- A time trial bike is typically faster than a road bike
and a road bike with clip-on aero bars,
but have you ever wondered by how much?
It's a question we get asked here at GTN all the time.
Is a TT bike worth the investment
or are you simply better off buying a road bike
and then putting your clip-on aero bars on it?
How many watts would you save
and ultimately how does that actually result
when it comes to a real life triathlon?
Well, to find out, I headed
to the Silverstone Sports Engineering Hub
to use their wind tunnel.
(funky music)
A wind tunnel can replicate conditions
pretty close to the real world,
just without the chance of any rain.
Now when you're riding outdoors,
you obviously experience wind resistance
and the faster you go, the greater that resistance.
So when in a wind tunnel, you can replicate the speed
that you'd be riding at by changing
that resistance accordingly.
And you can even change the angles
'cause when you are riding outside, it's probably unlikely
that you're going to have wind coming from directly
in front of you and, these angles are known as yaw angles.
Well, I have to admit, I was pretty excited
to head to Silverstone as I've never been in a wind tunnel
and I hadn't even done any aerodynamic testing.
The controlling of the wind speed and direction
is one part of the equation, but it's the results
that we're really interested in here.
And aerodynamics tend to be measured in CDA,
which is a drag coefficient.
Basically the resistance that you and your bike are creating
and the higher the resistance, the higher the CDA number.
The CDA can then be used to calculate the power,
in watts, that a certain position or certain wind angle
is either losing you or gaining you.
So the lower the CDA number,
which is what you're looking for,
the more watts you'll be saving,
and then in theory, the faster you'll be going
for the same amount of effort.
(lo-fi music)
Enough of the details.
Let's take a look inside the wind tunnel
and check out my first setup using the road bike.
A road bike is a beginner's choice for a triathlon
and perfectly adequate, but due to the position
it puts the rider in, it will give you a higher CDN number,
basically because it's less aerodynamic.
So I've chosen to ride on the hoods this time
as it's the go-to position on a road bike.
The drops would reduce the CDA, but realistically,
you're unlikely to stay in that position
for a full triathlon.
In order to replicate a real triathlon scenario
as close as possible, we decided to record data
at three different speeds, 30 40 and 50 kilometers per hour.
And like I mentioned, it's unlikely
that the wind will be directly head on.
So on top of the control, we're going to get data
at yaw angles of 2.5, five, and 10 degrees
throughout all three wind speeds.
So let's get started.
(calm music)
All right, nothing to report just yet
because the numbers are being calculated,
but I have spent my few minutes
in the basic position in the wind tunnel.
I have to admit, this isn't the scientific part,
but it's surprisingly cold.
It's amazing what it's like riding in the wind, but yeah.
Next we'll be on with the aero bars
and then we'll have something to compare to
because at the moment, these numbers
don't mean a huge amount.
But I've got a bit more peddling to do.
(funky music)
The bike setups on their own obviously look different,
but it's actually the rider position
that plays a larger part
in the overall effect on aerodynamics.
In actual fact, the rider counts for around 80%
of the total drag.
On the road bike, you can see that my arms were wide apart
and my body relatively upright,
which makes for a large frontal area.
And then with the clip-on aero bars,
it really reduces that, making me far more aerodynamic.
(funky music)
That's all the testing done with the road bike.
It's time to take things up a level
and bring out the time trial bike.
The time trial bike is more aerodynamic in its design
but also as a result of the position it puts the rider in.
And this isn't important in aerodynamics,
but the position that you can get into
on a triathlon TT bike actually makes a transition
from cycling to running that much easier
as your hips can remain more open than they would
on a road bike when you're riding with aero bars.
(funky music)
Alrighty.
That is testing done for the road bike
versus road bike with aero bars versus the TT bike,
and I'm sure this has not let me down,
but it doesn't really matter how much
'cause we know that this is going to be more aero.
It's time to go and crunch the numbers
and actually look at how big the differences are.
As expected, the difference is notable.
For dramatic effect, let's have a look first
at the 50 kilometer an hour test and that would actually
see a massive saving from riding on the hoods on a road bike
to riding on the TT bars on the road bike of 85 watts.
And then take that to the next level of the TT bike
and you'd actually see 108 watt saving
compared to the upright position on a road bike.
Now that sounds rather huge,
but what is the significance of that
and what does it look like in real life?
Let's take an Ironman for example,
and say you did the bike leg in five and a half hours.
Well, if you compare the TT bike compared to the robot
with the TT bars, that would save you four minutes.
The TT bike compared to the road bike
in just your standard upright position on the hoods,
well, that would save you a whopping 20 minutes.
It was the results from the yaw angles
that were most surprising though.
the TT bike actually had less drag
and therefore more watts savings at the larger wind angle,
or yaw angle, than it did straight on
compared to the road bike which got progressively worse
as the angles increased.
And this makes a difference between the road bike
and the TT significantly greater again,
so, when there's a crosswind,
and therefore, the real life difference
would actually be more notable.
It's not purely that front-end position,
but a combination of the rider and the bike.
To some of you that might sound a bit dramatic
and maybe leaves you questioning how you can compete
against riders on a TT bike if you're just on a road bike.
But please, before you despair
and consider maybe remortgaging your house
to get that upgrade, there are few other things
you need to think about.
First up is what pace do you currently race at
at the moment.
The faster you go, then the more benefit you'll get
from a time trial bike.
But if you're fairly new to cycling,
then you're probably going to find more benefit
from actually working on your fitness and your riding skills
than you will from that upgrade.
And then it actually takes quite a lot of time
to get used to a time trial bike
to find to getting yourself comfortable
and confident on a TT bike.
So buying a new bike and having that upgrade
doesn't automatically make you a better rider.
But if you're maybe considering whether it's time
to take that step, then why not check out our recent video
about when to get all the gear which we've had on GTN.
And then we go back to the question
that I mentioned at the start.
What are your goals?
Are you going to be mainly doing hilly races?
Are you going to be doing long-distance events?
Do you want one bike that's going to suit everything?
All of these questions I obviously can't answer for you,
but you've got to take all of them into consideration
and work it out for yourself.
But at the end of the day, if you want to go fast
on a flat course and for longer,
then a TT bike is going to be the answer.
Although even with that, you're still going to
have to do a lot of training
as it obviously doesn't power itself
and you've got to work on finding a position
that you can sustain to make sure you're still aerodynamic.
I have to admit that yes,
the differences in all three setups are significant,
but not actually as much as I expected.
And I find that quite reassuring that on a road bike,
if you find some clip-on aero bars
and get the right position,
you can still very much compete with people on a TT bike.
So if you've maybe made the upgrade from riding a road bike
to clip-on bars, or even the next step to a TT bike,
let us know how you found it and how you've got on
in the comments section below.
And whilst you're there, give us a like and a follow at GTN.