Hi, this is probably just an example of me overthinking something simple, but here is my question: If someone is coming over for a ride and I lend them a bike that has a fluted seat post, and they need to lower it so much that the flutes are into the seat tube past the clamp, is this going to be ok? Just for a ride or two, say, will the clamp hold? Is it a question of try it and see? Or should I swap the seat post out which would be kind of annoying.

Also apologies if I don't reply right away it's almost bedtime here!

It should hold.

(Seatpost fluting is a perfect example of form over function.)

Should not be an issue. Back in my BMX days, fluted seat posts were fluted from top to bottom.

Just remember many ST's and clamp areas are not smooth and may scratch and or gouge a nice SP.

This is one of my biggest pet peeves, it really sucks to screw up a good SP from poor finishing, someone using a too small SP or overtightening it.

I usually take a file or brake hone to them as the above also makes them sticky so you have to really jack the SP around to move it and screw it up even more.

No worries but I would not leave it there indefinitely for fear of it getting stuck.

If the bike is so big that you have to do that you're not doing anyone a favor

other thoughts to keep you up at night. Rain or washing the bike with the flutes below the seat tube allows water to enter the frame. But maybe you don't live in Portland or other wet areas.

Thanks for all the replies!
So it sounds like it should be ok, and while I was looking on ebay last night for fun I saw one of those fluted posts with the insertions marked in larger flutes, I they came on the Centurion Ironman bikes. So those were intended to go below the clamp area which kind of answered my own question.
Someone mentioned scratching, I am a little concerned about that but the seapost isn't pristine anyway so I should be able to polish it out.
We are in a wet area but he's only staying for a day or two so I would pull it back up to my height right after anyway so if it did get wet I could clean and grease it again inmediately.
And as for size I have my seatposts fairly high even on a 63cm frame, he is more like the intended size but his legs are shorter for his height, he'll be fine.

Thanks again

Hiya - hope you didnt get too hammered by the recent crap NZ weather !
Chuck a bit of grease in the flutes to minimise things getting in there too .

Thanks, it wasn't too bad just a few shrubs uprooted and some big branches flew around but no property damage. Hopefully you're the same!
I think this weekend I'll pull the post out, smooth-up the inside of the seat tube, regrease it and then keep the grease on hand to put in the flutes as per your suggestion.

Eww. There's got to be a better way!


Velobase

That describes about half the old road bikes in Japan. People here aren't very tall, and I come across many a bike on which the seat is almost resting on the top tube. It doesn't seem to do any harm.

Yep there's something obscene about that photo. Funny how a bike built for a discipline in which it is guaranteed to get soaked in water every event would have a seat post that funnels the water straight into the seat tube like that.

That seat post must be very thick walled to have those deep flutes.

Yeah I wonder, you'd hope so! Funny how much thinner the new posts are, I have a Ritchey that is very thin and very light but it just doesn't look right on some bikes.