How much accuracy do you demand from your bike computer?
#1
Senior Member
Thread Starter
Join Date: Jan 2019
Location: Toledo Ohio
Posts: 1,498
Bikes: 1964 Huffy Sportsman, 1972 Fuji Newest, 1973 Schwinn Super Sport (3), 1982 Trek 412, 1983 Trek 700, 1989 Miyata 1000LT, 1991 Bianchi Boardwalk, plus others
Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 583 Post(s)
Liked 700 Times
in
395 Posts
How much accuracy do you demand from your bike computer?
Not sure if this as been asked before, but how close is close enough for you on your old tech wheel sensor mounted bike computer. I have maybe 4 or 5 mounted, and recently have been playing with a phone gps app and comparing. The bike mounted ones save phone battery life, and are handlebar mounted for easy viewing. I don’t like a mounted phone bracket.
On a new build with 35mm tires, the default tire setting on the computer read about 4% high. I input another wheel circumference and got about 1% low. I think I will shoot for around 1/2% with error to the plus side. Kinda funny, compared to the old axle mounted clicker style Schwinn one I had in the late 70s. I would be curious to know how accurate that was before the little plastic star wheel broke.
On a new build with 35mm tires, the default tire setting on the computer read about 4% high. I input another wheel circumference and got about 1% low. I think I will shoot for around 1/2% with error to the plus side. Kinda funny, compared to the old axle mounted clicker style Schwinn one I had in the late 70s. I would be curious to know how accurate that was before the little plastic star wheel broke.
#2
Señor Member
Join Date: Oct 2004
Location: Hardy, VA
Posts: 17,937
Bikes: Mostly English - predominantly Raleighs
Mentioned: 71 Post(s)
Tagged: 0 Thread(s)
Quoted: 1492 Post(s)
Liked 1,099 Times
in
644 Posts
Not sure if this as been asked before, but how close is close enough for you on your old tech wheel sensor mounted bike computer. I have maybe 4 or 5 mounted, and recently have been playing with a phone gps app and comparing. The bike mounted ones save phone battery life, and are handlebar mounted for easy viewing. I don’t like a mounted phone bracket.
On a new build with 35mm tires, the default tire setting on the computer read about 4% high. I input another wheel circumference and got about 1% low. I think I will shoot for around 1/2% with error to the plus side. Kinda funny, compared to the old axle mounted clicker style Schwinn one I had in the late 70s. I would be curious to know how accurate that was before the little plastic star wheel broke.
On a new build with 35mm tires, the default tire setting on the computer read about 4% high. I input another wheel circumference and got about 1% low. I think I will shoot for around 1/2% with error to the plus side. Kinda funny, compared to the old axle mounted clicker style Schwinn one I had in the late 70s. I would be curious to know how accurate that was before the little plastic star wheel broke.
__________________
In search of what to search for.
In search of what to search for.
Likes For USAZorro:
#3
Full Member
Join Date: Nov 2019
Location: Greater Chicago Area
Posts: 250
Bikes: 1987 Schwinn Mirada, 1989 Trek 420, 1995 GT Timberline, 1979 Schwinn Super Le Tour, Co-Op DRT 1.3
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 103 Post(s)
Liked 85 Times
in
49 Posts
Not sure if this as been asked before, but how close is close enough for you on your old tech wheel sensor mounted bike computer. I have maybe 4 or 5 mounted, and recently have been playing with a phone gps app and comparing. The bike mounted ones save phone battery life, and are handlebar mounted for easy viewing. I don’t like a mounted phone bracket.
On a new build with 35mm tires, the default tire setting on the computer read about 4% high. I input another wheel circumference and got about 1% low. I think I will shoot for around 1/2% with error to the plus side. Kinda funny, compared to the old axle mounted clicker style Schwinn one I had in the late 70s. I would be curious to know how accurate that was before the little plastic star wheel broke.
On a new build with 35mm tires, the default tire setting on the computer read about 4% high. I input another wheel circumference and got about 1% low. I think I will shoot for around 1/2% with error to the plus side. Kinda funny, compared to the old axle mounted clicker style Schwinn one I had in the late 70s. I would be curious to know how accurate that was before the little plastic star wheel broke.
Likes For Miradaman:
#4
Just Pedaling
Join Date: Oct 2021
Location: US West Coast
Posts: 1,020
Bikes: YEP!
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 336 Post(s)
Liked 525 Times
in
351 Posts
Ditto-My phone is now my bike computer but I ran the same route that I used to run using a Garmin GPS and made my adjustments according to that. I get much less fluctuation from the BT sensors and smart phone than I do from my Garmin.
Likes For SpedFast:
#5
Senior Member
Thread Starter
Join Date: Jan 2019
Location: Toledo Ohio
Posts: 1,498
Bikes: 1964 Huffy Sportsman, 1972 Fuji Newest, 1973 Schwinn Super Sport (3), 1982 Trek 412, 1983 Trek 700, 1989 Miyata 1000LT, 1991 Bianchi Boardwalk, plus others
Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 583 Post(s)
Liked 700 Times
in
395 Posts
I think the app opened the can of worms . I understand the gps apps may be less accurate if riding with lots of turns as the gps pings are less accurate at corners. I guess my old method of recording a known distance with a car and setting my computers actually turned out to be pretty close. The apps are kinda cool and useful I think for setting up the computer. 4% on the first attempt was too far off for obsessive compulsive C&V guys though.
#6
SE Wis
Join Date: Apr 2005
Location: Milwaukee, WI
Posts: 10,524
Bikes: '68 Raleigh Sprite, '02 Raleigh C500, '84 Raleigh Gran Prix, '91 Trek 400, 2013 Novara Randonee, 1990 Trek 970
Mentioned: 40 Post(s)
Tagged: 0 Thread(s)
Quoted: 2750 Post(s)
Liked 3,406 Times
in
2,061 Posts
I like to go between section corners on a straight road to check it.
#7
Senior Member
Join Date: Jun 2006
Location: NW Burbs, Chicago
Posts: 12,062
Mentioned: 201 Post(s)
Tagged: 0 Thread(s)
Quoted: 3016 Post(s)
Liked 3,810 Times
in
1,411 Posts
I use the clock on the kitchen wall. If it +/- 10 minutes I can live with it.
#8
Senior Member
Join Date: Apr 2021
Posts: 4,083
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 2333 Post(s)
Liked 2,097 Times
in
1,314 Posts
I demand precision for speed on my bike computer when doing experiments (Crr and CdA). (I use a wheel sensor, not GPS)
#9
Senior Member
I have removed the computer and sensors from my bike. I did that decades ago when I realized I paid more attention to the screen than the scenery, more attention to the numbers than the nuances of my daily ride; caring more about the machine than the man.
Get rid of your computer.
Get rid of your computer.
Likes For Bad Lag:
#10
Senior Member
Join Date: Jul 2013
Location: NJ, USA
Posts: 1,282
Bikes: two blacks, a blue and a white.
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 445 Post(s)
Liked 849 Times
in
411 Posts
Another angle on this is to quantify the error into the real world: I do a 30 mile ride, and a 1% error equals about 1500 feet. Does that matter? Maybe, maybe not. Probably not.
Likes For blacknbluebikes:
#11
Senior Member
Join Date: Dec 2005
Posts: 17,167
Mentioned: 481 Post(s)
Tagged: 0 Thread(s)
Quoted: 3813 Post(s)
Liked 6,727 Times
in
2,617 Posts
Isn’t this C&V?
Likes For nlerner:
#12
Bike Butcher of Portland
Join Date: Jul 2014
Location: Portland, OR
Posts: 11,647
Bikes: It's complicated.
Mentioned: 1300 Post(s)
Tagged: 0 Thread(s)
Quoted: 4685 Post(s)
Liked 5,820 Times
in
2,292 Posts
On roads I haven't ridden on before I like to know where to turn. With cue sheets, accuracy isn't super critical for that use.
If you're wondering how many miles you've ridden, try the approach that @Andy_K and I use. We round up. Say the route is supposed to be 36 miles. With one significant digit, that's 40.
If you're wondering how many miles you've ridden, try the approach that @Andy_K and I use. We round up. Say the route is supposed to be 36 miles. With one significant digit, that's 40.
__________________
If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.
If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.
#13
Senior Member
Join Date: Jul 2007
Location: South shore, L.I., NY
Posts: 6,901
Bikes: Flyxii FR322, Cannondale Topstone, Miyata City Liner, Specialized Chisel, Specialized Epic Evo
Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 3257 Post(s)
Liked 2,098 Times
in
1,188 Posts
Computer just using GPS positioning, functions by dropping "breadcrumbs" as it where, usually about 1 second apart. I think that's the most accurate a Garmin can do. That means on some courses that are really twisty (mt. bike single track) you get a short course. I seem to recall way back when I had a Garmin 810, I did a comparison with a calibrated Cateye wireless old style computer, the Garmin was off maybe 1-2 miles in 100. With speed sensors now pretty common, as well as the new Multi-band GNSS, accuracy is much improved. Begs the question accuracy compared to what ?. Did somebody take one of those measuring wheels on the courses you ride ?, is that what you compare to ?. If I'm a mile in 20 that's good enough.
#14
Senior Member
Join Date: Oct 2012
Location: Berkeley CA
Posts: 2,541
Bikes: 1981 Ron Cooper, 1974 Cinelli Speciale Corsa, 2000 Gary Fisher Sugar 1, 1986 Miyata 710, 1982 Raleigh "International"
Mentioned: 98 Post(s)
Tagged: 0 Thread(s)
Quoted: 934 Post(s)
Liked 1,325 Times
in
492 Posts
On roads I haven't ridden on before I like to know where to turn. With cue sheets, accuracy isn't super critical for that use.
If you're wondering how many miles you've ridden, try the approach that @Andy_K and I use. We round up. Say the route is supposed to be 36 miles. With one significant digit, that's 40.
If you're wondering how many miles you've ridden, try the approach that @Andy_K and I use. We round up. Say the route is supposed to be 36 miles. With one significant digit, that's 40.
#15
aka: Dr. Cannondale
Join Date: Jul 2009
Posts: 7,738
Mentioned: 234 Post(s)
Tagged: 0 Thread(s)
Quoted: 2156 Post(s)
Liked 3,417 Times
in
1,210 Posts
I only use Cateye Strada Wireless cyclometers, and input the actual measured circumference of the wheel. It’s reasonably accurate.
__________________
Hard at work in the Secret Underground Laboratory...
Hard at work in the Secret Underground Laboratory...
#16
Crawlin' up, flyin' down
Join Date: Jan 2006
Location: Democratic Peoples' Republic of Berkeley
Posts: 5,670
Bikes: 1967 Paramount; 1982-ish Ron Cooper; 1978 Eisentraut "A"; two mid-1960s Cinelli Speciale Corsas; and others in various stages of non-rideability.
Mentioned: 40 Post(s)
Tagged: 0 Thread(s)
Quoted: 1033 Post(s)
Liked 2,542 Times
in
1,066 Posts
Whatever my Garmin 130 shows is plenty close enough for me. It's not like I'm setting records out there.
__________________
"I'm in shape -- round is a shape." Andy Rooney
"I'm in shape -- round is a shape." Andy Rooney
#17
It's MY mountain
Join Date: Sep 2006
Location: Mt.Diablo
Posts: 10,002
Bikes: Klein, Merckx, Trek
Mentioned: 70 Post(s)
Tagged: 0 Thread(s)
Quoted: 4340 Post(s)
Liked 2,984 Times
in
1,620 Posts
My first computer was a Push - there were settings for about 3 different wheel sizes I think. Circa 1984... toe clips, exposed cables, and DT friction shifters, and freewheels.
When electronics got better, you could input your tire circumference to the mm... and there were all kinds of arguments about how to get the perfect measurement considering tire size, air pressure, rider weight, etc... everyone wanted the highest accuracy possible, and it was a PITA.
Then when GPS came along, most people said "yeah, +/- 10% is fine".
I have both a Garmin watch and cyclocomputer... I pick whichever one reads higher to post on Strava.
When electronics got better, you could input your tire circumference to the mm... and there were all kinds of arguments about how to get the perfect measurement considering tire size, air pressure, rider weight, etc... everyone wanted the highest accuracy possible, and it was a PITA.
Then when GPS came along, most people said "yeah, +/- 10% is fine".
I have both a Garmin watch and cyclocomputer... I pick whichever one reads higher to post on Strava.
Last edited by DiabloScott; 04-21-23 at 01:31 PM.
Likes For DiabloScott:
#18
ambulatory senior
Join Date: Dec 2016
Location: Peoria Il
Posts: 5,999
Bikes: Austro Daimler modified by Gugie! Raleigh Professional and lots of other bikes.
Mentioned: 76 Post(s)
Tagged: 0 Thread(s)
Quoted: 1956 Post(s)
Liked 3,662 Times
in
1,680 Posts
The only time I worry about it is when touring. Sometimes it's handy when you get lost to know which unmarked gravel road to turn on. Other than that I really don't care.
Likes For 52telecaster:
#19
Senior Member
Join Date: Oct 2015
Location: PDX
Posts: 13,090
Bikes: Merz x 5 + Specialized Merz Allez x 2, Strawberry/Newlands/DiNucci/Ti x3, Gordon, Fuso/Moulton x2, Bornstein, Paisley,1958-74 Paramounts x3, 3rensho, 74 Moto TC, 73-78 Raleigh Pro's x5, Marinoni x2, 1960 Cinelli SC, 1980 Bianchi SC, PX-10 X 2
Mentioned: 269 Post(s)
Tagged: 0 Thread(s)
Quoted: 4520 Post(s)
Liked 6,405 Times
in
3,685 Posts
I only run GPS for evidence if something goes wrong to back up the cameras, lights and helmet, 24/7, 365, period.
Plenty accurate for me and my meager mileage.
It can help win the 1 or 10 million $$$ lawsuit when the army of lawyers tries to pick it apart.
Plenty accurate for me and my meager mileage.
It can help win the 1 or 10 million $$$ lawsuit when the army of lawyers tries to pick it apart.
Likes For merziac:
#20
Senior Member
Join Date: Feb 2008
Location: Peoria, IL
Posts: 4,482
Mentioned: 86 Post(s)
Tagged: 0 Thread(s)
Quoted: 1830 Post(s)
Liked 3,391 Times
in
1,586 Posts
Of course, this is limited by how accurately you can measure your wheel circumference, so you might only be getting 1% accuracy (or thereabouts). The circumference will also vary a bit with the tire pressure, so you might lose another small bit of accuracy as the tire loses pressure or the temperature changes. This is probably good enough for most navigation requirements.
Of course, the next question is: what is your standard for measuring distances, and is it any more accurate? Civil engineers and surveyors know how to achieve higher accuracy, but I haven't seen too many road signs marking distances in tenths of a mile or better.
Steve in Peoria
#21
Senior Member
Thread Starter
Join Date: Jan 2019
Location: Toledo Ohio
Posts: 1,498
Bikes: 1964 Huffy Sportsman, 1972 Fuji Newest, 1973 Schwinn Super Sport (3), 1982 Trek 412, 1983 Trek 700, 1989 Miyata 1000LT, 1991 Bianchi Boardwalk, plus others
Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 583 Post(s)
Liked 700 Times
in
395 Posts
I guess the impetus for the accuracy question is a one of personal truth. If I tell my wife or someone I went for a 15 mile ride, but it was actually only 14.5, it would just rub me the wrong way. I guess I have a ways to go before I decide to round it up to 20. I’ve heard fishing stories like that too.
Likes For sd5782:
#22
Cantilever believer
Join Date: Nov 2021
Location: Phoenix, AZ
Posts: 1,590
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 544 Post(s)
Liked 1,874 Times
in
846 Posts
I still remember lusting after this one pretty girl in 1982...
...wait, I mean her Pacer 2000 bicycle computer, which had 6 buttons and amazing functions.
(OK, she was pretty cute too).
Some times, I'm still think that one of the biggest improvements in riding technology wasn't indexed shifting, but electronic bike speedometers. Those of us that had to estimate mileage via Multitos or cable-driven speedometers back in the early 80s can commiserate.
In the early 1990s, I standardized my bike fleet on an Avocet cyclometer. One head that could move to many different mounts on each bike. just quickly changing the calibration number each time from a handy list. When properly calibrated, accurate to within well less than 1% error.
But how do I calibrate? I can do a rough estimate using a rollout on the driveway (several revolutions, butt on the bike). But to get the final number, I use a calibration course that is 2.151 miles long from my mailbox to the stop line at a nearby collector street intersection.
But how do I know that mileage? By using my motor vehicles, which have distance measuring instruments connected to the ABS or transmission sensors - super-precise odometers & speedometers that are calibrated over several miles of known-good mileposts around the state. When properly calibrated and synchronized with good surveyed mileposts, it'll tick over .000 right at each milepost. In fact, I have to adjust periodically for tire wear. And I verified with more than one vehicle. And my wife likes them, because she can see from the right seat exactly how fast I amspeeding driving in big numerals.
So now we have the wonder of GPS and 'smart' phones (I use RWGPS as our club has a group membership). How does it compare? Usually dead on, or differing by 0.1 mile depending on rounding, even with startup & stopping at intersections & destinations. Except if there is an extended on-foot break in the middle of the ride such as volunteer work, breakfast, etc. Then it's sometimes different, with the RWGPS invariably higher. Even though RWGPS pinky-swears that it is auto-paused and doesn't include that obviously-pedestrian-speed mileage in your riding... they often do include it in the final tally, even if they don't ding you for it on the average moving speed.
Am I overthinking this? Yes, and for almost 3 decades. And my carefully-hoarded pile of Avocet 45s (and other compatible ones) is ever-diminishing, so someday I may go all phone-based. So all I can say is: your mileage may vary.
...wait, I mean her Pacer 2000 bicycle computer, which had 6 buttons and amazing functions.
(OK, she was pretty cute too).
Some times, I'm still think that one of the biggest improvements in riding technology wasn't indexed shifting, but electronic bike speedometers. Those of us that had to estimate mileage via Multitos or cable-driven speedometers back in the early 80s can commiserate.
In the early 1990s, I standardized my bike fleet on an Avocet cyclometer. One head that could move to many different mounts on each bike. just quickly changing the calibration number each time from a handy list. When properly calibrated, accurate to within well less than 1% error.
But how do I calibrate? I can do a rough estimate using a rollout on the driveway (several revolutions, butt on the bike). But to get the final number, I use a calibration course that is 2.151 miles long from my mailbox to the stop line at a nearby collector street intersection.
But how do I know that mileage? By using my motor vehicles, which have distance measuring instruments connected to the ABS or transmission sensors - super-precise odometers & speedometers that are calibrated over several miles of known-good mileposts around the state. When properly calibrated and synchronized with good surveyed mileposts, it'll tick over .000 right at each milepost. In fact, I have to adjust periodically for tire wear. And I verified with more than one vehicle. And my wife likes them, because she can see from the right seat exactly how fast I am
So now we have the wonder of GPS and 'smart' phones (I use RWGPS as our club has a group membership). How does it compare? Usually dead on, or differing by 0.1 mile depending on rounding, even with startup & stopping at intersections & destinations. Except if there is an extended on-foot break in the middle of the ride such as volunteer work, breakfast, etc. Then it's sometimes different, with the RWGPS invariably higher. Even though RWGPS pinky-swears that it is auto-paused and doesn't include that obviously-pedestrian-speed mileage in your riding... they often do include it in the final tally, even if they don't ding you for it on the average moving speed.
Am I overthinking this? Yes, and for almost 3 decades. And my carefully-hoarded pile of Avocet 45s (and other compatible ones) is ever-diminishing, so someday I may go all phone-based. So all I can say is: your mileage may vary.
__________________
Richard C. Moeur, PE - Phoenix AZ, USA
https://www.richardcmoeur.com/bikestuf.html
Richard C. Moeur, PE - Phoenix AZ, USA
https://www.richardcmoeur.com/bikestuf.html
#23
Cantilever believer
Join Date: Nov 2021
Location: Phoenix, AZ
Posts: 1,590
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 544 Post(s)
Liked 1,874 Times
in
846 Posts
Relying on the precision of a gang of long-dead cranky guys in the 1800s with a magnetic compass, optical transit, and metal surveyor's chain.
And an a lot of places, they were pretty darn close - sometimes only yards, feet, or inches off after setting a township line. In other cases, though...
Still, as a civil PE who doesn't have his RLS, I shouldn't give them too hard a time, considering the difficulties of cadastral surveying back in the day.
And an a lot of places, they were pretty darn close - sometimes only yards, feet, or inches off after setting a township line. In other cases, though...
Still, as a civil PE who doesn't have his RLS, I shouldn't give them too hard a time, considering the difficulties of cadastral surveying back in the day.
__________________
Richard C. Moeur, PE - Phoenix AZ, USA
https://www.richardcmoeur.com/bikestuf.html
Richard C. Moeur, PE - Phoenix AZ, USA
https://www.richardcmoeur.com/bikestuf.html
Last edited by RCMoeur; 04-21-23 at 04:07 PM.
#24
Cantilever believer
Join Date: Nov 2021
Location: Phoenix, AZ
Posts: 1,590
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 544 Post(s)
Liked 1,874 Times
in
846 Posts
I guess the impetus for the accuracy question is a one of personal truth. If I tell my wife or someone I went for a 15 mile ride, but it was actually only 14.5, it would just rub me the wrong way. I guess I have a ways to go before I decide to round it up to 20. I’ve heard fishing stories like that too.
The first recitation of the ride describes the mileage as "almost 15 miles".
The subsequent retellings become "15-mile ride", "almost 20-mile ride", "epic ride far beyond a mere 10 miles", and so on.
Depending on rounding and precision... somewhat technically not entirely incorrect.
__________________
Richard C. Moeur, PE - Phoenix AZ, USA
https://www.richardcmoeur.com/bikestuf.html
Richard C. Moeur, PE - Phoenix AZ, USA
https://www.richardcmoeur.com/bikestuf.html
Likes For RCMoeur:
#25
Senior Member
Join Date: Feb 2008
Location: Peoria, IL
Posts: 4,482
Mentioned: 86 Post(s)
Tagged: 0 Thread(s)
Quoted: 1830 Post(s)
Liked 3,391 Times
in
1,586 Posts
I guess the impetus for the accuracy question is a one of personal truth. If I tell my wife or someone I went for a 15 mile ride, but it was actually only 14.5, it would just rub me the wrong way. I guess I have a ways to go before I decide to round it up to 20. I’ve heard fishing stories like that too.
There is also the idea of "good enough" accuracy for a given task. More accuracy costs time and money, usually.
Besides... no one really cares how far you (or any one of us) rode.
I prefer to measure rides in the number of donuts enjoyed...
Steve in Peoria
Likes For steelbikeguy: