Switching to Lower Gears for Climbing Right now, I've got a SRAM 11/26 cassette. I just moved to San Francisco, and some of the climbs out here (e.g., Mt. Tamalpais) are pretty brutal with over an hour of climbing. My cadence over some of the steeper sections towards the top tends to hover around 70, when I'd much rather be up at 80 or 90. I've been considering switching to an 11/28.

The thing stopping me from doing so is wondering if it would be better, training-wise, to grind it out for now until my power and endurance improve, bringing my ability up into the range where a 26t climbing gear is appropriate. I'm afraid if I switch to a 28t, I'll use it as a crutch. Should I stick it out with the 26t until I get stronger?
A cadence of 70 RPM while climbing is not unusually low, so switching to a lower gear may just encourage you to slow down instead of making you more efficient. But the only way to know for sure is to try it and measure the difference.

There isn't necessarily a right cadence. The article Technique - Pedal like a pro reports that seven pro cyclists (a small sample, I know) dropped their cadence from 80-100 RPM on the flats to 60-80 RPM on a 5% grade. Although Lance Armstrong is famous for climbing at 100+ RPM, this does not seem to be common.

I personally do better when I climb at around 70 RPM than I do at a higher cadence. The higher cadence just causes me to get out of breath faster. But this is different from person to person.

In the end, there's no harm in trying a different gear and seeing what works best for you.