|Current wheel/tyre||New wheel/tyre|
|/ R||/ R|
|Current RR:mm||New RR:mm|
|Current circumference:mm||New circumference:mm|
|Difference in circumference:mm or %|
|Global Tyres recommends an Upsizing only if the difference if less than 2%|
|So when your speedo reads 70mph, you're actually travelling at mph|
Please Note : A Speedometer error means an odometer error too.
It stands to reason that if you change the rolling radius of your wheels and tyres, and the speedometer no longer reads correctly, that your odometer will also gradually become inaccurate. Assume for example that you bought a car brand new and changed the wheels and tyres on day one from 195/65R14 to 205/50R15 - not an uncommon change. By the calculator above, that makes your speedometer over read by 1.7%. Consequently, the registered odometer reading will also be out by the same value. So for example, when you get to 10,000km of driving (in the real world), your odometer will actually read 10,170km. OK so that's not a huge difference but it is one of the reasons why most car dealers have a disclaimer on their second hand vehicles telling you that they won't guarantee the displayed mileage. ("Clocking" the odometer is the other reason). Odometer errors due to mis-matched tyres and wheels will happen on regular odometers as well as the newer digital ones.
Contact USPALARIVATTOM SHOPPE
Palarivattom, Cochin 25
Near Hotel Sarovaram, Vytila
Aroor Bye Pass, Cochin 682304
Companipadi, Aluva 683106
HELPLINE NUMBERS : +914842306414, +914842347024