odometer and non stock tires

[redorange]

up ko lang ulit ito

i just changed my 275/70R16 tires to 265/70R16 tires. in short, niliitan ko siya

kanina, after the tire change, wheel balancing etc, i test drove the vehicle on the skyway. at the same time, naka on rin ang GPS ko

sa speedometer reading, the needle indicated that i was running at 100kph BUT sa GPS reading i was running only at about 85kph. at the speedometer reading of 160kph, the GPS reading was only about 140kph

so which is more accurate? :question:

It depends on the accuracy of your GPS, the one I use is off by about 100 feet. But based on the info you provided here is what I got.

Original tires 275/70/16 or about 31.16 inches diameter.
New tires 265/70/16 or about 30.61 inches diameter.

Because your tires are now smaller your speedo would reflect a speed that is faster than what you are actually travelling. Travelling at 100km/h on your speedo if accurate would be 98.23km/h on the new tires and 160km/h would be 157.18km/h on the new tires. Your old tire and new tire have a difference of about 2% in diameter so you can calculate your real speed by subtracting 2% from your speedo if it's accurate.

Edit: The tire diameter difference is 1.7% but it's easier to calculate 2% if you're not looking for exact figures.

[111prez]

It depends on the accuracy of your GPS, the one I use is off by about 100 feet. But based on the info you provided here is what I got.

Original tires 275/70/16 or about 31.16 inches diameter.
New tires 265/70/16 or about 30.61 inches diameter.

Because your tires are now smaller your speedo would reflect a speed that is faster than what you are actually travelling. Travelling at 100km/h on your speedo if accurate would be 98.23km/h on the new tires and 160km/h would be 157.18km/h on the new tires. Your old tire and new tire have a difference of about 2% in diameter so you can calculate your real speed by subtracting 2% from your speedo if it's accurate.

Edit: The tire diameter difference is 1.7% but it's easier to calculate 2% if you're not looking for exact figures.

so the bottomline bro is that the speedo is no longer accurate. as for the GPS, i am not certain about its accuracy but i take it that civilian GPS units are about 25 feet less accurate than the military ones. by the way, i use a garmin gps III plus.

thanks for the info. i use the GPS for monitoring my speed also on the NLEX since the speedo might be off. the problem is, now both are off so i guess better nalang ang conservative driving