I've searched and searched for an answer to this but not found one, so please forgive if it has been asked and answered 1000 times. Anyway...

When you make an outfit in bodyshop and black out part of the alpha so that area is invisible, will bumpmap bumps still show on that area or not? For instance, if I make corduroy pants with big holes in the knees, and the bumpmap is ribbed even where the holes are, will the sim's knees look bumpy or smooth? I can't see bumpmaps with my graphics card, otherwise I'd just test it myself...

Yes, it will.

I noticed that in some downloaded clothing items when the creator had changed the texture and alpha channel, but forgot to edit the bumpmap. Now I have a lot of editing to do.

Thank you!! Hmm, in that case some of the clothes I made before discovering what that mysterious 3rd file was must look pretty weird with bumpmaps enabled.

and thats the reason why i dont make clothing

Aww, if you want to make clothing you shouldn't let that stop you! Just grey out the bumpmap file so it's all one solid shade of medium grey and you should be fine. At least that's what I read. Of course I have no way to test the theory. But I don't care because the clothes look good on my little sims and that's who I made them for. :D

Yeah, probably
It gets really weird when someone created a "nude" piece of clothing from a bikini and forgot to grey out the bumpmap.