Do I need a 400mm seatpost or can I get away with a 350mm?

it’s a 400 at the moment but I was looking at some others and they only come in 350

top of tape is at saddle rails

Where is the minimum insertion mark, that should tell you your answer.

I could imagine the marks are in a similar position from post to post.

On the verge of needing a 400mm I’d say, but it’s not quite so clear cut. Check min insertion mark see if its inside the frame or not…

I would ignore the post markings and ensure it goes below the top-tube, so at least 350mm.
Weight saving off your 400mm is negligible (probably under 30 grams).
Keep what you have?

PaulD

You need at least 1″ of seat post below the top tube/seat tube junction.

A 350mm will be too short.

It’s not just the minimum insertion mark you want to look for. The bottom of the post needs to be below the Top Tube/Seat Tube join. That looks pretty marginal to me and given that some saddles are “flatter” than others, might prove problematic in future.

on that post which is a 400 the min insert is 90mm so will be where 31 is on the tape

so with a 350 the min insert (assuming its 90 again) will be just inside the frame tube…but that bit of the frame is not supported at all so not sure if that matters

it does look borderline actually

right cheers

I’ll look for another 400 then, the one I have is rather burly and stiff, hence looking for another

A lot of 400mm posts seem to be inline and I need 10-15mm of layback

Have a look at the Controltech ones, they do 400mm with a slight layback. Think Easton may do one too.

Hmmmm, this reminds me I could do with a longer post for my Inbred. I think I am right on the borderline…

In your case, I’d play it safe and get a longer one.