reach and aerodynamics

neeb

Quick question for those in the know - on a road bike with normal bars, does increasing the reach offer any significant aero advantage on its own, assuming the drop to the bars is the same?

Alex_Simmons/RST

Maybe, maybe not.

bompington

Thanks Alex, that's very helpful

redddraggon

bompington wrote:

Thanks Alex, that's very helpful

There's no really hard and fast rules concerning drop and reach.

Look at Leipheimers TT position:

Not a lot of reach and bars are nearly the same height as his saddle, but his position is still aerodynamic.

http://www.cyclingweekly.co.uk/imageBank/l/LEVI%201.jpg

Bhima

Read this article: http://www.bikeradar.com/fitness/articl ... bank-20304

His time trial position was also changed, with the saddle height increasing slightly and his handlebars going up by a greater amount. The latter would have a small effect in increasing drag but, according to the BG crew, it should be more than compensated for via an increase in power. That's good news for Schleck, who traditionally has lost time to his rivals in races against the clock.

So i'd say comfort and power transfer are more important than tiny tiny tiny improvements in aerodynamics.

neeb

I know that aero doesn't necessarily mean faster, because there is often a tradeoff with power. I'm just wondering if longer usually means more aero, in the same way that lower at the front usually means more aero.

I'm guessing that it's still a "maybe, maybe not" thing depending on individual morphology. Obviously being lower at the front is going to make most people more aerodynamic, all else being equal, but I suppose the aero effects of stretching out are more unpredictable.

Just wondering because I know that dropping by bars a bit did make an appreciable (positive) difference to my speed. Recently I rotated my bars up slightly without adjusting the stem height or lever position (so the hoods are now angled up more, nearer and a little higher). If anything this has had a negative effect on my speed, although it is very comfortable. It occurred to be that this could be down to being less stretched out rather than being ever so slightly higher when on the hoods. I'm going to turn them back down again.

eh

Without the use of F1 style computing and wind tunnels my inclination is to say that a flat back is as good as it gets. Getting a lower head and shoulders than bum isn't going to add much, as the air passing by your head will still break over and around your bum/hips. And i'd also expect that since your stomach would be more scrunched up it could be hard to breathe fully.

So kinda:

O~O = good, (NB: ~ is supposed to represent a back parallel to the ground )

O\0 = not so great

If that makes any sense at all.

zammmmo

Longer can mean more aero - just look at the Superman position.

Alex_Simmons/RST

bompington wrote:

Thanks Alex, that's very helpful

Well sorry but unless you plan on a visit to a wind tunnel or use a power meter, really there is no way of properly answering your question. I have seen riders stretch and/or go lower and have worse aero as a result.

There are far too many variables at play to answer your question.

bompington

Alex_Simmons/RST wrote:

bompington wrote:

Thanks Alex, that's very helpful

Well sorry but unless you plan on a visit to a wind tunnel or use a power meter, really there is no way of properly answering your question. I have seen riders stretch and/or go lower and have worse aero as a result.

There are far too many variables at play to answer your question.

I know, I was just being facetious, I'm just not sure which smiley says that best.

I don't do TTs or anything similar but I do spend a lot of time commuting through very windy countryside - I personally find that the lower I tuck, the more cramped I feel & the less efficient my pedalling feels; that strikes me as being the biggest variable in the whole thing.

ded

bompington wrote:

the lower I tuck, the more cramped I feel & the less efficient my pedalling feels; that strikes me as being the biggest variable in the whole thing.

Which is why all the "how to set your bike up for TT" articles mention changing your saddle position or getting a wacky seatpost. Someone posted a link to a triathlete's site on here a while ago that gave a good explanation - was all to do with the angle your hip/leg made with your back which had a huge effect on power output...

bompington

ded wrote:

bompington wrote:

the lower I tuck, the more cramped I feel & the less efficient my pedalling feels; that strikes me as being the biggest variable in the whole thing.

Which is why all the "how to set your bike up for TT" articles mention changing your saddle position or getting a wacky seatpost. Someone posted a link to a triathlete's site on here a while ago that gave a good explanation - was all to do with the angle your hip/leg made with your back which had a huge effect on power output...

Which explains a lot in my case - I have short legs & a long body, & I find that in general I prefer my saddle set back a bit (particularly uphill). That makes the hip angle more acute & I've often thought that I would be much better off getting the bars further forward, just can't be bothered with the expense.

oldwelshman

Bhima wrote:

Read this article: http://www.bikeradar.com/fitness/articl ... bank-20304

His time trial position was also changed, with the saddle height increasing slightly and his handlebars going up by a greater amount. The latter would have a small effect in increasing drag but, according to the BG crew, it should be more than compensated for via an increase in power. That's good news for Schleck, who traditionally has lost time to his rivals in races against the clock.

So i'd say comfort and power transfer are more important than tiny tiny tiny improvements in aerodynamics.

Sorry not picking on you honest but once again your wrong.
At higher speeds such as in TT's the aero effect has more influence on speed than power. David mIllar for instance has a position optimised for aero position but it is not the position he generates the most power in. The results he got in wind tunnel showed that for a small compromise in power input, he got better aero position and speed from his most effective aero TT position so that is the position he rides in for TT.
On steep hills it would be a different matter as gravity outdoes aero effect.

oldwelshman

In reply to the op, as someone suggested a wind tunnel would be the best way to find out.
If you look at Orbrey's stretch position he was fast But may not be the same for everyone.
In theory I suppose if your stretched you lower your frontal surface area thus improving aero efficency so should be better

Bhima

:idea:

This is going to sound crazy but you can actually make your own windtunnel - we did it at school 8/9 years ago but on a very small scale. Sit on your bike in front of a fan with 1000 candles lit behind you, preferably in a grid formation on a series of shelves. Turn the fan on and see which body position can blow out the most candles!

Infamous

Or coast down a hill. Not as practical as the candles though, obviously.

neeb

Thanks for all the comments.

Yup, a wind tunnel would be the way to go, but I'm not quite in the league to justify it.. :-)

Also not sure I can be bothered with the 1000 candles and specially constructed furniture, although it's a lovely image.

Turned the handlebars back down again slightly last night (hoods 5mm further forward and slightly lower) and was faster today, but that might just have been down to the new bar tape..