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  #1  
Old 04-22-2017, 09:18 PM
pncguy pncguy is offline
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Why NOT KOPS?

I've read a lot about fitting recently and I have seen several articles and posts about how KOPS may get you in the ballpark of where you want to go, but isn't necessarily anything more than an easy place to put the fit. Some people talk about how if you rotate the bike about the BB, gravity moves, but the correct pedaling position stays the same.

Of course, I've never seen anyone talk about what to use if you DON'T go with KOPS. Anyone have any "I start with KOPS but then adjust because I want..." or "I start a different way and it is different than KOPS because...?"
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  #2  
Old 04-23-2017, 02:10 AM
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Ti Designs Ti Designs is offline
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Define your goal for setting fore-aft saddle position. If your goal is a simple method that requires very little tooling or understanding, KOPS is it. If you want to ignore gravity as a force, or you're fitting in space or in a free fall, fore-aft position would have to be set based on the strength of the larger muscle groups times the mechanical advantage of their pivots. The problem there is that in order to generate force you need a point of leverage, so how you're anchored to the bike comes into it. If you live somewhere where there is gravity, you need to start looking at center of gravity. I use a method called Center Of Gravity Range From Over The Pedal At Three O'clock To Center Of Gravity Over The Bottom Bracket, or COGRFOTPATOTCOGOTBB.
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  #3  
Old 04-23-2017, 09:34 PM
cmbicycles cmbicycles is offline
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Quote:
Originally Posted by Ti Designs View Post
Define your goal for setting fore-aft saddle position. If your goal is a simple method that requires very little tooling or understanding, KOPS is it. If you want to ignore gravity as a force, or you're fitting in space or in a free fall, fore-aft position would have to be set based on the strength of the larger muscle groups times the mechanical advantage of their pivots. The problem there is that in order to generate force you need a point of leverage, so how you're anchored to the bike comes into it. If you live somewhere where there is gravity, you need to start looking at center of gravity. I use a method called Center Of Gravity Range From Over The Pedal At Three O'clock To Center Of Gravity Over The Bottom Bracket, or COGRFOTPATOTCOGOTBB.
I think you need a better acronym for marketing purposes. Take out a few letters and you could have COGRO PATO COG OBB... (say it 10 times fast) its way easier to remember and should roll off the tongue as easily as KOPS in no time.
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  #4  
Old 04-25-2017, 10:05 AM
pncguy pncguy is offline
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Wow. I guess this isn't a very interesting topic. So it is either KOPS for simplicity, or try to get your COG between the pedal at 3:00 and the BB?

Where's they mystery and magic in that?
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  #5  
Old 04-25-2017, 10:27 PM
giordana93 giordana93 is offline
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1. This area of the forum has a tenth of the traffic compared to general discussion.

2. Kops has been beaten to death and usually falls between the idea that it is gospel or useless, and since the answer is in between..wait, my own point here is like that swinging pendulum or key dangling from the bony protuberance (or end of kneecap?).......

3. In other words, there is some value in kops as a fit metric depending on whom you talk to but it is not easy to measure exactly and repeatedly, especially on your own; it is at best a measure on a static position on an indoor trainer; its value varies by rider physiology and riding habits--pursuit or sprinter on a track will differ from a randonneur, a mountain goat, a fit twenty something or budding enthusiast just starting out to lose weight... See where I'm going with this?

Google keith bontrager and his piece on kops. It's an ok read (and you'll get 1000 hits of endless forum discussions if you want to wade through them.) even just searching past posts here, or those ti-designs has made among others ain't a bad start. When you think you've understood his post above (and I mean that, no derision) you'll be on the right path. Long story short, as he noted, it's a simple metric and while there is some virtue in simplicity, it is also limited. I'll say it for ti-d: a fit done on a trainer is barely a start to learning how to pedal properly.
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  #6  
Old 04-26-2017, 12:44 AM
nate2351 nate2351 is offline
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Sometimes KOPS just doesn't work with the bike. TT/Tri bikes are a perfect example. The more I fit the more I believe KOPS is useless. Saddle height, reach, and cleat placement are far more important.
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  #7  
Old 04-26-2017, 12:59 AM
rustychisel rustychisel is offline
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Originally Posted by nate2351 View Post
Sometimes KOPS just doesn't work with the bike. TT/Tri bikes are a perfect example. The more I fit the more I believe KOPS is useless. Saddle height, reach, and cleat placement are far more important.
You're setting your own metrics upon the original idea. KOPS was developed for 'standard' road bikes in the time of 72ยบ seat tube and head tube. Of course it doesn't work [as well] for TT bikes.

KOPS is not useless; it's a starting point for achieving fundamentally basic position upon a road bike and it's simple virtue is that it puts you in the ballpark for correct balance ie fore and aft positioning on the bike.

What can be in error with the idea? Well, just about everything, starting with femur to tibia ratio of the legs (there is a norm but many people differ from that), overall leg length to torso length ratio (there is a norm but many people differ from that), etc etc. Then there's the fact that sprinters, younger riders and trackies often want to be further 'forward' and higher, triathletes often want to be 'forward' but slightly lower...
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  #8  
Old 04-26-2017, 06:57 AM
fuzzalow fuzzalow is offline
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KOPS is too simplistic to be of any value whatsoever. To say that it is a valid starting point is hedging the value & idea of KOPS from the get-go - if it is used as a starting point, then what comes next? Rarely, if ever, is the follow up discussed, it is just a less than clever dodge in salvaging a faulty reliance on KOPS.

Turn the question around: Why KOPS? No one on this forum I'm aware of has ever validated and rationalized the KOPS concept or process. But in a different label the same concept of KOPS was staunchly defended by acceptance of a measuring tool to transfer bike coordinates as used by some mechanics in the pro peloton but as instead used by a consumer across different bikes. Same concept as KOPS it under a different guise. I'm sure the search function could unearth this thread.

I'm a civilian. There is a tendency to want to place credibility onto those who claim industry credentials. However I rarely hear anything explained by a pro that has much coherence. Caveat emptor. And as always, the true litmus test is to show me what you ride: the setup always reflects the body alignments in force & effect for that specific rider & bike implementation. And the implementation always reflects the conceptual model and biomedical precepts on which the fit & position is constructed upon. That is still an absurdly optimistic statement because I believe many pro fits have no conceptual basis at all. Lotsa lasers, precision measurement, database regression analysis and marketing whiz-bang. Caveat emptor.
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  #9  
Old 04-26-2017, 07:06 AM
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christian christian is offline
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Quote:
Originally Posted by fuzzalow View Post
KOPS is too simplistic to be of any value whatsoever.
KOPS may be of limited value to people who frequent this forum and have bicycling as a serious hobby. But for a likely majority of the population who fall in the fat part of the size/shape bell curve, it's a useful heuristic for getting the relationship between pedal and seat set somewhat close to optimal, so that further experimentation can set the personal ideal. In that way, it's no different from any fit "system."

I'd argue that for most people, "Lemond formula for seat height, KOPS for set back, and experiment from there." is as good as most "professional" fits.
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  #10  
Old 04-26-2017, 10:01 AM
MikeD MikeD is offline
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Right, why not KOPS? What's the alternative? KOPS puts you in a neutral position on the bike in terms of front/rear weight distribution and hip angle.
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  #11  
Old 04-26-2017, 10:51 AM
pncguy pncguy is offline
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What Mike D says is sort of the answer I was looking for. Yes, the question really should have been "what's the alternative?" Or, a better question probably would have been "when you're figuring saddle position relative to BB, what is the end result you're trying to achieve?"

I think the answer is "you want to position the body such that the weight is distributed roughly equally on the front and rear tires. Or, something like the well known COGRFOTPATOTCOGOTBB. (Sorry, the official marketing acronym hasn't been determined or approved by corporate yet.)

Sounds like I have even MORE reading to do. For now I'll rest comfortably in the fact that my current bike, which I have been riding since 1991, has never given me any problems. So I can't be that far off, KOPS or not.
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  #12  
Old 04-26-2017, 11:02 AM
fuzzalow fuzzalow is offline
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Quote:
Originally Posted by pncguy View Post
What Mike D says is sort of the answer I was looking for.
Well, there it is.

The genius in simplicity.

Until the question: What happens next?
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  #13  
Old 04-26-2017, 01:40 PM
pncguy pncguy is offline
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Oh, nothing happens next. I'm an engineer and I wanted to understand all this stuff I have been reading about fit. (Well, of course, as an engineer, LOTS happens next, but I wanted to know the end goal...)
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  #14  
Old 04-26-2017, 06:41 PM
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KidWok KidWok is offline
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I've used KOPS as a starting point for new cyclists, with the advice that it gets into the ballpark of the right fit.

Tai
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  #15  
Old 04-27-2017, 07:30 AM
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christian christian is offline
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What happens next is that you realize that the primary force vectors that affect a cyclist is the gravity on your upper body (down) and the reaction to the effective torque around the bottom bracket you can supply for the duration of the ride (up). Keeping those forces largely balanced means you will carry little to no weight on your hands and be in a balanced position. Doing so in a mechanically efficient position for pedaling means you are in an ideal position. There are a few ways to alter the relationship between these forces:

- increase power
- lose (upper body) weight
- sit more upright (shorter lever arm)
- move seat back (shorter lever arm in front of the fulcrum)

Note that moving the seat back, while retaining the same bar drop will close your upper body and require your hamstrings and iliopsoas to be more flexible.

So if you have a tiny upper body and make lots of power (and have the hamstrings to let you do it) you can close the angle between the upper body and lower body and ride in a low position comfortably. If you are chubby and make little power, you will be more upright. Compare Rasmussen with a local parson on a DL1....

But see, by the time you read this, you're already a person who reads bike forums about fitting. For getting a decent first position.... maybe KOPS?
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