Downsizing from 285's to 245's tires

[Tempted]

i assume your running 285/75/16's which are a 33" tall tire so dropping to a 245/75/16 which is a 30" tire so it will make a difference

I assumed it was a 285-70. Without knowing we can't say what or how much it will effect the performance.

 

[Swims350]

70 aint very common from what I've seen, a 75 is tho.

 

[badazzbulldog]

true that is the most common and either 235/75/16's or 245/75/16's were what these trucks rolled of the assembly line with

 

[whiplash473]

pretty safe to say that the city mpg's will go up tho with either one

 

[Dave]

They are 285 75 r16 AT's. The 245s are off of a 99 k2500 8 lug 6.5l diesel burb so I have no idea what gear ratio it has. I always thought the first set of numbers was the diameter of the tire?

 

[Tempted]

First set is width in MM. ~~285
Second is height in % of the width. ~~75
Third is rim. ~~16

So its 285mm wide, which is 11.2 inches.
Then you look at 75, which is the profile(sidewall from wheel to top of tire) and find out what 75% of 11.2" is. In this case, 8.4 inches.
Now double that and add it to your wheel size. 8.4 + 8.4 + 16 = 32.8" tall.

To answer your original question, now that we have the tire size, you will run higher RPM now. Should help fuel mileage around town and will feel a bit more perky from stops. If the speedo was geared for the 285s then it will now be a good deal off. It will show you are moving faster than you actually are.

 

[Dave]

Ok, thanks for clearing that up Tempted.