I have a very original road-registered 1979
SP370 that has done about 18,000 km from new.The SP370 in 1978 was
's first-ever 4 stroke dirt bike and was obviously intended to try and take some market share away from the extremely popular 
TT500 and XT500 which first came out in 1976.While I was lubing the chain I noticed that the rear brake had a bit of drag. I did some investigation.
The rear brake backing plate on this bike is a "floating" type in that the brake backing plate rotates relative to the swingarm as the swingarm moves up and down.
are known for using interesting concepts in their designs. Other cool brands also had floating rear brakes. went one step further and used a Bowden cable to actuate the SP370 rear brakes instead of a rod. In theory, either one of these design concepts should take away the influence of the rear suspension moving during braking but went for broke and had both. Of course when rear disc brakes came into fashion they avoided braking bump issues by being hydraulically activated.
So my surprise was to find that the rear brake backing plate was able to rock on the axle and when it did, it caused the brake shoes to make light contact with the brake drum.
When I pulled it apart I found that, yes, the backing plate bearing had a lot of internal play, but the wheel bearings and the cush drive (sprocket carrier) bearing were perfect.
I suspect that this one rolling element bearing failed prematurely (only 44 years old after all) and not the others because someone had flipped out one of the rubber bearing seals at some point, allowing the lube to dry out and allowing moisture and dust inside.