changing tire sizes

[ucfireman]

If I buy a truck with 18 inch wheels and tires and late go to a larger wheel/ tire combination, what is involved with resetting the speedometer?
Is it just get someone to tell the computer the tire size or more complicated?
This would be a 2023 Ram with 18s now and later probably some factory take offs.

 

[Skeeter XRi]

The wheel size is irrelevant, the overall tire diameter is what would affect your speedometer. If you change from a factory 18” wheel and tire combo to a set of 20” takeoffs, it’s very likely no changes will need to be made as the 20” combo will probably have a lower profile tire.
If you do have to calibrate it though, most of those changes are done through programming these days.

jim

 

[John Cooper]

If I buy a truck with 18 inch wheels and tires and late go to a larger wheel/ tire combination, what is involved with resetting the speedometer?
Is it just get someone to tell the computer the tire size or more complicated?
This would be a 2023 Ram with 18s now and later probably some factory take offs.

If you go to a larger tire, then yes you will have to reprogram your speedometer.

Say (just for example) you go from a 235 tire to a 285 tire.

 

[transfixer]

If I buy a truck with 18 inch wheels and tires and late go to a larger wheel/ tire combination, what is involved with resetting the speedometer?
Is it just get someone to tell the computer the tire size or more complicated?
This would be a 2023 Ram with 18s now and later probably some factory take offs.

You might want to do some checking first, Chrysler corp changed the way you access all their vehicles ecm's starting in 18/19, now requires a wifi gateway subscription, or going to a lot of trouble to bypass the onboard gateway, I have HP Tuners which is generally the most common program used for changing things like tires sizes or differential ratios, but the later Chryslers require a different way of going about it, it might end up being rather expensive to do,

Also make sure you changing tire sizes isn't going to affect your powertrain warranty , many times it does, especially if the dealer is a stickler for details, and you will likely need that powertrain warranty by the way !

 

[killerv]

It'll be different but just a few mph. If you have the waze app, it will tell you how fast your going with the new tires compared to your speedometer.

But yeah, tuner will do it, but I'd check to make sure you doesn't mess with warranty.

 

[hopper]

If I buy a truck with 18 inch wheels and tires and late go to a larger wheel/ tire combination, what is involved with resetting the speedometer?
Is it just get someone to tell the computer the tire size or more complicated?
This would be a 2023 Ram with 18s now and later probably some factory take offs.

Just curious as to why you want 20s?

 

[transfixer]

Just curious as to why you want 20s?

Most people these days are going with bigger tire/wheel combinations for looks, but many times the downside is if the chosen wheel/tire combination weighs more than the stock setup, you're adding in more rolling resistance due to the extra weight, and if the overall circumference of the tire is larger than the stock was, then you are effectively changing the final gear ratio, which will almost always result in less mileage along with the heavier tire/wheel combo

Also wider wheels and especially offset wheels add more leverage pressure to your axle and hub bearings, causing them to fail earlier than they should. we see it constantly in the shop, but people have to look cool I suppose ?

 

[hopper]

Most people these days are going with bigger tire/wheel combinations for looks, but many times the downside is if the chosen wheel/tire combination weighs more than the stock setup, you're adding in more rolling resistance due to the extra weight, and if the overall circumference of the tire is larger than the stock was, then you are effectively changing the final gear ratio, which will almost always result in less mileage along with the heavier tire/wheel combo

Also wider wheels and especially offset wheels add more leverage pressure to your axle and hub bearings, causing them to fail earlier than they should. we see it constantly in the shop, but people have to look cool I suppose ?

I get that. I've had to change speedo gears on my jeep for 33s. The 20s at least on my wife's explorer is rough as heck. I'm thinking of going smaller wheels to gain more rubber for more cushion. Am I way off?

 

[transfixer]

I get that. I've had to change speedo gears on my jeep for 33s. The 20s at least on my wife's explorer is rough as heck. I'm thinking of going smaller wheels to gain more rubber for more cushion. Am I way off?

smaller rims/more rubber definitely gives a better smoother ride, I've driven some vehicles at work with the large rims, rubber band tires and don't see how customers can live with the ride ? feels like there is no suspension give on most of them

 

[ucfireman]

Just curious as to why you want 20s?

Not necessarily looking at 20s.
The truck I saw just had chrome wheels, nothing too fancy.
I know some of the fancier models have nicer looking wheels.
Was thinking maybe later sometime just buying a set of "takeoffs" and wondering, if they are bigger overall, how much hassle it is to re adjust the speedo. With everything being electronic these days.

 

[Geffellz18]

I honestly wouldn’t worry too much about calibrating the Speedo.
Seems like a big hassle for no realized benefit.
If you want to know what difference the different setup made, just roll through one of the areas where there’s a speed sensor that tells you your speed a few times and you’ll know.
The tire store I use primarily didn’t have my cars factory size, so I just had them put one size smaller-205 vs 215 factory spec. My cars about 2mph slower than the Speedo reading with these tires based on the numerous speed sensors I pass by everyday for work.
Had a buddy a long time ago pull over to speak with a police officer to clock him after we lowered his truck and installed new rims/tires. He was more to an happy to help out!

 

[bigchiefchoctaw]

Most people these days are going with bigger tire/wheel combinations for looks, but many times the downside is if the chosen wheel/tire combination weighs more than the stock setup, you're adding in more rolling resistance due to the extra weight, and if the overall circumference of the tire is larger than the stock was, then you are effectively changing the final gear ratio, which will almost always result in less mileage along with the heavier tire/wheel combo

Also wider wheels and especially offset wheels add more leverage pressure to your axle and hub bearings, causing them to fail earlier than they should. we see it constantly in the shop, but people have to look cool I suppose ?

Spot on and perfectly stated..