Determine Set Back, beyond KOP

[Clancy]

Ok, so I know there's much debate out there and I'm not trying to start anything here except to try and get a deeper understanding.

First, I determine my set back by setting the saddle close to where I think it should be than tweak it while riding up an moderate incline, 4-5 degree, so that I have minimal weight on my hands resting on the top of the bars.

I also use seat posts that have set-back.

This always gets to where my knee is fairly close to over the pedal axle. But, I don't determine position by doing the standard knee over peddle, rather I get it close by doing that, but finalize it by riding.

This has worked for me but now I wonder if there's more to it.

Obviously too much will cause less weight on the front wheel and make for a light front end.

I wonder if I would be better off if I used a straight seat post, little longer stem, and place my weight further forward. Would this improve handling?

Can too much set back impact power transfer?

Does HT angle have an impact on set-back?

And, knowing there is a broad range, but is there a general range of set-back that's considered optimal? If one is outside that window does that mean something might be askew?

Last, I measure my set back by placing the bike with rear tire up against a wall. Measure from center of BB back to the wall, measure from tip of saddle to the wall, subtract the two and that's my measurement.

[ergott]

This is about as universally accepted as it gets.

http://kirkframeworks.com/2009/06/19/riding-tip-3/

[MattTuck]

Another good read.

https://www.stevehoggbikefitting.com/bikefit/2011/05/seat-set-back-for-road-bikes/


And I know that Ed (TiDesigns) has some similar ideas for setback and balance.



Mods, remember that post I made a few weeks ago about how the Bike Fit sub-forum is dying? This is the kind of post I was referring to when I said it should live on the GD for a while, but be archived in the bike fit section.

[Black Dog]

This is about as universally accepted as it gets.

http://kirkframeworks.com/2009/06/19/riding-tip-3/

This.

[Clean39T]

Another good read.

https://www.stevehoggbikefitting.com/bikefit/2011/05/seat-set-back-for-road-bikes/


And I know that Ed (TiDesigns) has some similar ideas for setback and balance.



Mods, remember that post I made a few weeks ago about how the Bike Fit sub-forum is dying? This is the kind of post I was referring to when I said it should live on the GD for a while, but be archived in the bike fit section.

I'll second that.

[Gummee]

Funny enough, in the Steve Hogg post, there's 'in front of KOPS' 'behind KOPS' and 'KOPS' in his pics (top to bottom) It may be completely random, but it's funny for a post claiming it isn't valid...

I've always wondered how one takes a fit customer from one place to another without a reference point. If you don't know where you're starting, how do you make changes and if those changes don't work, where do you reset to?

The reason KOPS has stuck around is it's a repeatable, fairly predictable **starting spot**

At least that's my opinion. I'm not a 'pro fitter' by any stretch.

M

[oldpotatoe]

This is about as universally accepted as it gets.

http://kirkframeworks.com/2009/06/19/riding-tip-3/

KOPS is not etched in stone nor brought down from the mountain top but a decent place to start. A small 'c' constant for sure...along with knee bend degrees, since everybody's legs/femurs/lower legs are different lengths from one another.

[dave thompson]

As OP ^^said^^ it's a starting point. Importantly is gives a reference point, KOP, that you can measure from, return to and start again. Kinda like reach for your legs.

[ergott]

I think centering the saddle rails on an offset seatpost is as good a starting point as any really.

[54ny77]

You might try the COBB method, which is Crotch Over Bottom Bracket.

https://lh5.googleusercontent.com/-cXYjVDkjgYY/Ts_mc5GGQpI/AAAAAAAAE8c/0MtK7JgeVz8/s640/BellyWhopper%252520Bicycle.jpg

[Clancy]

This.

And this is exactly how I go about getting mine positioned.

But, in doing so, does this weight the front for best handling?

That's my question in relation to using the above method in determining set back.

[echelon_john]

I know funny, and *that's* funny.

You might try the COBB method, which is Crotch Over Bottom Bracket.

https://lh5.googleusercontent.com/-cXYjVDkjgYY/Ts_mc5GGQpI/AAAAAAAAE8c/0MtK7JgeVz8/s640/BellyWhopper%252520Bicycle.jpg

[Tickdoc]

Can do 50 mph with minimum exertion.

Hmmm.

[bshell]

to do with pedaling forces on the knee and the joint's health and safety?

I was always under the impression that this subject was the starting point for position and fit but reading the thread it looks like I'm mistaken?

Which I would actually welcome greatly because I'm often anxious about how I'm loading my knees.

[Ti Designs]

https://docs.google.com/document/d/12zYKom8pt1-dqVc9iYkfKOkZZ12Gh-DpTuV78JY4jcM/edit

[classtimesailer]

Your saddle set "properly" will have the middle of its rails in the seat post clamp.
I'm no expert, but I think it looks the best that way and when I take my position and match it up with all the experts, guess what? I'm within a centimeter and guess what else? My butt slides back and forth more than that depending on the road and my pace and whatever.

[moonhoo]

KOPS does not work well for folks with short legs for their height.

I can't say how many times bike shop fitters with plumb bobs have said things like I need a 76d seat tube and a zero offset seatpost.

I think, "How do you still have a job?," but politely say, "no, please don't write that number on the spec sheet."

[zap]

Your saddle set "properly" will have the middle of its rails in the seat post clamp.
I'm no expert, but I think it looks the best that way and when I take my position and match it up with all the experts, guess what? I'm within a centimeter and guess what else? My butt slides back and forth more than that depending on the road and my pace and whatever.

What seatpost...0, 5, 15, 20, 25 offset?

Let's not forget seattube angle.

[zap]

.

[Mark McM]

Setting saddle setback based on position the center of gravity over the pedals clearly makes more sense than position the knee over the pedals (KOPS). But how do you measure the position of the center of gravity? Simply eyeballing might not be very accurate.

Perhaps one of the reasons that KOPS has remained popular is similar to the reason that judging components by their weight is popular - it is very easy to measure (even if it doesn't mean much).

As for setting setback relative to center of gravity - using this also makes bike fitting more time intensive. Using KOPS for setback makes bike fitting a simple sequential proces - first you set saddle height, then you set saddle setback, then you set handle reach, and finally you set handlebar height - done!

But center of gravity is dependant on both setback and upper body position. So after setting an initial setback and then setting handlebar height and reach, you might find that the center of gravity isn't where you'd like it to be. So you have to adjust the setback, which in turn means you have to find a new handlebar height and reach. Keep iterating until the center of gravity finally ends up where it needs to be. I can see why some bike shops and fitters might prefer the simpler, more direct approach of using KOPS.

But that still leaves the question - how do you actually measure the position of someone's center of gravity?

[MikeD]

But that still leaves the question - how do you actually measure the position of someone's center of gravity?


Bike on trainer, level, bathroom scale under the front wheel.




Sent from my iPhone using Tapatalk Pro

[jamesau]

But that still leaves the question - how do you actually measure the position of someone's center of gravity?

See post #4 here: https://forums.thepaceline.net/showthread.php?t=163401

[Ti Designs]

Perhaps one of the reasons that KOPS has remained popular is similar to the reason that judging components by their weight is popular - it is very easy to measure (even if it doesn't mean much).

So it's not right, but it's easy to teach...

As for setting setback relative to center of gravity - using this also makes bike fitting more time intensive. Using KOPS for setback makes bike fitting a simple sequential proces - first you set saddle height, then you set saddle setback, then you set handle reach, and finally you set handlebar height - done!

But center of gravity is dependant on both setback and upper body position. So after setting an initial setback and then setting handlebar height and reach, you might find that the center of gravity isn't where you'd like it to be. So you have to adjust the setback, which in turn means you have to find a new handlebar height and reach. Keep iterating until the center of gravity finally ends up where it needs to be. I can see why some bike shops and fitters might prefer the simpler, more direct approach of using KOPS.

But that still leaves the question - how do you actually measure the position of someone's center of gravity?

The fitter needs to understand two things. The first is range of motion, which is the limiting factor on hip angle for most of us. The second is where the center of gravity is, but it's not really center of gravity, it's the body's reaction to it's own position. If you sit on a chair and lean forward, weight transfer is to your feet on the floor and the glutes hold you up. Once your center of gravity gets past where your feet are on the floor, the quads come into the action. That's not really your center of gravity, but I'm more than happy to call it that to explain position.

The fitting shouldn't be based on where the handlebars are, people get very involved with where their bars are because their eyes are mounted in the front of their head - it's what they see, it's what they want to adjust. The fitting is all about saddle to pedal, your position should work with your hands behind your back. If it doesn't you have too much weight on the bars.