Switching from 24.5lp tires to 22.5lp

REALITY098765 · Dec 5, 2019

HaulinCars said: ↑

Don't forget about the change in overall gearing!

That may well be more of an issue than speedometer/odometer inaccuracy. Changing tire sizes can (WILL) affect your engine RPM at any given speed. It can also make a good performing truck feel like a dog (usually when going from small to large). Moving the RPM out of the optimal range can have a big affect on your MPG and therefore an even greater affect on your bottom line than whatever you saved on the tires in the first place. This is exactly why there are so many different differential gear ratios! Changing tire size is no different than changing rear gears, or transmission gears. They all have an affect on usable engine power and the speed/engine RPM relationship.

Going from large tires to smaller tires will give you better acceleration but less top end speed as you will run out of acceptable engine RPM range.

Going from small tires to larger tires will give you less acceleration (Read this as "guts" or pull power.. Can make you think you need a lower gear than first to start off with heavy load/up hill..) but will allow you a higher top end speed before you run out of usable engine RPM. (Assuming you have enough "acceleration" to actually get you to that speed in the first place...)

Note that, "Acceptable RPM range" means either what is safe for the engine or what is best for MPG, whichever applies to you, (are you trying to save fuel or get there faster?)
Click to expand...

The torque to the ground does NOT change with tire size so the ''pulling'' power is the same.
Now the smaller tire will raise the rpm at a given speed so you might gain HP with the higher rpm.
2 truck being equal starting at the bottom of a hill, the truck with the taller tire will reach the top first providing the same number of shifts . The truck with the shorter tire may even have to shift 1 more time also.

cgilliland · Oct 13, 2021

REALITY098765 said: ↑

The torque to the ground does NOT change with tire size so the ''pulling'' power is the same.
Now the smaller tire will raise the rpm at a given speed so you might gain HP with the higher rpm.
2 truck being equal starting at the bottom of a hill, the truck with the taller tire will reach the top first providing the same number of shifts . The truck with the shorter tire may even have to shift 1 more time also.
Click to expand...

you just blew some minds but you right
fascinating really

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Switching from 24.5lp tires to 22.5lp

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