Plumb bobs and such is fun to play with, I have a general starting point of 5cm behind BB for myself.
But everytime I setup a new bike or saddle, I eventually wanted to move the saddle so it fits under my seatbones better. It is like no matter if I set the thing far back or forward, my butt kind of wants to sit in the same spot in space. e..g if I put the saddle back more, I ended up sitting at the nose more instead of really sitting back.

I understand the setback is the first then you set, then the cockpit, but I am not buying this, if this was so important, everytime you change your setback, you may need a new stem as well.


So is there anything wrong with what I am doing? The new saddle is ok but it's kind of killing my butt so I want to push it forward a little (5-10mm) so that I get more contact.

It is important and that is pretty much exactly what you need to do. If you need to sit further back without changing your reach, you just get a shorter stem.

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Go with the flow.

I agree with fa63, get your setback on the saddle done first then add the appropriate length stem to match your previous position.

If your stem is too long on the new bike then it may pull you too far forward ruining your whole position.

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If it were that critical, you wouldn't see countless pros and others compensating for a too-small frame by cranking their setback to the max. That being said, assuming your frame is close to the correct size (and not too big), the correct setback relates more to your fore/aft balance than any KOPS relationship. The KOPS relationship approximates the position in which you will not experience too much weight on your hands, and one in which taking your hands off the bars will not result in the need for a drastic rearward flinging of your CG to enable the move. The smaller the frame, the easier this move becomes. This is an over-simplification, of course, but the point I'm trying to make is that the plumb-bob is not necessary. Other aspects of the fit are more practical to evaluate, and sometimes the frame choice dictates some of the fit aspects and makes analysis of someone else's position difficult.

Smaller frames generally have steeper seat tube angles, so you have to run more setback to achieve the required BB-saddle distance. this is why you commonly see pros on 25mm+ setback seatposts with their saddles pushed all the way back. Also, the right amount of setback doesn't have to result in satisfying KOPS; for instance, I have long femurs and I am well behind where KOPS would put me.

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Make a flat saddle your starting point - determine this with a long spirit level. But note that some saddles might suit you more with a slight nose-up or nose-down position. We are only talking 1 or 2 degrees, but these small amounts sometimes impact significantly on position. Note that it is much more common for saddles to be positioned slightly nose-down, as opposed to nose-up.

And I am sure there are a lot of riders out there who would feel the benefits of saddles with more padding.

It is an ITERATIVE process: you should adjust saddle position such that you end up with BOTH the seating position you feel best at (on your butt) AND the position in relation to the cranks that you feel proper (whether that is KOPS or not is another subject).

But Yes, you do end up needing to select a stem length that also gives you correct extension AFTER you have adjusted everything.

That's why I end up buying about half a dozen stems and reselling them on ebay!

I personally end up with a version of KOPS that is "front of kneecap over center of pedal spindle".

I guess all I am saying is I wanted to move the saddle a little so it supports my butt more, since I drop a plumb bob from the tip of the saddle, it may not really mean too much to replicate between different saddles.

I don't feel that the stem is causing me to shove forward, enough time riding on the bar top would let me confirm it is not too far.

I ride a small Italian frame (48cm) with 7cm of setback.
Nose of saddle behind c of BB.
I have a 25mm setback post & an Arione slammed all the way back on the rails.
Most of the small frames I have aeen have a steep seat angle (74/75) with a slack head angle (69/72).
Any weenies know of asmall frame with slack seat and steeper head angles???

Interesting! How tall are you? I'm 170cm tall. But I can't really ride anything with less 75° SA angle. Take a look at the BMC SLR01.

I'm about the same height - 169cm.
Saddle height is 70cm, sitting behind the BB just seems to work for me

Ah, I see! My saddle height is maxed out at 67.5. I'm sure we have different femur lengths, that's why you need more setback. Thanks

Yes.

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