Brake system? On what? Only bolts I know about are backing plate bolts, wheel cylinder attaching bolts, banjo bolts and if you have disc calipers, they have bolts? There is no special corrosion or strength consideration there.
I agree with Grigg. Grade 5 at hardware store or "hardware" store. Everybody gets up tight about bolts, but they never break.
As far as spec-ing them. Not sure what you mean by that. But they are spec-ed by: diameter-no of threads per inch-courseness-class: 4-40 UNC-2B or just 4-40. If you mean what size to get, get same size as bolts you are replacing. (In a Tap and Die set, there is a thread gauge that tells you the pitch and your calipers tells you the Dia.) Nothing wrong with cleaning up your bolts and reusing. If they are not rusted, they are as strong as day one. You always need new lock washers. Only a museum piece would need SS. All hardware has corrosion protection of some sort. There are grades, which is the type of metal/processes used to make them , which translates to strength. A Chinese grade 5 will meet the strength requirements of U.S. grade 5. SS is no bang for big bucks. Except trim screws. Keep away from children. Other opinions may apply. Void where prohibited.
