noimagination

I recently had to replace the left-hand brake/shift mechanism (Shimano) on our tandem due to corrosion inside the mechanism. The right-hand shifter still works, though I can see corrosion there and the brake lever doesn't return to the release position after braking (I have to move it there with my fingers). So that shifter is likely due for replacement soon as well.

The LBS mechanic said the corrosion was due to rain or perspiration. We don't ride our tandem in the rain, much - I mean, we've been caught in sprinkles a few times, but that's it. And perspiration doesn't seem likely as I keep my hands on the hoods or drops, so I don't see how much perspiration can get inside the shifter body during the brief times I'm braking and the mechanism is exposed. However, I will be more conscientious about wiping down the bike after use.

I think that moisture got into the mechanism during transport. We use a roof rack, and we've driven through rain with the bike on the roof several times over the years. I will get a "bra" to minimize the driving rain hitting the bike, but my question is: is it a good idea to use compressed air to dry out the shifter mechanism after it gets wet, or will that just drive moisture into crevices and make things worse?

Thanks for any advice.

(Note: I'm not interested in debating roof rack vs hitch rack vis carrying bike in the car. Hopefully my thread won't degenerate to that type of debate in this forum, as it likely would in the General forum.)