Bikers are all rich white folks. Not.

Based on a study using the best available data (which I'll recognize may not be perfect), it seems that:

1) white people remain somewhat overrepresented; but 2) bicycling appears to be trending toward racial parity.

And:

Contrary to popular convention, the biggest share of bicyclists isn't yuppies, it's low income people. In fact, the lowest-earning quarter of Americans make nearly one-third of all bike trips.

More details here.