Four years ago, we were just starting to see bikes show up spec'd with *gasp* 150mm dropper posts. That seemed like plenty of drop for most riders, and at the time the vast majority of participants in a similar poll
to this one thought the same thing.
Fast forward to 2020, and 150mm of drop seems to have become the bare minimum, while 170 and 200mm dropper posts have become much more common on larger frame sizes. Seat tube lengths have gotten shorter and shorter, and many companies have modified their frame designs to provide room for fitting a longer post without running into a pivot or kink in the seat tube.
What's the reason for this increase in average dropper post length? Did everyone's legs suddenly grow six inches longer? Nope, there wasn't a global growth spurt – it's modern geometry that's the culprit, specifically steeper seat tube angles.
With those steeper seat angles, there's not as much change in the position of the seat in relation to a rider's body between full extension and full compression. The seat now travels in a more vertical path, compared to the more diagonal route it would have followed with a slacker seat angle. Hence, more drop is needed to get the seat fully out of the way for descending.
Different bikes and different riders, but a similar saddle position for descending.
Is it possible to have too much drop? Of course, but it would take a seriously long dropper post to reach that point. As it is, many modern droppers have adjustable travel, which allows them to be fine tuned so that the fully compressed position puts the seat exactly where a rider wants. In most cases, that's a couple inches above the kneecap when the pedals are in the 3 and 9 o'clock positions – take a look at photos from World Cup DH or EWS races and you'll see the the similarities in seat heights and descending position.
How much longer will dropper posts get? That's a good question, and one that doesn't have a totally clear answer. We are seeing more and more bikes with 34.9mm seat tube diameters, which allows for posts with more robust internals, and there's no doubt that 200mm dropper posts will become increasingly common over the next couple of years. I could be wrong, but I doubt we'll see posts longer than 250mm any time soon. After all, seat angles can only get so steep, and it's not necessary to have a seat positioned at ankle height to get down a gnarly run. We'll see.
For now, vote below for your ideal dropper post length.