My max is down a hill (don't know the grade, but I estimate it's about 5-7%) on my way home from school. If it's dry (no ice/snow), and I have my summer slicks on, I have no difficulty reaching close to 60 km/h. The highest max I know for sure was 57 km/h (just over 35 mph), but I'm pretty certain I've been down that hill faster than that, I just don't look at the max every day. I should add that the speed limit is 50 km/h on that street... Ehrm...

Now, on wintery streets (salted, so ice free) with my 2" studded knobbies, I've only been able to get up to 50 km/h even (31 mph). And if I have cars going down with me, I'm down to about 40 km/h max (25 mph).

My average speed for the entire commute is about 22-23 km/h (14 mph) in the summer, and 18-19 km/h (12 mph) now in the winter. The main problems are other traffic and several red lights. I think my average would probably increase by 20% without them.