2020 PW bigger tire question

[sawman556]

So I put 285/75R17's on my new 2020 PW. My dealer doesn't seem to know how to update the VIN or whatever to get the speedometer and odometer correct. Who knows about this so I can explain it to my dealer? Thanks.

 

[smurfs_of_war]

So I put 285/75R17's on my new 2020 PW. My dealer doesn't seem to know how to update the VIN or whatever to get the speedometer and odometer correct. Who knows about this so I can explain it to my dealer? Thanks.

Wait... so if I move to a 35", the dealer has to program the speedo? Why is it I don't seem to recall this with my '15 2500 when I went up in size?

 

[sawman556]

Wait... so if I move to a 35", the dealer has to program the speedo? Why is it I don't seem to recall this with my '15 2500 when I went up in size?

Bigger tires will throw your speed off. Most guys use an aftermarket thingy the plugs in the OBD2 port that can correct it. I think there is a way the dealer can update the VIN or something. That's what I'm trying to find out.

https://www.discounttire.com/learn/tire-size-calculator

 

[ZLAYER]

This subject is beat to death on here. There are a few options. I chose the Tazer Ram. It hooks up pretty easy and allows you to change tire size so that your speedometer runs accurately (which also affects your odometer). It also allow you to change several other settings. Research on here, on YouTube, and on their site.

 

[Ram Wagon]

So I put 285/75R17's on my new 2020 PW. My dealer doesn't seem to know how to update the VIN or whatever to get the speedometer and odometer correct. Who knows about this so I can explain it to my dealer? Thanks.

Didn't your truck come with the 285's, my 2018 did. And those are only roughly 33.5 inch tires. (unless i missed something in your post)

 

[62Blazer]

The factory diagnostic tool the dealer has should have an option to change the tire diameter in it. However sometimes these only allow the option to change to different factory available tire sizes....been years since I dealt with a factory Mopar diagnostic tool. Just keep in mind that at least on paper there is only around a 3% difference in circumference (of the distance the truck will travel during each full tire revolution) between a 285/70R17 and 285/75R17 so I wouldn't be too concerned about it.

To address some of the other questions:
You don't HAVE TO adjust the speed calibration when going to a larger tire, but the larger the tire the more the speedometer, odometer, and the shift points will be "off". With a larger tire the truck will going faster and further than what the speedo and odo are actually showing. The shift points will also not be 100% optimal.....though I will say that a bunch of the trucks running around with larger tires probably don't have the speed calibration modified. At least half of the people I have talked to with larger tires on their truck look at you with a blank stare when you start talking about speed calibration and gear ratio changes! I bought an '16 PW last December and swapped the stock tires for 35's with no changes. While I do plan on getting some sort of device to adjust the tire size soon, I also didn't notice any obvious changes in driveability after putting on the larger tires. I've been running lifted and big tire trucks for going on 30 years now (lifted an old Toyota FJ40 Landcruiser and put bigger tires on it back in high school and currently have another truck on 40's).

 

[sawman556]

The factory diagnostic tool the dealer has should have an option to change the tire diameter in it. However sometimes these only allow the option to change to different factory available tire sizes....been years since I dealt with a factory Mopar diagnostic tool. Just keep in mind that at least on paper there is only around a 3% difference in circumference (of the distance the truck will travel during each full tire revolution) between a 285/70R17 and 285/75R17 so I wouldn't be too concerned about it.

To address some of the other questions:
You don't HAVE TO adjust the speed calibration when going to a larger tire, but the larger the tire the more the speedometer, odometer, and the shift points will be "off". With a larger tire the truck will going faster and further than what the speedo and odo are actually showing. The shift points will also not be 100% optimal.....though I will say that a bunch of the trucks running around with larger tires probably don't have the speed calibration modified. At least half of the people I have talked to with larger tires on their truck look at you with a blank stare when you start talking about speed calibration and gear ratio changes! I bought an '16 PW last December and swapped the stock tires for 35's with no changes. While I do plan on getting some sort of device to adjust the tire size soon, I also didn't notice any obvious changes in driveability after putting on the larger tires. I've been running lifted and big tire trucks for going on 30 years now (lifted an old Toyota FJ40 Landcruiser and put bigger tires on it back in high school and currently have another truck on 40's).

Thanks for your reply. I will be getting a 3rd party tool after I do my research. I had my truck out on the highway yesterday. My speedo was saying 70 and my phone GPS was saying 72. Not a big deal. The mileage is my bigger concern over time.

 

[sawman556]

Didn't your truck come with the 285's, my 2018 did. And those are only roughly 33.5 inch tires. (unless i missed something in your post)

The truck came with 285/70R17 which are roughly 33 inches. I put 285/75R17 on which are roughly 34 inches. I wanted a tire that was a little better in the mud so I got Trail Grapplers and went up a size. I'll probably go back to a AT after I'm done building my house.

 

[sawman556]

This subject is beat to death on here. There are a few options. I chose the Tazer Ram. It hooks up pretty easy and allows you to change tire size so that your speedometer runs accurately (which also affects your odometer). It also allow you to change several other settings. Research on here, on YouTube, and on their site.

I will most likely get the Tazer. I have one on my Hellcat and it works good.