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Old 08-06-05, 06:47 PM   #1
askrom
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Cyclometers Have Stupid Average Calculation Formulas!

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?
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Old 08-06-05, 07:10 PM   #2
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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.
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Old 08-06-05, 07:47 PM   #3
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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.
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Old 08-06-05, 07:56 PM   #4
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Quote:
Originally Posted by askrom
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
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Old 08-06-05, 08:09 PM   #5
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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
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Old 08-06-05, 08:38 PM   #6
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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
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Old 08-06-05, 10:10 PM   #7
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My old old Specialized SpeedZone computer lets you start and stop it..
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Old 08-07-05, 08:26 AM   #8
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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.
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Old 08-07-05, 09:16 AM   #9
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Ride like the car drivers. Full throttle when the light turns green, full brakes right before the stop line at the red light.
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Old 08-07-05, 10:52 AM   #10
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Quote:
Originally Posted by Moose
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.
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Old 08-07-05, 10:54 AM   #11
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Old 08-07-05, 01:52 PM   #12
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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
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Old 08-07-05, 02:39 PM   #13
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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!
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Old 08-07-05, 05:26 PM   #14
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Quote:
Originally Posted by Moose
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.
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Old 08-07-05, 05:33 PM   #15
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Quote:
Originally Posted by sestivers
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.
Now I just mash it, coast, and slow gently, like a sane person.
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Old 08-07-05, 05:37 PM   #16
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Just ride, watch traffic and ignore the 'puter!
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Old 08-07-05, 05:39 PM   #17
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Who worries about average speed in traffic anyway?
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Old 08-07-05, 05:39 PM   #18
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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.


Quote:
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.


Quote:
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.

Last edited by askrom; 08-07-05 at 05:49 PM.
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Old 08-07-05, 05:45 PM   #19
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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...
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Old 08-07-05, 05:51 PM   #20
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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!
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Old 08-07-05, 06:23 PM   #21
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Cateye Astrale 8 has a manual stop and start. It runs about $35.
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Old 08-07-05, 06:32 PM   #22
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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.
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Old 08-08-05, 02:38 AM   #23
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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

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.
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Old 08-08-05, 04:46 AM   #24
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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.
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Old 08-08-05, 08:35 AM   #25
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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.
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