I’m trying to improve the aerodynamics of the front of my P2C. I’ve hidden the various cables as well as possible. The fit is pretty dialed in. So now I’m wondering how much would be gained by dropping the whole cockpit while maintaining the same pad height by using spacers stacked between the basebar and the aerobar, like you can with the new Zipp Vuka Alumina.
I might not be explaining it well: Picture a less radical version of the TT setup you see for some pros like Bradley Wiggins. The basebar is down low, the armrests and aero extensions are perched on top of a stack of spacers. I have roughly 4 cm of spacers under the stem, so in theory I could get rid of the spacers, drop the basebar as low as it would go, and stack 4 cm of spacers under the armrests to get them to the right height. Is there much aerodynamic gain from getting the basebar as low as you can, even if you keep the same position on the bike? Or am I just spending a lot of time to save half a watt?
I’ve done this with my bike. I’m not sure on the exact watts saved, but it will put you in a lower position through turns or any other time while by the brakes. Also, the pad risers have a more airfoil design compared to the round stem spacers.
So I would say it will be faster and look more pro, but I have no actual numbers to offer you.
I guess I was thinking it would get “closer” to the more current bike designs that put a premium on integrating the stem/cockpit into the frame and having it flush with the top tube: lower stem more at the level of the top tube, maybe more aero.
Am I misunderstanding the reasoning behind the superbike designs? Or am I just exaggerating the potential gains from having the cockpit lower and the just the pads/extensions up in the air.
The pros run a low basebar so that their torso is horizontal even when on the basebar when going around turns or on climbs.
that is not always the reason, often the reason is that is just how their particular bike ‘works’ (p5, shiv, etc). It is a slightly more aero and more structurally sound solution, when cranking hard on the base bar
you can get low on a normal ‘high’ basebar by just bending your elbows.
No you have the right idea. Aero pad spacers are more aero than round steerer tube spacers, and it is more structurally sound that way, since you only put big torque on your bars when on the base bar.
It is still a pretty small difference aero wise.
Might be worth it to you for the stiffness and safety of your steerer tube though! Or could you size up on your frame?
I guess I was thinking it would get “closer” to the more current bike designs that put a premium on integrating the stem/cockpit into the frame and having it flush with the top tube: lower stem more at the level of the top tube, maybe more aero.
Am I misunderstanding the reasoning behind the superbike designs? Or am I just exaggerating the potential gains from having the cockpit lower and the just the pads/extensions up in the air.
I am in a similar situation to the OP. How do lower base bars affect climbing position, which seems good with they way they are now (higher). Will that be a problem, or just adaptation?
I am in a similar situation to the OP. How do lower base bars affect climbing position, which seems good with they way they are now (higher). Will that be a problem, or just adaptation?
you will probably just lower your hands and bend your elbows less.
But you would have to try it to see how it affects you in particular. It may also be annoying if you do group rides on your TT bike and have to ride on the hoods a lot with them super low. Just depends.
The savings are still quite insignificant, but the bigger reason risers between a basebar and armrest pads is “more aero” is because the risers actually let air flow through vs. no risers essentially damming the air between the basebar and armrest pad. Same reason why you see fork manufacturers going to much wider CX style forks. It’s been shown that having a tight fit with a rotating wheel is very detrimental even though it doesn’t look as aero.
I’m trying to improve the aerodynamics of the front of my P2C. I’ve hidden the various cables as well as possible. The fit is pretty dialed in. So now I’m wondering how much would be gained by dropping the whole cockpit while maintaining the same pad height by using spacers stacked between the basebar and the aerobar, like you can with the new Zipp Vuka Alumina.
You may not like my answer, but if I may…
I measure people’s aerodynamics quite often. People whose living depends on it. Yes, there are more experienced – and probably better – people than I doing this, like John Cobb and Len Brownlie. But I’m going to guess that they will tell you the same.
Aerodynamic generalizations are a myth. Get lower? Not all “lower” positions work. Elbows in? Not everyone benefits from this.
Your aerodynamics are personal. I would even say that your path to getting more aero is going to be unique, too. Your shape is unique. And your aerodynamic “formula” is only going to be obtained by measuring your aerodynamic drag properly. Wind tunnels and aero field testing are the key.
So please keep this in mind as you collect answers to your question. There is not enough information to properly answer what you need to know.
You make some very good points re. positioning and aerodynamics. If only I had access to a wind tunnel. I’m wondering about a slightly different thing: If you hold your position constant, is there any aerodynamic gain from lowering the basebar a few centimeters and maintaining the same pad position by stacking 4 cm of spacers between the basebar and the pads. So it’s really a question of equipment aerodynamics, not body position aerodynamics (though I appreciate that one can influence the other).
How I understood it last was that the pads sitting directly on the bars is as good as spacers. It’s when the pads are only slightly above the bar that there is a problem.
As with most things relating to aerodynamics, the answer is “it depends.”
I got nothing out of dropping my pad cups to the basebar when I tested at A2, but this isn’t to say that others will see exactly the same result. It depends on your basebar/extension setup, AOA, etc.
OP: As others have said, the new superbikes have different front end setups that are motivated by aerodynamics but are functionally different from what we have on the P2. I’m assuming that you’re interested in saving drag by rearranging your front end setup such that you have a more favorable interaction between your pads and your basebar, or between your arms/aerobar extensions and your basebar, or between your base bar and your frame. You’ve got no way of knowing unless you test in the WT…you’re probably talking 1-2W at most for the 4cm of spacers, and I’m going to make the assertion that you couldn’t accurately test this in the field. You have bigger fish to fry. Every age grouper does. Furthermore, climbing becomes more difficult if you drop your bars too low. My basebar was super low on my Softride and I ended up having so much weight over my front end that my rear tire would slip if I was climbing up a steep enough grade (when I stood up, and occasionally even in a “seated” climb).
I’ve heard that having the pads ON the basebar, or HIGH above it are both very aero, and that middling separation is worse.
But I’m sure that is one of those things that can ‘depend’ on the pad, basebar, and extention configuration.
The savings are still quite insignificant, but the bigger reason risers between a basebar and armrest pads is “more aero” is because the risers actually let air flow through vs. no risers essentially damming the air between the basebar and armrest pad. Same reason why you see fork manufacturers going to much wider CX style forks. It’s been shown that having a tight fit with a rotating wheel is very detrimental even though it doesn’t look as aero.
set-up a local 5 mile TT that is a flat out and back & do this once per week.
if you have a power meter, great – use it & collect data – if you don’t, save your money because this is the only way to properly train.
collect data including time of the day, time it took, humidity, wind direction & speed, and make sure your doing the same training plan every week.
remember, you may be getting into better shape as you move along so make a scale of 1-10 that reflects how you feel, your diet and sleep patterns for that week/day.
the more TT-tests that you have, the better your data will be.
keep the set-up that your comfortable with for at least the first 4 weeks.
try to get someone to video you while riding this TT ‘once in a while’ ecspecially towards the end of the ride when your ‘choking up & and using the entire saddle.’ You will be amazed and what you can learn about what happens to your body when your tired that you never even thought about. Video’s will show the giant hump in a rolled back & the monster mashing caused by not cleaning the mud off your shoes (the back & up sweep that helps level out your watts and stay closer to your load.)
collect all data, all videos, and make some adjustments – but don’t rebuild front ends 'for a look.’
*there is no one but ‘you’ that can collect, practice and analyze this much data for such a cheep price (that really is “pricele$$”) And if your willing and you have done some homework, your going to find that watts vs. position is a grey area no matter who you are (pro or ag’er) – but this grey can shrink over time and someday you might refine your position into something that is quite black & white.
–good luck–
(ps: I have always wanted to do this experiment and document it properly and present it to ST as some type of documentary, but life gets in my way (and yours,) and I simply never get it together!)
You make some very good points re. positioning and aerodynamics. If only I had access to a wind tunnel. I’m wondering about a slightly different thing: If you hold your position constant, is there any aerodynamic gain from lowering the basebar a few centimeters and maintaining the same pad position by stacking 4 cm of spacers between the basebar and the pads. So it’s really a question of equipment aerodynamics, not body position aerodynamics (though I appreciate that one can influence the other).
What about trying virtual elevation? Beg, borrow, or steal a power meter, get yourself Golden Cheetah (http://goldencheetah.org – it’s free!) and follow the protocol on this thread.
Sure, there are restrictions on the course and how windless a day you need, but it’s the closest thing to a real answer you’re going to get without a wind tunnel. It’s certainly better than an eyeball test, and definitely better than recycling some conclusions that are correct for someone else but totally wrong for you.
Sounds like an interesting test, just for the sake of more data. I’ve got the powermeter and the Golden Cheetah. My guess is that if the bar arrangement makes a difference of just 1-2 watts, it would be hard to even see it - it would just get washed out by all the other variables. Which is probably another way of saying that it doesn’t matter enough for an age grouper to worry about it.