why use a Set Back Seatposts ?

[sales guy]

Originally Posted by macaroon

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.

Long legs. I've tried a straight post and it puts me over the front too much. Hurts my knees a bit too.

[macaroon]

Originally Posted by sales guy

Long legs. I've tried a straight post and it puts me over the front too much. Hurts my knees a bit too.

More "reach"? Check this one out, 77 degree seat angle! http://www.geometronbikes.co.uk/G16.html

[sales guy]

Originally Posted by macaroon

More "reach"? Check this one out, 77 degree seat angle! http://www.geometronbikes.co.uk/G16.html

Hell No! I can't stand slack geometry. Hate the way they ride and the way I feel on them. I have a new 29'er being made for NAHBS in a custom geo. Can't wait for it to be finished. It'll be a rocket.

[Kontact]

Originally Posted by macaroon

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

The BB is in front of the seat, because the seat tube is angled back. So from the saddle your leg is angled forward toward the crank. The number of degrees it is angled forward is pretty much the same for short and tall people, so it makes no sense to change the effective seat tube angle with different set back posts for different leg lengths.

[marciero]

Originally Posted by Mzilliox

Hey Charles, I used to wonder the same thing.
Here is my take, and im not sure how accurate it is, so take it with many grains of salt.

...

2. From a geometry standpoint, you dont want too slack of a seat tube for a few reasons, but mainly to keep the wheels where they should be, and the rider's front center where it should be...

This. It seems that lots of bikes, esp. race bikes, have rather tight rear triangles with little clearance between seat tube and rear wheel. For riders that do require setback, putting the saddle where it needs to be with slack STA rather than setback seatpost would require lengthening chainstays, thereby changing weight distribution, handling, etc. Even on bikes with more wheel clearance, slackening the STA would make for tighter wheel clearance disproportionate with other clearances. I suppose you could use the Hot Tubes curved seat tube approach...

[Kontact]

Originally Posted by macaroon

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.

And you missed mine. It is very difficult to spend all your time climbing since you eventually get to the top and have to go down the other side.

[ultraman6970]

77 degrees in a mtb/dh or whatever bike??? cant imagine that and I dont do mountain biking. Dude maybe wants to be different?

Originally Posted by sales guy

Hell No! I can't stand slack geometry. Hate the way they ride and the way I feel on them. I have a new 29'er being made for NAHBS in a custom geo. Can't wait for it to be finished. It'll be a rocket.

[Kontact]

Originally Posted by marciero

This. It seems that lots of bikes, esp. race bikes, have rather tight rear triangles with little clearance between seat tube and rear wheel. For riders that do require setback, putting the saddle where it needs to be with slack STA rather than setback seatpost would require lengthening chainstays, thereby changing weight distribution, handling, etc. Even on bikes with more wheel clearance, slackening the STA would make for tighter wheel clearance disproportionate with other clearances. I suppose you could use the Hot Tubes curved seat tube approach...

Or put a dent in it, or split it, or mold it out of carbon in any old shape you like.

That said, you would have to angle the post back quite a few degrees before you used up the standard tire clearance of a 410mm chainstay.

[sales guy]

Originally Posted by ultraman6970

77 degrees in a mtb/dh or whatever bike??? cant imagine that and I dont do mountain biking. Dude maybe wants to be different?

the headtube is 62.5. That's slack. Most are 68.5 or 66.5 now.

[marciero]

Originally Posted by Kontact

Or put a dent in it, or split it, or mold it out of carbon in any old shape you like.

That said, you would have to angle the post back quite a few degrees before you used up the standard tire clearance of a 410mm chainstay.

Indeed. The bikes I ride these days certainly have a degree or two to spare.

[pasadena]

The rules changed recently, so many more pros are pushing saddles forward and tilting the nose down now that it is legal.

Originally Posted by macaroon

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.

[PacNW2Ford]

Originally Posted by Kontact

Or put a dent in it, or split it, or mold it out of carbon in any old shape you like.

That said, you would have to angle the post back quite a few degrees before you used up the standard tire clearance of a 410mm chainstay.

Not true: with a 70mm BB drop and a 73.5°, you're already running out of room to get an inflated 25mm tire out with horizontal dropouts.

[Kontact]

Originally Posted by PacNW2Ford

Not true: with a 70mm BB drop and a 73.5°, you're already running out of room to get an inflated 25mm tire out with horizontal dropouts.

You just described my 51cm Lemond. I see well over 1/2" of clearance.

But there is a reason vertical dropouts came into vogue. I'm not sure who makes good use of vertical dropouts - it usually seems like people have them in them adjusted full forward.

[ergott]

Originally Posted by ergott

Use whatever seatpost you need to center the rails (more or less) and achieve this.

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

For me that's a setback seatpost with typical bikes my size.

Yes I quoted myself. Don't compare yourself to pros, it doesn't work. Do the above and you will happy on your bike.

[alancw3]

setback seat posts are only another dimension of fitting a bike to the rider. imho if a bike is fitted properly a zero setback should be used. but most people buy a used bike and have to fit by seat post setback and stem length.

i have used both over the past 50 years and i can tell you that there is nothing like a zero set back post for a solid feel while riding. if i were having a bike custom build i would specify a zero set back seat post as part of the design.