I've not worked on 8" floppy drives, but have on tons of 5.25" single- sided drives. Older single-sided ones (usually 35-track from the 70's) had load solenoids for the pressure pads, as with a double-sided unit.
The pad is to provide good contact between the media surface and the head beneath. I think older media must have ablated more than latter- day media does, as it is rare to find a single-sided 5.25" drive with a load solenoid. The pad is always in contact whenever the drive door is closed. Double-sided drives of course retained the head-load solenoid for some years, but eventually those were done away with. So, I think that unless you are using a drive 24/7, a pad in contact with the disk should not be a serious concern. That the pad IS properly in contact is important of course, and pads should be inspected to see that there is enough 'meat' left on them to provide the pressure needed. Aft of the pad, at the base of the head-sled pressure arm is a notch into which the end of the spring rides. Close examination of the sled will probably show some higher and lower notches into which you can move the end of the spring, to provide more or less pressure as needed, to tune a particular drive. In the old days, someone running a drive on a BBS or other heavy application might wear a pad out. We'd just steal one from a cassette tape and stick it on the arm. The cassette tape pad was square and the originals were round, but it never seemed to make any difference. These days there are no cassettes floating around to cannibalize, so I buy felt pads for furniture from Amazon, trim them with a razor and stick them on a drive I'm refurbishing. Atari, Commodore, Tandy... Many of the 80's 8-bits used this very scheme on their single-sided drives and this solution is good for all of them. I had someone insist to me recently that the felt pads I was buying were acrylic and the originals were Rabbit Hair and that it was crucial that the replacements be made of rabbit hair. In practice, and that is 40 years of practice, any old pad will do just fine. If it looks like the right thing it will serve the purpose. Just pick off the old nub of a pad and stick on your newly cut one and go. Common faults I've been noticing are that disk drives made in the 70's, 80's, and 90's are failing in common ways. I attribute these failures mostly to lack of lubrication. After 30 years they get a bit gummy and the actuators have to work harder to move the head sled, which puts a greater load on the darlington drivers which power the actuators, which causes the drivers to fail. Replacing the drivers will often restore the drive to working order, but they will fail again in short order if the original probelm is not resolved. I simply clean the rails and stepper bands, touch a little wd40 to the rails to free the head sled, cycle the head back and forth a buncha times manually to exercise it and distribute the lubricant, then follow that will a little white lithium grease for a longer-lived lube. Not only will the drive run better and a lot quieter when lubricated, the loads on the actuators and their associated electronics are greatly reduced, making for a like-new drive. The second thing that is happening quite often is electrolytic capacitors are failing, leaking or not. I had a pair of drives the other day which made quite a racket when spinning free even without media installed. Replacing the electrolytics on the spindle motor's board got rid of the noise and made it possible to properly tune the RPM's, which had been just all over the map. best, Jeff
