Descending Technique and ACTION SHOTS

[maxim809]

In order to keep the 2022 Pro's Thread on topic, let's branch the descending topic to its own thread here.

Good discussion around [knee-in vs knee-out] when descending was taking place in there. Novel ideas and perspectives were being presented. I found it interesting and I'd like to see this discussion continue here, in a GENERAL descending thread.

The world is your oyster.

• knee in vs knee out
• steering with hands vs hips
• optimal ratio for applying body weight over the wheels: front/rear/balanced?
• tucking vs pedaling
• course conditions vs tire selection
• racing lines vs braking lines
• The Great Braking Debate Thread
• frame geometry's impact on steering
• motorcycles, and how this does or does not apply to bikes
• would dropper posts really make you faster on road?
• speed wobble… what do?!
• vanishing point -- does it matter?
• isn't it amazing that some Pro's climb faster than I can descend?
• ACTION SHOTS of very cool cornering! <<<<<<<<<<<<<<< MORE LIKE THIS!!
• and many more topics your little heart can conjure up

[Mr.Gib]

Thanks maxim809. It wasn't my intention to throw a grenade into the pro thread.

I simply maintain that knee-in primarily affords the advantage of being able to lean the bike more and with more control. All other things being equal, more body mass toward the outside of the turn relative to the contact point with the road, must be compensated by greater bike lean to maintain the same balance. Greater bike lean is an advantage in directing the bike through a tighter radius. So why move mass to the inside (with knee out) and limit the amount available bike lean?

Secondarily, the knee-in position makes it easier to keep body weight off the saddle and control the use of the legs as suspension members. The knee out is inefficient in this regard. Generally having ankle, knee, and hip in good alignment is essential for the legs to function optimally regardless of activity.

Throughout the debate in pro thread, there were some nice photos of good riders with knee out, a couple with knee in, some superficial back and forth, and a few personal insults. What stands out is that no one challenged the basic proposal - that you can do everything with your knee in that you can do with it out, and that it comes with some additional benefits (availability of greater lean and better control of contact with the road). If one feels that it doesn't matter and that either method can be used to descend like a demon, then how about aerodynamics?

[Mr.Gib]

And I'll make an additional contribution. This photo of Sagan shows a few key things common to great descenders at the extreme.

Note where the zipper of the jersey is relative to the line formed by the angle of bike lean. Sagan's center of mass is outside of the bike.

Note where the saddle is. It is completely under his right glute - not centered under his body. Both of the these details are a good demonstration of "leaning the bike more than the body" which is the goal of my knee-in "theory". Really just another way of saying that the angle of bike lean is greater than the angle formed by the line between the center of system mass and road contact point(s).

Also, judging by the lack of distortion of his groin/glute area, there is likely next to zero pressure on the saddle - the key to superior grip.



To my eye this is miles better than Nibali and Froome above. Perhaps the Nibali photo just catches him at a particular moment, but at the very least it shows a lot of weight on the saddle. Harder to see the saddle in the Froome photo. Yes Sagan's knee is slightly out, but the lack of contortion in the ankle joint tells the story. It's a good athletic position. Compare to Nibali and Froome, I think we are looking at different technique - closer to Jobst.

[basilic]

watch Cancellara catching the peloton back in 2009 - his knee is out more often than not, esp. when the curve is tighter and he cannot see the exit. When he catches them the guys in the peloton have their knees in, and he zooms by, knee out. I doubt he's using the knee to change the c.o.g., his lean angle changes much more at will. To me it looks like natural body English, whatever his reasons are.
https://www.youtube.com/watch?v=FN6Z8UgVOuw

[TobinHatesYou]

What stands out is that no one challenged the basic proposal - that you can do everything with your knee in that you can do with it out

I challenged it by saying knee-out keeps your pelvic/hip muscles/soft tissue engaged and your entire leg more rigid. For me this is crucial in tight radius turns. You can do whatever the hell you want with your knee in a sweeper, that's not up for debate.

In all the photos shown in this thread so far, Nibali is clearly the only one entering a hairpin.

[basilic]

about the scheme above with forces as arrows: looks wrong or incomplete to me. In a turn the rider is subject to a centrifugal force to the outside, and one leans the bike to counteract that using gravity.
Centrifugal force (outward) = mass*radius*angular speed squared
Weight (downward) = mass*g
tangent(lean angle) = C/W = (radius*angular speed squared)/g

The angle concerns the line between c.o.g and contact point, it says nothing about the c.o.g. in relation to the plane of the bike.

[Karvalo]

I simply maintain that knee-in primarily affords the advantage of being able to lean the bike more and with more control. All other things being equal, more body mass toward the outside of the turn relative to the contact point with the road, must be compensated by greater bike lean to maintain the same balance. Greater bike lean is an advantage in directing the bike through a tighter radius. So why move mass to the inside (with knee out) and limit the amount available bike lean?

Who says it is? Have you tested this or calculated it or does it just 'feel' true? Here's a test - hold your bike upright and walk it round the tightest turn you can. Now lean it over at 45 degrees and walk it round the tightest turn you can. Be honest, the lean didn't help, did it? Also, when you are riding the bike on the road when are you ever near the limit of the radius the bike can turn around anyway? If bike lean angle and turn radius are connected (they're not but let's humour you) shouldn't you be advocating for different amounts of knee in to tune the lean of the bike on different radius corners?

Secondarily, the knee-in position makes it easier to keep body weight off the saddle and control the use of the legs as suspension members. The knee out is inefficient in this regard. Generally having ankle, knee, and hip in good alignment is essential for the legs to function optimally regardless of activity.

Your weight is on the outside leg. All of this above is irrelevant.

What stands out is that no one challenged the basic proposal - that you can do everything with your knee in that you can do with it out, and that it comes with some additional benefits (availability of greater lean and better control of contact with the road).

That's an untruth. Your basic proposal was that sticking the knee out "only interferes with the bodies ability to maintain good traction, adjust position and balance against the road contact point." None of these are true. This basic proposal has undeniably been challenged.

What stands out is that no-one (including you) has supported your basic proposal. You've claimed to have sound physics based arguments in your favour, but have never supplied them. PLease, tell me using physics why keeping the knee in increases traction.

If one feels that it doesn't matter and that either method can be used to descend like a demon, then how about aerodynamics?

We're talking about corners that you have to slow down for anyway

[Karvalo]

about the scheme above with forces as arrows: looks wrong or incomplete to me. In a turn the rider is subject to a centrifugal force to the outside, and one leans the bike to counteract that using gravity.

Yes, there is a missing term from the mass point. It will be equal and opposite to the friction force (for an in balance turn).

The angle concerns the line between c.o.g and contact point, it says nothing about the c.o.g. in relation to the plane of the bike.

Why does it need to?

[Karvalo]

Note where the saddle is. It is completely under his right glute - not centered under his body. Both of the these details are a good demonstration of "leaning the bike more than the body" which is the goal of my knee-in "theory".

Then he is demonstrating that it is equally possible with knee out. So why are you obsessing about knee position?

Yes Sagan's knee is slightly out, but the lack of contortion in the ankle joint tells the story.

It's all the way out. It's the classic knee out position.

It's a good athletic position. Compare to Nibali and Froome, I think we are looking at different technique - closer to Jobst.

You do know we have eyes too?

[basilic]

The angle concerns the line between c.o.g and contact point, it says nothing about the c.o.g. in relation to the plane of the bike.

Why does it need to?

not sure I understand your question.
All I'm saying is that mr Gib's claim that the c.o.g should be outside the plane of the bike doesn't follow from basic physics.
Maybe if tire grip varies between the center and sides of the tires this may become relevant.

[Karvalo]

All I'm saying is that mr Gib's claim that the c.o.g should be outside the plane of the bike doesn't follow from basic physics.

Ah I see. I thought you meant the diagram should explain it.

Maybe if tire grip varies between the center and sides of the tires this may become relevant.

Some do. But the lean required to get onto the shoulder compound is not much, and turn radius isn't a factor in that (as Mr Gib appears to be saying).

[Lina]

The Sagan and Froome pictures are from a different angle. It looks like if you took the Froome picture from the same angle as the Sagan picture they'd be in nearly identical position. Including their zipper on the "outside" of the frame.

Also one reason for knee out being so popular and knee in not so popular with pros is that when you have a bit of saddle to bar drop your thigh and abdomen would want to occupy the same space if you were to do knee in while tucked. Just look at the Sagan picture and imagine what were to happen if he did knee in instead of knee out. Yeah he'd still be able to do it but his abdomen would now be resting on his inside thigh. Knee out simple facilitates staying low while still having all your weight on the outside pedal.

[warthog101]

In order to keep the 2022 Pro's Thread on topic, let's branch the descending topic to its own thread here.

Good discussion around [knee-in vs knee-out] when descending was taking place in there. Novel ideas and perspectives were being presented. I found it interesting and I'd like to see this discussion continue here, in a GENERAL descending thread.

The world is your oyster.

• knee in vs knee out
• steering with hands vs hips
• optimal ratio for applying body weight over the wheels: front/rear/balanced?
• tucking vs pedaling
• course conditions vs tire selection
• racing lines vs braking lines
• The Great Braking Debate Thread
• frame geometry's impact on steering
• motorcycles, and how this does or does not apply to bikes
• would dropper posts really make you faster on road?
• speed wobble… what do?!
• vanishing point -- does it matter?
• isn't it amazing that some Pro's climb faster than I can descend?
• ACTION SHOTS of very cool cornering! <<<<<<<<<<<<<<< MORE LIKE THIS!!
• and many more topics your little heart can conjure up

When people view a motorcycle cornering it is generally in the racing format.
World SBK and motoGP are the two most heavily televised forms of motorcycle racing.
There is not a great deal that applies to bicycles.
In motoGP they have ~300hp being put through a rubber contact patch roughly the size of the palm of your hand.
They are braking from speeds of up to 355kmh.
Braking, cornering speed and acceleration determine how fast they get around a circuit. Those who do that best are fastest. They stick their knee out to gauge their lean angle and hold the bike up as it loses traction through that contact patch. The body is off the bike to limit the much higher lean angle, hold the bike more upright on the meat of the tyre.
With respect to braking and cornering there is far, far more skill involved but they also have far more rubber on the road and can control the behaviour of the bike with the throttle, that controls how much of that power is released at what point.

Descending is important on a bicycle but there is less, rubber, less speed and less control as there is no throttle.
Bicycle racing is far more dependant on how much power your cardiovascular system will allow you to put through the pedals at the end of a race or for extended duration through the race.

Yeah I love riding my bicycle but watching motorcycle racing is far more interesting imo, even if that is controversial on a cycling forum.

157kg bike weight without fuel.
https://youtu.be/RXQcX7xzdxY

[TobinHatesYou]

Just be glad we aren't doing the dangly leg in medium radius corners.

[warthog101]

Just be glad we aren't doing the dangly leg in medium radius corners.

Yeah not the speed and weight to make any point to it.
You'd need to clip back in to pedal also.
Not put your foot back on the peg and wind on the throttle as you weight the peg.

https://www.asphaltandrubber.com/racing ... planation/