Clocked a truck going 81 mph in a 55 zone. driver swears she was only going 60 mph. big tires on truck, not from factory. did the big tires really make that much difference in her actual speed?

I believe that the speedo is probably calibrated for the stock size tire that came on the car from the factory. You might need a motor-head to help you out with this one. http://www.csgnetwork.com/speedocalibcalc.html

Jump how big were those tires. I think they create a variance but not sure 26 mph would fall into that category.

nope

the smaller tires give you a faster reading on your speedometer but big tires make it seem like youre goin slower because it takes longer time for them to get around once so yes it is a huge difference and screw you for bein a cop

Maybe if the new tires were double the width of the original tires. Here's a calculator to see how much a difference it makes: http://www.miata.net/garage/tirecalc.html

Yes..the tires make a big difference in speedometer speed/actual speed but that is the drivers problem and nobody elses. By the way..why don't you know this?

For their sake yes, but I don't really know.

No

Share your answer...