I’ve done the calculation Bird provide to get the right size dropper for my Aeris 120, and it’s saying 155mm max, so looking like I could squeeze a 150mm post in (will be a brand x ascend). But, it’s pretty close to the limit, 5mm isn’t all that much, and I’m not sure it’s the best idea.

Any thoughts?

6ft, 32″ leg on a large with 470mm ST.

I wouldn’t worry, 5mm is 5mm and I doubt it’s a case of 156mm and the frame snaps.

Do it and sell if it doesn’t fit. You can always change to a lower profile saddle or chop a few mm off the seat tube.

Or platform shoes.

Moar drops is always betterer.

/edit – PJay, I assume that OP is concerned that his post might not fit in the frame, leaving his pedalling position too high.

Yeah that makes more sense. I’ve been at the lager.

If you’re on a 175mm crank consider getting a 170mm.

Big differences between models of post on rail to collar measurement. E.g. Bikeyoke Revive fits in where some models with less drop would not.

What max insertion depth is the Bird? If it’s internal, you also have to make sure the cable stop is included in the measurement and the fact it may need a bit of extra clearance to route the cable neatly.

Can’t find the relevant dimensions for the Brand X, here are the ones for the Revive by way of comparison.

https://www.tftuned.com/revive-dropper-post-316/p3266

The formula on the Bird website takes into account the dimension for clearance that is need for the lower collar and clamp. That is the 75mm that you need to subtract.

You could be controversial and fit a 125mm dropper?

Wait what?! When did the 150mm brand x come out?

I’ve got an idea, try it out, if it doesn’t fit, I’ll swap it for my lightly used 120mm 😀

Ascend XL 150mm

Think I might leave it until I’ve got the rest built up, try it with solid post to be definite on pedalling height then order.