Knee above spindle
 

What's worse, in front or in back?

Knee Over Pedal Spindle is an ancient myth that just won't die. There are many other issues to consider for a proper fit.
https://sheldonbrown.com/kops.html

KOPS as the ONLY position to be in is a myth. Sure.

I still find KOPS (knee over pedal spindle) as a useful reference point but yes, there are other factors to consider.
Being behind KOPS has the advantage of moving your centre of gravity rearwards on the bike which takes the weight off your hands/arm/shoulders and is considered to be a more comfortable position for casual riding however it can make it harder to spin the cranks at higher cadences.
Being in front of KOPS serves to open up your leg angles and makes it easier to spin higher cadences however it also moves your centre of gravity forwards on the bike which places more weight on your hands/arms/shoulders.

Positioning yourself right at KOPS is considered to be a good compromise between performance and comfort however, yes, there are numerous other factors that should be considered as well.

The article is right that at any position around a fixed point the riders leverage on said fixed point will be the same, upside down, right side up, laying flat...doesn't matter. However, having said that: Laying on your face over the handle bars does tend to get tireing with out something like aerobars. TT bikes aren't exactly known for randoneurring. Likewise, being rotated back puts all your weight on your sit bones, making for a sore derriere. Hardly anyone's first choice for a grand tour is an Oma/Opafiets. Rotate far enough back on the other hand & you have a recumbent. And on a recumbent, you're not sitting your sit bones, but rather your back & hips.

KOPS is a rule of thumb for a starting point for fitment on standard diamond frame bikes. That's all. What was the term? Gravity constraint?

Anyhow, OP: Neither fore/aft is better or worse than the other. It only determines weight distribution at the various contact points on the bike.

Jump to 3 min mark...

KOPS is a starting point for cleat placement, not the end point. Personal experience will dictate the eventual final placement.

Surely you mean saddle position.

In my opinion and experience, the stronger you are or more specifically, the higher your average power for a given ride, the further forward you should be to optimize your fit. Even weak riders doing a 20 minute crit race (me) will average quite a bit of power. If you’re an elite rider doing a 14 hour ride, then perhaps you’ll still want to scoot back.

Varies by bike, it's not a hard-fast rule. Heck, KOPS is impossible on my bikes.

Starting point for reference for future tweaking or for setting up a new bike the same as the one you like. I happen to like my saddle a little behind KOPS. Just seems more comfortable to me, probably for the reasons given above. I'm not a racer, just a nice bike enjoyer.

So, no one ever wrecked a knee by racking up milage 1 cm in front of KOPS.

After reading quite a bit thanks to another recent KOPS thread here earlier today I decided to try shifting my saddle back, and moved it around 1.5cm or so. I then did a 32 mile ride with the new position. I was actually quite shocked at how big a difference it made, and I think for the worse. My position until now has been pretty darn close to KOPS, and I've felt pretty good about it, but wanted to see if shifting it back a bit took more of the weight off my hands.

The way my knees extended changed very noticeably, and uncomfortably. I don't know if it feels worse because it is worse, or if it feels worse right now because it's different than I've been used to. As I went through this one ride, though, I realized that just shifting my saddle back by 1.5cm or so, if I decide to keep it, will probably require me to also drop my seat post by several mm. It's mind-boggling to me that it was so noticeable, but my knees feel almost hyperextended now on the front part of the pedal stroke, so dropping the seat a smidge would help with that. I also tend to spin around 85-90rpm on a middle-of-the-road cruising pace (lower cadence for an easier case) and 85-95 at a higher effort, and that was noticeably less comfortable.

Before just putting it right back where it was, I may just split the difference and try it 3/4 of a cm back towards the original position and do another ride that way and see how it feels. If I still don't like it's going back to KOPS. My KOPS position may be based on a mythology, as others have said, but it happens to have been a pretty darn good fit for me personally. I'm still surprised at how much difference it made, though. I wouldn't have predicted that.

Knee-Over-Pedal was a big improvement for me over Knee-Under-Pedal.

I've never heard of being in front of KOPS hurting the knee. It just puts more weight on your hands/arms/shoulders.
Being behind KOPS can be hard on the knee for some, and generally makes higher cadences more difficult.
For sheer casual riding at no more than a moderate pace, being behind KOPS is more comfortable than being in front of KOPS yet if you can comfortably handle the weight on your arms where you are then there isn't really a reason to move back anyway.

A 1.5cm move in one go is a HUGE move and not generally recommended unless you were WAY out in the first place. Yes, you need to drop your saddle down when you move back and raise it when you move forwards.
Being behind KOPS generally doesn't help with higher cadences either.
1.5cm behind KOPS is WAY back in the casual range. Just being 0.5cm behind of, or in front of KOPS will make a noticeable difference.

IMO:

A saddle to far forward will cause the knees to pronate out, to far back and the knees will pronate in. Neither is particularly good from a mechanical aspect . You will never see a bent or angled piston rod in an engine operating at peak performance.

Comfort will be best realized when a bicycle is a proper fit from the beginning. A correct frame size, both stand over and top tube length. Frame geometry is what you buy from the manufacturer. Strip the components, decals and paint, and what is left- geometry. Not quality or hype.

Next, the correct crank arm length for the individual. Think about how to fit how to fit shorter stature riders with long lower leg bones or tall riders with short ones . Proper saddle height as it affects bottom dead center crank position will dictate fore and aft positioning Of the saddle rail in the seatpost.

Stem length and bar width are the final pieces.


All will be done in relationship to the rider - height, weight, fitness level and ride purpose. Also to be considered
is the person - bad knee, hip or shoulder, neck or any of number of different physical challenges. Your fit details will likely change in relation to overall level of fitness, or factors affecting any physical attributes.

With mtb seat angles getting very steep (76 degrees and steeper is not uncommon) some people have complained that it bothers their knees.

They are generally dismissed in the group-think that pervades the forums and industry, but I have definitely seen a few people claim this as their experience.

Other find it has helped them pedal.

So there you go.

I stated from the start that its multifactorial.
I raced as a juvenile with a custom frame with a 78º seat tube angle and it never hurt my knees. LOTS of weight on my hands, but my knees were fine. Long story.
Anyway, the excessively LONG cranks on MTN bikes will hurt your knees. Absolutely.
Its multifactorial.
Being behind KOPS can encourage people to grind rather than spin the cranks and a lot of grinding can hurt the knees. I recommend that being significantly behind KOPS, is only for a casual position where the rider isn't going to grind the cranks. Not for racing/performance riding.

I was totally into KOPS until a back injury put me on a recumbent. I took my upright bike position and rotated it back to put my feet on the pedals, around 90 degrees, and set the seatback position and angle from there. The resulting fit has worked great. Clearly not KOPS! This led me to the same point made in the Sheldon Brown article linked above: KOPS is no hard and fast rule. What is true, I think, is that an average proportioned person with excellent core strength and flexibility, on an average proportioned bike, with goals more toward performance, KOPS is a good starting point for saddle fore-aft position. Other longstanding rules of thumb, like look down while in the drops and the bars should hide the front axle, have an equal number of qualifiers.

In the world of ultra and randonneuring, moving cleats aft has become almost commonplace, to eliminate hotfoot. Impact on the effect of KOPS should be obvious. I'm now working to get my fit dialed in on an upright bike. With a relatively long torso, focus more on randonneuring distances, and a variety of past injuries, none of these rules of thumb have much value to me.

Well, whatever I might have made of this before this little experiment, I'm definitely a believer right now. I'm still undecided whether I'll split the distance and move the seat halfway back to where I had it before. Half of me still wants to see if an improvement could be had. The other half of me thinks my original position ain't broke and doesn't need fixing.