[R6CKETRIDER]

I have a technical question: how does the R6's computer calculate the speed at which you are traveling and how many miles you've traveled? Does it calculate miles traveled by counting rotations of the drive tire (like in an older car)? And does it do the same for calculating speed, or does it measure something else like output shaft RPMs or the RPMs of the sprockets based literally on the # of teeth, i.e. diameter/circumference of the sprockets?? (Sounds like it could be the winning explanation)... Let me know about both odometer and speedometer reading calculation methods, that is, if they are different...

My goal here is to identify the legitimate scientific explanation of what actually causes the speedometer error when you do the -1 +2 etc. gear change... I would think that theoretically a change in gearing would only change the rate of acceleration, not cause an inaccurate speedometer reading, but I guess that depends where/how the speed is calculated! So is the speed actually calculated with a formula involving the circumference/diameter of the sprockets i.e. number of teeth or is it done some other way??

As a side note, I know that a change in overall tire and/or wheel circumference/diameter would throw off your speedo/odo's accuracy assuming that the vehicle's speed/distance traveled is calculated in a formula based on the circumference and RPMs of the drive tire (or is that part of this statement not necessarily true?), but that's not really an issue with bikes... I was told by someone studying physics that it would take a tire literally twice the diameter of the original to throw off the MPH just 3-5 MPH... what do you guys have to say to that statement?

BOTTOM LINE: I just want to know how the bike's computer calculates speed to confirm why the speedo would be affected (i.e. adding more inaccuracy to the stock calibration error) after a sprocket gearing change!!! And yes, I'm aware that the speedo is intentionally calibrated high from the factory so leave that part out of your answers ... GOOD EDUCATED ANSWERS ONLY PLEASE!!! Please correct me if anything I've said is wrong or let me know if I'm missing anything, cause I'm not an expert... Thanks!! :dblthumb

 

[kman458]

The speedo reads the rpm on the output side of the tranny and was programed to know that each time the sensor goes around that the rear tire travels a set distance. This is how you end up with MPH and distance. When you change the gearing you change the ratio of how far the rear wheel travels compared to trans output shaft rpm so you get a greater or lesser reading. Changing tire height also effects things the same way. The larger in diameter the rear tire the farther you go on each rev so the speedo will read slow while going smaller will lead to slower indicated speeds. What a speedo healer does is to intercept the signal and then change the output to correct any error in the speedo either from changes in gearing or tires or to just correct the error made into the speedo. At one time speedos were driven of the front wheel so the speedo was not affected by gearing changes.

 

[kevin_stevens]

^^ plus a gear position sensor, BTW.^^

KeS

 

[R6CKETRIDER]

The speedo reads the rpm on the output side of the tranny and was programed to know that each time the sensor goes around that the rear tire travels a set distance. This is how you end up with MPH and distance. When you change the gearing you change the ratio of how far the rear wheel travels compared to trans output shaft rpm so you get a greater or lesser reading. Changing tire height also effects things the same way. The larger in diameter the rear tire the farther you go on each rev so the speedo will read slow while going smaller will lead to slower indicated speeds. What a speedo healer does is to intercept the signal and then change the output to correct any error in the speedo either from changes in gearing or tires or to just correct the error made into the speedo. At one time speedos were driven of the front wheel so the speedo was not affected by gearing changes.

Thanks for the clarification, I appreciate it! :cheers

 

[Teej]

^^ plus a gear position sensor, BTW.^^

KeS

Depends.

If you're taking RPM from the ignition as I suspect, then you need a gear position sensor.

If it's reading the tranny output rpm...no gear info would be needed (at least not to calculate speed/distance. If it displays the gear, that's another matter).

 

[kevin_stevens]

Depends.

If you're taking RPM from the ignition as I suspect, then you need a gear position sensor.

If it's reading the tranny output rpm...no gear info would be needed (at least not to calculate speed/distance. If it displays the gear, that's another matter).

Agreed. :cheers

KeS