Quote:
Originally Posted by benb
You should get accustomed to sticking the bike's rear wheel in a corner and measuring the X/Y position of the BB and the X/Y position of the front/top of the saddle. It allows you to adjust two bikes to fit exactly the same with quite a bit of precision.
You are looking to measure "Y" as the vertical distance from the center of the BB to the top of the saddle.
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On two bikes with the same STA, all three sides of the triangle will be the same length - from center of BB to top of saddle along the STA, the vertical height of the saddle from the BB, and the distance of the horizontal line connecting the other two sides of the triangle.
If you go to a bike with a different STA, the vertical distance should remain the same. To make sure that it does, you can calculate the distance up the STA by putting the following in Excel =(vertical height from old bike) / COS(RADIANS(90-STA of new bike).
If you only know the height along the STA from the old bike and want to know the vertical height, use =(height up the STA) x COS(RADIANS(90-STA)).