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Average Speed(26 posts)

Average SpeedBigFatSal
Sep 29, 2003 11:00 AM
So, my brain doesn't work so great on Mondays, but does a bike computer calculate "Average Speed" based on time or based on distance? Or does this speed/distance/time thing all somehow magically work together???

Actually, never was very good at those word problems in math class.... ;>)
math is hardmohair_chair
Sep 29, 2003 11:06 AM
average speed = distance over time.

10 mph = 10 miles / 1 hour
20 mph = 10 miles / 30 minutes (1/2 hour)
40 mph = 10 miles / 15 minutes (1/4 hour)
60 mph = 10 miles / 10 minutes (1/6 hour)
Mine work both waysCory
Sep 29, 2003 11:30 AM
I'm not sure I understand the question--it just calculates the average speed, the distance traveled over however long you ride, and expresses it in miles or kilometers per hour.
My newer computers figure average over the time I'm actually riding--they stop if I lean the bike against the wall and go in for a cappuccino. I have one older one, though, that has a running clock--it computes the average from the time I start until the time I finish, unless I remember to pause it when I stop. If I ride the new one to work, I average about 18mph. With the old one, my average drops to 11 or 12....
Moving averageXeo
Sep 29, 2003 12:02 PM
In other words the computer computes a moving average and a total average. The total average incorporates time off of the bike while the moving average does not.

My friend has a Garmin Etrex vista that does this also. It can tell you average speed, while moving only and tell you overall average including pit stops.
What's the best computer for moving averageKristin
Sep 29, 2003 12:15 PM
I have a Cateye Enduro II. It only computes moving average, but it calculates in such a way that rolling stops really kill my overall average. Are there computers that do this better than others??? I'd like a computer would increase my average by at least .5MPH. Better yet, I'd like a computer that would only calculate speeds above 10 MPH. :-P
Or mabey I should just get a second magnet. nmKristin
Sep 29, 2003 12:15 PM
If you put on three magnets, you too can do a 3mile TTMR_GRUMPY
Sep 29, 2003 12:39 PM
Just change your circumference calibration to 4000mm (nm)Chen2
Sep 29, 2003 12:42 PM
This is a strange conversation!Zman
Sep 29, 2003 2:04 PM
You are either keeping track of time and distance or not! Pretty simple.

The computer will only do what it is designed to do, track wheel movement. I do not see a point in eliminating time, time is what it took.

I have a Flight Deck and can track time 2 ways, Elapsed Time (ET, like in a time trial situation) or riding time. The riding time gives the most effective time if you take breaks or hit stop lights and things like that. But the ET is what real racing is all about and if you have a set route you should consider this option. The VAST majority of people use the riding time option.

What you could do if stopping is a issue and greatly reduces your average speed (duh!) you can use a factor. Un-needed stops reduce momentum, you can actually give this "lost time" a value. If you use a computer program you could then deduct this value from the actual value to give a "effective average speed". If "rolling" stops are killing you then I have some advice, STOP! If you can do a track stand then do one, but make sure that your magnet is on the opposite end of the receiver.

I once went on a 80+ mile ride with my buddies that included a gazillion stop lights. At the end of the ride I found that I was the slowest of my group in average speed. How can this be? This is how: My buddies would stop at the lights while I screwed around. My little movements would add many minutes over the course of 80 miles. Hey, when bragging rights are on the line you need to do what you need to do. I finally stopped and my average went up. I also can anticipate a light better from a dead stop and I start out faster.

That would be my advice, whatever I said!

And your are correct Kristin regarding target zones for weight loss.

Z
The Formula (known only to select physics and math PHDs)terry b
Sep 29, 2003 12:02 PM
(miles ridden/minutes spent riding) * 60
The Formula (known only to select physics and math PHDs)BigFatSal
Sep 29, 2003 12:43 PM
This looks like the same basic formula that Mohair also advised. And it seems so obvious when you put it in such basic form.

Funny how the mind can overcomplicate something so simple! Thanks, this was much easier than I convoluted it to be..... (well don't I feel like a dumbass!)
you see, I hate math tooterry b
Sep 29, 2003 1:24 PM
this one, for being so painfully simple eluded me for a long time too. ask me to do a full factorial experiment with the associated T or F tests - no problem. the simple stuff - ouch.

my favorite puzzler is why does the Moon always show only one side to the Earth? I mean, it is rotating after all.
It's called "Tidal Lock" and the Earth-Moon is in a 1:1 ratiorussw19
Sep 29, 2003 7:24 PM
Some of the planets have really cool tidal lock characteristics. For example, Mercury is in a 3:2 lock with the Sun. That means that a day on Mercury is actually longer than a year on Mercury. For every 3 revolutions around the Sun, it only rotates twice on its axis. In other words, on Mercury, 3 years is 2 days. This was quite a shock to astronomers when they found this out. For hundreds of years it was thought to be in a 1:1 ratio, but due to Mercury's very elliptical orbit, the speed of revolution around the sun at perihelion is much faster than the average orbital motion.

On the other hand, the Earth and the Moon are locked into a 1:1 tidal lock. That means that the Moon rotates once in its orbit in the same period that the Earth rotates on its axis. So as the Moon goes around the Earth, we only see one face of it.

Another example is Io, one of Jupiter's moons is also in a 1:1 Tidal Lock with Jupiter. And Venus is almost in a tidal lock with the Sun, but it is still a few hundred thousand years off of it being a perfect 1:1 ratio. As the rotational motion continues to slow down due to slight amounts of friction in the space around it, it will eventually lock with the Sun.

Russ
Wait, I always thought it was:TimA
Sep 29, 2003 1:22 PM
((miles ridden/minutes spent riding) * 60) + 5. I mean if it wasn't for those stop lights, dogs, roller bladers etc., I would have easily averaged 5 mph more.
only in the Internet Forum World ;-) (nm)terry b
Sep 29, 2003 1:24 PM
Check your computer's calculations!MisJG
Sep 29, 2003 12:16 PM
Weird thing happened when I checked the calculation of average speed that my computer reported. It was wrong! It was faster by about one mile per hour! I keep meaning to bring in the actual numbers to post here, but I keep forgetting to do it. Anyway, I did a ride that was broken into two parts (my commute to work and home). I recoreded what the computer said was my average speed for each segment. Then I added the distances and times together to get an average for the complete ride and the average (by math) was outside the average range of the two rides!
i.e.
Ride to work avg s = 17.5 mph
Ride home avg s = 18.0 mph

Logically, since the distance is roughly the same as it's just a to and from work route, the average for the two segments added together should fall somewhere between the two averages (between 17.5 and 18.0 mph). It did not. So out of curiosity, I checked the computer average speed calculations for each segment and found them to be wrong!

The only thing I could think of was that maybe the computer didn't count the whole ride in it's avg speed calculations and only counted, say, the last ten minutes worth of riding. That would account for the differences (and probably a cheaper computer to manufacture) but this is only my conspiracy theory. Can anyone add to that?
Check your computer's calculations!KEN2
Sep 29, 2003 1:12 PM
On my Avocet, even though below a certain threshold (around 2.5 mph) the computer shows zero as mph, the automatic timer continues until the wheel comes to a stop. If you do a lot of start and stop on your commute, it's likely that this accounts for a lower overall average, i.e. it's averaging in zero mph for a few seconds, which add up.
That's what I was talking about in my postKristin
Sep 29, 2003 1:23 PM
Annoying as all get out when you have to stop alot. I had taken to last-minute, panic breaking at intersections, but I was scaring drivers, so I had to give it up.
re: That's what I was talking about in my postloki_1
Sep 30, 2003 6:41 AM
"but I was scaring drivers, so I had to give it up"

Now that is funny.
Magnet too far from sensor??Kristin
Sep 29, 2003 1:19 PM
I've gotten weird numbers after I replaced my fork and my magnet and sensor weren't lined up perfectly. Mine's pretty picky and needs to come within 3 mm of my sensor or it won't register every rotation. It was picking up only about 3 out of 4 of the passes. I was really getting depressed about my speed until I saw my average go from 15MPH to 0 while I was still moving forward. Then I realized that my sensor is ultra-picky.
Supergo WirelessXeo
Sep 29, 2003 2:16 PM
Kristin,

I bought a generic supergo cordless computer for about 35 bucks and it works great. There is a little animation of a bicycle with the wheels turning when it is recording and it stops when you are off the bike or come to a complete stop. It also features a plus or minues sign next to the bike indicating whether or not your average speed is increasing or decreasing (nice motivation factor). It only records moving average and I'm pleased with the performance.

Of course average is slightly lower due to frequent intersections and stop signs but you can never completely get rid of that factor.

~Marc
Magnet too far from sensor??Ironbutt
Sep 30, 2003 3:13 AM
Kristin, Check the manual for your computer. If my memory serves me correctly, Cateye computers have either a manual or an automatic start feature. Set up the computer for manual start. That way, as you slow for an intersection or a traffic signal, you can just touch the start/stop button to stop the computer recording and touch it again when you are back up to speed. This will definitely raise your average speed!
Nice. A cheat. I like it!Kristin
Sep 30, 2003 4:13 AM
Manual? You mean those blue print schematics in 6pt that came with the computer?? :)
Well, basically it takes the elapsed miles and elapsed time ...Humma Hah
Sep 29, 2003 12:44 PM
... so it is based on both.

More or less, anyway. My Cat Eye will report rolling time since last reset, and miles since last reset. If you divide miles by the time in hours, you always get a slightly higher average, by about a tenth, than what the computer reports. Go figure!

Most computers have some setup options. I assume you are using an automatic start/stop function (most of us do). In this case, the timing only runs when the bike is moving. This makes our average speeds look better than if we admit we can't pass a convenience store without stopping for a snack.

Measuring distance is pretty straightforward, except you may lose a couple of revolutions waking up the computer before it starts to record.

Elapsed rolling time is a little funky. The computer may not start timing for two wheel revolutions after the wheel starts turning, and will keep running for something like 3 seconds after we stop. If you do a lot of very slow riding, or start and stop a lot, this can throw off elapsed time a little.
bragging rights formulatarwheel
Sep 30, 2003 5:12 AM
The formula that many cyclists use when discussing average speeds, particularly on internet formulas, is simple: What was your speed when tooling along on the flats? If your computer showed 25 mph while riding on the flats in a paceline, than that's what your average was for the ride. That explains why so many guys claim to average 25 mph on rides.
Ah HA !!! I knew it (nm)litespeedchick
Sep 30, 2003 7:22 AM