind
as well. If you're traveling at a slower speed and
there's a very big crosswind, you don't get as much of that draft zone behind the rider
as you would do if you're traveling really quickly and there wasn't a lot of wind. The
rider who's got someone drafting them, their aerodynamic drag drops by about 3.5% on average.
If you want to help speed someone up, sit on their wheel, [laughs] obviously, not nearly
as much as if you're on the flat and the importance of it will depend on how fast you're going
up the climb. Ollie: As a rule of thumb, is there a speed
that you would-- because this makes it easy for people to follow if they don't have a
power meter or whatever, but is there a speed where you'd say, "Right now, you're going
fast enough that you want to be actually thinking about trying to draft and right now, you're
going slow enough that you shouldn't care just get up the hill." [chuckles]
Xavier: Even if you're going down at like 15 km/h it does make a difference a bit, but
I'd say that just over 20 km/h is worth it, it's only for extended climbs. If it's just
like a one-minute, two-minute climb, it's not going to make that much difference.
Ollie: Using your model, let's do a theoretical example. If we say, for the sake of argument,
pick one of my favorite climbs, one we've spoken about before, Sa Calobra in Mallorca,
how much time could I save through drafting up Sa Calobra if I drafted the entire way
behind another rider, if we say that the system mass of me is 76 kilograms with me and the
bike and the kit, and then the power I would do would be 330 watts?
Xavier: We have to make a few assumptions with that, so 330 watts, 76 kilos, we'll set
your aerodynamic drag at 0.35 meters squared which is a ballpark. Normally, if you're on
the hoods then somewhere between 0.3 and 0.4 and is pretty standard, so we'll set it at
that. If we reduce your aerodynamic drag by 30% like we just said, then that would see--
There are two ways of looking at it. It would either save you 8.5 watts or it would save
you somewhere in the region of [inaudible 00:07:48] 3 seconds.
Ollie: Well, last time I did it, I did it, my think is 30:57 of base, roughly on those
numbers. I was a little bit heavier than I am now, so I've got to go back. Now, unfortunately,
because of lockdown, we can't go to Mallorca, but we've found the longest climb near to
where we are that we have which is called the W, it's out of Nailsworth. It's quite
well-known. It's 2.57 kilometers long, average of 6%. I'm going to send Hank to ride up it.
Can you do a model prediction of what you think he will do at a set power drafting and
what he will do at a set power not drafting? Because that's all we're going to try to do
and experiment. Xavier: Sure. He's already got the KOM on
this climb. Well, I'll do a few different scenarios depending on how hard he's going
to pedal. If we assume he pedals as hard as the KOM, the important thing with this particular
climb is that the first half of it is very steep. It's about 9% around 1,300 meters,
and then it flattens off a lot about 1.6%. The speed in the second half is far, far higher
than the first half. It's basically nearly double what you get.
When he did his KOM effort, he averaged about 21 km/h for the first half and 40 km/h for
the second half. If we take that 30% drag reduction and we give him that for the first
half, then it reduces his power output required to travel at that speed, about 21 km/h, that's
20.7, by around 12 watts or so. No apps, not loads. In terms of time, it would save him
about 5 seconds in the first half. The second half is really interesting.
If we reduce his aerodynamic drag by 30%, in the second half when he's traveling a much,
much higher speed, it reduces his power required to travel at that speed, 40 km/h, by about
90 watts. He goes from needing somewhere in the region of 480 watts to do 40 km/h at 1.6%,
to 390 which is absolutely loads. Really really interesting. What I suspect will happen is
that the first half will be similar I think because that kind of margin, 10 watts or so,
will depend a bit on how well you're taking the corners, gearing, that kind of stuff.
The second half is where you're going to see the big improvement. If Hank goes out and
does it at 300 watts now I'd imagine that it'll be somewhere in the region of 10 to
20 seconds is what I'd expect. Again, it depends a lot on condition. What the wind is doing
on that flatter section at the top because if it's a really big headwind, I think you'll
see big improvements. You might even get that 10 to 20 seconds just on that part and a handful
of seconds on the steeper bit. Ollie: Thanks or your time, Xav. Always a
pleasure. Good luck helping athletes in the National Hill Climb this year. Hopefully,
it goes ahead. Xavier: Fingers crossed, yes.
Ollie: Hopefully, Rich Bussell can take the win this year as well.
Xavier: I know he's keen for sure. He's certainly getting his training in.
[music] Ollie: On to our practical experiment then.
Hank is going to ride up the W three times. He's first going to ride at a target speed
of about 320 watts with no drafting assistance whatsoever and we'll see what time he does.
This is our baseline. He's next going to ride up the climb behind a draft in the form of
his dad on a motorbike. Hank: [unintelligible 00:11:34] today. Good
little [unintelligible 00:11:37] camera set up.
Ollie: He's going to aim to hold the same power that he did without a draft. Therefore,
in theory, he should be quicker while drafting but we'll see what happens and see how much
quicker he is. He's then going to ride up a third time and in this instance, he's going
to try and match the time and the speed that he did while drafting behind his dad and we'll
see what the power difference is because in theory again, he should have to put out much
more power without the benefit of drafting. Particularly, if Xav's correct on that top
flatter section. Hank: Now, the interesting thing about this
specific climb is it's pretty steep at the bottom but then plateaus at the top but it
gives an average gradient of 6%. It's about the most alpine climb I can find in the Cotswolds
so it's got a few switchbacks in there too. I'm going for Skytrain. I've got my Pinarello
F12 a bit like the Skytrain and I'm also going to use a motorbike for drafting because I
think that's a little like how Kiryienka would act like. Yes, a motorbike. I better stop
procrastinating and get on with these sessions. [music]
That's effort one complete. I felt quite good. I was still quite fresh. I averaged about
320 watts but we'll wait and see what the time is. Now, to go and do the second time
up. This time I'm being drafted using my dad's motorbike as my peloton. It was easier to
get him to do the session than to get a big SkyTrain as you can probably imagine. Round
two. [music]
Still picking up speed and my watts are going down. That's test two complete. I tried to
sit around 9 to 11 miles/h at the bottom when it was nice and steep. Then as it plateaued
and came on to the top where we had much more of a headwind and I could see my wattage just
plummet, I just stayed at constant pace. Even rising the speed to around 22 /h. I guess
in my heart of hearts it's going to be, well, a big win for the drafting but I've got one
more set to do. I better go and do it. [music]
Right, quick disclaimer. The route I did or the Strava KOM that I was trying to go for
is slightly longer than the section I set for myself and that was because it got a little
bit of traffic towards that junction so I had to cut it a little bit shorter down to
2.24 kilometers instead of the full length of this segment. Luckily enough, I've still
got that KOM. I'm going to go into the results now. The
first run I did wasn't drafted. That was sitting at the 300 watts that Ollie gave me to try
and sit at and I was going to the whole run, so the 2.26 kilometers without drafting. I
did that in 6 minutes and 39 seconds with an average wattage of 321 watts. That's pretty
close to the 300 watts that Ollie set me. My average speed
Hank: was 20.4 km/h. The next run I did was drafted but it's trying
to stay at that 300 watts. I did it in a time of 6 minutes and 20 seconds, so shaving 19
seconds off my previous run. I averaged less watts, I averaged 315 watts and my speed was
21.3 km/h, so that's a whole km per hour faster across the whole climb. Run three wasn't gonna
be drafted but that was going to sit at the 21.3 km/h that I set in the previous run.
I did it in a time of 6 minutes and 32 seconds, so 12 seconds slower. I averaged 339 watts,
so it's quite a lot of watts more than my previous ones, and I'd sat on a speed of 20.8
km/h. I think you can tell then from the data that
drafting, well, makes it a hell a lot easier. Right, Ollie, I guess, mate, it's back to
you. I get to get out of this kit. Ollie: Thanks for that, Hank. What's pretty
amazing for me when I look at the results is that the modeling is, well, quite surprisingly
pretty consistent with what Hank actually did. This is especially the case when we break
the climb into the two halves like Xav suggested. The steeper first half of the climb, Hank
averaged 320 watts and went 16.1 km/h when he was drafting behind his dad. Then on the
second half of the climb, he only had to average 242 watts to travel 34 km/h. Shows that the
drafting makes a significant difference as soon as you start going that little bit faster.
Now, when he's trying to ride at the same speed as the draft but without the draft,
the difference is stark. He's still getting a benefit on the first half of the climb,
the steeper bit, as he had to average without a draft 343 watts, 20 watts more to try and
nearly match his speed, and he was still slightly slower, 15.4 versus 16.1 km/h. On the second
half, it really starts to show. He did 324 watts, he must have got a bit tired after
the first half of the climb, and he averaged 32.6 km/h versus 242 watts going 34 km/h drafting.
That's pretty consistent with Xav's prediction, he also said he had a slight headwind which
would have exacerbated it a bit, but that's 80 watts roughly difference which is blimming
massive. I guess, in conclusion from this, drafting is significant even if you're going
at speeds of around 15 km/h on steep climbs, and as Nico says there's also a massive psychological
benefit to be gained by holding the wheel and having that pacemaker even on bits where
drafting isn't as important and you're going slower. If you're chasing seconds, then this
is something well worth considering, but if you are going slower and you're not putting
out those big power numbers and you're going around 10 km/h you don't need to be worrying
too much about drafting. That said if you are riding on a slower bit
of a climb, but coming up further down the road is a sort of flatter, faster section
in that climb, it's probably worth trying to hold the wheel just so that you get the
massive benefits that you can get on the flatter, faster sections. If you're going up a really
steep climb, or you're going to be averaging less than 10 km/h like me on the [unintelligible
00:18:38] where I was just clinging on for dear life. [chuckles] You don't need to be
really concerned about drafting. If you're anything like me, you'll just be concerned
with trying to get up and not die. I hope you've enjoyed this video and found
it informative. If you have, then please share with your friends and give it a Like. Let
us know in the comments and on social media what your thoughts are on drafting on climbs,
and what your experiences of it are as well. If you'd like to support this channel and
what we do, then why not head over to shop.globalcyclingnetwork. We've got all matter of goodies over there.
T-shirts, mugs, and loads, loads more. Also, in case you're wondering where my t-shirt
begins and my milky-white arms end, I can't tell either. I've been inside so long, I just
need to go out and get some color on. I'm like Casper the friendly ghost. It's ridiculous.
Hank: Just want to say a massive thank you to my crew. I brought the dad and his sister
to do some filming today. Absolutely epic. It was good day. It's sweaty, and it's hot,
and it's nice, but, for me, it couldn't be better with the family.
[00:19:52] [END OF AUDIO]