Speedo correction for larger tires?
When is it necessary to get a speedo correction for larger tires? I went from a 265/75 to a 285/75 both 16 inch. Would the height even change?
Forum Discussion
The auto Garmin GPS only give MPH in whole numbers so I used my expensive Garmin form my boat as it give MPH to the one tenth MPH. Our 2004.5 Chevy D/A CC LB 4X4 in cruise at 58 MPH on the speedometer on flat roads is actually going 60.7 MPH with the 265/75/16 "E" LTX Michelins with 80 PSI in them. Tires are new and put on in late October 2013. That means I need to add approx 5% to the odometer distance indicated to be accurate. 100 miles indicated means I'd actually gone approx 105 miles.
I didn't check the speedometer with a GPS when the truck was new with the OEM 245/75/16 "E" Bridgestone tires but the tire charts lead me to believe 58 MPH indicated would have been 58 MPH actual knowing what the 265's numbers acually are. The 245's were only on for 29,000 miles.
Worn down tires are approx 3/4"+ smaller in diameter and alters your speedometer and odometer also. So does having less than full inflation or overloading a tire as the tire squats more so the radius distance on the road contact side is less than if fully inflated. Radius X 2 = diameter X 3.16 equals the circumference or distance traveled with one complete tire revolution.
Max weight loaded underinflated worn down tread tires can make more than a 10% difference (error) on the speedo and odo and give false by 10+% MPG even hand calculated. More revolutions and less distance actually traveled. The GPS doesn't lie as it's accurate!
I didn't check the speedometer with a GPS when the truck was new with the OEM 245/75/16 "E" Bridgestone tires but the tire charts lead me to believe 58 MPH indicated would have been 58 MPH actual knowing what the 265's numbers acually are. The 245's were only on for 29,000 miles.
Worn down tires are approx 3/4"+ smaller in diameter and alters your speedometer and odometer also. So does having less than full inflation or overloading a tire as the tire squats more so the radius distance on the road contact side is less than if fully inflated. Radius X 2 = diameter X 3.16 equals the circumference or distance traveled with one complete tire revolution.
Max weight loaded underinflated worn down tread tires can make more than a 10% difference (error) on the speedo and odo and give false by 10+% MPG even hand calculated. More revolutions and less distance actually traveled. The GPS doesn't lie as it's accurate!
