Hey all. I have a Cannondale T800 after spending all my earlier years on mountain bikes, mostly crappy ones. I took a trip a few days ago with a friend who has a lightweight mountain bike and I took my 800. I expected to leave him int he dust but he incredibly managed to outpace me, not that it was a race or anything. But it became obvious that there wasn't a clear speed advantage for me, beit caused by the bike or the rider. So I ask, how does the speed of a tourer, particularly the 800, compare with the speed of road bikes and mountain bikes?
If both bikes have been similarly maintained (brakes not rubbing, good hubs, etc), then there are only three other factors that can significantly affect speed: 1) tires (knobbies will slow you down), 2) weight (only when accelerating, which includes uphill), and 3) the engine (the rider).
There's another possible factor to consider. There are differences in riding technique. Touring riders learn how to conserve energy to go the distance on a loaded bike. Non-touring road riders, especially those who pride themselves on fast recreational riding or racing, go for speed instead. They develop a different method of riding to suit their goals.
For what it's worth I am trying to perfect a technique that a friend tought me. Maybe it's noobish, but I'll throw caution to the wind as I've been riding with regular pedals for years and am new to clips.
Normally, I pedal "pushing down". Yes, I know, we're all supposed to pull too, or even eventually achieve a full circular movement where are muscles are always pushing perpendicaular to the cranks, but I havent managed to do that efficiently for more than 1 nanosecond yet.
When I get to a hill, my lega are already warmed up and my "push down the pedals" muscles have been working for a while. When they get tired, I try to start "reverse pedaling", a.k.a. ""pulling instead of pushing", and it uses a whole other group of muscles altogether. Anyways, for short hills, it helps me push forward without losing too much speed and without becoming too tired.
I find that method useful on long days (long for me), ~120km.
A fourth factor to add to EmmCeeBee's list is air resistance. A typical touring bike will be set up for a more upright posture than a road bike -- therefore, more air resistance -- but not as upright as a mountain bike.
The biggest difference, though, always comes from the rider. Take a dozen riders and a dozen bikes of wildly varying types, assign the riders to the bikes at random...and for the most part, the faster riders will still be faster, no matter what they're riding. (I know this because I'll be the one getting passed, no matter what everyone's riding!)