Tire size and the computer

[XCELLR8]

I have been a Ram owner for about 3 week now and have my first question about tire sizes and the on-board computer. As far as I know during my research the Ram comes in two tire sizes, the base 265/70/17 and 275/60/20. the 265s have a OD of 31.7" and the 275s spec out at 33". Is there two different computers for the two different tire sizes? Just one computer that gets programed depending on tire size ordered? Or, do they just plug in a tire size no matter what size is going on the truck? I ask this because when I'm driving on the highway at 60mph (speed limit is 55) I get a lot of people passing me, more than when I'm in my car on the same drive to work.

 

[Thor09]

Your computer would be programmed to its stock tire size. The biggest the computer can be programmed is 275/60-20 (33"). The older truck you could change to bigger sizes but not these. If you want to program anything bigger than 33", you need to get a tuner.

 

[Stangshcky12]

you need to get a tuner.

Which unfortunatly for 2011 isnt possible

 

[XCELLR8]

Your computer would be programmed to its stock tire size. The biggest the computer can be programmed is 275/60-20 (33"). The older truck you could change to bigger sizes but not these. If you want to program anything bigger than 33", you need to get a tuner.

Ok, thanks for the info.

 

[quietpeen]

looks like the answered your question. what tire size are you thinking about running?

 

[XCELLR8]

looks like the answered your question. what tire size are you thinking about running?

I will be getting some rims and tires come spring time, but the question was geared towards me being passed a lot on the highway compaired to my car. I know the car is 1mph slower than the speedo reads and I will have the truck tested soon. So I was kind of wondering if they may have set my computer to the wrong size of tire from the factory.

I would like to run a 285 to 305 when I get some rims.

 

[quietpeen]

Ahhh ok.....i would bet that you are getting passed by people speeding rather than your speedo being off

 

[Thor09]

I will be getting some rims and tires come spring time, but the question was geared towards me being passed a lot on the highway compaired to my car. I know the car is 1mph slower than the speedo reads and I will have the truck tested soon. So I was kind of wondering if they may have set my computer to the wrong size of tire from the factory.

I would like to run a 285 to 305 when I get some rims.

To double check my tuner setting with my tire size, I turn on my GPS going down the road. If you have one to try, I would use it to verify your speedometer.

If you get 285/70-17 tires, that is a 33" diameter, the same as 275/60-20 (33")

 

[Mad Cow]

I use my GPS.

 

[TheSatinPumpkin]

Also physically measure the tread height of the tires to get the actual height vs just going by the tire ratio size. Some manufactures actual diameter w/ new tread can be a little +/- than the advertised tire ratio.

GPS is a good idea as mentioned.

 

[XCELLR8]

If you get 285/70-17 tires, that is a 33" diameter, the same as 275/60-20 (33")

That is the set up I was leaning towards. 17x8 with 285 BFGoodrich All-Terrains.