How to measure a dropper's insertion and stack
The usable travel of a dropper is NOT the number on the box: it's decided by the insertion (what the post must go into the frame) and the stack (what it takes up between the collar and the saddle rails, dead height). Measure the usable depth of the seat tube (until it hits a bend, pivot or bottle cage) and your saddle height: the travel that fits is the largest one that respects the post's minimum insertion and keeps stack + travel ≤ your saddle height. It's the measurement that closes which dropper fits you.
If you only measure the diameter, you're missing what matters. This is the math that stops you buying a post that ends up too high.
The two measurements that count
Insertion. Every dropper asks for a minimum length inside the seat tube. To know how much fits, put a tape or a rod into the tube until it hits a bend, the swingarm pivot or the bottle cage nut: that's your usable depth. If it's less than the post's minimum insertion, it won't fit.
Stack. It's the height between the frame collar and the saddle rails with the post up. It's height you "spend" without it being travel. Two droppers with the same travel but different stack perform differently: the one with less stack lets you raise the saddle more or fit more travel.
The math
Put the two together: the maximum travel that fits you is the largest one that meets both (a) that the post's minimum insertion fits in your usable depth, and (b) that stack + travel doesn't exceed your saddle height (otherwise, fully dropped, it stays too high to pedal). With those two checks you get it right.
Key facts
Tell us your saddle height and frame model and we'll work out the maximum travel that fits you. Message us on WhatsApp
Frequently asked questions
What is insertion?
The length of the post that must go into the seat tube. If the tube is short or has a bend, that insertion won't fit.
What is stack?
The dead height between the collar and the saddle rails; it isn't travel. Less stack = more travel on the same bike.
How do I work out the maximum travel?
The largest one that respects the minimum insertion and keeps stack + travel within your saddle height.
Related
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