Heres a question, I just put 33x12x50x17's on my 05, the overhead console tells me I get pretty much a consistent 10.5 to 11mpg in town, Is that infact wrong being I have 33s now instead of the stock 245x70x17'x. If I bring it to the dealer to recalibrate my speedo and overhead console will that 10.5 to 11mpg change for the better??

Thank you

 

Yes.

 

I agree. When you change the tire diameter it will cause your odometer to be wrong. The overhead console computes MPG off the same sensor that your odometer gets its mileage from. When I went from 265/70R17 to 325/65R18 my trip of 70 miles went down to 55 miles. So lets say that it takes the same amount of gas as it did with the stock tires (which it doesn't cause the new tires weigh more) It would calculate the mileage fro mthe new odometer reading "55 miles". that was a reduction in mileage. Then add the weight and size of the new tires. Basically the same trip on stock tires I was getting 18mpg, and the new trip was taking 10-12mpg without the computer being reprogrammed. After changing the tire size, the milage came up to 15mpg. Just a side note, when you go to the dealer, they can't always input the exact size from the scan tool. For my case we had to select a custom size function, which required the number of revolutions the new size made per mile. In my case the tires are 581 revs/mile. Hope this helps for anyone else wondering the same thing.

 

I HAVE 35X12.50X18'S ON MY 02 RAM AND WHEN I HAD MINE RECALIBRATED IT CHANGED FOR THE WORESE BUT I ALSO HAVE THE GAS HOG 360 IT SAID I WAS GETTING 14.5MPG BEFORE RECALIBRATION AFTER IT SAID 11.5. AFTER THE SUPERCHARGER ITGETS 13.5 WITHOUT A HEAVY FOOT AND ANYWHERE FROM 8.5 TO 9.5 WITH A HEAVY FOOT.

 

Bigger tires mean speedo is reading slow, and your odometer is also not recording the correct miles (less miles) yet you are burning the same amount of gas. Less miles +same gas = less MPG

 

Well thank you all very much for the info, The truck has an appt Saturday to get it calibrated

 

Yeah I havent had mine recalibrated as of yet for my 35's but when my truck reads that the fuel is empty, I can only pump at most 19-21 gallons into it, which means I have appx 5gallons still in the truck... I thought I was getting horrible mileage from looking at the overhead, but when calculated, it is actually much better!

EDIT: How much does it cost to have the dealership recalibrate the speedo?

 

Yeah, how much would it cost to have the dealership calibrate this? Also, can you tune it yourself if you have the Superchips Programmer? I am about to put 33's on my '04. Thanks ahead of time.....

 

I am taking mine to the dealor Saturday and they are charging me 25 bucks, I called one other dealer in town and they said 130.00, LOL can you guess what one I will bring it to?