I’m all for substituting mild steel for stainless where prudent.
Both for its aesthetics and anti-corrosive properties.
I’m tolerant of its sheen not quite approaching that of chrome and value it’s low maintenance qualities.
I have sleeved fork seal holders and stanchions, substituted headlamp and mudguard bolts, made brackets for instruments and headlamp all with 316 or 304 stainless. I feel it’s worth the effort to polish these components as they will stay bright.
But I’ve always been wary of using stainless on stressed items.
I always remember the comparison with ordinary steel where it corrodes visually and then inwardly before weakening and failure.
Stainless corrodes invisibly inside and will fail suddenly with no surface imperfection.
It’s called Stress Corrosion Cracking (SCC) and is hastened by the presence of chlorine a chemical component of common salt.
For the above reason stainless is not used for stressed components such as spindles, suspension or engine parts.
Also it’s yield point is usually very close to its Ultimate Tensile Strength giving no warning of overload, just fracture. Common stainless is rated 70 denoting it’s UTS is around 7 compared to the 8 of lower grade ordinary bolts. The 0 designates the refusal of the manufacturer to designate a specific yield value.
Mild steel bolts are designated say 8.8, 10.9, 12.9 etc increasingly high tensile. The number after the decimal point denotes the yield value, the number in front is the UTS.
70 is relatively soft and liable to snap without warning.
So I like my machines bright and shiny and stainless fits the bill, but where do you draw the line for both safety and reliability.
It’s easy to get carried away as I did recently.
I’d just modified some incredibly cheap stainless mudguards from China ( 3 for £19 ) made stainless brackets from tube with drilled pressed flat ends. My rims are stainless and I had polished the alloy hub bright.
The front end now looks great all except for the manky front brake actuating lever, but wait, didn’t I see a stainless one for A10s advertised on e-bay?
Yes I did and identical design to the original except 3/4” longer for extra leverage!
I bought one, it was the same length as my original so not too happy about that, I was looking forward to using lighter effort.
But then maybe I got my brain in gear.....
How can something of the same dimensions, or longer, of inferior strength material and subject to stress corrosion be a safe substitution for a manufacturer’s item?
Especially given that manufactures pare material to the minimum for low cost and weight.
Supposing I survive the accident how do I explain to the insurance company or to the grieving relatives of my victim(s) that I substituted this safety critical item just for the sake of a bit of bling?
It’s indefensible.
I thought perhaps this was an isolated item that I came across, but no, there are many advertised and not just brake levers but spindles, torque arms etc.
Nothing to say these items had been tested, beefed up, or certified.
The best I could find was from my seller “tested on my bike,”—- so must be alright then!
I think it’s at least a bit worrying, given that in the absence of MOTs for classic vehicles the onus for keeping roadworthiness sits squarely on the owner.
Thanks for reading,
Steve.