How accurate are distances on e bikes
- Thread starter CanNik
- Start date
JGcycle
Well-Known Member
- Region
- Canada
- City
- Saint John
I have compared my e-bike odometer readings to my car odometer readings, and have found that my e-bike odometer reads a bit low.
For a distance of 20km shown on the car odometer, the e-bike shows about 19.8km. Mind you, I don't really know how accurate my car odometer is. For reference, I ride a 2023 Voltbike Bravo, and my car is a 2013 Toyota Corolla.
For a distance of 20km shown on the car odometer, the e-bike shows about 19.8km. Mind you, I don't really know how accurate my car odometer is. For reference, I ride a 2023 Voltbike Bravo, and my car is a 2013 Toyota Corolla.
Tars Tarkas
Well-Known Member
You can probably adjust the wheel size in your controller. That will, in turn, adjust the speed and distance readings. I've found those adjustments aren't necessarily all that accurate, so you may need to go through some trial and error.
I've checked my bike odometer against Google Maps on my phone, which is easy.
TT
I've checked my bike odometer against Google Maps on my phone, which is easy.
TT
mrgold35
Well-Known Member
My 4" fat tire Radrover wheel size was set to 26" in the controller. I noticed my mph was off by 1-2 mph on the neighborhood speed limit radar detectors. It wasn't until I got my wife her Radcity and noticed our mph and distance travel didn't match up on a ride (she was more accurate with neighborhood speed limit radar and phone apps). I was able to change my wheel size to 28" and everything matched up since. I figured the rim is 26"; but, the circumference of the fat tire is closer to 28/29 inches for a more accurate speedo reading.
harryS
Well-Known Member
I believe the bike is more accurate, if the design is right, but they often are not.
Many ebike displays only allow input of the wheel size, like 20,24, 26, etc, . Actual tire size is what matters, so they're often way off. An $8 bike computer takes the actual tire diameter in cm and the results will change with tire pressure.
Look at what surveyors often use to measure lots, which is a bicycle wheel on a stick.
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Many ebike displays only allow input of the wheel size, like 20,24, 26, etc, . Actual tire size is what matters, so they're often way off. An $8 bike computer takes the actual tire diameter in cm and the results will change with tire pressure.
Look at what surveyors often use to measure lots, which is a bicycle wheel on a stick.
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JGcycle
Well-Known Member
- Region
- Canada
- City
- Saint John
After switching from the stock Kenda Small Block Eight 2.1 x 27.5 to Schwalbe Big Ben 2.0 x 27.5 tires, I had to change my wheel diameter setting from 27" to 26" to get a "closer to accurate" speed and distance reading. The Schwalbe tires had a much lower profile than the Kenda tires, even though they were a very similar size.
old guy 666
New Member
- Region
- USA
When I ride with my wife we get 4 measurements, my bike, her bike, Map My Ride, and what her phone says. The range is pretty close for all 4, 25.8 to 26.5.
Jeremy McCreary
Very Stable Genius
- Region
- USA
- City
- Carlsbad, CA
Great idea! For various reasons, I rely on RideWithGPS for distance and my ebike display for speed. Accuracy is probably good enough for my purposes, but I'll check the distances reported by both against Google Maps just for kicks.
Question is, if Maps and RideWithGPS disagree, which to believe? Given the high lateral resolution available from GPS measurements, thinking RideWithGPS. Maybe our resident GPS expert @dodgeman will weigh in.
As for those digital speed feedback signs, all 3 in my neighborhood consistently show 14 mph when my ebike display shows 15. Given the fact that the signs were designed to clock cars and trucks, no idea which is right.
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6zfshdb
Well-Known Member
- Region
- USA
- City
- Northeast Pennsylvania
The accuracy of any given bike display will vary due to many of the reasons described above. Those readings from GPS based apps or receivers are particularly susceptible to errors caused by topography and sky obstructions.
I test my displays using this method. I have a flat straight smooth surface bike trail nearby. I accurately measure the distance between two fixed points, usually a quarter mile. I ride at a steady speed and use a stopwatch to measure the time it takes to travel between those points. The speed is then easy to calculate. You can also compare the measured distance with your display.
An easier, but slightly less accurate way is to use Google earth. zoom in on a nearby flat level stretch of road and use the measuring tool to determine the distance between two utility poles. Carefully ride that stretch with the stopwatch and do the math for speed and distance comparison.
I test my displays using this method. I have a flat straight smooth surface bike trail nearby. I accurately measure the distance between two fixed points, usually a quarter mile. I ride at a steady speed and use a stopwatch to measure the time it takes to travel between those points. The speed is then easy to calculate. You can also compare the measured distance with your display.
An easier, but slightly less accurate way is to use Google earth. zoom in on a nearby flat level stretch of road and use the measuring tool to determine the distance between two utility poles. Carefully ride that stretch with the stopwatch and do the math for speed and distance comparison.
Tars Tarkas
Well-Known Member
Accuracy would be nice to count on but short of sending your bike off to a NIST service center for calibration and certification... how much does it really matter? Within reason, anyway? I adjusted my wheel size years ago, checked once, it wasn't perfect, but I shrugged and moved on. If my bike tells me I just rode 29.6 miles, in most cases, if anyone asks, I'm gonna say I rode 30.
TT
fooferdoggie
Well-Known Member
I used to use mile markers when I had a speed sensor computer. but they showed 10ths of a mile or less so you could really dial it in. but tire pressure can change it too. so its never going to be perfect.
Nvreloader
Western Nevada
- Region
- USA
I know that my Garmin 60cxs GPS is way more accurate than my bike,
my setting on the wheel size is set to 26" and the circumference measures at 2474MM = 97.4015" div by 3.14 = 31"+ for the Kendra 26 x 4.5" tires & 25/30#'s.
So I go by the GPS and have checked it against the NHP radar units and the speed reads correctly.
my setting on the wheel size is set to 26" and the circumference measures at 2474MM = 97.4015" div by 3.14 = 31"+ for the Kendra 26 x 4.5" tires & 25/30#'s.
So I go by the GPS and have checked it against the NHP radar units and the speed reads correctly.
PCeBiker
Well-Known Member
- Region
- Canada
I downloaded a GPS speedometer App to my phone and compared that to my e-bike speedometer.
I found a straight flat obstruction free highway and I could see my speeds in real time then fine tune my display settings until the speeds matched exactly.
(My KT display allows me to adjust my speedo by less than 1 kph)
I had 21 satellites tracking me, so I know my phone App was pretty accurate.
If you know your actual speed vs. your speedometer, converting to distance is easy math.
I found a straight flat obstruction free highway and I could see my speeds in real time then fine tune my display settings until the speeds matched exactly.
(My KT display allows me to adjust my speedo by less than 1 kph)
I had 21 satellites tracking me, so I know my phone App was pretty accurate.
If you know your actual speed vs. your speedometer, converting to distance is easy math.
fooferdoggie
Well-Known Member
Phones suck for accuracy. I can compare my phone to my Garmin to my bike computer. the phone is always higher in milage.
PCeBiker
Well-Known Member
- Region
- Canada
Hmmm,..
I was thinking that the phone app was accurate because I was on a perfectly flat road, going a consistent speed with a clear view to the entire sky and 21 satellites tracking me?
I wasn't going up or down turning or stopping.
I was only looking for my real time instantaneous speed.
I didn't check any distances.
If my speedometer reads accurately, then my odometer will be accurate too.
fooferdoggie
Well-Known Member
I think part of it is its going other things. where my Garmin has one job. I have compared several gamins to each other and they are always very close. including my Garmin watch.
fooferdoggie
Well-Known Member
yep.
Stefan Mikes
Gravel e-biker
- Region
- Europe
- City
- Mazovia, PL
This matter has been discussed in EBR Forums for many times.
The short answer is: The accuracy of the odometer depends on the Wheel Circumference set properly in the e-bike software, and it might still differ from the map distance. The GPS distance is by any means the most accurate.
The shortest answer is: If you ride a lot, you stop worrying about the odometer accuracy
The users who upload their rides to Strava can always correct the distance and elevation gain to the map using Strava tools. I even stopped doing that; the life is too short to waste it for such considerations.
Even 100 km off this way or the other does not matter with such a distance ridden in a year.
The short answer is: The accuracy of the odometer depends on the Wheel Circumference set properly in the e-bike software, and it might still differ from the map distance. The GPS distance is by any means the most accurate.
The shortest answer is: If you ride a lot, you stop worrying about the odometer accuracy
The users who upload their rides to Strava can always correct the distance and elevation gain to the map using Strava tools. I even stopped doing that; the life is too short to waste it for such considerations.
Even 100 km off this way or the other does not matter with such a distance ridden in a year.
6zfshdb
Well-Known Member
- Region
- USA
- City
- Northeast Pennsylvania
If you are really serious about finding the true speed / distance accuracy of your devices, the best way for the average rider to do it is this:
First, accurately measure the distance between two points on a smooth flat straight road. Longer distances yield better results but measurement can be tricky. Mile markers and vehicle odometers are not always accurate so it's best to do it yourself. Rather than spend a lot of time with a tape measure, Google Earth is an easier way.
Zoom in on a suitable road and add two placemarks at visible points like utility poles:
Use the ruler tool to find the true distance between your marked points. There is some error associated with Google Earth but in flat open terrain, it is usually +/- 3'.
Ride your "course" and compare the readings on your devices with the GE measurement. None will agree exactly. Ride the course again as soon as possible, since GPS readings can change with the satellite horizon. You will likely get different results. Adjust your bike's display to match the GE measurement. If this isn't possible, make a note of the difference and calculate a "fudge factor". At least you'll know how accurate it really is.
Errors are introduced in many ways. GPS measurements are taken between satellite acquisition points, which are never in a perfectly straight line and do not follow the exact line of travel. They also do not compensate for elevation change. It is also impossible to ride a bicycle along a perfectly straight line, especially at low speeds. Every movement of the handlebars introduces minute errors, which can be significant on long rides.
Note the GE example above is less than .5 miles and is for illustration purposes only. Distances of 2 or more miles are necessary for the best result.
Yeah, what can I say. I'm a geek. I do however agree with Stefan above. If you ride enough, these distances become less meaningful and are more for reference than accuracy.
First, accurately measure the distance between two points on a smooth flat straight road. Longer distances yield better results but measurement can be tricky. Mile markers and vehicle odometers are not always accurate so it's best to do it yourself. Rather than spend a lot of time with a tape measure, Google Earth is an easier way.
Zoom in on a suitable road and add two placemarks at visible points like utility poles:
Use the ruler tool to find the true distance between your marked points. There is some error associated with Google Earth but in flat open terrain, it is usually +/- 3'.
Ride your "course" and compare the readings on your devices with the GE measurement. None will agree exactly. Ride the course again as soon as possible, since GPS readings can change with the satellite horizon. You will likely get different results. Adjust your bike's display to match the GE measurement. If this isn't possible, make a note of the difference and calculate a "fudge factor". At least you'll know how accurate it really is.
Errors are introduced in many ways. GPS measurements are taken between satellite acquisition points, which are never in a perfectly straight line and do not follow the exact line of travel. They also do not compensate for elevation change. It is also impossible to ride a bicycle along a perfectly straight line, especially at low speeds. Every movement of the handlebars introduces minute errors, which can be significant on long rides.
Note the GE example above is less than .5 miles and is for illustration purposes only. Distances of 2 or more miles are necessary for the best result.
Yeah, what can I say. I'm a geek. I do however agree with Stefan above. If you ride enough, these distances become less meaningful and are more for reference than accuracy.
