Dark line down the back of my Aero jacket

[navetsea]

if your jacket fits snug on the back, and you ride or drive for a long time while sitting against car seat or wearing a backpack, that horizontal crease on the upper back armpit to armpit across the back might develop, especially when the jacket has no action back/ gusset and the sleeve is not designed/ rotated forward for riding.

here are 3 jackets on me with the same pose,
the brown one is not designed for riding, it has sleeve vertically down, not turned forward at all and non gusseted shoulder with a little lower armhole
the grey one has sleeve designed for riding slightly turned forward , very high armhole, but not guesseted
the black one has sleeve turned forward, and with small biswing gussets on each shoulder
see how much different creases forming on the back, if I wear those snug non gusetted jacket on the bike with backpack on my back, it surely will develop horizontal crease across the back.

 

[OldOilPull]

I reckon that'll take a very long time to wear out. Maybe it'll never fully go but over a period of years you can bet it will become insignificant. Just look forward into the future - that jacket has a lifespan as long if not longer than you do. Imagine how much this will matter in a year. Five years. Ten years. Twenty. The jacket will have just entered it's prime by that time and the crease will be, if not gone then, just as good as.