Frame builder Mitch LaMoure even installed S&S couplings on his everyday bike.
And they don’t rust in the rain!!
A comment from Mitch regarding his BTC equipped bike
"I’ve been building hand crafted frames since 1983. As an active cyclist I started racing road bikes in 1976. I raced for many years as a cat 1 & 2 racer and now race as a master. If you want a folding bike, the S & S coupling is the only way to go. You can ride your own bike with all the benefits of a folding bike. I ride mine every day, rain or shine (which is a must here in Oregon), with no adverse affects."