At our institute it is not common to upload a pre-print of your submission to arXiv. I got told by a friend that it is basically a no-brainer and there are virtually no downsides in doing so. I checked with the journal I want to publish in, they even allow submitting arXiv links, so I am safe from there.
Since nobody at my institute seems to upload their pre-prints, should I ask my advisor before doing so? He is also co-author of the paper.
My field of research is materials science (and to some extent more general physics).