Interesting that people use "shallow" as the opposite of "steep" (for an ascent), when it isn't really, and certainly it sounds odd to say "a shallow hill". I

Interesting that people use "shallow" as the opposite of "steep" (for an ascent), when it isn't really, and certainly it sounds odd to say "a shallow hill". I prefer "gentle", but I've always wondered if there are other languages that do have a specific single word meaning "not steep" that you can use to describe mountains etc. At any rate, it depends a lot on the surface, the bike, the length and the sort of muscle development you have in your legs. For me on a decent road bike on a smoothly paved road, anything up to about 15% for a km or so is definitely easier than walking - I can do it a lot faster for a lot less effort. But on a loose gravel/heavily rutted surface, I'd probably have trouble staying upright for long at 15%+ on a typical road bike, and even 15% on a smooth road for much more than a kilometre gets very tiring (accepting it's pretty tiring to walk too, but it seems to put a different sort of strain on your muscles). I'm not sure if you'd consider 15% "very shallow" (I certainly wouldn't call it "very gentle"!).