When do I need 36 mm and when do I need 38 mm suspension fork stanchions? Is a stiffer suspension fork better? Or is flex actually a good thing? Flex is not a simple topic. In our field test, we explain the advantages and disadvantages of 36 mm and 38 mm stanchions, stiffness, and flex in mountain bike suspension forks. SR Suntour provided us with two almost identical suspension forks, the AURON36 and DUROLUX38 X – the only difference between them is the stanchion diameter.