05-28-2014, 04:18 AM
(05-28-2014, 02:53 AM)Ridem32_imp Wrote: I think on my abs mode the speed sensor reads off of the ring mounted on the wheel so no matter the size of the tire the speed and odometer should not change! I larger tire would have to turn more then a smaller tire would but the speed should read the same due to the reading coming from the ring on the rim. That's just what's stuck in my head. Heck I could be wrong but just can't see how a bigger tire would change speedo reading when the sensor and ring still the same size
Changing the size of your tires certainly does throw the accuracy of the speedo and odometer off. The ABS sensor only gives the software one piece of the equation... RPMs. Doing the math for distance and speed (which is just distance/time) requires knowing the geometry of the wheel itself since a larger wheel travels further with each rotation than a smaller one does. Changing the geometry of the wheel without changing the equations the software uses will produce an inaccurate result. The more dramatic the change, the more inaccurate the result.
Since we are talking about relatively minor changes to wheel diameter here, I'm sure that the speedo inaccuracies would be fairly negligible (+/- a fraction of 1 mph). However, the odometer reading would become increasingly inaccurate as your bike ages and, assuming your bike has a good long life, could eventually be thousands of miles off.