Do I need to get my Speedometer recalibrated?
 

So I went from having P265/70R17 tires on my truck and changed them out to P275/55R20's and I was wondering if I should have the speedometer recalibrated so the shift points and such are still proper?

Also I should mention my truck 2012 Dodge Ram 1500 ST

Tire is barely more than a quarter inch taller, nah won't make a bit of difference to the transmission.


Difference on the speedo won't even be enough to mean the difference of getting a ticket or not...

If you have a smart phone, get you an app that reads speed and gor a drive. See if there is a difference between what it says and what your speedo says. Decide from there.

Just what hammerZ71 said James - a couple 10ths of a mph at 62 mph/100kph

http://www.1010tires.com/Tools/Tire-...5R20/275-55R20

Discount tire has a calculator
http://www.discounttire.com/dtcs/infoTireMath.dos
looks like you tire changes makes about a 0.62 mph diff.

old tires 65 mph
new tires 65.62

Not worth the time to change, imo.

Thanks everyone. Means I'm just going to leave it alone.

not to hijack this thread, but i presume the trucks have something to compensate for what wheels/tires the come with since the difference beween at 265/70-17 and a 275/60-20 is even bigger?

programming or a different gear somewhere?

Back in the day it was a physical geared drive in the trans. You could adjust the speedo by buying a gear-drive with more or less teeth to adjust the ratio. Now, with electrical systems, it's a simple programming step for the dealer.

don't waste your time and as soon as the tire gets a 1000 miles on it, it will be the same size as the stock tire. some tires run tall and some short so you are chasing your tail