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+--- Thread: Tyre size and circumference to adjust speed (/showthread.php?tid=602)
Tyre size and circumference to adjust speed - r1sm - 09-11-2024
Hello.
This is a public service announcement to help others.
My goal was to adjust the display speed to Waze GPS, so that I wouldn't always have to do the mental arithmetic to drive +3 km/h over correct speed (smooth traffic flow).
1. Tyre size
Changed it successfully to 235/50R19
1. Circumference
Calculated would have been 2253 mm, but that was far off. Read below what SPAyceTech shared on the subject. In short, Volvo does it's own thing here.
After much trial and error up and down with values I landed on 2120 mm. Seems to be a good fit.
The following information on the subject is from SPAyceTech.
The tire size and circumference are separate items in config, but Volvo uses them together, within the limited options offered in VIDA (only factory option tires and sizes are covered).
When you run a "tire size" software in VIDA, it sets both the tires size and circumference values.
Tire size is used for steering stops. This allows the fitting of larger wheels/tires and resulting adjustment of the maximum steering angle so the tires do not rub on the wheel liners, suspension parts etc.
I do think the circumference config is what is used to correct for distance and speed calculations throughout the car, like the speed display on the dash, odometer distance etc.
There is no indication of the proper measurement of circumference. We don't know what Volvo is measuring and using as a value there.
The values Volvo uses for a tire circumference don't usually match an online calculator. An online calculator is only a very generic rough guide of approximate dimensions of an actual tire.
Hope it helps someone else as well.
Cheers,
R
RE: Tyre size and circumference to adjust speed - IMAY2023 - 09-16-2024
Thank for the info.
I guess in Europe it's different. In the US I tested this with several different GPS software and all three of them indicated the same speed what Car's odometer shows.
waze, google maps, Apple, IGO on Android.