Whether you use moving average speed or total average speed, the result is always 41.

Average speed is a better indication of road/traffic/weather conditions than physical condition. For a round trip, my fastest days are those with zero wind & I make all of the lights. So they aren't an indication of riding stronger, just getting lucky. I ignore avg speed and focus on HR & power.

im talking about all the Strava Wars that go on here. i.e. - some random guy did 20mph hour on a 30 mile ride and I did 21mph on a 30 mile ride, so regardless of any other fact, I must be faster. If it is the same exact race, sure, it's a useful comparison.

What do you mean that "most average speed is calculated over time rather than distance"? Average Speed = Total Distance / Total Time. The debate here is how to calculate total time; is it the ride time including stops or the moving time only?

In your example, the rider travels 10 miles at 10mph (60 minutes) and another 10 at 20mph (30 min)... this means the rider traveled a total distance of 20 miles / 1.5 Hours for an average speed of ~13.34 mph. I would be surprised if there were a bike computer to calculate this as 15 mph average speed. I think the "simple logic" applied above is simply false logic but that may be what you are trying to convey here.

I thought that his phrasing was hard to follow, but:

over time: riding for 1 hour at 10 mph and 1 hour at 20 mph, the average speed would be 15 mph
vs
over distance: riding for 10 mlles etc and another 10 miles etc as you described would be 13.3 mph.


Since none of the ideas about "average speeds" are useful for comparisons, I just take whatever Strava says and don't worry about it further.

OP, see what you've done. You mentioned the word average and the word speed in the same post.

Savvy members of the 41 know this just isn't done.

If you did 1 hour at 10 and one hour at 20, you did 30 miles / 2 hours for an average speed of 15mph. This is not the same as the previous example. I cannot tell if this "average speed over time" is actually something the people calculate or if people are just confused about how average speed is calculated.

I assert that average speed is a very specific thing: average speed = total distance / total time.

This "average speed over time" seems to be a weighted average of the speeds weighted by the percentage of total ride time you spend riding at that speed, which is very different than average speed.

Most cycle computers stop when the wheel with the magnet stops. Thus the average speed they display does not count time stopped. With my Garmin Edge 800, I could adjust the "stopped" speed. I think the factory setting was 2 mph. I have mine set to "stopped." So that's what most folks are talking about when they talk about average speed on a ride: distance/moving time. I find average moving time to be a valuable metric for fitness as long as one considers the route and conditions. If you ride a route at 16 and another person rides it at 18, chances are pretty good that they're a faster rider than you. Much faster.

However, there are also brevets, randonneuring rides, which only count elapsed time: time from the official ride start (whether you started then or not) to the time when you come in and finally get your card time-stamped. Rider finishing times are listed alphabetically, however the time shown is elapsed time rather than moving time. Thus it's more of a contest with no BSing to be done. Be that as it may, it is possible to ride faster and take shorter breaks than another rider and still finish with a greater elapsed time simply by not running lights or hitting more red lights or getting a flat or whatever. Thus randonneurs stress that brevets are not races. If you're into increasing your average speed over long distances, meaning distance/elapsed time, then riding brevets is a great way to learn to do that. It can be great fun, also great pain, so it's all good.

The two situations are different, that's the point. Each calculation is correct and equivalently calculated: total distance over time. By "average over time" he means consider riding a certain time at each speed. By "average over distance" he means consider riding a certain distance at each speed. The variable values are different, so the answers are different, but the calculation is the same. There is no "weighted average" involved. 15 is what I told you, and you confirmed it, with the normal delta s/delta t arithmetic.

His point was speculating that people sometimes think of "over time" when the real situation is "over distance" and that's where they make the mistake.

So what about average cadence? Does the typical bike computer factor in 0 for any time that you spend coasting?

On the computers I've used, the crank magnet behavior is the same as the wheel magnet behavior: no tick, no record. However if you're coasting with the cranks horizontal and you're holding the crank magnet right over the sensor, you'll get silly readings.

15 is what you told me and I confirmed, however when you restated the example, you changed it from riding 20mph for 30 min to riding 20mph for one hour which changed the average speed from 13.34 to 15.

My point is that riding 10mph for 10 miles, followed by 20mph for 10 miles IS NOT an average speed of 15mph. In this example, the average speed is always 20 miles / 1.5 hours = 13.34 mph. You can arrive at that number multiple ways but the average speed is always 13.34 mph.

*** I brought up the weighted average, because the comment that I am addressing stated that somehow simple logic leads us to an average speed of 15mph. I can only assume he arrived at this number because .5 of the ride distance was at 10mph, and .5 was at 20mph... .5 * 10mph + .5 * 20mph = 15. This is not how average speed is calculated and leads you to the wrong number.

What confuses me is this concept of average speed over time and average speed over distance. Both time and distance are factored into average speed already.

Post edit: Ultimately I see what you are saying now that he was using the 15mph as an example of how average speed is often miscalculated. As for your strava calculation, if I am not mistaken, Strava stops the timer when you are not moving so it calculates average speed based on ride time rather than total time.

I gave you two different examples, to show you what the other guy meant.

If there are further questions, I'll let him speak for himself about it.

No way, dude.

Garmins are configurable. Usually people set them to include zeroes for power (you get fresher as you rest, and a weighted average with them is a more accurate representation of your fitness than without the pauses) and exclude for cadence.

Average Speed = Distance * Donuts Eaten

Donuts are good.

But I still say we should standardize on Googles. That is, how long Google Maps expects over how long it takes us. Say, Google says my commute is 42 minutes and I do it in 24, my average speed would be 1.75 Googles.

I'm highly disappointed by Google's calculation of cycling trip time. It quotes down at like 12mph with no regard to traffic or climbs etc. They need to raise the bar and improve resolution to include minutia in their calculations; else what's the point of Google even providing such a service.

Yes, that was what I was trying to convey, though not as clearly as I intended. The phrase "simple logic" or the word "most" should not have been used. What I meant by "simple logic" was the faulty logic that if I rode half the distance at 10 mph and the other half at 20 mph, that the two distances would have equal weight and the average should be the median of 15 mph. As you pointed out, the correct logic would be that only the total distance and total time are relevant and you rode at 10 mph for 2/3 of the total time thus having a greater effect on the average speed. I didn't expect that any bike computers would use faulty logic to come up with 15 mph in the example, but it would be easy for someone to use the "simple" but inaccurate method to come up with 15 mph and then be discouraged when their computer revealed the correct 13.3 mph.

This can be disheartening when you have had a great average speed over a relatively long ride only to have the life sucked out of that average by hitting a steep grade, strong headwind, or a bonk during just a few miles at the end.

With Google who knows, but I have the impression that they do consider elevation changes and lights at least. When I check a local road, North Point Pkwy for example, it's slower uphill than downhill.

I'd like to see them take into account traffic, like they do with driving time, and also weather. And then scale it to the individual. They have the data - Google has a better idea of where I've been, and how long it took, than I do.