Seatpost question

[jih]

setback post is essentially the same as a slightly slacker seat-tube angle. So design around where you want your saddle, and then decide based on what gets you that position with the other variables you need like tyre clearance.

It doesn't matter that much so long as the saddle is in the right place so at the end of the day you might as well choose what you think looks better.

[kgibbo1868]

A road bike should always be designed around a setback post for proper look and rear tire clearance too.

R5 RCA would beg to differ...

The RCa was specifically designed around a setback seatpost, and has slacker seat tube angles (than a “proper” road bike) in the same size would typically have. Simply a design choice by Vroomen and Co. But slacker seat tubes decrease the amount of clearance for the rear tire, particularly where shorter chainstays are being used. Setback posts have been used traditionally for years simply because on average, they were needed in order to get the rider in the most optimal riding position while maintaining a nice tight road race geometry. Today I think a lot of basic reasons for design have been either forgotten, ignored, or simply thrown out the window for some stupid marketing reason in an attempt to depart from the norm to sell more bikes to the easily swayed consumer. In the case of zero setback seatposts, that reason might be lighter weight for example, a dumb reason to compromise fit. And nothing looks dumber than a saddle clamped at either extreme of the rails. Well, I suppose there are much dumber things but don’t get me started.
As for skinny 27.2mm posts, they are fine but I don’t like the aesthetics of them sticking out of today’s rather large diameter seat tubes. Positionally, if you really want to get aero, then that will often require moving the saddle forward some, and a zero setback post may be fine, at the expense of a more traditional (and comfortable) position. I think very few people have such morphological abnormalities that makes a zero setback post a preferred option on a normal road bike. Mostly I think some folks might think it looks cooler (I don’t), or they don’t really have an ideal fit.
For the OP, who is getting a custom frame with a horizontal top tube, my personal opinion would absolutely be to go with a setback post. Especially with today’s trend of larger tires you want to keep as much clearance between the tire and seat tube as possible. Thus, all else equal the builder can go with a slightly steeper seattube than would be possible if the bike was being designed around a zero setback post.
Go with the setback post.

Thank you very much for taking the time to give a well considered answer! I think a Hz TT and setback post will work out fine. I am going with a very experienced builder who is well respected and we will go through a very detailed fitting process prior to finalizing frame geometry.

[Calnago]

Sounds good... presume you’ll share the finished bike here in the forum maybe?
Oh, and I just reread the first line of my earlier response and noticed a glaring error. I said the RCa was specifically designed around a setback seatpost, which of course is wrong. I totally meant it was specifically designed around a “zero” setback seatpost, so worse than a typo, an entire word omission. I’m sure someone would have picked up on that sooner or later.

[kgibbo1868]

Sounds good... presume you’ll share the finished bike here in the forum maybe?
Oh, and I just reread the first line of my earlier response and noticed a glaring error. I said the RCa was specifically designed around a setback seatpost, which of course is wrong. I totally meant it was specifically designed around a “zero” setback seatpost, so worse than a typo, an entire word omission. I’m sure someone would have picked up on that sooner or later.

Yes, I am looking forward to sharing the process along the way. You can expect many questions from me along the way.

[shimmeD]

I think ti with a curve are the coolest/sexiest seatposts out there eg https://moots.myshopify.com/products/mo ... 7214848016