I think I've seen BB heights on touring bikes listed from the low 260s up to 270. Non-touring-specific bikes generally run a little higher. I think 269 is close to what my Long Haul Trucker was, based on measurements I'm seeing online. 170 cranks were no problem on flat surfaces. But once it got rocky, as in off-road, there was more care required to avoid pedal strikes. If you're looking to stay on roads, gravel or otherwise, you might be able to keep your 175s, but if you have any thoughts of about leaving the road, I'd probably leave the larger tires on to keep the BB up higher.