How does your odo work?

[PaD]

I guess most bikes have a sensor somewhere on the frame and a magnet on a wheel ( or rear disc on my bike) to count wheel revolutions. But what happens with that information?
I have found that the odo on my Specialized Vado does not always record the same distance as the trip meter. After a long wait I got this explanation from Specialized.
” The issues is in the km capturing in the motor.
In current motor this is only done every 5km, so each 5km the memory in the motor is saving the total value.
In certain cases the display is showing 49.8km and the after you shut down the bike the motor is providing 45km and causing a difference. ”
That means that if I really would like to know exactly how many km I’ve done on my Vado I have write down the trip meter info and make my own record.
Specialized seems to be fine with that. I don’t understand why anyone would choose to do it that way.
What’s it like on you bike?

 

[christob]

I believe my odo sensor is within my rear hub motor. I do log every trip in a spreadsheet... I capture the trip odo reading, and the master odo reading each time (then I reset the trip odo to zero before each new trip). Over the 1,600 miles biked on this bike, the sum of all trip odo values is now about 4 miles lower than the current master odo. Interestingly, the trip odo displays to 1 decimal position (xx.x) while the master odo only displays whole miles (xx). So I'd expect to perhaps have sum of all trip readings be within +/- 1 mile of master, at any time, not +/-4. But I'm not concerned about it.

 

[PaD]

I believe my odo sensor is within my rear hub motor. I do log every trip in a spreadsheet... I capture the trip odo reading, and the master odo reading each time (then I reset the trip odo to zero before each new trip). Over the 1,600 miles biked on this bike, the sum of all trip odo values is now about 4 miles lower than the current master odo. Interestingly, the trip odo displays to 1 decimal position (xx.x) while the master odo only displays whole miles (xx). So I'd expect to perhaps have sum of all trip readings be within +/- 1 mile of master, at any time, not +/-4. But I'm not concerned about it.

Thanks for your answer.
4 miles difference over 1600 wouldn’t concern me either.
The difference you see is what I think can be expected when the odo does not display decimals. I suppose ( but I don’t know) that the odo internally records decimals so when you reset your trip meter the odo can be anywhere in a whole mile, from just over to just under. Even if your odo displayed decimal there could be a difference every time you reset the trip meter.
The Specialized method can loose anything from 0 to 3miles everytime you turn the battery off. Thatks how I understand the answer from Specialized.

 

[6zfshdb]

I've been told the odometer sensor on my Pedego is located inside the hub motor housing. I use a GPS to track mileage as well as other ride statistics. The trip meter and the GPS always differ to some degree and it's hard to tell which is more accurate. To keep a record of my rides, I download the ride data to my computer and use software to determine the actual mileage. All three methods of measuring ride mileage differ to some degree but the error is usually less than 2% and not significant IMO.

I've found over the years that revolution counter odometers are not always the best method to measure mileage. Changing tires with even a slightly different circumference or a change in tire pressure can result in large errors on long rides. Some counter odometers allow calibration but it can be tricky to get the right settings. Using wheel diameter or circumference isn't the most accurate. The actual rolling circumference under load is best but can be difficult to measure. Skidding the tires on loose surfaces or test rotating the wheel can also contribute to the error over hundreds of miles.

 

[PaD]

@6zfshdb
Thank you
It's interesting to know how carefully different riders are logging their rides and how.
I found my trip meter and my old Gpsmap 60 were showing pretty much the same distance.

 

[harryS]

Mid-drives need a external wheel sensor to count the revolutions. Hubmotors usually have built-in sensors, but can use wheel sensors. Both are only as accurate as their determination of tire size. A manufacturer can set that pretty close, I guess.

My DIY ebike conversions have controllers that only ask for wheel diameter. They're way off, usually 10% high, which is OK because it makes my wife feel good about her mileage. I track most of our riding on a spreadsheet, using the numbers off the odometers.

A bike computer that uses the wheel circumference is nice. On my regular bike, I measured it by rolling the bike with my weight on it. That calibrates very close to Google Pedometer.