Why are average speed readings so different on group rides?
 

Did a group ride today. We pull into to our rest stop and I hear people sharing their average speeds, as we seemed to be pushing it quicker than usual, so folks got curious. One says 18.2, another 18.6, another 19.1.

Are these devices that keep track of such stuff that erratic, or can little things make for legit differences in speeds in a group ride? There was occasional surging, but we basically stayed together.

Not that it matters any, but I've experienced this a few times. Just wondered what's up with that. Folks say speed doesn't mean anything, and maybe this is another example of that.

Any of you have autopause on?

Some people start them when they get on the road. Some start when they roll. Some start when they start the ride, some start from the car, others not till leaving parking lot etc.

I assumed that everybody is working w/ a device that is measuring average speed when not stopped. But could be wrong.

Yeah, that happens. Wouldn't think that would cause that much difference on a longer ride (30-50 miles). But maybe so.

It is likely they are not all calibrated precisely.

Also, if a group takes a few hills and Joe gets to the top first and Jeff arrived 30 seconds later several hills per ride.....it adds up.

On our hammer ride recently I got about 21.5, a few dropped riders in the second group got just under 20.

Nature of the beast.

You can start wars over how a computer pauses or how a person records their power averages.

Different starting points, strava doping, setting gps to not record when speed drops below 10 mph, etc

Average speed is a fool’s metric.

Or maybe the only relevant one. Given I often have to be home at a certain time, how would I know what routes I can ride without some idea of my average speed?

Some devices measure differently. Some folks have a Cateye, others a Garmin, a Wahoo, some folks have AutoPause set to below 6mph, others to When Stopped, some folks using speed sensors, etc.....

I've seen some AA going full tilt to a red light and then stopping rather than coasting. They don't want their average speed to drop.

I've seen others have Auto Pause set to 10mph, I have mine set to 3mph so it doesn't include if i'm walking the bike.

Finally i've sen the wrong tire size set.

Garmins report average speed as distance divided by time. They also have a metric called average moving speed which is what you describe. Maybe Wahoo and whoever else only reports moving speed? That would explain some discrepancy.

Auto pause stops the clock when the device realizes you're stopped and starts again when it detects motion. It uses GPS to do this so there's some lag. To the point, if you go from zero to cruising speed and it takes a few seconds to resume, it's going to miss the part where you were going slowly getting back up to speed.

I find Strava's real-time average speed is usually abysmally slow. Of course, that could be me. :P

But, I think it may have to do with starting Strava, then taking a few minutes to actually get on the road. Then a few stops.

It may fix it somewhat with post-processing.

Did anyone already have miles logged that included their ride from home to the start point?

It was a ride of about 17-18 riders, and a few did start elsewhere. I don't know if those were among the ones that reported their times.

The autopause and stops as mentioned already, but also I've seen GPS acting more flakey on some devices than on others. Making a jagged path, which results in a longer distance travelled than someone with a smooth GPS track, resulting in a higher "average speed".

On a similar note, I regularly ride with about five guys that all have garmins and not one of us is ever reading the same temperature.

I guess I'm just lucky because I don't care what someone else's average is.

Fact: In a race, the rider with the highest avg mph speed wins.

I have a Garmin watch. There's frost on all the cars outside and it says 90F. :p

We had a guy with a 10mph autopause setup in our group once. He was slow enough up a few hills he’d lose about 1/2 mile distance per ride recording versus the group. “Hey dude? You’re short a mile.”

There are a few factors, even for identical courses: speed sensors, differences in how often GPS data is collected, as well as riding techniques like whether or not one makes abrupt stops.

Red lights are generally gonna kill average speed, so anyone who starts recording in town (or rides through town to get to the ride) is going to have a lower average speed, and IME, coasting to a light to avoid unclipping kills it even more. Check some local Strava weekly leaderboards: guys and gals with the highest average speeds are driving somewhere and letting it rip, but not doing any commuting or around-town riding.

Not a fact.

I would lose just about every climb I do around here.

Frequently on group rides we end up with several different elevation totals on Strava. We've generally attributed the difference to Garmin vs phone app etc. but it is confusing to go up and down the same hills and find a several hundred foot difference.