Originally Posted by thenorm
one of the biggest things for cornering speed on loose roads (gravel, snow, etc) will be tires. without knowing your tires, i couldn't recommend crazy speeds.
Sailor is right though, the signs are meant for all vehicles, RV,s trucks, etc, so cars can generally take them a bit faster.
1 piece of advice, don't drive faster than you can see. Don't cut blind corners, and don't commit too hard to a corner if you cant see the exit, all it would take is 1 decreasing radius at too high speed and you will quickly run out of road and head down a ditch (or worse).
Some great hints from thenorm & JoeyWhat.
"Slow in & Fast Out" is good for any unknown road, particularly gravel when the surface is constantly changing.
Dive in slower then you think you could, then as you see/feel conditions and the corner exit you can speed it up as you complete the turn & exit it.