Tire size verse speedo error-More question
Thread Starter
|
Registered User
Joined: Feb 2012
Posts: 23
Likes: 0
Were the 20's the original wheels. If not, they could have been giving you a false reading, and now your reading the correct speed. Those RPM's seem pretty high. What engine and gearset do you have. When you went to the shorter tire, did the truck "wake up" at all? Dropping 2 inches of sidewall would numerically raise your effective gear ratio and may feel like the truck has a few more cojones off the line.
Champion
Joined: Aug 2007
Posts: 4,702
Likes: 2
From: N. Florida
Wheel size has no effect - it's tire diameter that is key. If you look on the diff, you may find a metal tag. If it has "39" or "3.9", it's a 3.92 gear set. If so, it came with 20s. From your rpm at speed, my guess is you have 3.92s. My truck has 3.55s. With 265/70x17s, it turned 2,020 rpm at 80. Now with 285/70s, it turns 1,980.