Honestly - I still think you are calculating something very wrong here unless your entire route is uphill? I swear I am not trying to sound like a dink - I took my 6 year old on a bike ride that was about that far the other day and she averaged almost 9 mph vs. your 10 mph and she is riding a 20" wheeled, single speed Trek Mystic girls bike. There has to be another explaination here because something just isn't adding up?

Are you counting time spent stopped to wait for traffic signals, etc in the total time?

Try using www.mapmyrun.com and enter your route - this site is awesome.

Wow. That site is awesome. Thanks.

I'm bascially riding a 2.3 mile loop. The elevation difference is 242ft. The low point is at the beginning and the high point is around the middle. Is that bad as far as hills go?

I don't spend more than a few seconds stopped during the ride.

That'd be ~968 feet of elevation for four laps, which is more than I see in a 60 mile ride. Might be easier to judge if you could link the course map+profile

100 ft/mile is often considered pretty hilly. That would certainly slow you down, especially if you are heavy (I don't remember if you said and I don't care to go back and look through all the posts). It also would make the extra weight of the mountain bike have more affect, and the suspension

Too vague.

Here are some numbers.

http://74.125.93.132/search?q=cache:...&ct=clnk&gl=us

Power 1-sp 3sp-L 3sp-1:1 3sp-H 6sp-24 6sp-19 6sp-13

50W 96 90.6 93.4 87.3 94.2 94.1 92.1
100W 97.3 92.8 95.7 90.9 96.2 96.4 94.9
200W 98.1 94 96.9 92.9 97.4 97.6 96.9
400W 99 95 97.9 93.9 98.1 98.4 97.8

I doubt you'd feel the difference between a "$5k bike" and a "decent" fixed-gear.

Here's a link to the loop I'm riding: http://www.mapmyrun.com/route/us/va/...27170038680981

I got my time down to 45:30 for 8 miles today (I do the loop 3 times and ride 1/2 mile to/from the loop)

I'm 5' 11" and 185 lbs.

10.6 mph.

Help us out and provide the average MPH too.

If you want to do more road riding (outside of this one event), then get a road bike. But don't expect magic.

I'd guess that you would have maybe done 12mph on a road bike with the reduction in resistance (thinner high-pressure tires, no cheap-assed suspension) and a better aerodynamic position (if you use the drops).

I alternated between a mountain bike with slicks and a road bike for commuting over a period of several years. The difference was 4 mph - about 20 mph on the road versus 16 mph for the mountain over a 22 mile one way distance and included time at traffic lights and intersections where cars caused me to stop

Stupid but honest question - he's doing loops and ending at the same elevation that he started out at... shouldn't he be making up a little time on the down side, anyway?

I'll take a stab at this and say "a little." The potential energy you gain from climbing the hill = mass * gravity * change in height. Going down the hill converts that potential energy to kinetic energy (0.5 * mass * speed^2) but the faster you use it up (i.e. higher speed) the more is lost to wind resistance (doubling your speed = 4 times as much wind resistance). Basically, going down the hill faster will be a less efficient use of the energy you stored when you pedaled up the hill.

A little but you never get back as much time as you lose going uphill. It's the same as in a headwind/tailwind situation. You spend far more time going slower than you spend going faster, so you don't have enough time to make it up.

To illustrate an example, if you climb up an 8% grade at 4mph for an hour you would go 4 miles. Using the calculator here, if you turned around and went back down that 8% grade and put out the same power you would go 37.2 mph, or 45mph in the drops. At 45mph, that 4 miles would take 5 minutes and 20 seconds. So the 8 miles total would take 1 hour, 5 minutes, and 20 seconds, at an average speed of 7.35mph. If you use the calculator and remove the grade, the same rider could have done the 8 miles in 29 minutes and 49 seconds, or 26 minutes and 31 seconds in the drops.

Good explanation of the energy equation!

The simpler explanation is that you can't really go fast enough to make up for the loss of time that going slowly uphill costs.

Let's say there's a 10 mile run up a mountain. Let's say one travels up at 5 mph for 10 miles (2 hours) and coasts down at 40 mph (0.25 hours) (reasonable numbers for "normal" people on a "good" grade).

That ends up being 20 miles over 2.25 hours. The average speed would be 8.9 mph. If this course was flat, 15mph (in an aerodynamic position) would be fairly easy to do.

If you could increase your downhill speed to 80mph (just like umd), your average speed would be still low: 9.4 mph.

It's very hard to go fast enough (due to aerodynamics and the simple reluctance to go very fast on a bike) to make up the loss of speed going up hill for such a long time. (In my example, it took 8 times as long going up as going down.)

Hills do horrible things to your average speed!

I don't know if it was due to bike weight, components, wheels, gears, etc., but when my wife and I went from hybrids (I would say lighter and less tire than mountain bikes), our speeds were better. So, yes, I think it will make a difference. I like the suggestions you've received to borrow a bike. My wife did that for her first tri and then bought the same bike later.

If you're not strong up (short) hills, bike weight is not going to make a huge difference. I suck just as much on rollers on my mountain bike as I do on my road bike,

Don't worry about it. If you call me a weenie it should make me work harder and that's what I need anyway :-)