I just received a set of Shimano SUS shift cables. The specifications say the cables are SS. I usually check to see if a metal is SS or carbon steel (or aluminum) by using a magnet. Aluminum and SS are not magnetic. I just checked the Shimano SUS cables and they are magnetic. Just to see if I am not going wacky I checked the SS spokes on my road bike and they are not magnetic. Also checked some Campy Ergo shift cables and they are not magnetic. What gives with the Shimano SUS cables ?
Bob

Plenty of stainless steel is magnetic

As noted above there are different classes of SS. It's been a while since I've gone deep into the materials engineering but from what I can remember, there is Ferritic, Austenitic (spelling?), and Martensitic (spelling?). Depending on the microstructure of the SS (dependent on cooling rates) it can affect the magnetism of the SS. IIRC, the ferritic SS is magnetic.

OK, The Shimano SUS is a magnetic grade of SS then. I did notice that it wasn't as strongly pulled by the magnet as carbon steel. I did a little checking with some SS hardware I have and found that grade 316L hardware is not magnetic at all but I found that grade 304SS is magnetic.
So the magnet test is not always a good indicator !
Thanks for the information guys. This forum is a storehouse of knowledge.
Bob

It wasn't magnetic-- you made it magnetic by applying a magnet. This is some quantum-level stuff, ya'll. From Scientific American:

"A piece of ferritic stainless steel is typically unmagnetized. When subjected to a magnetic field, however, it will become magnetized and when this applied magnetic field is removed the steel remains magnetized to some degree. This behavior is a consequence of the steel's microstructure. Specifically, in its natural state ferritic steel consists of small regions called magnetic domains, which are fully magnetized, but in general the direction of magnetization is different in each domain. As a result, the sum total of all the domains gives the piece a zero magnetic moment. An external magnetic field orients these magnetic domains. Depending on the steel and the applied field, the orientation is achieved by a combination of selective growth or shrinking of particular domains and the rotation of magnetization within the domains. If the applied field is sufficiently strong, the steel will retain a significant fraction of its magnetization as long as the steel has an adequate number of imperfections that keep the domains from rotating and growing or shrinking."

Also, Zero Magnetic Moment would be a pretty great band name.

I will take your word for it. This is way above my pay grade

You could say the same about carbon steel.
In the context of the post, "magnetic" was inferred to mean "attracted to a magnet".
KISS

All I know is that fridge magnets stick to the SS on my fridge, but not my neighbor's. From that small sample of empirical evidence, I deduce there are different alloys of SS.

(In another sample of kitchen science, the same neighbor demonstrated that his cell phone will not work inside his (unpowered!) microwave. It does in mine, so his is superior in shielding radiation. My deduction is that he spends more on appliances than I do.)

Typically 400 series is magnetic and 300 series not. Working SS (threading/drawing etc) will also induce a small amounts of magnetism.

https://www.fastenal.com/content/fed...ss%20Steel.pdf

You will go faster on a steel bike riding in a north direction because of the magnetic attraction of the north pole.

You can't, and you shouldn't. Unless you've found some carbon steel that magically possesses a zero magnetic moment.

Sigh.

"The most popular stainless steel is Type 304 (aka 18-8,) which contains approximately 18 percent chromium and 8 percent nickel. At room temperature, the thermodynamically stable crystal structure of 304 stainless steel is bcc; nevertheless, the alloy's nickel concentration, as well as the small amounts of manganese (about 1 percent), carbon (less than 0.08 percent) and nitrogen (about 0.06 percent), maintains an fcc structure and therefore the alloy is nonmagnetic. If the alloy is mechanically deformed, i.e. bent, at room temperature, it will partially transform to the ferritic phase and will be partly magnetic, or ferromagnetic, as it is more precisely termed.

Popular ferritic stainless steels are iron-chromium binary alloys with 13 to 18 percent chromium. These alloys are ferromagnetic at room temperature. Like all ferromagnetic alloys, when heated to a high enough temperature--their Curie temperature--the ferritic stainless steels lose their ferromagnetism and become paramagnetic--that is, they do not retain their own magnetic field but continue to be attracted to external ones."

The OP asked why his stainless steel cables were magnetic. . Because of the crystalline structure of stainless steel, they can to some degree either ferromagnetic or paramagnetic. Screws are not generally subject to mechanical deformation, so they will not enter a ferritic phase. But you can coil an SS shift cable into a hoop-- and while I'm not a magnet doctor, that sounds a bit like mechanical deformation to me.

Or use the bike as an impromptu compass if you get lost in the wilds. Toss it in the lake and see which direction it spins