irc

Seemsto be a bit of a debate about stainless steel bolts.

"Stainless steel work hardens and becomes brittle, potentially leading to breakage when subjected to cyclic stress. However the only place you really need to be wary of this on a bike is the saddle clamp, although discretion should be used if you suspect there may be such stress imposed elsewhere."

https://www.bicycles.net.au/forums/v...ic.php?t=97139

But I have no engineering knowledge. So I have no idea if the above is correct.

Steel Charlie

My local Ace Hardware has a nice selection of metric stainless. I use that and titanium for everything on my bikes that I can. Never had a problem.

79pmooney

Question - do you sweat? Does the seatpost see that sweat? If it does, you may have a complete circuit through dissimilar metals. The steel may not be touching the carbon but if the circuit is there, the galvanic reaction will happen. The good thing here is that what is degrading is the sacrificial zinc on the steel bolt. It lasted plenty long enough for you to spot it. Did its job.

Like others here, I am a fan of the right material for the job. But I am less of a fan of stainless steel on many land applications because for things like bolts, quality non-stainless does the job better. (Less galling, less damage to matching threads. Harder.) Now, in marine applications in salt environs 24/7 stainless steel is a gift to mariners. But the stainless steel devices there are bigger, heavier and less precise for the most part than their land based equivalents. Granted, some of this is due to both the probable lack of service abilities out at sea and the importance in terms of life and death.

If it were me, I'd grease the heck out of that bolt with marine grease and put it back in for in another 5-10 years and see if more needs to be done. (I don't know that marine grease will stop galvanic action. But from what I see here, I'm pretty certain that bolt can handle more of that it has seen and the marine grease certainly won't hurt.

79pmooney

I've broken saddle clamp bolts. Twice. 1979 or so Avocet post. No recollection of the bolt material. (They broke '79 and '86 during my "crazy years".) They could well have been stainless or just poorly spec'd or used in a setting that was poorly designed or fabricated. This was Avocet. Every Avocet item I used broke en-ride except those wonderful seats Selle Italia made with their logo.

I had another Avocet post years later for my Ticycles bike that broke at the clamp. My takeaway? The problem is mainly Avocet and less the bolt material.

I'm pretty certain the bolts in most of my Japanese seatposts are chromed steel of unknown but appropriate grade. My customs use Thompson hardware.

terrymorse 

I did a little searching on high strength steel vs stainless bolts, and I found this:

Tensile strength (ksi):
12.9 steel - 170
stainless - 70

Torque (M6, lubricated, N-m):
12.9 steel - 18
stainless - 6

Now I知 re-thinking my choice of stainless. But first, I知 going to re-torque the SS bolt to 6 and see if that holds the saddle snugly.

terrymorse 

Update: I torqued the new stainless bolt to its rated 6 N-m, and the saddle is not movable, so I知 calling this a successful job.