I often use the previously described 60/60 method (60 MPH for 60 seconds) to see just how close I am with tire size. It work really well for those who don't have a GPS. For more accuracy, set the cruise at 60 and do 5 miles vs. 300 seconds. This will get you REALLY close.
And as Jack said, the speedo is nearly always 2 MPH faster than the actual vehicle speed so even if you're 1-2 MPH off, you should still be safe.
Take care.
__________________
Bill Cohron - The Mad Doctor  
Power Hungry Performance - The ORIGINAL in Ford performance tuning... Since 1997!
(678) 890-1110
www.gopowerhungry.com - Home of the Hydra Chip, Minotaur Tuning Software, and the new Orion Reflash System for Navistar!
Bring back  Windows™ XP and 7. 
Windows™ Vista and Windows™ 8 is a pain in my a$$! 
Windows™ 10 is only slightly less annoying! 
Windows™ 11 is garbage! 
Much to my surprise, I'm actually quite enjoying Linux! 
|