91 Civic, manual transmission, here. I am doing a timing
belt replacement. The front of the car is on jackstands, and
I put the transmission in 5th gear. I freed the pulley bolt
just fine, but then I wanted to rotate the engine so #1
piston was at TDC blah blah. I thought turning either of the
front wheels by hand would, via the manual transmission,
also rotate the engine. But no luck. I put the pulley bolt
back in and rotated the engine to get #1 to TDC. As I turned
the crankshaft pulley (via a socket on the pulley bolt), the
front wheels turned roughly in synch with the pulley's
rotation just fine.

What might have prevented my turning the engine by manually
turning the front wheels?