I have an old Schwinn mountain bike from around 1988, and for the first time in its long, faithful life, I need to fix a few things on it. I'm not much with tools, but I thought all nuts & bolts were fairly standard. That is, either metric or conventional. Unfortunately, I can't get either set of wrenches to fit snugly.

I guess I could use an adjustable, but is this a problem often encountered? Does Schwinn make a set of custom sized combination wrenches (10.50mm? 5.25/16"? )?

Thanks,
Joseph