roca rule wrote:
Would you say that you can descent faster on a mountain bike than on a road bike?
Typically and technically speaking, a mountain bike will descend as fast as a road bike under the same rider.
What are the differences?
-A mountain bike on a dirt road will see massive and abrupt changes in speed. Dirt roads in the mountains are typically ridiculously steep (ever wonder why they aren't paved?). In a typical descent in the Santa Monica Mountains a rider can go from 10mph to 45mph in a matter of seconds, then needing to go back down to 15mph about 30 seconds later. Disc brakes are remarkable for the needs here, as terrain can change very rapidly. Dirt road descents are typically not very long, and not very straight - although those do exist, they are rare. Often after a few seconds of descending the terrain will change rapidly, necessitating a dramatic reduction in speed and/or trajectory.
-A road bike is often able to descend at a fast speed for a longer period of time as the roads are comparatively more gradual and descents are significantly longer, allowing the rider to accelerate with gravity or pedal strokes until a terminal velocity is achieved.
-A good comparison would be a mountain bike and road bike descending a very steep, very technical road with off-camber turns, changing radii, and other hazards. If you put both on slick tires, my money is on the telemetry of speed being relatively close in top speed, delta values, and slowest speed. Local examples include Tuna Canyon (down) and Las Flores (down). Of note: RedBull staged a downhill TT/race on Tuna many years ago.
-A road bike with slick tires on a dirt road will not be as fast as a mountain bike with dirt tires on that same road, and vice versa. "Horses for courses" as the idiom goes.
Continue talking amongst yourselves.