So today I managed to do a complete dismantling,cleaning, and lube/grease of my Stradic 4000fi. I decided to change the main bearing due to it being a bit rough and noisy. Boy what a difference it made, 100 times smoother. I also decided to tackle the anti-reverse clutch. Something I was hesitant to do but thanks to this forum and the many people that give advice and tutorials I was able to get thru it and finish. I usually do all maintenance on all my reals but it's my first complete dismantling of my Stradic. Wheww I'm glad that's over with. But back to the reason I wrote this post. Upon working on the anti-reverse clutch I noticed some corrosion on the barrel rollers. To my amazement I realized they weren't made of stainless steel. I took a magnet and those suckers stuck right to it. Why would Shimano not use stainless?? It works fine but I feel I'm going to visit that clutch again one day. Anyways just thought Shimano should of use stainless barrel rollers. That would of been the best thing to do IMO.
I believe that reel is a fresh water reel and under normal condition and lubrication, that bearing would be fine...and cheaper.
Most stainless is magnetic. A magnet is not a true test. Stainless Steel contains steel in different percentages.
Material-wise it's a balance of corrosion resistance, impact resistsnce, and compatibility of the pins with the metal insert that runs through the ARB. i.e. Pins that are too hard will end up wearing down the insert and vice-versa. That said, Stradics are indeed marketed as a freshwater reel. Even so, they have a good track record being used in the salt (HI)--so long as care is taken to service them when new, and at regular intervals thereafter. It sounds like the reel in question was running for some time with the ARB pins totally dry.
The magnet test can be a bit misleading for stainless. Just because its magnetic does not mean its stainless. By definition, stainless is any steel alloy that contains more than 10.5% chromium.
In general, only 300 series alloys are non-magnetic. And they are typically low strength, with the primary concern being corrosion resistance.
Most stainless grades that can attain a high level of hardness(400 series and PH grades) are magnetic. This would include the standard material for stainless bearings (440C).