Mechanics

[rspecker]

A lot of bike fit advice focuses on the balance point rather than on KOPS; this advice makes sense to me for determining fore/aft position over the bike. For example, I know it is particularly important for me to not have too much weight on my hands.

But, there must also be an optimal position with respect to the mechanics of pedaling itself. And it doesn't seem like the center of balance answers this. Once you find your fore/aft position, how do you know where to put the bottom bracket relative to the saddle and the handlebars? How high should the saddle be? And how long should the cranks be?

Presumably there is an ideal pedal stroke shape, and there are stronger and lesser muscle groups, and there are mechanics of the hips and knees (and maybe ankles) that all transfer power to the pedals, cranks and frame. Why isn't the right place to start in considering a rider's bike fit the mechanics of pedaling itself? And after that position is determined then the bike geometry places the rider in a comfortable position for weight distribution and bike handling and aerodynamics.

I suppose seated position and standing position both come into play because the design needs to perform in both--so no doubt this topic is very complicated!

Maybe I am missing the point and balance is all inherently relative to the bottom bracket anyway, so the balance point answers everything. But (I think) that is 100% the answer only if: (1) some (lucky) people's body's are just naturally better "balanced" and proportioned for power; or (2) the relative position of hips, knees, ankles to bottom bracket and pedals don't matter (i.e., KOPS or something similar really is meaningless and there is no optimum mechanics for power). Neither of those 2 choices make sense to me (or, at least #1 is sort-of depressing), so that is why I am writing this!

I understand this is a giant topic, so any pointers to articles/books that have covered this would be welcome.

Thanks

[Peter P.]

You either choose Balance, Mechanics, or compromise on both.

There is no Pefect Position. There is a Range of positions under which you will perform optimally and still be comfortable. The human body is remarkably adaptable.

It's good to have an education on bike fit. The more you learn the more you'll understand that it's not as precise as you may think is required.

Two books I have for reference are Andy Pruitt's Complete Medical Guide for Cyclists, and Bike Fit, by Dr. Arnie Baker (available on-line from roadbikerider.com).

[SPOKE]

Balanced and comfortable is usually the fastest for the longest IMO.

[Gummee]

I can understand moving away from KOPS for specific needs: behind a bit for climbing and maybe forward a bit for the track/crits.

...but it seems that KOPS is a great place to start. After all, pressing straight down on the pedals seems like a pretty efficient thing to do. No?

'Balance' is such a nebulous term. Yeah, great. You're balanced. Where over the bike does that put you? Is it duplicate-able from bike to bike?

I don't claim to be the world's best fitter, but seems that the (ancient) rough guidelines of 'stem obscuring the handlebar' and 'KOPS' do pretty good for 99% of the people.

YMMV (and I'm willing to be convinced, but its gonna take some convincing)

M

[1centaur]

You only need to be balanced enough to maneuver as you need. Unless you are descending mountain passes near the limit, the range of acceptable balance points is fairly wide. The mechanical efficiency window is narrower.

[carpediemracing]

I think that balance vs KOPS is not really a valid way of comparing ways of determining pedaling efficiency. They're not really similar variables. Meaning Balance may get you the same position as KOPS. The two are different things, they measure different things.

Also, unless a rider sits inside their saddle (think like a horse saddle or a foot deep U shaped thing you straddle), a rider will regularly move forward and aft on the saddle. This changes everything, even while seated.

Pretty much everyone slides forward on the saddle when going harder/faster (aka "on the rivet"). Some people move back when powering through high effort low cadence efforts. Only when spinning does a rider stay relatively still in one spot on the saddle. In most higher effort situations the rider is way over the front of the bike, sitting on the tip of the saddle.

In addition there's a huge variable with "saddle position" when out of the saddle. Most riders move forward significantly (in terms of saddle position) when out of the saddle. I don't know of anyone that moves back when out of the saddle while pedaling.

[ShoMyOFace]

Balanced and comfortable is usually the fastest for the longest IMO.

x2