Tilford on Sagan
Last Post 09/13/2013 05:22 PM by Elle S.. 27 Replies.
Author Messages
Inferno7

Posts:278

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09/10/2013 09:23 AM
http://stevetilford.com/2013/09/10/peter-sagan/
Oldfart

Posts:489

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09/10/2013 09:36 AM
Yeah pretty much. I saw that final TOA stage. Pretty amazing the way he turned like that. Weight over the outside like a mountain biker.
Entheo

Posts:317

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09/10/2013 09:48 AM
i think it was a stage in the giro, a few years ago... final corner, maybe uphill if memory serves... sagan just railed it, balance was perfect, like a classically trained dancer, shot thru the other riders like a hot knife thru butter. knew then that i was watching someone special.
Master50

Posts:245

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09/10/2013 02:08 PM
Driving the medical car on the stage in Black Diamond I was just amazed at how he just goes wherever he likes. Riding out in the wind beside the team car and joking with the Director. I just never looks hard for him. He just seems to be part of the bike or it is part of him. He gets bottles while his team grinds away on the front to protect his energy. He is a very special rider and it will be a while until we see it's depth. Right now he is just having funs it seems and I wonder how he will transform the sport, he is that good.
Keith Richards

Posts:754

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09/10/2013 02:12 PM
He is a bike RIDER. He knows how to ride a bike. ANY bike.

Not a lot of guys racing on the road are really adept at bike handling.

http://www.youtube.com/watch?v=gLDMhKHlEIA

How many guys in the pro ranks can do this? Him and.....
----- It is his word versus ours. We like our word. We like where we stand and we like our credibility."--Lance Armstrong.
Orange Crush

Posts:1231

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09/10/2013 02:43 PM
That final corner in Calgary was something to behold, it rendered the sprint a formality and giving him enough time for the lassoo tribute...roped that one in real easy.
bobswire

Posts:302

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09/10/2013 03:22 PM
You're all familiar with the term "a mans man", Sagan is "a cyclists cyclist". Seriously who can he be compared to?
ElleSeven

Posts:48

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09/10/2013 03:25 PM
It's not just the angle of the bike; it's that his upper body is essentially upright, his COM remaining almost directly above the contact patch. This is known in the trade as "angulation," a term that Sean Yeats bummed from GS skiing when he and a few other riders noticed how skiers "corner" and negotiate slalom gates, with a sharp angle between the upper and lower physique, like the hands on a clock at 4 o'clock or 8 o'clock. It is by far not only the fastest way to go round a bend, because speed actually assists the physics, but the safest by far as well, since the body mass presses straight down as against aiding centrifugal action. You need virtually no traction, either, which everyone else in that photo is depending on entirely to keep their bikes from sliding outward. Had that surface been damp, only one rider would have got through upright: Sagan.
Oldfart

Posts:489

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09/10/2013 03:28 PM
Down stairs on a road bike is no big deal. Up them on the other hand takes skill and comfort. A friend of mine can ride like that. He's a former flatland BMX rider. He can ride a mountain bike really fast up and down and has been the provincial cross champion and I think he was second or third at the national cross champs, in masters 30 plus. Sagan is like that in terms of comfort on the bike like it is simply an extension of himself. He's not a sprinter like a Cavendish or a climber like a Pantani. More of an exceptional all rounder.
ChinookPass

Posts:480

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09/10/2013 04:06 PM
I hope he can win De Ronde before Cance and Boonen retire. Stages of the Tours of Colorado and Alberta? meh.
ElleSeven

Posts:48

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09/10/2013 04:16 PM
Sorry, Yates, not Yeats. Beg your pardon. Not the guy who said, "Things fall apart," but the one who said, "Stuff breaks."
Keith Richards

Posts:754

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09/10/2013 05:37 PM
There is a phrase I used to hear back before watt meters and all...back when you were taught about riding a bike well as opposed to just producing max watts, "lean the bike, not the body."

Sagan got that memo.
----- It is his word versus ours. We like our word. We like where we stand and we like our credibility."--Lance Armstrong.
Oldfart

Posts:489

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09/10/2013 05:55 PM
Oh you still need traction L7. What he did allows the bike to lean more and thus turn more sharply. Some of the other riders are doing to old school head over the inside which I was taught a long long time ago. Bikes on dirt or pavement to seem to turn better when you lean the bike and not the body. With modern skis that actually hold a carve you can really feel the g forces. Same on a bike and you need grip to do that. I think some riders try and copy motoGP riders who lean off the inside but that is because the GP bikes are already as leaned over as they can be so the riders have to do that so as not to touch down and slide out.
Orange Crush

Posts:1231

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09/10/2013 05:59 PM
Posted By Jim Laudolff on 09/10/2013 04:06 PM
I hope he can win De Ronde before Cance and Boonen retire. Stages of the Tours of Colorado and Alberta? meh.


Not necessarily de Ronde, but he'll net a big one next year. He's ready now.
ElleSeven

Posts:48

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09/10/2013 06:32 PM
Old Fart, can we agree on very little traction by comparison? In any case I'm referring to the traction sometimes loosely called "adhesion" that is used to resist side-load and centrifugal energy, not the element of traction that allows the tire to rotate without slipping in its direction of travel. Angulation drives so much orthogonal down-force into the contact patch that what little mass lies to the inside of the contact patch [principally the bike frame, one leg, and one arm] barely acts on the tires at all. It's a bit like a circus clown balancing on top of a ball: the trick is to keep the ball directly between your COM and the ball's contact point on the ground. Also, as the grouch -- Sean's one-time teammate who taught me this technique -- has pointed out here in the past, comparisons with motorcycle cornering methods are problematic. Same physics, and therefore some dynamics in common, yet the completely flip-flopped relationship between rider and vehicle mass will place the motorcyclist's unified COM very close to the ground, whereas with a bicycle that unified COM will be at or even above the saddle.

There are additional gains for angulation, too, such as the way in which the wheels track in near-linear alignment rather than in a de-stabilizing tangent; no active deceleration is needed while the bike is passing through the apex; and so on. But the main pay-off is that it requires surprisingly little athletic ability. (Sagan is, despite his immense natural athletic prowess, not using natural ability here; he's using a learned skill.) Your grandpa can be taught to do this. And watching gramps drop the local Ones on a descent can be among the funnier delights of the training week!
JS

Posts:61

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09/10/2013 10:13 PM
Posted By Elle S. on 09/10/2013 06:32 PM
  (Sagan is, despite his immense natural athletic prowess, not using natural ability here; he's using a learned skill.)

Nope, not even close. Your logic suggests that anybody can "learn" to do what he did and that is simply not true.
Oldfart

Posts:489

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09/10/2013 11:55 PM
Yeah not everyone can learn. But I did. Good point L about motorbikes being far heavier than the rider. That is certainly way different. I think leaning the bike more than the body allows the bike to just turn more quickly with less steering whereas a more upright bike needs more steering input to turn at the same radius. Sometimes on slick north shore roots and baby heads at slow speeds one does try and keep the bike more upright otherwise you go down. But that's different. I read somewhere that to turn a bike tighter mid turn, like to avoid something to push down on the inside grip. That leans the bike more and also moves your body to the outside. Some riders recommend for off road to lean the bike, not the body and push down on the outside grip straight down to push the tire into the ground. I'm not sure I agree with pushing down on the outside grip actually pushes the bike straight down but I do think it puts your body in a better position. Been thinking about this quite a bit this summer after reading some tips on off road turning. Thinking a bit more, you still have the same 156 pounds of bike and rider (in my case.on a good day) stuck the ground on the same contact patches trying to hold the same forces. Same traction requirement no? That's why the rider with the not so leaned over bike over steers and front wheel washes out.
durielk

Posts:41

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09/10/2013 11:57 PM
I think Sagan is great.
He can corner, what he did on the last turn was take the apex away from the lead rider on the outside. In racing you should protect the inside otherwise Sagan dives in, turns harder and is gone. Once the leader lost control of the inside (& the apex), he had to check up and change his line to way out wide. But that is racing! It is going to be hard to beat him, put it in the books for Sagan.
CarbonGecko

Posts:39

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09/11/2013 07:57 AM
L7 I think you need to explain yourself to the physics challenged like myself.

In my thinking Sagan's corner required MORE traction. He went around the corner faster in a shorter arc and generated more centrifugal force. (Centrifugal force isn't really an independent force, it is the inertia of bike and rider that wants to continue to go in a straight line). That inertia had to be compensated by his tires traction or the tires would have slid out.

It would seem to me that what Sagan is doing by leaning (angulating) the way he does is more effectively maintain traction. It allows him to maximize the diagonal vector that loads his tires more and generates more traction. That allows him to corner faster. Just like skiers angulate to maximize the effectiveness of their edge. Two skiers trying the same arc at the same speed; if one can cause their edge to grip but the other can't then one generates enough traction to make the turn, the other has insufficient traction and slides out.

The riders who lean further without angulating start to have less of a diagonal vector and more of a horizontal vector. That reduces their ability to load their tires, it decreases their traction, and they have to slow down or take a longer arc. Because they have less traction, they need to decrease their inertia or the amount of traction they are generating will be overcome and their tires will slide out.

I guess what I am asking is that if Sagan is cornering sharper, at higher speed, and generating more forces... how can he require less traction to make the turn?
Keith Richards

Posts:754

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09/11/2013 09:43 AM
Posted By jeff sanford on 09/10/2013 10:13 PM
Posted By Elle S. on 09/10/2013 06:32 PM
  (Sagan is, despite his immense natural athletic prowess, not using natural ability here; he's using a learned skill.)

Nope, not even close. Your logic suggests that anybody can "learn" to do what he did and that is simply not true.


I somewhat disagree. Anyone can be taught a technique, but not everyone will "get it". Can anyone learn the principals to the cornering technique that Sagan is using and become a better rider for it? No question the answer is yes.

Will they be able to do what he did in a race situation? No...well, a few might "get it" and be able to. But that leads back to what I said up thread, who is teaching cornering technique? The advice most people get is "hold your line".
----- It is his word versus ours. We like our word. We like where we stand and we like our credibility."--Lance Armstrong.
durielk

Posts:41

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09/11/2013 10:01 AM
What Sagan did was go around a corner more like a motocross rider, who is standing on his pegs which allows the bike to be controlled and angled separately from the rider. It allows greater bike lean & quicker changes in direction, and quicker adjustments to the turn, and the bike is riding more on the side of the tire.
Most riders typically go with the standard butt on the seat turn, where one leans mostly with the bike or leans the body a little more than the bike, like MotoGP racers. They do it to keep the tire patch bigger with the ground as the tires profile has a flatter appearance (on the side of the tire after a certain angle, there is very little patch on the ground) & they are anticipating hitting the throttle ASAP. But changes in the corner or direction are more difficult, they set up for a corner & they are locked in within a narrower arc of control.
If you go around a corner, the tires load up the same if the arc of the corner is the same, whether the tire is more vertical or horizontal, the loading is similar. The patch contact with the ground is dependant on the tire profile. Once the maximum load is reached, they all are going to slip or step out.
Orange Crush

Posts:1231

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09/11/2013 10:41 AM
Its like the kids' track and field coach said, anyone can learn a trick/skill but if they can be taught to "get it" at a young age (< 10 yrs give or take), they can operate several steps above those that get taught the skill at a later age. Sagan is one of those rare occasions where ability, interest and drive lined up at a very young age.

My friend's oldest kid at age 10 is showing some amazing bike handling and snowboarding athetism. I am sure that if he applied himself he could give Sagan a run for his money in terms of bike tricks by the time he reaches that age. But so far the stars do not align in that he's not really interested in competitive sport.
C2K_Rider

Posts:172

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09/11/2013 12:40 PM
Seems like he did what I do on descent curves - actively push the inside bar towards the outside of the turn. You can see he keeps his left arm straight and right is flexible as he dives to the left. When I do it, it feels like the bike is pulled into the curve without losing speed. Only a couple other riders in the front are doing that, the rest have both arms bent, which means they are just leaning. I just wonder about it because a descent curve has a definite radius and cant, while a flat street does not. The technique might be different.
jmdirt

Posts:727

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09/11/2013 08:56 PM
While I am far from a physics expert, when certain things like centripetal force and coefficient of friction are absent, the analysis is incomplete.

Food for thought: why does banking or a berm aid cornering speed?

Yes, you can "teach" people to corner like that but only about 2% will actually be able to do it.
ElleSeven

Posts:48

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09/12/2013 05:19 PM
jmdirt, I suppose we could get into the pure physics but I think we should probably do that off-line. It would involve some pretty extensive unit-vector calculus and whatnot, and I can't see a proper discussion coming off in less than fifteen pages, which wouldn't be tolerated as a forum entry!

Where does the 2% figure come from? When I was yakking with my "guru" this morning, he said that he'd never yet encountered anyone, no matter how ill-adept in a native sense, who couldn't learn to do this pretty well. By "pretty well" he would not mean, "as well as a pro who uses the technique." He would mean, "faster than what they did previously, and, more critically, way, way, way safer."

jmdirt

Posts:727

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09/12/2013 10:11 PM
When I said that only 2% will actually be able to do it like that, I was referring to doing it as well as a pro (we were talking about Sagan weren't we?). I was being generous with 2%.
longslowdistance

Posts:720

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09/13/2013 08:44 AM
As far as motorcycles go, the optimal is angle the bike under the rider off road ( slippery surface) but keep aligned on asphalt. At least that is what my teachers say.
ElleSeven

Posts:48

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09/13/2013 05:22 PM
Maybe the best way to address these questions is the old-fashioned empirical way: go out and try it. Change direction not by steering (in the conventional sense of aiming the handlebar towards the exit) but by pushing down and forward on the inside drop (exactly as CK describes). All the other elements -- the exaggerated bike lean and angulation, the COM shift, and so on -- sort of take care of themselves. Counter-steer/Angulation is so easy, the main danger is that you'll remove a hand from the bar to slap your head.


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