
Mine came with a 125mm dropper, and I have set high enough that it could handle a 150mm dropper (which I think the bike I test rode had – it was one of the first of the Australian delivery 2017s, and the Bontrager dropper wasn't ready so it came with a Reverb). The short real seat tube also means there isn't much wiggle room. On the extensive Fuel EX threads on MTBR I have heard taller riders complaining that they can't get the seat far enough forward for climbing because they have too much seat tube exposed. Set the seat higher (ie on a smallish frame for your height) and it will be slacker. Set the seat lower than this point (and I don't know where Trek defines it) and the effective seat tube angle will be steeper (ie on a biggish frame for your height the seat will be further forward). The actual seat tube is 66.2°, so whilst Trek's specification charts say all frame sizes have an effective seat tube of 74.7°, in reality that only happens for one specific seat height.
