Here is an illustration of the 21" Kibo Dirt Drop with a quill stem.
For a height of 5' 10" we have estimated an inside leg measurement of 81.3m (32"), and a saddle height of 71.8cm.
It will be worthwhile measuring your inside leg measurement - if it's longer than 32" than it's likely the saddle will need to be higher than that shown in the images. To do this 1. Get a book and stand with your back against the wall, 2. Place the book in between your legs as high as it will go, 3. Move away from the wall keeping the book against the wall and finally, 4. measure from the top of the book to the floor. It will also be useful to measure the saddle height (bottom bracket centre to the top of the saddle) on your current bike and compare it against the illustrations.
If you would like a specific illustration showing your current saddle height (measured from bottom bracket to top of saddle) or based on your inside leg measurement, then click here to send us your measurements in mm and the frame size(s) you are interested in and we will create it and email it to you.
Standover height - compare the standover height in the illustration above (i.e. 21" - 79.3cm) with the combined measurement of your inside leg measurement plus the thickness of the sole of your usual cycling shoes. Our recommendation is not to be over concerned with standover height - the most important element of choosing frame size is comfort when riding. At standstill most riders tend to have one foot on the pedal with their body to one side of the top tube. However if you do tend to stand with both feet flat on the floor with the top tube between your legs then standover is important.