
Zippers between backpacks - which are stiff?
I have an old Synapse 25 (~2016) where the zippers never quite fully "broke in" (i.e. glided smoothly). I have used zipper lubricants, but they still don't glide smooth.
I also have an very old cordura Brain bag I bought used in 2021, those zippers are a dream and glide smoothly.
I'm in the market for a new Brain bag, and I'm wondering if the zippers are more similar to the very old cordura brain bag or the old synapse. As of now, on the website, it seems like the Brain bag and Synapse 25 both have #10 YKK zippers in their main compartment (https://www.tombihn.com/collections/all-tom-bihn-stuff/products/synapse-25?\_pos=3&\_fid=d6d3e6534&\_ss=c%3Fvariant%3D46514712674493&variant=46514712674493 and https://www.tombihn.com/collections/all-tom-bihn-stuff/products/brain-bag?\_pos=12&\_fid=d6d3e6534&\_ss=c%3Fvariant%3D41750504276157&variant=41750504276157).
Even direct comparison between the two bags shows the zippers on the main compartments may be the same, so why do they glide so differently?