# Plumb one or both knees?



## woodys737 (Dec 31, 2005)

Coaches and/or masters of physics,

When getting plumbed for KOPS, should I check both knees rather than just one? Both times I can recall only having the right knee plumbed. That goes for checking knee extention too?

Splitting hairs maybe? But, it seems that if one leg is longer, the cleat position should not be the same from left to right.

Just thinking.


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## jerman (Jan 28, 2005)

*Great Question*

Has anyone ever had a Serrotta fit kit done? I've heard it's about the best there is.
I just wonder if it checks both knees and also checks extension of both legs?
Thanks.


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## kbiker3111 (Nov 7, 2006)

When I do fittings, I'll check both and make an estimate between the two. Obviously though, KOPS isn't the be all end all. You need to make sure the rider is comfortable on the bike and has the correct pedal stroke. 

Really though, I'm no expert and I've definitly never been to Serotta or anything.


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## Spear Legweak (Mar 27, 2006)

*Maybe None!*

A message from the guru himself http://sheldonbrown.com/kops.html


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## wim (Feb 28, 2005)

*Wide range of error.*

There's no point in plumbing both knees. When establishing KOPS for one knee, the range of error is much wider than any difference betwen the left and the right knee could ever be. For example, just lowering the heel during the KOPS procedure will move the plumb bob string about 2 cm behind the pedal axle; raising the heel will move it about 2 cm in front of it. Unless you've had the fitter observe you over time as you ride hard, or had a ride video made of yourself, there's no way of knowing how you articulate your heel (both left and right) around the crank circle when you ride with power

The problem with KOPS is that it's generally established in a static environment, yet is supposed to find the best position for powerful, dynamic riding. In my view, KOPS establishes a starting point for good front-rear weight balance on the bike, but that's about it.


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