Changing the tire size on my 2023 5th gen sport

I recently put a lift and 35 inch tires on my truck. I can't find an answer on changing the tire size so my speedo works properly. I talked to dodge and they told my I had to buy a speedometer calibrater for $400 CAN. I booked it in, cable doesn't fit the new fully digital dash. I'd really like to fix it. I'm 6km/hr out at 100km/hr.

I'm dealing with a similar issue where the dealership either doesn't want to do or just won't. I'm seriously considering doing it myself with Alpha OBD.theres a bunch of information on how to do it yourself on that forum. Good luck

What you need is AlfaOBD software (on a tablet, phone or laptop), an interface cable/device (USB or Bluetooth) and you can change it yourself. You go into the software and there is a drop-down list of tire sizes to choose from. Pick the one which matches what you have. If it's a 2023, you'll also need a Secure Access Gateway cable. It's a little more complicated on a newer truck, but there are threads on the forum on doing it. I bet youtube too.

Search out AlfaOBD software on these Ram forums...there's lot of discussion how to change tire size. Anything newer than '18 needs a SAG.

Or...call another dealer service dept, and see if they'll do it. That might be the path of least resistance. They probably don't want to void the warranty??

If you know a guy who has a 'good' Professional style scanner with current software, like a buddy, or a service shop, they ought to be able to do it too. A snap-on scanner has the ability to change tire sizes. IDK if there's a 35" tire on that list or not. Maybe?? Probably should call and check first. I know there's like 33" tires. Maybe worth a call to Discount Tires see if they can do it.

I just did this basic process.
I made a small change to a larger tire size to a 33-inch tire, 275/60/R20 from the factory size 275/55/R60.
Process basics:
1 Obtain the following items:
A Security Bypass Cable (Amazon has several) any of the red cables should work I have one very similar approx $20.00
B OBD code scanner (I have the MX+) approx $150.00
C Software Jscan for Apple or Android AlphOBD (I have Android so I use AlphaOBD.) approx $50.00 for Alpha
D GPS tracking software for your phone
2 Read all you can on the proper software you are going to use
3 Watch all the videos (most are on using AlphaOBD)
4 Install Security Bypass Cable (watch videos) this will take some time to ID cables and install the Bypass cable
5 Install the OBD reader (install software and check to see if the reader needs updates and update if needed
6 Learn how to read the information from the truck (take notes)
7 Learn how to save/make backups/configuration files (store your starting baseline before making any changes and label it as baseline
8 Determine the tire size in mm, revs per mile/km, and diameter in inches/mm (Tiresize.com)
9 Get a driver/Helper
10 Determine baseline speeds vs. indicated (you ride shotgun to run the software)
11 Start making test runs and follow-up runs until you reach the proper numbers in the truck (take lots of detailed notes as you work on this process.)
12 Save your backup when you have determined the proper tire size

Not stated there are several hours of learning to be completed and note taking, the potential cost of equipment to run your selected software. I consider these as tools and as such are investments and are reusable. Buy the best quality, the first time and save money in the long run.

When I did this process it took me longer to hook up my bypass cable than the whole adjustment process.

I hope this helps you map your path forward.

BlueHemi1500

I might be wrong, but I think the 2023+ don't work with AlfaOBD (not yet) @Jimmy07 are you aware if it works yet?

If I recall correctly even dealers can't do it. Even my 21 Rebel, I can change it, but it's still out. If I would put correct values in, my truck would go in limp mode, park sense, blah blah would stop working.

If this is true or not. I asked relative who works on 1500 to check into it. They claim in U5 they moved code and disabled it from being changed because
it was throwing off the front and back sensors. No clue if it's actually true, as it come from one person from another, etc...

Tire size change does work on all 2019-2024 5th gen’s with alfaobd, but once you program the tire size over a certain circumference (somewhere around 2700mm), the park assist module doesn’t like it and the park assist system disables. Most people get speed corrected pretty close before reaching that threshold with most 35” tires.
Z Automotive is supposed to be coming out with a device for park assist that will stop this from happening when adjusting tire size over that threshold.

The big PITA problem with the cheap 12+8 security gateway bypass cable for $20 is you must connect it directly to the security gateway module and remove it before visiting the stealership.

My time is far too valuable to cheap out on the bypass cable and have to R&R everytime I use it or visit the dealer.

I bought a KaodTech Security Bypass cable for $55 US. It has 2 connections to the Can bus system, one connection to the OBD2 port (only required when you're tweaking) and one connection to a USB interface like an OBDlink SX or a Bluetooth interface like Mx+.

Detailed installation instructions are included. It requires about 5 minutes to install if you're moving slowly or 2 minutes if you carefully follow the installation directions.

I installed mine last year and keep it tucked up under the dash. You have the option to not change the OBD2 port configuration and then the stealership can still connect to your truck.

I have no difficulty precisely tweaking the wheel size difference between my summer & winter wheels using an old standalone TomTom GPS to verify the results.

I would recommend setting & testing the accuracy of the AlfaOBD preset value for 35x12.5R18 for 35" or the closest value to your tire size and then adjusting as required using a standalone GPS.

I counted about 148 different preset tire sizes in the version of AlfaOBD that I use.




When I fine-tuned the speedo for my wheels, I started with the closest AlfaOBD preset value and then calculated the % of error, tweaked, and re-tested. It only required 2 or 3 adjustments to match the GPS speed.

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