Speedometer Misread w/Smaller Rims

[JDNugent]

I had a set of 22” rims on my 2016 RR Autobiography LWB and switched to 20” rims w/dedicated Blizzak snow tires on them. I noticed a 10 mph difference between the speedometer and my Waze GPS . I wonder if this is because of the smaller rims? Has anyone had a similar experience? Thanks

 

[joey]

Welcome to the forum. This issue isn't the rim size it is the outside diameter or the tires. Check out the sizes here for a good visual reference. https://tiresize.com/comparison/

 

[Shoshone]

I think the I D tool allows you to customize tire size for speedometer calibration.

 

[JDNugent]

I think the I D tool allows you to customize tire size for speedometer calibration.

What is the I D tool?

 

[Shoshone]

https://www.gap-diagnostic.com/products/iidtool/