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Discussion Starter · #1 ·
Hey Everyone,

So I know KOPS isn't the end all be all and just a starting point, but I seem to be 1-2cm ahead of KOPS even after a bike fit. I get this by dropping the plumb bob over my knee and seeing where it lands in relation to the end of the crank arm. I wanted to ask the correct way of measuring...

Is it from end of the knee cap (longest part sticking out) to the end of the crank arm, or the tibial tuberosity to the pedal spindle? I've read both methods and trying to determine which is the right one.

And yes, I know my bike fit is most important, but really just seeing how close I am to KOPS out of curiosity.
 

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Hey Everyone,

So I know KOPS isn't the end all be all and just a starting point, but I seem to be 1-2cm ahead of KOPS even after a bike fit. I get this by dropping the plumb bob over my knee and seeing where it lands in relation to the end of the crank arm. I wanted to ask the correct way of measuring...

Is it from end of the knee cap (longest part sticking out) to the end of the crank arm, or the tibial tuberosity to the pedal spindle? I've read both methods and trying to determine which is the right one.

And yes, I know my bike fit is most important, but really just seeing how close I am to KOPS out of curiosity.
tibial tuberosity is what was used in any bike fit I have had where they look at this.
 

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Either method is acceptable. Dropping the plumb bob OVER the top of the knee and having it just graze the END of the crank arm is easier to see, which makes it more convenient, not necessarily more correct or accurate. Dr. Andy Pruitt recommends this method for its simplicity as well.
 

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Discussion Starter · #4 ·
Thanks guys. I take it being a little in front or back is a preference thing? Due to different anatomy like long femurs I find it harder to achieve KOPS
 

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Thanks guys. I take it being a little in front or back is a preference thing? Due to different anatomy like long femurs I find it harder to achieve KOPS
I'm like 2 cms forward. The only way I can ride with enough drop to feel like I'm not sitting up like a sailboat. Otherwise my knees hit my chest.
 

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but I seem to be 1-2cm ahead of KOPS even after a bike fit.
When you do this, try dropping or raising your heel and see what happens. What I'm getting at is, it's difficult to get it accurate. Not only that, it turned out to be useless way of setting up for me and I have long femurs too.

Try this video instead.

 

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Where does he recommend saddle fore-aft?
With or without setback and what amount?
He advocates typical KOPS position, so whether you need a setback seatpost or not and the amount is still determined with a plumb line.

His theory about seat angle is, taller riders are prone to back problems when the back-to-thigh angle gets too acute, which is what happens when you slacken it to accommodate longer femurs. (73 degrees is assumed to be used in conjunction with setback seatposts). Note that Zinn offers extra long crank arms on his web site.
 

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Discussion Starter · #12 ·
Quick question I forgot. I assume your foot also has to be level horizontally with the crank arm when measuring? Assuming you don't drop your heels or point down when you pedal.
 

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Quick question I forgot. I assume your foot also has to be level horizontally with the crank arm when measuring? Assuming you don't drop your heels or point down when you pedal.
Technically, this is done by a second person who observes your foot position at the 3 o'clock position while pedaling, then tries to replicate your foot position while setting up KOPS for you. If you don't have the luxury of an assistant then yes; a horizontal pedal is fine.
 

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what is so inaccurate if you know you pedal fairly horizontally? KOPS in itself is debatable right?
The method to get it accurately is very difficult. As someone mentioned already, someone else needs to watch the movement and determine what the rider's natural foot angle is. Slight dropping or raising the heel can throw the knee location off thus making the measurement inaccurate.
 

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BTW, if you are trying to further improve your fit, KOPS isn't something to go back to especially after you've already gotten the fit done (post #1).

Are you having pain somewhere or not getting the power output (being passed by some ol-man on beach cruiser)?
 

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Discussion Starter · #18 ·
Just curious that's all. Seems to get a ballpark and knowing you pedal fairly horizontally, it's accurate enough. Especially if you're not trying to get perfect KOPS
 

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Until someone comes out with a better method than KOPS, I'll use it. Right now I don't know of any.
A better method for...what exactly? Why do you use it again? What's it helping you do on the bike? Simply figure out a place to put your saddle with no consideration of reach or drop or hip angle or anything?
 
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