I've seen these terms thrown about in this forum, but I'm not sure I actually understand the difference between them. The time average speed sounds pretty straightforward to me: distance traveled / time elapsed. So how does "moving average" differentiate from the former? Is it more like the average cruising speed over a given distance?

"moving average" means that if you stop for 10 mintes, you don't count that as part of the time.

^ Which, by the way, is what most bike computers (the ones w/o GPS) report.

My computer counts what I believe is the time average, that is for the time it's awake (it sleeps after 5 minutes), it does distance/time, so that takes into account slowing down before a stop, waiting at a light etc. A lot of people here will post typical cruising speed as their average and it's a very different number and assumes they're going on a perfectly flat road with no headwind (and then they add 10-20% for good measure).

Ahh, got it. Thanks. That's what my cateye reports, too. But it doesn't really reflect what speed I cruise at. I could be cruising at 19-20, or even 22 mph for most of the ride, but slowly rolling through rest stops or intersections beats the computer-reported number down to ~17 mph... it's kind of annoying.

right, in this case, you should present your average speed on BF as 25mph.

Hahaha. True that.

On one of my longer runs there's an inevitable two minute traffic light which just kills my running averages, so I set my Garmin to automatically detect when I'm stopped.

Yeah, those starts and stops are bad for your average speed, if you care about it. So are hills.

Correct, but it's a complicated web, like if you change one number in Excel, a bunch of formulas might get recalculated. Since your BF average speed is 25 mph, it means you had a couple sprints at 32 mph when you were only going up a slight hill.

My computer does time average. That is, if I want to try to figure out how fast I went, I look at what time I left, what time I returned and figure the elapsed time, then I go to Google Maps and plot out my route, and divide the number of miles I rode by how long I was out riding.

True average speed as recorded by a bike computer has at least one useful feature. How long is it going to take you to get somewhere.

One of my friends wanted to get an electric bike and make the ferry in a certain amount of time. He thought that a ten mle ride would be done in half an hour if he rides that bike at 20 mph. He had to leave at a specific time no matter what. He was ready to go and buy the bike, but I explained to him that (I ride this route all the time and know about all the intersections and slow areas, I measured this at least a thousand times over 18 years) That he would have to travel well over 25 to get an average of 20. Probably more like 27-28. There are two traffic light controlled intersections that he must stop at etc.
At least I saved him from buying an electric bike.


Unfortunatly he still uses the car.

Average speed lets me meet people in various places and distances at the right time on my bike. If I am late I can put the bike computer on average speed display, and see how much I need to work to get there on time.

+1, though you forgot to mention the headwind and the chest cold you're getting over

Fixed that for ya ... I don't think you can give your computer credit for manual calculations you preform, especially when you actively researched the data you need to feed into them.

I think he meant his desktop computer

So that's how it works around here? Even if I'm trudging along at "only" 19-20 mph, I'm to report 25 mph average speed on BF?

Maybe I should look into racing then...

Yeah, probably. But I still say it's Doohickie doing most of the work, and then handing the credit over to the computer.

*I* am my own bike computer. pallen has seen my bikes; he can verify I ride nekkid, computer-wise.