Compendium of Internet Fit Advice


#841

more setback closes your hip angle, dropping your shoulders forward and down, so you don’t need a choad stem anymore

(until your knee hits your collarbone)[/quote]

then why do TT guys move their seat forward to open the hip angle and get lower on the bike?

actual serious question.


#842

[quote=dorth]sorta an xpost from the geometry chat thread, but lets talk setback.

I’ve read several times that riders with long femurs will generally favor more setback, but why? …obviously riding style and rider preference (or ignorance) come into play here, but what is it about long femurs, or other variances of a persons physiology (like ???) that would influence a more setback position?
[/quote]

the femur thing is magical bullshit. it’s only a “thing” since it’s the practical consequence of KOPS. actually it’s sortof a compelling counter-agument to KOPS.

the bike has only 3 contact points. i find it helps to think of the relation between those points and erase the bike from your mind. focus on saddle height, reach and “drop” (which measures the angle between the two). if you want to change setback, all other things being equal, you’re effectively rotating the rider around the axis of the bb. the sweet spot is reached when the rider’s weight is balanced over the bike, neither too much weight on hands, or too little weight to “get over” the pedals.

when you pedal a bike, you’re effectively keeping your body from falling forward by applying rotational force around the bb spindle. the greater the force, the farther forward you’ll need to remain balanced. this is why track, tt and cross bikes have the rider positioned further forward while beach cruisers and touring bikes position them further back, not because of any physiological difference between these riders.


#843

more setback closes your hip angle, dropping your shoulders forward and down, so you don’t need a choad stem anymore

(until your knee hits your collarbone)[/quote]

then why do TT guys move their seat forward to open the hip angle and get lower on the bike?

actual serious question.[/quote]

i think it depends on what your end goal is

closed hip angle means more hamstring engagement, but the hamstring on the bike is not nearly as strong as the quad for power output.

sitting further on the seat means you’re not only keeping your hip angle open and gettin’ low/aero, but you’re leaving more room in your chest to breath (hence short crank trend for tridorks) and using more quad to get more power.


#844

Yeah I’m not convinced that the femur thing is real.

If it is, it plausibly relates to hip angle just as well as KOPS, something like longer femurs = hip joint sweeps a smaller angle over the crank cycle = you can close the hip angle more.


#845

the long femur thing is real. if you’re going off KOPS, you do need your saddle further back.
but tbh, if i scoot my seat forward, it’s too much weight on my arms.

i don’t think KOPS is such a big deal as it’s made out to be for your knee joint so much, but fore/aft of the saddle is the key player in weight distribution and balancing quad/hamstring engagement. cuz i am able to scoot forward on my saddle and get low/put some power down while riding and it does not cause me any knee pain.


#846

As stated in one of the OPs… KOPS is bullshit, considering the two fastest bikes are recumbents and TT bikes.


#847

more setback closes your hip angle, dropping your shoulders forward and down, so you don’t need a choad stem anymore

(until your knee hits your collarbone)[/quote]

then why do TT guys move their seat forward to open the hip angle and get lower on the bike?

actual serious question.[/quote]TTs are short and the position is meant to be as uncomfortable as you can stand for the parcors so that you can maximiuze power. TTs are generally just a watts game and the biggest engine wins.


#848

You push higher peak watts on a road bike

Tt bike position is about power, but after aero has been taken into account


#849

Good point.


#850

TT position is about getting as aero as possible and still making decent power. I’ve read accounts of people giving up 10w or so for better aero.


#851

I got laughed at suggesting similar elsewhere a few years back. Do you have any link to support? Would give me good “jerk store” material in my head.

I’m pretty sure there are guys giving up some watts for Aero in the pro ranks. Also giving up good bike handling, but that’s another story.


#852

depends on your role

a dude like hansen absolutely gives up wattage for aero

in the break at 40+km/h, 15w lost will quickly be made up through what is saved in aero


#853

frontal chain is more efficient over a TT effort than any hamstring recruitment. Sustained power output will be higher.

recruiting posterior chain(glutes, hamz) and lower leg muscles can increase instantaneous power output, but will lower absolute energy output over a sustained duration. They are less efficient (generally, though a muscle biopsy is the only way to confirm, and this is EXTREMELY variable person to person) Part of the reason anterior chain is more efficient is blood supply: Direct major arterial supply. Posterior is fed through penetrating branches with less total flow/fuel.

lots of people become considerably faster in a TT after switching to mid foot cleat position: take out lower limb muscles so they don’t have to stabilize the foot when applying power: isolate prime movers.

next time youre at a cross race look at the femur/tibia variation amongst the pro field. It’s huge. Sports tend to select a certain body type, but cycling seems to have a large amount of variation.

even at the top end of other sports, there are huge variations in proportions: people are in no way set to a certain proportion. I’ve seen huge differences in femur/tibia and humerus/radius-ulna and torso length. Limbs tend to be somewhat symmetrical, but this makes sense since they develop using the same set of HOX genes and during the same embryological period. Even though torso length is also highly variable, more or less everyone has the same # of vertebrae, they just change in size (random :a giraffe even has 7 cervical vertebrae.wtf.)

so, it goes without saying that some riders may be able to gain huge advances in aerodynamics by rotating forward about the bottom bracket without losing hardly any power up until the point that their hip angle is so closed that it impedes lung capacity/expansion.

Hansen is crazy as shit, but you can’t argue that his position is about as aerodynamic as you can get on a road bike.


consider, too, that he runs crazy long cranks. He has a pretty short torso too. You can see a good shot of this here:

compare this with fabian: totally different proportions, totally different fit, still incredibly skilled at sitting in the wind and hurting people

I think it’s fascinating how high the variation is in body types that can win a bike race. It’s part of why I still find cycling to be an interesting sport in contrast with running, which, for me, got boring quickly.

I should add wiggins, because I think he does it the most beautifully. I will sorely miss him in the peloton.


#854

fuck i love tarck! this is all really interesting


#855

[quote=ergott]
I got laughed at suggesting similar elsewhere a few years back. Do you have any link to support? Would give me good “jerk store” material in my head.

I’m pretty sure there are guys giving up some watts for Aero in the pro ranks. Also giving up good bike handling, but that’s another story.[/quote]

Wish I could remember. It would be from personal accounts of wind tunnel testing. I’m sure it’s something Coggan has mentioned at some point or other. He’s done a fair bit of aero and Crr testing.


#856

Hansen’s position looks like shit.


#857

You know who remembers that? Pepperidge fa…er…Graeme Obree remembers…


#858

hansen is what i would look like if i put a 0 setback post on my bike lols


#859

Internet Fit Advice ShartQ: I’ve been having a recurring problem in one of my knees. On occasion, I get a sharp pain in my left knee under load (behind the lower part of the kneecap, specifically) in the first 15-20 minutes of a ride. The pain mostly dissipates quickly and doesn’t recur strongly as long as I don’t mash carelessly. Overwhelmingly, it occurs on a bike with 175mm cranks. The others in the fleet are 170/172.5.

The SQ: has anyone else experienced knee problems or other noticeable issues due to a minor difference (175 vs. 172.5) in crank length? I’m 5’11" but with stubby 30"-inseam legs. Do I replace the crankset with a shorter one or is it more likely that this is being caused by another fit-related variable?


#860

2.5-5mm is a pretty tiny difference… But, if that really is the only fit variable, you can always move that saddle slightly lower and/or further forward to compensate for the longer crank.

That being said, I have a really hard time believing crank length alone is responsible for the presence of sharp pain. Wiser men than me have said that knee issues rarely have to do with the knee, but moreso with mobility/flexibility (muscle, ligament, joint) issues ‘upstream’ (quads, IT, hips) or ‘downstream’ (lower leg muscles, ankle, achilles). If you’re not already doing some self-work with foam roller/balls/stretching on the whole system, I would suggest that.