Question, I currently have Goodyear GSA Wrangler P265-70R-17 tires on my 2004 Dodge Ram. I want to change this tires for some LT tires (same sizes of tires), I understand that the truck will probably will ride as a truck, oh well. Is this change on the tires will do any damamges to the truck. The new tires can be inflate up to 80 psi. The P tires that I currently have does not do the towing capacity I need. I am towing a 5400lbs towable trailer. I also installed rear air bags helper. Hopefully this will be it. Any other suggestions? Thanks.

 

One thing to make note of is the overall diameter of the original tires vs. the replacement tires (or revolutions per mile difference). If there is a difference of 1/2" or more (or the RPMs vary more than 4-5), you may want to have the computer reset for the new tires so your speedometer remains fairly accurate.

 

Is that an easy thing to do, reset the computer?

 

Does changing the tire size effect ABS?

 

I did not change the size of the tires at all. I used the same size but LT tires instead of P tires.

 

Changing the tires size + or - 2" is the time for the computer to be reflashed. Not only does changing tire size affect ABS it also affects the shift points of the trans. I have heard that the dealer can flash up to 34" tires. When you change tire size you are also changing the overall gearing. Bigger tires give you a loss of grunt. Thats why the guys that put on the tall tires go with lower gears(higher numerically) to get back some of that power. If you go above the flash limits then its time for a gear change. I am currently deployed right now and will be back home on 12 may. There I have a spreadsheet that calcs the true tire size and gear changes needed. If anyone cares to have it, I can email it.

I have just put on 285/70R17 to replace my 265/70R17. I noted that there is no difference,on a flat road at 70mph, of rpms before and after the tire change.

 

Are all Rams equiped with the same gears and brakes? What I mean is when I bought my truck it had 17x8 wheels and 245/70r17 tires. But the truck right next to mine on the lot came with 20x9 275/55r20 tires. the service deptartment said that the trucks were designed to handle the 20's so the 17" would still ride fine. They claim that there is no difference. Is that right? I could understand taking an older dakota or silverado with 15"or 16" wheels stock and replacing them with 20 inch, you would have to reprogram and change gears/brakes.....but what about Rams since most come with 20 inch stock?

 

The standard gear ratio for a 1500 Ram equipped with 17" wheels and tires from the factory, is 3.55 (rear end). The standard gear ratio for a 1500 Ram equipped with 20" wheels and tires from the facotry, is 3.92 (rear end). However, some 1500 Rams with 17" wheels and tires do have the 3.92 rear end. For example, mine does, but I ordered it with that option.

As far as brakes, there's no difference from 17" wheels or 20" wheels.

If you change from one tire size to another, and the overall diameter of the tire changes, and you don't have the computer reset, your speedometer will be off. That holds true whether it's a Dodge, a Ford, or a Chevy.

 

Hey MAZZ thanks for clearing that up. Dealerships will tell you anything to get you to buy a truck. I called the service dept. at my lcoal dodge dealer and they looked up my VIN and i have 3.92. So I guess I got lucky with that. So I assume my 20x10 will be fine but I do need to adjust my speedometer. Thanks again

 

the 20" have diameter of 32.99" the 245's have a 30.5" diameter. I would get it flashed.