why use a Set Back Seatposts ?

[Kontact]

To get the same position using the same section of rails on a saddle, a bike using a zero setback seatpost would have to seat tube angle that is 2.5° shallower than standard.

So instead of a 73° STA, you'd need a 71.5° STA. Has anyone seen many of those, lately?


Open Cycles uses 72.5° STA, across the board, so they think everyone should have the equivalent of a 74° STA. Which is ridiculous.

[avalonracing]

I'm a normally proportioned 6'0 guy and prefer a zero setback post and a 74ºSTA. Must be from spending too many years riding the rivet.

[Kontact]

Originally Posted by avalonracing

I'm a normally proportioned 6'0 guy and prefer a zero setback post and a 74ºSTA. Must be from spending too many years riding the rivet.

You have an atypical riding position that is closer to something on a tri bike.

[macaroon]

The key thing is really pelvis angle and torso angle and whereabouts they are on the bike.

Short torso/long legs? Probably want an inline seatpost

Long torso? You'll likely want a setback seatpost.

There's a current trend in pro cycling for small frames/long stems/very low bars. This sort of setup usually requires an inline seatpost, but it really all depends on individual body proportions.

I think a common myth is that long legs mean a setback seatpost to get KOPS. So if you've got very long legs, you'll end up with a massive amount of saddle setback and all your weight will be way off the back of the bike.

An inline post might also be beneficial if you spend all your cycling time riding up big hills. Going up hill slackens your seat angle even more meaning your weight goes even further backward.

I'm not in the mood to type more at the momet.

Fuzzalow covered it well some years ago.

[Kontact]

Originally Posted by macaroon

The key thing is really pelvis angle and torso angle and whereabouts they are on the bike.

Short torso/long legs? Probably want an inline seatpost

Long torso? You'll likely want a setback seatpost.

There's a current trend in pro cycling for small frames/long stems/very low bars. This sort of setup usually requires an inline seatpost, but it really all depends on individual body proportions.

I think a common myth is that long legs mean a setback seatpost to get KOPS. So if you've got very long legs, you'll end up with a massive amount of saddle setback and all your weight will be way off the back of the bike.

An inline post might also be beneficial if you spend all your cycling time riding up big hills. Going up hill slackens your seat angle even more meaning your weight goes even further backward.

I'm not in the mood to type more at the momet.

Fuzzalow covered it well some years ago.

I totally, totally disagree with this.

You set your saddle position based on your legs, nothing else.

You set your reach AFTER you have found saddle position.


Long and short legs have the same proportions and require a similar degree of set back.



The hill climbing part would be sensible only if climbing hills never involved going back down them.

[macaroon]

Originally Posted by Kontact

I totally, totally disagree with this.

You set your saddle position based on your legs, nothing else.

You set your reach AFTER you have found saddle position.


Long and short legs have the same proportions and require a similar degree of set back.

What do you mean "based on your legs"? As I said, KOPS is a myth, it's been discredited by various respected people. Once you read what they're on about, it all makes sense.

Niki Terpstra using a setback seatpost the wrong way round! Check his position though, works perfectly for him. If he was going for a ride to the shops he might want some high handlebars and a bit more saddle setback for comfort; correct tool for the job etc.

[macaroon]

Originally Posted by Kontact

The hill climbing part would be sensible only if climbing hills never involved going back down them.

Well duh, it's all about compromise isn't it! No bike will handle and ride the same uphill as it does downhill.

[Kontact]

Originally Posted by macaroon

What do you mean "based on your legs"? As I said, KOPS is a myth, it's been discredited by various respected people. Once you read what they're on about, it all makes sense.

Niki Terpstra using a setback seatpost the wrong way round! Check his position though, works perfectly for him. If he was going for a ride to the shops he might want some high handlebars and a bit more saddle setback for comfort; correct tool for the job etc.

KOPS isn't a "myth", unless you believe that KOPS is describing some sort of actual phenomenon. In reality, KOPS is a tool that happens to produce fairly reliable results for setting leg angle. That's all it is for.


If we could see the hip joint easily we would simply locate the hip at a certain number of degrees from a line running through the BB. We can't, so we use KOPS to approximate it.


Whether you have a 28" inseam or a 34" inseam, you still want the same proportional seat height, and you want your leg to extend in front of you by the same angle. If you don't you start changing not just leg angle but pelvic angle and weight distribution. A person with long legs has no good reason to sit right above the cranks than a short person does, so they both use the same average leg angle.


Don't be fooled by a couple of guys riding in outlandish positions. That isn't how road bikes are designed to work, and it isn't how saddles are designed to interface with the pelvis. The guy in the picture, pro or not, looks ridiculous and is riding on his taint.

The reason pros are using smaller frames is because all the high end bikes have tall head tubes to suit the 50+ riders who have incomes to buy $10,000 bikes. So the pros can only get their stems down by dropping a frame size and using a long stem. That has nothing to do with set back.


I state all of this as someone who worked closely with a top fitter for several years and produces an ergonomic bike saddle. You are way off.

[Kontact]

Originally Posted by macaroon

Well duh, it's all about compromise isn't it! No bike will handle and ride the same uphill as it does downhill.

Which is why you would have the same set back whether riding on flats or hills. Because you don't want to descend with all your weight on the front wheel.

Duh.

[sales guy]

I need a setback post for my long legs. 6'3 and a 36" inseam. Need it on a mountain bike too.

Setback posts help for fitting. It really is that simple.

[avalonracing]

Originally Posted by Kontact

You have an atypical riding position that is closer to something on a tri bike.

Maybe... Kinda like the guy in post #21

[Kontact]

Originally Posted by avalonracing

Maybe... Kinda like the guy in post #21

Your poor groin.

[macaroon]

Originally Posted by Kontact

Whether you have a 28" inseam or a 34" inseam, you still want the same proportional seat height, and you want your leg to extend in front of you by the same angle. If you don't you start changing not just leg angle but pelvic angle and weight distribution. A person with long legs has no good reason to sit right above the cranks than a short person does, so they both use the same average leg angle.

I don't really understand what you mean by
leg extending infront of you by the same angle?
use the same average leg angle?

Originally Posted by Kontact

Don't be fooled by a couple of guys riding in outlandish positions. That isn't how road bikes are designed to work, and it isn't how saddles are designed to interface with the pelvis. The guy in the picture, pro or not, looks ridiculous and is riding on his taint.

It's more than "a couple of guys" though. Everyone seems to be doing it nowadays; super slammed stems and the saddle forward. I agree though, the bikes will probably not handle best in this position. As for how the saddle interfaces with the pelvis, everyone is different. Some people roll their pelvis further forward than others, Chris Froome sits pretty much bolt upright.

[macaroon]

Originally Posted by Kontact

Which is why you would have the same set back whether riding on flats or hills. Because you don't want to descend with all your weight on the front wheel.

Duh.

You kinda missed my point. Ideally you wouldn't have the same setback, ideally you'd be able to adjust it (along with the position of all the other parts) for riding uphill. And then adjust it at the top for the descents. But if you're spending the majority of your time going UP hill, you might prefer to set your bike up to make it most comfortable/efficient for that purpose.

[macaroon]

Originally Posted by sales guy

I need a setback post for my long legs. 6'3 and a 36" inseam. Need it on a mountain bike too.

Setback posts help for fitting. It really is that simple.

Setback posts on an MTB is strange aswell. The industry seem to be making seat angles steeper and steeper as it aids seated technical climbing.