I think I may have found a possible path to make 37 inch tires work better for me.
In another thread somone posted that 295/70/R18 tires can be programmed with a 3.31 gear without a CEL. The diameter for a 295/70/R18 is 34.3 inches.
The tire I want to run is the Toyo RT 37x12.50R17LT which has a diameter of 36.8 inches. I am running a 3.55 gear.
I used an online calculator and determined that the RPM at 55 MPH with a 36.8 inch tire and 3.55 gear in 6th gear is 1195. The same calculator gave 1195 RPM at 55MPH with a 34.3 inch tire using a 3.31 gear in 6th gear.
If all of this is correct, it would seem that I could use the 37x12.50R17LT Toyo RT with my 3.55 gear and just get the dealership to reprogram to a 3.31 and 295/70/R18 tire and my speedometer and shift points would not be impacted by going to a 37 inch tire.
Questions:
-Are there any issues that I am missing with this approach, are the calculations correct?
-Will I have trouble getting the dealership to program the truck to my specifications... different gear and tire size than what I am currently running in order to accommodate the final drive ratio change due to running larger than stock diameter tires?
Thanks!
In another thread somone posted that 295/70/R18 tires can be programmed with a 3.31 gear without a CEL. The diameter for a 295/70/R18 is 34.3 inches.
The tire I want to run is the Toyo RT 37x12.50R17LT which has a diameter of 36.8 inches. I am running a 3.55 gear.
I used an online calculator and determined that the RPM at 55 MPH with a 36.8 inch tire and 3.55 gear in 6th gear is 1195. The same calculator gave 1195 RPM at 55MPH with a 34.3 inch tire using a 3.31 gear in 6th gear.
If all of this is correct, it would seem that I could use the 37x12.50R17LT Toyo RT with my 3.55 gear and just get the dealership to reprogram to a 3.31 and 295/70/R18 tire and my speedometer and shift points would not be impacted by going to a 37 inch tire.
Questions:
-Are there any issues that I am missing with this approach, are the calculations correct?
-Will I have trouble getting the dealership to program the truck to my specifications... different gear and tire size than what I am currently running in order to accommodate the final drive ratio change due to running larger than stock diameter tires?
Thanks!
