TdF climbing aero gains

topcattim

Any views on a point of disagreement in our house? I'm not convinced that there is very much drafting gain to be had when the TdF riders are all lined out when they are climbing. I'm figuring they climb at about 20 to 25 kph (of course, this varies according to gradient and distance) - I accept that mathematically there will be some drafting gains at this speed, but I figure that they are pretty small. I absolutely get that there is a pacing/pyschological advantage to following someone's wheel, but is there a drafting gain as well?

homers_double

If theres a head wind maybe, but maybe its a psycholgical game they play too?

"I can't get this ****er off my back wheel"?

ben@31

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19661192#p19661192]homers double[/url] wrote:

If theres a head wind maybe, but maybe its a psycholgical game they play too?

"I can't get this ****er off my back wheel"?

No aero gain but motivated to keep up. Being paced up the hill.

Having read some blurb on a TT / Tri bike, you need to average over a certain speed to reap any aero gain ( I think it quoted 25 or 26 mph).

iPete

25 or 26mph(!?) have you never drafted anyone before?

But yes, there are gains to be had climbing up in a big bunch, they may sometimes be small but they are there.

Sirius631

You can answer this for yourself, with a bit of experimentation.

Just waft your hand back and forth, slowly. You will be able to feel a breeze, as the air is pushed out of the way. As you are imparting a force on the air, the air is also imparting a force on you. Chests and legs are wider than hands, so will be pushing more air out of the way. The force to be overcome whilst climbing might be smaller than when charging along a flat road, but it is significant, even if it is small compared to the effects of gravity.

topcattim

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19661417#p19661417]Sirius631[/url] wrote:

You can answer this for yourself, with a bit of experimentation.

Just waft your hand back and forth, slowly. You will be able to feel a breeze, as the air is pushed out of the way. As you are imparting a force on the air, the air is also imparting a force on you. Chests and legs are wider than hands, so will be pushing more air out of the way. The force to be overcome whilst climbing might be smaller than when charging along a flat road, but it is significant, even if it is small compared to the effects of gravity.

I think that the way that you answer the question gets exactly to the question I'm trying to ask, but still leaves me wondering! I agree that there must be a force exerted by the air being moved out of the way, but I'm not sure how significant it is when compared to the other forces that are acting on the riders.

For example (and deliberately choosing figures that skew the example ), if the air being moved out of the way counts as 20% of the forces the riders overcome at 20kph, and if the remaing forces (friction, gravity..er, what else..?) counts as 80% and if drafting someone reduces the "moving air force" by 25% then, drafting someone makes an overall difference of 5% of the total power the rider requires.

I guess I'm wondering what a more accurate set of percentages might look like?

trek_dan

I always wondered this too, but when I actually rode Alpine climbs its amazing how much faster you can ride when paced.

w00dster

This is worth a read, read all the way through the page (not the best website, seems to look like the article has finished but it carries on). Some interesting points made.

http://bicycles.stackexchange.com/questions/10326/why-is-it-easier-to-follow-a-cyclist-up-hill

From my personal experience I would say the physcology side of it is a major contributer. If I'm leading up a hill I generally know I'm going to be attacked, its then the mind games that start, do I try and distance them or save some energy. I try not to lead up a hill though as I know I probably won't be quick enough to respond to an attack.

Brakeless

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19661240#p19661240]ben@31[/url] wrote:

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19661192#p19661192]homers double[/url] wrote:

If theres a head wind maybe, but maybe its a psycholgical game they play too?

"I can't get this ****er off my back wheel"?

No aero gain but motivated to keep up. Being paced up the hill.

Having read some blurb on a TT / Tri bike, you need to average over a certain speed to reap any aero gain ( I think it quoted 25 or 26 mph).

Most (every) fast club run would be a lot less than 25mph and there are huge drafting gains for everyone other than the pair at the front. Even at much slower speeds you're still pushing air out of the way and will benefit from sitting on a wheel.

JackPozzi

Some data (and a nice graph albeit with tiny writing on the axis) from Michele Ferrari. Mainly covers drafting on the flat but some mention of climbing

http://www.53x12.com/do/show?page=article&id=89

steadyrollingman

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19661261#p19661261]iPete[/url] wrote:

25 or 26mph(!?) have you never drafted anyone before?

But yes, there are gains to be had climbing up in a big bunch, they may sometimes be small but they are there.

Think he means that the benefits of an aero bike only really become apparent at those speeds.

I've also questioned the value of drafting up a 10% hill though - I've never had the opportunity (or the legs) to try it, but I assume 95% of the benefit is having someone acting as a pacemaker.

topcattim

Interesting stuff. When I read those links, it looks as though there are some very different opinions out there, but that it boils down to "not a lot of difference, but if you are right at the ragged edge of your power, then that might be all the difference required".