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Originally Posted by snguyen268
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Do you think I should consider 78mm to 80mm BB drop?
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IMO BB drop should consider the smallest diameter wheel/tire combo you anticipate, and how you ride. I like as much drop as is reasonable on my bikes. My Bingham has 75mm drop and is designed for 650Bx38 tires. In theory, that gives a BB height of (584/2+38)-75=255mm, or just over 10 inches. That's pretty low! In practice, it's a couple of mm higher because the GK slicks measure 332-333mm in radius on the BTLOS rims, not 330mm. For many years I rode the original style Eggbeaters with the Ti axles, which are shorter than the stock steel axles, and provide very good cornering clearance. Recently I switched to Eggbeater 2 pedals with steel axles, and they are wider. For the first time that I can remember, I hit a pedal on the pavement pedaling through a tight turn recently!
My all road bikes are not set up for rowdy off road riding, more for the type of dirt roads we have in New England. So when I ride something like D2R2 I'm a bit more careful than others might be on the bits of jeep road/single track. Usually I have 42mm tires on, so get a bit more BB height.
My Firefly was designed with 78mm drop which in theory gives a BB height of 258mm with 700Cx25 (622/2+25)-78=258. That seems low for a road bike but in practice it measures 265mm. The radius of the GP5000 700Cx25 tire on Easton R90SL rims is 341+mm, and I think the BB drop may be very slightly smaller than what the build sheet shows.
I'm sure that framebuilders know a lot more than I do from a few measured data points what actual BB height will result for a given wheel size and tire size based on the BB drop. And I know that people's opinions of minimum BB height will vary too.