seat setback (long)

[rspecker]

I had a lot of saddle pain recently (sitz bones) until a fit guru at a bike shop moved my saddle forward about 1cm or a little more; and tilted the saddle up very slightly. I think I'm about exactly KOPS in the new position. The saddle is not high, and perhaps if anything is slightly low.

Saddle pain has diminished dramatically. I also the think the new position may have improved my spinning somewhat.

But . . . My seat post has a -5mm setback only (e.g., almost no setback), and the saddle is jammed pretty much all the way forward on the rails. So if I wanted to have the seatpost in the middle of the saddle rails I would actually have to have a forward "setback" of about +5mm (or maybe even +1cm).

This change has impacted the handling of the bike--I liked the handling better when I was back more.

I suspect there is nothing I can do about this, but I thought I'd ask. Maybe I could shorten the stem from 12 to 11 cm? Would this allow me to move the saddle back while at the same time preserving the benefits of the saddle position from the standpoint of the soreness of sitz bones? But presumably if I did this it would move me back from KOPS and therefore I might not get the benefit of the better "spinning" position (but maybe I could shorten the crank arms to 170 from 175? ugh!).

I'd also be curious what frame geometry tweaks are used to deal with this.

Is the 73 degree angle changed?

Does the top tube length affect the distance between the saddle and the bottom bracket (and therefore KOPS)?

Does the crank arm length matter for spinning and/or saddle comfort?

I know that it is not possible to do a bike fitting over a bulletin board, but if any of you have insights into this I'd welcome them.

Thanks!

[1centaur]

How tall are you, what size frame are we talking about, and do you have any reason to believe your body proportions are very unusual?

Pending those answers, I suspect you will hear that your frame is too big and KOPS does not work for everyone.

STA and stem length are more about weight distribution/balance than about your saddle position. TT does not affect saddle to BB/pedal distance, which is a key distance for power/technique, but may affect your comfort if you are reaching too far forward on a long TT.

Finally, do you think you are flexible/inflexible? With greater core strength and good flexibility the butt can often be moved back and comfort retained.

[RPS]

I also the think the new position may have improved my spinning somewhat.That’s not uncommon. A lower saddle makes it easier for me to spin also. Additionally, if I set my saddle too high it makes my hips rock and leads to a sore butt.
So if I wanted to have the seatpost in the middle of the saddle rails I would actually have to have a forward "setback" of about +5mm (or maybe even +1cm).A few seat posts are made for triathlons and time trials that do exactly that. They allow riders with road bikes to set them up as if they had a steeper seat tube.
Maybe I could shorten the stem from 12 to 11 cm?It won’t make as much difference as you think. Assuming you don’t move back in the saddle, you are mostly moving your hands back 1 CM; the torso which is where most of the weight is remains in approximately the same place. If you assume the handling difference is due solely to weight distribution, I doubt it will make much difference. Fortunately it's easy to try -- and can always put it back.

[SoCalSteve]

I had a lot of saddle pain recently (sitz bones) until a fit guru at a bike shop moved my saddle forward about 1cm or a little more; and tilted the saddle up very slightly. I think I'm about exactly KOPS in the new position. The saddle is not high, and perhaps if anything is slightly low.
Saddle pain has diminished dramatically. I also the think the new position may have improved my spinning somewhat.

But . . . My seat post has a -5mm setback only (e.g., almost no setback), and the saddle is jammed pretty much all the way forward on the rails. So if I wanted to have the seatpost in the middle of the saddle rails I would actually have to have a forward "setback" of about +5mm (or maybe even +1cm).

This change has impacted the handling of the bike--I liked the handling better when I was back more.

I suspect there is nothing I can do about this, but I thought I'd ask. Maybe I could shorten the stem from 12 to 11 cm? Would this allow me to move the saddle back while at the same time preserving the benefits of the saddle position from the standpoint of the soreness of sitz bones? But presumably if I did this it would move me back from KOPS and therefore I might not get the benefit of the better "spinning" position (but maybe I could shorten the crank arms to 170 from 175? ugh!).

I'd also be curious what frame geometry tweaks are used to deal with this.

Is the 73 degree angle changed?

Does the top tube length affect the distance between the saddle and the bottom bracket (and therefore KOPS)?

Does the crank arm length matter for spinning and/or saddle comfort?

I know that it is not possible to do a bike fitting over a bulletin board, but if any of you have insights into this I'd welcome them.

Thanks!

From past experience, I have a strong feeling that the comfort came from tilting the saddle up and not from moving it forward...Also, not clear if he also lowered the seatpost, this may help as well...

You may want to try keeping the same tilt and moving the saddle back to its original spot....I think you may find this to be the best of all worlds. You will have your saddle comfort and your handling will come back...

Give that a whirl, you got nuttin' to lose...

Good luck,

Steve

[rustychisel]

you got nuttin' to lose...

Steve


except your nuts... :beer:

[cadence90]

There are some good answers to your questions here, but as has also been pointed out, only you can really know in the "end".

KOPS is for those Keystone guys, not for determining proper fit on a bicycle.

[Peter P.]

"I suspect there is nothing I can do about this, but I thought I'd ask. Maybe I could shorten the stem from 12 to 11 cm? Would this allow me to move the saddle back while at the same time preserving the benefits of the saddle position from the standpoint of the soreness of sitz bones? But presumably if I did this it would move me back from KOPS and therefore I might not get the benefit of the better "spinning" position (but maybe I could shorten the crank arms to 170 from 175? ugh!)."

From what I've read, you liked being more BEHIND the front wheel before your position was moved forward. This is where the handling changed.

However, you like the new KOPS seat postion, too.

You don't want to shorten the stem; you want to LENGTHEN it to get the upper body position you had before your seat was slid forward. However, this may NOT make the bike handle the same as the old position because you'll be a little bit more over the front wheel.

DON'T MESS WITH THE SADDLE FORE/AFT; YOU JUST CHANGED IT AND YOU LIKE IT! MOVING IT BACK NEAR WHERE IT WAS DEFEATS THE PURPOSE OF MOVING IT TO WHERE IT IS NOW!

It's clear to me you already understand some of the ramifications of futzing with the new position. That's good.

I'd also be curious what frame geometry tweaks are used to deal with this.

If you have a zero setback post and you're almost full forward, then you'll want a steeper seat angle to put the seat in the middle of the rails. But as long as you've got some range adjustment left, it doesn't seem necessary to me to worry about this. There's nothing magical about the handling of a bike whose saddle is in the middle of the rails. As long as there is some adjustment available to give you KOPS, you're seat angle is fine.

"Is the 73 degree angle changed? No; the seat angle didn't change; your position on the bike did."

"Does the top tube length affect the distance between the saddle and the bottom bracket (and therefore KOPS)? "

No, top tube length does NOT affect KOPS, just upper body position, reach, and position over the front wheel. It's this last attribute with most contributes to the change in handling you're experiencing.

"Does the crank arm length matter for spinning and/or saddle comfort?"

It certainly does for spinning, but less so for saddle comfort. In fact for me, it's too esoteric to even consider crank arm length as a factor in saddle comfort.

I think you need to give your new fore/aft/KOPS position SEVERAL THOUSAND MILES before you try to make changes. The body can take a long time to adapt to an unfamiliar position. Personally, after riding with my saddle fully rearward for over 20 years then deciding to try KOPS, it took me that long to get used to a more forward position. I thought for sure I'd have to get a longer stem too, but I adapted to that. I can't honestly say the handling of my bike was affected by the changes in position. For what it's worth, I did the SAME thing to all three of my bikes, at the same time. It took some months to get used to the more forward position, but now it's natural.

Write down ALL the dimensions you can gather from this new position on your current bike. Get yourself a little diary and make entries describing what you like and don't like as the thoughts strike you.

After a year, go to a fitter with an adjustable bike like a Serotta Size Cycle and try to duplicate the current position then add in the changes you think you want-a steeper seat angle and longer top tube, perhaps. A good fitter will LISTEN and be willing to experiment. Or, visit a local framebuilder.

You already have a good knowledge of what affects fit; you should be able to articulate your needs/wants/desires and easily get a bike which achieves your ideal position, or at least addresses the nagging little things that don't feel right.

But for now, give the current changes in position a full season. If you DO want to experiment, changing that stem length 1cm longer won't mess up your KOPS position, won't cost a bundle and might feel be the solution to your fit problem.

[rspecker]

"I suspect there is nothing I can do about this, but I thought I'd ask. Maybe I could shorten the stem from 12 to 11 cm? Would this allow me to move the saddle back while at the same time preserving the benefits of the saddle position from the standpoint of the soreness of sitz bones? But presumably if I did this it would move me back from KOPS and therefore I might not get the benefit of the better "spinning" position (but maybe I could shorten the crank arms to 170 from 175? ugh!)."

From what I've read, you liked being more BEHIND the front wheel before your position was moved forward. This is where the handling changed.

However, you like the new KOPS seat postion, too.

You don't want to shorten the stem; you want to LENGTHEN it to get the upper body position you had before your seat was slid forward. However, this may NOT make the bike handle the same as the old position because you'll be a little bit more over the front wheel.

DON'T MESS WITH THE SADDLE FORE/AFT; YOU JUST CHANGED IT AND YOU LIKE IT! MOVING IT BACK NEAR WHERE IT WAS DEFEATS THE PURPOSE OF MOVING IT TO WHERE IT IS NOW!

It's clear to me you already understand some of the ramifications of futzing with the new position. That's good.

I'd also be curious what frame geometry tweaks are used to deal with this.

If you have a zero setback post and you're almost full forward, then you'll want a steeper seat angle to put the seat in the middle of the rails. But as long as you've got some range adjustment left, it doesn't seem necessary to me to worry about this. There's nothing magical about the handling of a bike whose saddle is in the middle of the rails. As long as there is some adjustment available to give you KOPS, you're seat angle is fine.

"Is the 73 degree angle changed? No; the seat angle didn't change; your position on the bike did."

"Does the top tube length affect the distance between the saddle and the bottom bracket (and therefore KOPS)? "

No, top tube length does NOT affect KOPS, just upper body position, reach, and position over the front wheel. It's this last attribute with most contributes to the change in handling you're experiencing.

"Does the crank arm length matter for spinning and/or saddle comfort?"

It certainly does for spinning, but less so for saddle comfort. In fact for me, it's too esoteric to even consider crank arm length as a factor in saddle comfort.

I think you need to give your new fore/aft/KOPS position SEVERAL THOUSAND MILES before you try to make changes. The body can take a long time to adapt to an unfamiliar position. Personally, after riding with my saddle fully rearward for over 20 years then deciding to try KOPS, it took me that long to get used to a more forward position. I thought for sure I'd have to get a longer stem too, but I adapted to that. I can't honestly say the handling of my bike was affected by the changes in position. For what it's worth, I did the SAME thing to all three of my bikes, at the same time. It took some months to get used to the more forward position, but now it's natural.

Write down ALL the dimensions you can gather from this new position on your current bike. Get yourself a little diary and make entries describing what you like and don't like as the thoughts strike you.

After a year, go to a fitter with an adjustable bike like a Serotta Size Cycle and try to duplicate the current position then add in the changes you think you want-a steeper seat angle and longer top tube, perhaps. A good fitter will LISTEN and be willing to experiment. Or, visit a local framebuilder.

You already have a good knowledge of what affects fit; you should be able to articulate your needs/wants/desires and easily get a bike which achieves your ideal position, or at least addresses the nagging little things that don't feel right.

But for now, give the current changes in position a full season. If you DO want to experiment, changing that stem length 1cm longer won't mess up your KOPS position, won't cost a bundle and might feel be the solution to your fit problem.

Thanks to all for the helpful responses.

I understand the point about position over the front wheel--but actually what I felt was a decrease in stability (or my perception of it at least) over the rear wheel. On the descent I feel like I need to slide back on the saddle.

On the point about seat angle, just to be clear if I were to ever order a new frame this type of issue might be addressed by changing the 73 degree seat angle, is that right? I don't really understand the seat set-back and seat angle issues in frame design.

I will take the advice not to tinker right away--although I did just finish 4 days and c. 330 miles on the bike (awesome trip down CA central coast!)-so I have a pretty good feel for it right now.

Cheers!