Is it normal for (longer?) dropper post to flex?

My 125mm KS Dropzone doesn’t. My 100mm RSP Plummet doesn’t. My 150mm E13 TRS+ dropper does.

Flex or wobble?

Not wobble, just feels a little bit springy back and forwards. Wasn’t sure what it was at first, thought maybe it was bike frame, or wheels or tyres, but pretty sure it’s the dropper. Sometimes overly enthusiastic pedalling is enough, others just get bounced around a bit by terrain.

Just wondered if a bit of spring/flex in 150mm+ droppers is to be expected? (ok maybe this is what you mean by wobble)

I suppose you might need to be riding a hardtail to feel it.

Would have thought so. It’s the same when you ride a pair of Fox 32’s or old revs at 150mm, just a bit noodly. You’ve got 80odd kg of weight putting force through a 150mm long lever, it’s going to flex a bit unless it overbuilt, then we’ll all complain it’s too heavy.

But noticibly so? I kind of pretended maybe my alu HT frame (Bird Zero TR) had a bit of veritcal complience at first and on some terrain I can just go with it, but on boring(!) terrain that you just want to ride along that’s mildly bumpy it’s a bit annoying.

Consider it this way. You have what is at best comparible to a 27.2 post held by some bushings. Given that people spec 27.2 posts in certain types of bikes for extra comfort from the flex (Vs wider posts) it’s not surprising you can feel flex in a longer dropper.

I remember being surprised by how comfy my Mk1 Honzo was. Sent Reverb for a service and fitted a regular post. Suddenly it really wasn’t a comfortable bike. A bit of flex in a seatpost is a good thing.