I'd be really surprised if that were ever the case.
Narrower bars seem to be always faster, cannot imagine a mechanism where making your entire profile wider with your legs will ever be faster.

I asked basically the same thing a few years back, and had responses from the veritable Mr Coggan and a certain Jack Mott amongst others. Nothing very conclusive.


I'm not sure that you can compare this scenario to forks and a front wheel. The argument around forks I think is that the body they are next to is an aerodynamic shape and it may be better to have three separate aerodynamically efficient bodies in the air than one big body where each shape is negatively affecting the windflow around the others. I'm not sure that still stands up when you are looking at the whole bike + rider. It may be a simpler case of bigger vs smaller frontal area for the whole outline of bike + rider.


But it is definitely worth asking 3 years after I did, with all the Alphamantis and tunnel testing that has taken place since then. Somebody might have tested this?


For me, I had been recommended to widen my stance width for a particular knee tracking observation. I didn't really see any rise in power, and I'd never really had any issues with pain, so I was wondering if it was worth switching back to a narrower stance width from an aero POV.

I've gotta ask the obvious and say why on earth does it matter?

I understand some need to change for personal body movement reasons.

The real world aero difference is likely to be so low that it would be ridiculous to consider changing and risk injury or changing body movement for any reason other than being necessary for personal movement.

Kinda like when you see peoples knee move outwards on up stroke. Possible poor fit but most likely due to personal body movement issues and in fact possibly preventing injury!

So say someone reverts with 5 watts.

Would you then try this for 5 watts and risk causing injury through change of leg rotation movement and hip etc?
Madness imo but carry on.

You make some very pertinent points here, and the smart bet is to favor injury prevention and accommodating the rider's natural biomechanics over aerodynamics.

If I were to consider adjusting stance width in hope of an aero gain, it would make sense to look first at crank arm length to limit the range of motion of the feet. That wouldn't necessarily be primarily for aero gains, but focused on getting the rider into a range of motion that is appropriate for them. I've seen plenty of instances where knee tracking improves significantly because they have more room between the torso and thigh, the hip isn't reaching the point of impingement, etc. From there, perhaps that could provide an opportunity to narrow the stance, but it would be a very low priority objective.

We also have some pretty severe equipment limitations in this area. I know there are some especially narrow cranksets available, but most are limited by chainline and BB shell width. At best, you might bring the feet a few millimeters closer to each other.

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Xavier Disley knows the answer. If I remember correctly narrow is faster. Think the lotus Hour Record bikes, super narrow at the BB.

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BoulderCyclingCoach.com

Generally narrower is faster. Someone recently posted WT results testing this (maybe Jens?) and I seem to remember 3 watts is about what he found.

In terms of the physics of the problem, you might think about your hand when swimming. The optimal finger placement is not to have the fingers touching each other, but a slight gap between each finger. This create high pressure areas between you figures, so the total "frontal area" appears like a larger flat plate, which has more area and a horrible Cd. Wide gaps just make you fingers look like the 4 small cylinders they basically are.

Like most things in cycling "narrow is aero",.... about 90% of the time.

I changed q-factor a few years ago and it caused significant problems with knee pain, so for me it was not an option. Just saying.

In general, Narrower if faster- but there are several things to consider.
1.) As others have mentioned- There is not really equipment out there that allows you to make a significant difference.
The older Walser frames used a special narrower rear hub and bb to allow for this.

Also- Trek made some prototypes of their tt bike like this for Armstrong back in the day- He hated it, allegedly let Ekimov have the bike. Ekimov gold gold in Sydney on it.

2.) What do your legs do and do you have power?
Narrow is good if it brings everything in.
Narrow is bad if it causes injury or discomfort, causes your feet or ankles to contact the cranks or frame, and/or if if causes your knees to splay out like Yosemite Sam.

I think JeffP has tried to quantify this, maybe he will chime in.

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The Walser TT bikes that Jan Ullrich rode had a very narrow custom BB.

Likewise, the Obree hour bike used a trick narrow BB, I think that was where the famous washing machine bearing ended up.

I wouldn't be surprised if the major manufacturers look at this area for drag reduction in the future, it seems ripe for some typical industry marketing guff.

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´Get the most aero and light bike you can get. With the aero advantage you can be saving minutes and with the weight advantage you can be saving seconds. In a race against the clock both matter.´

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Problem with narrow bb is that you need an "old style" crank or heavily modified crankset.
Modern cranks with a spindle already attached won't go any narrower.

Also, the narrow Walsers used a narrower rear hub- So custom rear wheels for training and racing.

Might be faster- but not really practical as a retail model.

  
That's correct. I went from .217 to .214 with the Campy Record Pista cranks -- even though it was the last run of the day (tired).

So yeah, maybe 3-4 watts. Now you could scoff at that. But it works out to ~15 seconds difference in a 40K TT. I wouldn't be surprised if the good old Campy square taper BB saves another half a watt over most of the PressShit BBs out there too.

That being said, I may still sell my old P3 with the 150 MM Campy Pista crankset (apparently the only one in existence). Stay tuned.....

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I don't know how wedging a bike between your legs affects aerodynamics or if you can take the bike aero dynamics and the body aero dynamics and add up the theoretical drag, (I assume you cannot, because the presence of another object will affect what happens to the drag of a nearby object in a fluid)....but in any case, the speed skiers all go wide leg. I have tried wide stance and narrow stance on skis and wide is faster since the air can get around a narrower pipe (one leg) vs a fat pipe (2 legs) and reattach more easily. Its actually remarkable feeling the delta in speed on a steep downhill going wider

I'd be cautious about transferring skiing aerodynamics to cycling. A downhill racer goes for a wide stance since he can tuck his chest between the legs, plus it's more stable. He also doesn't have a bicycle between his legs. Whatever data I've ever heard about for cycling has indicated narrower legs are faster.

I quite agree.

There was a Norwegian nutcase who built a red replica/tribute Obree bike with a cut 'n' shut Tiagra bottom bracket spindle, IIRC.

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´Get the most aero and light bike you can get. With the aero advantage you can be saving minutes and with the weight advantage you can be saving seconds. In a race against the clock both matter.´

BMANX

Which is why I prefaced it "not sure how wedging a bike between the legs affects things". But stability aside, legs apart on skis is faster than legs together.

Also related to wedging a bike between the legs, I believe early test on softrides and zipp 2001's with a rider on top showed them to be faster, and I believe this was less to do with the bike than the fact that there is a large gap between the two legs (no bike frame) allowing for better re-attachement around the legs. I would be interesting if TJ or someone from Dimond can comment on that aspect.

My personal downhill "windtunnel" on the bike, I have not had a single modern bike descend faster than my 1995 softride...by the way, the test hill (blacks lake hill in Gatineau Park in Ottawa) is the same one that I've used on skis. Sure, atmospheric conditions change, but when you go down the same hill a zillion times on every bike you own, you see some trends emerge.

But I would agree that when I press my knees together on the top tube of any bike, that is the fastest position on that bike while coasting, so with the bike in there between legs, I generally agree with "narrower is better" given that the bike fills the gap between the legs. But what if you could go with a really wide stance on a narrow width bike....maybe that is better aerodynamically than narrow if you can create enough space between bike and legs.

You can be certain if a speed skier could go faster narrower, they would figure out a way to ski that way and go fast (different than downhiller or GS skier). Look at the airfoil they attach to the back of their calves....if they could put feet together they would have a front semi teardrop fairing and a rear semi teadrop....but they create a full teardrop on each leg instead cause that's the fastest.

I would thing that pelvis width would play a factor as if the q-factor was too narrow and you splay your knees out or not have an in line pedal stroke you could become less aero. I would set my q-factor to what feels most comfortable and I could put out more power especially when fatigued and you lose form.

They use that stance because they'd die if they went narrow.

Source- lived many years in Les Arcs and know quite a few speed skiers.

Have you seen this?

https://cyclingtips.com/...obrees-old-faithful/

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Hi Jeremy, yes, I had seen that.

My first thought was to wonder what a collaboration between Rob English and Obree would look like - get those two geniuses together!

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´Get the most aero and light bike you can get. With the aero advantage you can be saving minutes and with the weight advantage you can be saving seconds. In a race against the clock both matter.´

BMANX