Bicycle Mechanics - Cyclometers Have Stupid Average Calculation Formulas!

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08-06-05, 07:47 PM
Do any cyclometers have a feature that cures this problem?:

I ride in New York City. I am often forced to ride at under 5 miles per hour, and it's almost always because I am coming to a red light, weaving between stopped cars, avoiding pedestrians, etc. On a typical 8-mile commute to my office, I can cruise at 22mph for half the ride along a nice bike path -- but the rest of the ride is spent dealing with traffic and pedestrians. As a result, my average speed ends up plummeting to around 14mph. It's so disheartening!

The problem seems to be that the computer keeps ticking the clock as long as it thinks your wheels are spinning at all. But whenever I'm riding at 5 mph, I don't think it even counts as biking. It's bullsh!t time, really. I'm just moving my bike through bullsh!t to get back to the part where I get to really ride again. Why should time spent doing non-biking destroy my average?

Even when I'm exhausted and climbing the biggest hills around here, I never go below, say, 8 mph. I wish my computer could be smart enough to know that any time spent biking at speeds under around 5 mph should NOT be counted towards calculating my average speed.

So the TOTAL DISTANCE reading should be calculated constantly, no matter how fast I'm riding.
But the AVERAGE should be calculated based on a TIME and an ALTERNATIVE DISTANCE reading that only accumulate when I'm in excess of a minimum speed that I think fairly represents the speed below which I am not "really" biking.

Are there any computers smart enough to do this?

TommyMcG
08-06-05, 08:10 PM
Yes, such a computer is the human mind. Your commute speed is being accurately calculated but you are not happy with the results. Set your target on breaking your previous record and adjust your expectations given the situation with traffic. Look at your average speed on courses not in traffic and calibrate your effort on those courses with your commute and develop a correlation which you can use to "correct" your commute time. We all would look better if all the worse scores could be thrown out. :)

08-06-05, 08:47 PM
You make it sound like I'm trying to cheat. I'm not -- think about the math. If the CLOCK and the ODOMETER are stopped when I'm under 5 mph, it doesn't raise the average speed for the time I'm actually riding over 5mph.

Maybe you don't bike in city traffic a lot, but it's really nothing like cycling along an open road. In addition to my commute, I also go on long rambling rides through the city, along unfamiliar routes, that look something like this:
-- 10 minutes at 20mph along a path
-- 10 minutes at 5mph in deadly stop-and-go traffic
-- 5 minutes at 20mph along a path
-- 1 minute at 2 mph along that same path, avoiding 20 families who have chosen that section of path to have a mass picnic.
-- 5 minutes at 15mph along a street with a bike lane
-- etc.

For rural riders, a few minutes out of an hour spent slowing down or speeding up from a stop light wont affect their average. But for a city biker, a good quarter of the total time on the bike is spent in such situations.

I am perfectly aware that the standard calculation is "accurate" for what it's measuring. It's simply dividing distance by time. It's smart enough to stop the clock when the bike is stopped, which allows cyclists to come to an occasional complete stop without wrecking their average speed. All I'm asking for is recognition that city cyclists spend a lot of time not technically at a complete stop, but moving so slowly that they're not really biking at all.

I alread do the mental calculations you suggest but I don't like it because it doesn't tell me how fast I'm actually cruising (a) compared to other days when I'm on the open road or (b) compared to other cyclists. I want my average speed to tell me how fast I go when I am actually trying to keep up a high speed. I want to know my average so I can know how good I am as a cyclist. Your advice kind of defeats the point of having a cyclometer in the first place, as if knowing one's cruising average wasn't useful information. Which is a perfectly valid philosophy but it's not really for me.

desmobob
08-06-05, 08:56 PM
You make it sound like I'm trying to cheat. I'm not --

I thought he hit the nail on the head, actually.

You could move into the country, but then you might have to find a cyclocomputer that would not count the time you spent waiting for cows to cross the road, time spent stuck behind hay wagons, etc.

;)

Good riding,
desmobob

chroot
08-06-05, 09:09 PM
If it's a wired computer, just pull it out of its mount and put it in your pocket when you're in the city. It'll definitely stop recording.

If it's wireless, it should have an "off" button. Use it, perhaps? My computer (Polar CS200) has a pause feature as well as an off button.

- Warren

shoerhino
08-06-05, 09:38 PM
Put a toggle switch between the computer and the speed sensor. Should allow you to turn the computer off and on easily. The next question is where to mount the toggle switch...

Tim

robo
08-06-05, 11:10 PM
My old old Specialized SpeedZone computer lets you start and stop it..

Moose
08-07-05, 09:26 AM
Even if on your 8 mile commute you rode 22mph for 4 miles and were slowed to a crawl of 5mph for the entire remainder of 4 miles your average should still be just over 16mph.

sestivers
08-07-05, 10:16 AM
Ride like the car drivers. Full throttle when the light turns green, full brakes right before the stop line at the red light.

AndrewP
08-07-05, 11:52 AM
Even if on your 8 mile commute you rode 22mph for 4 miles and were slowed to a crawl of 5mph for the entire remainder of 4 miles your average should still be just over 16mph.
That is 11 minutes for the first 4 miles and 58 minutes for the 2nd 4 miles, 59 minutes total average 8 mph. You want to know how well you are cycling - look at your average for the commute, cruising speed is not that important you need to improve your acceleration from the stops, which will be reflected in your overall average.

dobber
08-07-05, 11:54 AM
Two plus two will always equal four.

toomyus
08-07-05, 02:52 PM
the way i see it , you have two options to fix your problem. one is to disconnect the speedo head unit when ur in traffic and reconnect it as u get back to speed. the other way is put your speedo on manual mode ,not automatic, therefore you can tell your speedo when to record your average time and when to not record it. thats about all you can do to actually show your a strong cycler. good luck

kritter
08-07-05, 03:39 PM
How about you take your total mileage and the hours it takes to get to work and divide them...oh wait thats what your computer does!

If computers didnt work under 5mph...45 minutes of my climb wouldnt be recorded!

08-07-05, 06:26 PM
Even if on your 8 mile commute you rode 22mph for 4 miles and were slowed to a crawl of 5mph for the entire remainder of 4 miles your average should still be just over 16mph.

Your math, I think, is wrong. You're averaging 22 and 5 to get 16, which is not how an average is calculated. An average is just time/distance.

So, to use your representative example: 4 miles at 22mph is 11 minutes. 4 miles at 5 mph is 48 minutes. Total is 59 minutes, just about an hour. So my average would be, in fact, 8 mph.

slvoid
08-07-05, 06:33 PM
Ride like the car drivers. Full throttle when the light turns green, full brakes right before the stop line at the red light.

Uh... I burned through \$50 worth of disc brake pads in 3 months commuting doing this. :p
Now I just mash it, coast, and slow gently, like a sane person.

zonatandem
08-07-05, 06:37 PM
Just ride, watch traffic and ignore the 'puter!

F1_Fan
08-07-05, 06:39 PM
Who worries about average speed in traffic anyway?

08-07-05, 06:39 PM
If computers didnt work under 5mph...45 minutes of my climb wouldnt be recorded!
Maybe you're in mountain country, but the hills around here (NY/NJ) aren't so bad. I never go that slow on open roads on my bike (that's the whole reason I think a threshhold is fair). My gearing wouldn't even permit going 5mph on an uphill without me tipping over!

But you raise a good point: How slow is slow? This is why my imaginary feature would be customizeable. Let's say you set it as low as 2mph. Does anyone actually bike at 2mph? 2 mph is practically a track stance! If a bike is moving at 2mph, you can pretty much bet the cyclist is walking the bike.

So, to go back to the math, here's an extreme example. Lets say I bike 10 miles at 20mph (30 minutes), then walk my bike for 10 minutes at 2 mph (.3 miles). You know what the resulting average is? 40min/10.3miles = 3.8 mph.

My old old Specialized SpeedZone computer lets you start and stop it..
I'd be doing this every 5 minutes here in NY. And anyway, the problem with this approach is that my "real" odometer, which tells me how far travel distances are (but would not, ideally, be used to calculate my alternate average speed), would not operate. I'd get an accurate average, but an inaccurate distance.

Ride like the car drivers. Full throttle when the light turns green, full brakes right before the stop line at the red light.
Ha, beleive it or not I try this. But, again, a lot of the ride is in busy but moving traffic or in pedestrian-crowded parts of bike paths, where I'm moving but not really cycling.

jswilson64
08-07-05, 06:45 PM
So, go buy a BASIC stamp computer, some wheel sensors, and make one that works the way you want.

Oops, sorry, that's the answer you would have got had you posted your query in any number of tech forums. Maybe I'm just being cranky, but what, exatly, do you want anyone here to do about it?

Maybe you should use a GPS - my Garmin Etrex Legend is "smart" enough to stop the average-speed clock when it's not moving...

08-07-05, 06:51 PM
what, exatly, do you want anyone here to do about it?

I guess I'm hoping that someone knows of an actual cyclometer that has this feature instead of telling me that I'm cheating or something. Or maybe I'm hoping a cyclometer manufacturer is reading this board! :-)

Anyway, thanks folks!

shoerhino
08-07-05, 07:23 PM
Cateye Astrale 8 has a manual stop and start. It runs about \$35.

va_cyclist
08-07-05, 07:32 PM
Or how about this -- turn on the computer when you're going downhill, and off when you're going uphill. That will really improve your average speed.

womble
08-08-05, 03:38 AM
My admittedly casual understanding of how a cycle computer worked was that it divided total distance by time travelled.

Time travelled is calculated by the sensor noticing the wheel-mounted magnet go past it. Once the wheel stops, the computer will stop counting time within six seconds of stopping.

So I guess you want a computer that defines "stopped" as < 5mph. Sounds a bit egotistical to me :D

Who cares what average speeds are during a commute anyway? Total time is the important thing. Average speed is only useful when you can do long, uninterrupted rides.

lisitsa
08-08-05, 05:46 AM
Or you could get a Cateye Velo1 entry speedo, which doesn't have an average function but has all the other useful features expect cadence. (only costs 20 bucks). I went back to this speedo because of exactly the same problem you have, and I also like the one-line display, which mean I don't have to look at my speed when I'm really tired chugging along at 8mph, so as to not get disheartened.

sestivers
08-08-05, 09:35 AM
You could also wear a stopwatch. When your speed drops below 5 mph, start the watch. When the bike stops or goes back above 5 mph, stop the watch. At the end of your ride, subtract your stopwatch time from the cyclometer's computed time and do the calculation yourself. You'll get some free distance, but probably not more than a half mile or so.

I would forget to start/stop my stopwatch at least several times on a ride like that though. 8 miles is too short a distance to get an accurate representation of your real average speed no matter how you do it anyway.

noisebeam
08-08-05, 04:38 PM
The problem is you are comparing your 14mph to others, not yourself on your same commute. If you ride the same exact route, keep track of the Av time and you will note a trend. The traffic conditions will average out over a few months. You will also learn how to get better times by riding up fast to stops, stopping fully, then accerating hard up to speed again when its time to go. This builds strength. If you get behind slow moving traffic, just keep with the flow, typically these places happen in the same spot if you commute on a regular schedule and they will average out, so your trend over several weeks will show improvement.

Again, don't worry about the absolute number, 14mph may sound slow, but in fact it may be fast for that route. Finally keep in mind those slow sections to allow you to recover so you can go faster for the fast parts, so not counting them is really not right.

Al

kritter
08-08-05, 09:11 PM
But you raise a good point: How slow is slow? This is why my imaginary feature would be customizeable. Let's say you set it as low as 2mph. Does anyone actually bike at 2mph? 2 mph is practically a track stance! If a bike is moving at 2mph, you can pretty much bet the cyclist is walking the bike.

My computer stops recording speed at 2.4 but I believe the timer keeps going but im not positive...if im chugging at 2.4 mph im usually pretty close to heat stroke or heart attack and my timer is the least of my worries...and yes joggers and walkers pass me...much easier to walk or jog the stuff then to ride it!

I can keep my balance as long as the wheels are turning no matter how slow im going as long as im going.

same time
08-09-05, 11:11 AM

Get rid of the computer! Your bike works just fine without it.

Avg Speed is the reason why I got rid of mine years ago. I was always looking at the number and trying to keep my speed up. If I got home and my avg speed was lower than last time, I felt like I hadn't improved. Then I started worrying about the stuff you're talking about - time spent at stoplights, traffic, pedestrians... I started turning the computer off and back on again whenever I stopped for a stoplight. It was an old Cateye with the buttons right next to each other, and sometimes I would accidently press both buttons together and reset all information. Arrgh! I would be angry.

Then one day I took the computer off and loved it. What the heck do you need the info for anyway? Who cares how fast you're going? Go the right speed to stay safe in traffic, look around at all the pretty people, have fun riding your bike.

DieselDan
08-09-05, 11:32 AM
Just Get Over It!!!!!!!!!!!!!!!!!!

stevetone
08-14-05, 02:30 PM
Why would anyone care what their average speed is on a measly 8 mile ride? That's not even far enough for a decent warm-up...

Phantoj
08-15-05, 11:58 AM
One of my friends works for Garmin and has a Garmin Forerunner 301 GPS speedometer/HRM. He says, "It has an autopause function that can be programmed to stop the stopwatch any time the speed falls below a user settable threshold. I have it set to 3 mph."

So there you go. I think they are over \$300, but pretty cool. (GPS=REALLY wireless!)