But, I can ride a mountain bike at 55 mph.
In the mid-90s, when I working at Destinations Cyclery, the guys at the shop and I did a lot of mountain biking on the motorcycle trails in the Rampart Range area. To get to our starting point, we drove up Jackson Creek Road, until we reached Rampart Range Road. There, we would park the car, and unload the bikes.
The trails up there were a lot of fun. You could hear the motorcycles coming from a distance, so we would just get off the trail and let them go by. So, we never had any trail-user conflicts with those guys. Hikers stay off of those trails, because of the motorcycles, so we never had to worry about coming around a corner and encountering hikers.
Once we got back to the car, we would typically decide who was driving down, and the rest of us would take off down the road, toward Castle Rock. It wasn't totally a downhill, but the last two or three miles dropped a couple of thousand feet, and had a lot of curves (some of them close-to-180-degree switchbacks). The gravel was usually deep enough to put you into a power-slide on the fast turns, and the washboard was wicked in places. It was a heck of a fun ride.
The last 1/2 mile, or so, before the road flattened out was a straight 15% slope that allowed you come out of the last turn and just gun it for all you were worth. Our goal was always to hit 60 mph, but the washboard had a way of scrubbing off your speed even as you pedaled your heart out.
But, one particular day, things almost came together. I was riding my Specialized S-Works FSR, the road had been recently graded and I think I must have had a tailwind. Anyway, I came down the straight with my head down, pedaling for all I was worth. I passed whoever was in front of me (I think it might have Brian), and got into a bit of a wobble. But, I pulled out of it, and coasted to a halt.
As the rest of the guys caught up to me, we all compared our "max speed" readouts on our cyclometers. Two or three of the guys had topped 50 mph, but we were all surprised to see that mine read 55.8 mph!
It was one of the few times that I was ever the fastest on the bike, with that group...and it felt good!