Setback vs straight posts and their comparing comfort...

[TronnyJenkins]

I'm trying to figure this out. The Flite on the carbon post feels amazing. The same saddle on that zero setback post feels like a 'hatchet'. Think it's more to do with the clamping area on the saddle, or the posts themselves? Or maybe the saddles just vary due to manufacturing and break in? (comfortable one has always been comfortable though...)

[jtbadge]

Do you have the same setback and saddle height, relative to the bottom bracket? That would be the first thing I would be concerned about.

That said, conventional wisdom says a Thomson is pretty stiff compared to a carbon anything, setback or no.

[PaMtbRider]

Looks like they are on two different bikes. A whole lot of things besides seatpost could be contributing to the different feel.

[Louis]

Do you have the same setback and saddle height, relative to the bottom bracket? That would be the first thing I would be concerned about.

+1 on this.

To correctly compare them you need your sit bones to be in the same spot for both posts.

[mj_michigan]

What JT said.
If you move the saddle, your whole balance on the bike changes.

I haven't personally experienced a change in comfort by moving the saddle forward/backward, but I did notice a remarkable change in what muscles get loaded more (quads vs hamstrings). Getting a good balance there led to consistently faster rides.

[b33]

Am I not seeing two posts on two different bikes?

[fa63]

The saddle is clamped near the center of the rails with the zero-setback seatpost, and pretty far to the back with the setback seatpost, so it looks like the setback is similar.

VeloNews did a study on this a while back; here is the link (they have removed the graphics unfortunately):

https://www.velonews.com/2012/12/bikes-and-tech/from-the-pages-of-velo-getting-the-most-from-your-post_267560

The conclusion was that zero setback seatposts tend to be harsher than their setback counterparts. The Thomson zero setback seatpost was one of the worst offenders in that regard.

[TronnyJenkins]

Yes- certainly two TOTALLY different bikes. I tried my best to get the fit MM perfect (height measured from crank center both down the seat tube and vertically) and setback from BB. Sorry for the lack of info.

Reason for posting is that I would love to make the Bianchi more comfortable. I have two other steel bikes, another Bianchi and an Eddy,, one with the same saddle one with an early nineties Selle Italia Flite Trans Am and both of those feel great. So going down the list of things to check came to the post...

[skouri1]

rails flex a bunch too if clamped not in the center (or even if centered, if the clamp area is narrow).
I think flex posts (ie ergon/canyon) make a real difference. Syntace hiflex as well, but you need a lot of post showing.

At your saddle height (not far from mine), i thin the flex is pretty minimal.
Diameter, I suspect, would make a bigger difference.

[Louis]

Assuming your sit-bones position relative to the BB are identical (as is reach and all other fit stuff) the seatpost itself (setback or no setback) won't have a significant impact on how a bike rides, but where it clamps to the saddle rails could have a impact, depending on how long and stiff the rails themselves happen to be.

Think of it in terms of a whole bunch of springs in series (and a few in parallel too). The stiffness of the seatpost itself (even though the setback is a bit of a cantilever, which will reduce the stiffness of the setback post a bit) is very high compared to all the other springs in the system. Softer spring have a much larger effect on overall stiffness than stiff springs.

If you could magically change the TT length of a given frame such that a set-back and a non-setback post put you in exactly the same place relative to the bb and the bars, and both clamped the seat rails in the exact same place, I bet that in a blind taste test you wouldn't be able the tell the difference between the two seatposts.

[TronnyJenkins]

Assuming your sit-bones position relative to the BB are identical (as is reach and all other fit stuff) the seatpost itself (setback or no setback) won't have a significant impact on how a bike rides, but where it clamps to the saddle rails could have a impact, depending on how long and stiff the rails themselves happen to be.

Think of it in terms of a whole bunch of springs in series (and a few in parallel too). The stiffness of the seatpost itself (even though the setback is a bit of a cantilever, which will reduce the stiffness of the setback post a bit) is very high compared to all the other springs in the system. Softer spring have a much larger effect on overall stiffness than stiff springs.

If you could magically change the TT length of a given frame such that a set-back and a non-setback post put you in exactly the same place relative to the bb and the bars, and both clamped the seat rails in the exact same place, I bet that in a blind taste test you wouldn't be able the tell the difference between the two seatposts.

That makes a lot of sense. Thanks for the detailed post.

[false_Aest]

I have no idea what Velonews said and I'm too lazy to read that right now but I'm also seeing that one saddle looks far more broken in than the other.

Having recently gone from a Toupe with 3-4k miles to a brand new one (same model, year, etc) I definitely noticed a difference -- the older one is "softer"

[pasadena]

did you crash on the Bianchi?
The saddle nose looks smashed in and up. The rails are deformed compared to the other one.

[ergott]

The setup on the right is just asking for broken rails on a ride. I'd highly recommend putting a straight post on there to better center the clamp on the rails.

Fix the bike comfort with tire and pressure changes.

[saab2000]

With few exceptions, seat posts aren't designed with comfort in mind. They're designed to hold a saddle in a position in space. I firmly believe that in most cases any perceived difference in comfort with a seatpost is purely mental. The only difference might be a very long post on a sloping top tube bike but then the flex would be very disconcerting, at least to me.

As mentioned tune your comfort with tires.

The difference in seat posts here is tiny compared to the differences in everything else on those two bikes.

[ergott]

With few exceptions, seat posts aren't designed with comfort in mind.

Yeah, the ones that work need more exposed post. It's one advantage of sloping TTs. Long posts that legit have flex.

[Charles M]

This is partly about fit

The type of saddle rails and where the clamp attaches will allow the rails and saddle "suspension" to work differently depending on position.
BUT- clamping incorrectly can create a spring board that the rails are NOT designed to handle (Like the Pic above right)

It's also about post design... There are posts with some give, especially the ones designed to move, from Ergon, Specialized...

And much like the confusion about handlebar / Stem flex, which winds up actually being Steer tube flex because too much steer tube is exposed, seat post exposure (out of the frame) allows for more flex as the lever gets longer.

Then there are suspension posts.

All things need to be considered together (and if you're ignorant, thrown out...)

[TronnyJenkins]

did you crash on the Bianchi?
The saddle nose looks smashed in and up. The rails are deformed compared to the other one.

It’s interesting that you bring attention to that because the moment that saddle showed up I thought the nose looked high. And it feels that way when it digs into tender bits before my sit bones have a chance to make contact.
Maybe I’ll try the broken in one on the straight post and see how that feels...

I’m assuming you all are referring to the carbon post when you say “the one on the right”. Due to a difference in formatting, it appears to be on the bottom for me. I’m within the limits on the saddle clamp area, but I could see potentially using a straight post.

At the risk of sounding ungrateful, I can distinguish the difference between tire choice and pressure and unusual saddle pain. Can’t get much more comfy on clinchers than the G+ in 25mm flavor IMO. Though I can believe that my carbon post and saddle rails are flexing due to saddle clamp position.

Thank you all for your input so far. I value it.

[chiasticon]

If you could magically change the TT length of a given frame such that a set-back and a non-setback post put you in exactly the same place relative to the bb and the bars, and both clamped the seat rails in the exact same place, I bet that in a blind taste test you wouldn't be able the tell the difference between the two seatposts.what if you took two of the same bike, one with a zero setback post and one with a 20mm setback post, put the saddle rails dead-center on the former and pushed it 20mm forward on the latter... assuming your bike position is correct with this, would you notice a difference?

[93KgBike]

Some of them want to abuse you; some of them want to be abused.

https://www.cyclingabout.com/wp-content/uploads/2015/07/Seatpost-Damping-1000x367.jpg