While there is a standard for claims of speedo deviation, it usually is not claimed due to the 10mph or larger discrepancy commpn for tickets. You are right on

While there is a standard for claims of speedo deviation, it usually is not claimed due to the 10mph or larger discrepancy commpn for tickets. You are right on about snow tires, but mine are larger, and my summer tires low profile. But those who swap wheels also tend to mentally recalibrate while passing those speed signs. I have to on all my motorcycles, as manufacuturers all seem to want me to think I am going 15% faster.