.....choose to use a layback post?
Not trolling and nothing to do with any frame of mine just curious.
Ive seen a few custom frames posted on Instagram with layback posts fitted.
I've used layback posts over the years mainly to help extend reach and create a less compromised body position on the bike but Shirley that's negated with a custom frame?
Again I know that using a layback post can add comfort by throwing in additional compliance but would you not look to add that into the frame design - safety allowing?
What am I (obviously) missing?
Because the angle and position of the seat tube are governed by many things (primarily the proximity of the rear tyre).
So on my cx bike I want a certain saddle position, bb position, chainstay length and tyre clearance. With a straight seat tube joining the bb shell centrally, I can only achieve that with a lay back post.
On my 29ers I use a curved seat tube, so can design around an in line post if I want to.
Good question OP.
On my 29ers I use a curved seat tube, so can design around an in line post if I want to.
Why can't you use a curved seat tube on a CX bike?
Shorter chainstays / wheelbase?
well you can, you can have what you want when you buy custom.
I can make a cx with a curved seat tube if I wanted, but it is easier to use straight and a post with a bit of lay back. And too much bend isn't UCI compliant 🙂
My 29ers have sub 410mm chainstays and chunky tyres. It would be one hell of a lay back post for them to work with a straight seat tube....
All goes back to the early simple seat clamp / post designs I guess. Lugs, also road designs with short rear ends and straight steel seat tubes, not much space there. Historic stuff. Now, probably just component choices and aesthetics.
Cervelo started designing around inline posts a few years ago. 1 to 1.5 degree of seat angle would make little difference to the forces there, or the comfort difference unless all designed as part of a system that's trying to optimise that - carbon layups, dropped stays etc.
Saddle choice can mean a change in post is needed
I have an old brooks pro which needs a layback post to get me in the right position
You have 2 choices
- A straight seat tube like 99.n% of bikes and a seat post with setback (like ~80%? of seat posts)
- A curved seat tube which when going custom would be a viable option but as 99.n% of frames a person buying the custom frame will have seen they are conditioned into thinking that is how a bike looks and how their custom bike should look.
Because that's how they want they frame made and the possition and parts they want to use. Surely this is the main benefits of a custom frame, not a disadvantage.
Obviously the OP would have a frame made differently (as would I and everyone else).
They knew what they wanted beforehand but not what they needed until afterwards.
I’ve used layback posts over the years mainly to help extend reach and create a less compromised body position on the bike but Shirley that’s negated with a custom frame?
That's a bodge for them but that's not why they exist.
Many folk also negate the fact that lots of seat post although not visually bent are infact 25mm lay back in the head.
Yes, my estimate is that around 80% of seat posts have set back and yes it is typically around 25mm. A layback seat post, one that is actually bent, is fairly rare outside of Thomson.
But again, the choices are a bike that looks traditional with a straight seat tube and a setback seat post or a more whacky looking bike with a curved seat tube and inline post.
I would take the straight seat tube option as to me it looks better which would be an an important part of having my own frame made!
Like this?
[img] 
[/img]
Yes, lay back seat posts were more common in the 80s on BMXes. I had a few myself as back in those days we used to actually sit on the seat now and again although most posts didn't last long as they bend too easily (and the aluminium fluted posts usually bent before you even got on the bike)
