The Canon EF-S 17-55mm f/2.8 lens seems prone to collecting grit underneath the manual focus ring. Just weeks after I originally bought the lens, I went to the beach. Afterwards, the manual focus ring could not be turned without difficultly and grinding sounds. I sent it to Canon and they fixed it under warranty. However, within a few months, the lens once again managed to collect significant grit underneath the manual focus ring. Since I don’t really use manual focus much for lenses of this focal length, I resolved to ignore the problem.
Recently, however, I decided to revisit the problem and see if there were any solutions. Canon gave me a quote for $219 + shipping to fix the problem. It definitely didn’t seem worth that much money. I started cruising the forums and came across this thread where someone recommended vacuuming the lens. I honestly thought this was a bit crazy and would never work but decided to try anyways. I started vacuuming with the brush attachment and pushed it around the manual focus ring a few times. I turned off the vacuum and turned the focus ring. Much to my surprise, I noticed an immediate difference! There was still plenty of grit in there but I could feel an improvement.
With this encouragement, I started vacuuming in earnest. I brushed perpendicularly to the barrel (as shown in the picture above) as well as parallel to the barrel (which I think creates more suction since all bristles are in contact with the surface). As I vacuumed, I turned the focus ring back and forth. I probably spent 20 minutes doing this, but now the ring turns as smoothly as when I got it.
I am still surprised that this works, but I guess it makes sense that if particles can enter the lens then they can exit the same way. Anyways, maybe this technique will work on other lenses with similar symptoms.