Shortening seat tube on steel frame

I’ve had my on-one 4560b for around 9 months now and really like the bike, it’s the largest frame size (20 inch). I’m about 5”11, and the seat tube is slightly too high at the moment to get the dropper down to a respectable height.

The dropper is as low as possible at the moment and even with a 125mm dropper, when it’s fully extended it’s a few mm too high. I’m considering ‘trimming’ the seat tube at the top. Maybe 2-3cm or so, any reason not to? Can’t see how this would weaken the frame, and it’s 2nd hand so not going to be able to claim warranty (and it’s on-one, so wouldn’t happen anyway).

Thoughts?

If you could live with a shorter dropper it would remove the need to trim the frame. I’m the same height as you and run the newer RSP 100mm dropper on my 20″ Fatty.

I know this isn’t what you’re asking but it could be an option.

even with a shorter dropper, wont it still be the same as a longer dropper, when they are both at their lowest in the frame ?
if you do cut the seat tube, dont forget to leave enough for the seat clamp, you might not, but its the sort of thing id do. i was considering this on my large codeine

even with a shorter dropper, wont it still be the same as a longer dropper, when they are both at their lowest in the frame ?

exactly

The main issue is the seat at it’s lowest height.

Get it cut, as long as you leave maybe 20mm minimum above the TT joint, cut a vertical slot too, you’ll be fine.

i have done this on aluminium frames, don’t see why steel should be different.

as long as there is plenty of post in the seat tube, the clamp does not snag on any welds and you have a nice rounded off slot to allow it to compress should be fine. But kiss goodbye to any wtee.

Why don’t you just not raise the post to full height.

Running the post a few MM into its “travel” is Shirley not going to make any difference.

when it’s fully extended it’s a few mm too high

I took that to mean the saddle is too high in the extended position, so a dropper with a shorter overall collar to rail length would fix the problem.

Swap saddle to a lower rail to top. Or cut the seat tube. It’s steel, you won’t die. Paint the wound and cover with a nice seatpost collar.

Thanks all. Thought it would be fine just wanted to check with the masses to see if anyone had done previously.