Old 07-01-19, 06:58 AM
Doug Fattic 
Join Date: Dec 2009
Location: Niles, Michigan
Posts: 399
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I think it is unlikely that your very high bottom bracket height and steep seat angle are anywhere near ideal. If you were somehow able to build 2 different frames and tried both out I bet you would like the one this is swallower and lower better.

The way I like to find seat tube angle is by using an adjustable fitting bicycle to help establish the seat, pedal and handlebar relationship and let that dictate the frame design. If the purpose of the custom frame is not racing or performance riding but rather to be comfortable than it makes sense to have a higher handlebar position (like you have done). As the bars come up the seat needs to go back for reasons already mentioned. This is why Dutch bikes (or old Schwinns) with upright handlebars have very swallow seat angles. You would find that moving the saddle back takes weight and pressure off of your hands on the brake hoods. Riders that have only been fit on production frames discover that more saddle setback (more than their bike allowed) is a wonderful revelation in riding comfort.

Of course as your seat angle gets swallower the front of your bike comes back getting the front tire in the way of your toes. Now you have to decide what you want to compromise. If overlap is a real problem you can build around MTB 559 wheels instead. Or you can live with the overlap.

Like duanedr said, BB drop is determined by BB height. I like it to be as low as possible. If I was building a frame like yours for myself, my seat tube angle would be around 72 and my BB height using 170mm cranks would be around 260mm.
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