Noob question, sorry guys. what kind of BB clearance do I need to look for to make sure 175mm cranks won't hit on tight turns? I have long legs so this is important as I'm transitioning from a 64cm conversion to (hopefully) a new fixie. Thanks!

Iono, but I have 170s on my bike and I scrape pretty often. Of course mine is a conversion so the BB drop is probably a little less than a real track frame I would presume.

why can't you use shorter cranks and pull out the seatpost?

It depends on the bike...

My 62 Pug has 11.5 inches of clearance so running 170's is no problem at all as if I strike a pedal I figure I am probably already screwed...and I push this bike really hard.

Some of my other conversions run lower clearances and I don't run anything less than a 170 crank so I have to be mindful of what I am riding and how hard a turn I can make. I have two old Kuwahara mtb's that have been converted to fixed gear bikes that actually have less clearance than the pug.

I use one of them for messenger work (it has 170's) and have not had any issue with pedal strikes but know it cannot corner as sharply as my pug (which is also seeing this kind of work). The other runs 175's and is used for commuting / touring and I have yet to strike a pedal.

It all comes down to rider skill and knowing the handling limit's of one's bike...since I also ride geared bikes and rarely coast I have to know when I am about to cross that line but on a geared bike the consequences are far less severe.

This bike has very low pedal clearance but is still so stable and manoeuvrable from a fairly upright position that I have yet to strike a pedal.

Impossible to answer since you don't tell us the bb height. All that you can get is irrelevant speculation. You might also want to define what "tight turns" is in terms of lean angle on said frame.

Providing complete information is so unimportant these days.

qft