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4th Gen Ram Tech2009 - 2018 Rams and the 2019 Ram Classic: This section is for TECHNICAL discussions only, that involve the 2009 - 2018 Rams and the 2019 Ram Classic. For any non-tech discussions, please direct your attention to the "General discussion/NON-tech" sub sections.
By using the tire calculator it appears that going from the stock 275-60-20's to a 305 -45-22 will keep your speedo pretty accurate - only a 0.6% change. When the speedo reads 60 mph, you'll be going 59.7 mph. Close enough for me.
Last edited by Thatmarkguy; Apr 8, 2009 at 02:55 PM.
Since this is a tire thread. Is 35 psi correct for the stock 20 inch Goodyear tires. I think they are the Wranglers. My tires look low, but the psi is at 35. I thought that was standard.
I believe the computer reads the wheel sensors to get your speed and distance. If this is so then you do not have to worry about the speedo and odo being off when you put on a new set off tires. I do not have a manual and can't confirm this, so for those who have put on different tire sizes and done tests to see if your speedo is off feel free to correct me.
I was traveling with the needle right at 60 and I came across a radar speed display thingie and it said 58, which pegs it right at about 3% off, as calculated.