Is there any reason NOT to replace standard steel screws, nuts, etc. with stainless versions? I hate seeing rust anywhere so I am thinking as it shows up on fasteners, I will just replace them with stainless ones. Now I know that stainless is "softer" than, for instance, high speed tool steel. However, fasteners are not made of HSS, and many are stainless now anyway. Even though some of the screws may look highly specialized, almost all seem to be standard metric sizes available at a good industrial fastener supplier, though not a regular home center or hardware stores. You can get most of them in regular steel there, but for stainless you have to go to the specialists or online. I know they cost a little more, but not enough to even think about because there are not that many.

Any comments from the pro mechanics and engineers?

Every decent touring bike seems to come with stainless steel fittings. I wouldnt use anything else. They are certainly stronger than titanium. Ive sheared cheap non-stainless rack bolts, but never stainless M5 allens.
My engineering supply catalogue also shows nylon bolts. Ive wondered about fixing fenders with these. Would they survive?

I've always used stainless. Bike shops around here carry them as normal stock. They are a bit expensive but worth it.

If nylon bolts will hold license plates on cars with all the vibration they are subjected to, then it would seem thay could hold on a bike fender without too much difficulty. It's worth a try, anyway.

Most Mtb`s come with stainless bolts, i`ve never used other like titanium and nylon.

A friend of mine (enigneer) didn`t recommend titanium, because they have to put more material on the bolt to get the same strength of stainless steel, and often the replacement ti bolts have the same content of material.

Maybe its expensive to replace all the bolts to stainless, but it sure looks better and its easier do maintenance because the bolts don`t wear off.

Rainman, If you don`t find them at your LBS or hardware store, maybe you can check out a motorcycle shop with customize works.
They often use replacement bolts in a huge varity of sizes and colors for their projects.

FWIW, the material properties for 'real' stainless steel are pretty d@mn close to that of ordinary mild steel. Hardened steel, however, may be brittle, but that's not the same thing as stainless (one is an actual alloy, the other is a process done to steel). Titanium will work about the same, too, but will set you back $5-10/screw!! Aluminium screws, however, are significantly weaker than steel.

Thanks, D*Alex! Most of my fasteners do seem to be stainless, but the few that aren't are aggrevating me.

As as addenda to what toolfreak was saying... Litespeed uses stainless bolts and not Ti. Which points up the better holding quality of stainless. (not to mention the reduced cost.)