Dealer won't change tire size in OBD

[Rob H 88]

Just put a slightly larger tire on my 1500 BTS edition and speedo is off by as much as 5 mph. Went to the dealer to have them input the correct tire size and was told the truck automatically senses tire size and auto adjusts speedo. Said only time they manually adjust is w 40 inch tires. Need a new dealer.

 

[Dean2]

Yes you do!!. However, my suggestion, get an MX+, Koadatech security cable and download AlphaOBD. For the same price as the dealer making that one change you now have the ability to do a whole lot more, including the inflation limits on your TPMS system.

I would have happily paid the dealer to fix the Fog light drop out, adjust TPMs limits etc but despite having a great Dealer, there is stuff they just can't access. They are locked out by Stellantis. That was actually what convinced me to get the AlphaOBD.

 

[turkeybird56]

Just put a slightly larger tire on my 1500 BTS edition and speedo is off by as much as 5 mph. Went to the dealer to have them input the correct tire size and was told the truck automatically senses tire size and auto adjusts speedo. Said only time they manually adjust is w 40 inch tires. Need a new dealer.

Yeah U probably do need a new dealer.

 

[Quick_Shifter]

Only trucks with factory gps can automatically calibrate tire size but there are still limitations. But the dealer didn’t completely lie

 

[Rob H 88]

Well if that's true and I have no reason to doubt you, then that seems to be a terrible flaw in the design as many truck owners change their tire sizes and by not providing a means to correct that would throw thousands of speedometer s off.

 

[crash68]

@Rob H 88 there is also Tazer DT if you don't to go the AlfaOBD route.

Tazer DT – Z Automotive

www.zautomotive.com

 

[John Jensen]

It's amazing what customers are told. Usually the "dealer" is a salesperson or a Service Advisor. I wouldn't believe anything those people say.

 

[Rob H 88]

True, I totally agree and that's why I called later to talk to the service manager who came from Ford and admitted he didn't know much about Ram yet but conferred with his coworker who supposedly knew a lot about Ram and basically just gave me a run around with no solution. Newdealer here I come

 

[pscarbor]

It's amazing what customers are told. Usually the "dealer" is a salesperson or a Service Advisor. I wouldn't believe anything those people say.

I took my 2010 Ram in for a required five year inspection (lifetime engine/PT warranty). They wanted to charge me $265 to replace one of the license plate lights that had burned out. Service advisor tried to tell me that they would have to pull the rear bumper.

I drove two blocks to an O'Reillys, got two bulbs for $5, threw one away, and replaced the burned out bulb in about two minutes. Dealer service really sucks!

 

[2021Ram3500]

Get the AEV ProCal kit. It will adjust for different size tires. I found that their formula didn't do very well so I got out my GPS and used that to get a more accurate speed.

 

[Regcabguy]

Just put a slightly larger tire on my 1500 BTS edition and speedo is off by as much as 5 mph. Went to the dealer to have them input the correct tire size and was told the truck automatically senses tire size and auto adjusts speedo. Said only time they manually adjust is w 40 inch tires. Need a new dealer.

Lawyers and liability. Costco won't install anything but a stock sized tire even if you bring in your own.

 

[garyfattmann101]

pscarbor, good luck with "lifetime warranty". My 2007 chrysler had that lifetime power train warranty! What a joke. in 2023 chrysler dealer told me car was too old to fix under warranty! They just told me it is a warranty until u need it! So they basically told me up yours! If u look online u will find everyone getting screwed

 

[John Jensen]

pscarbor, good luck with "lifetime warranty". My 2007 chrysler had that lifetime power train warranty! What a joke. in 2023 chrysler dealer told me car was too old to fix under warranty! They just told me it is a warranty until u need it! So they basically told me up yours! If u look online u will find everyone getting screwed

I have three relatives with lifetime warranties, none have been screwed. One has a 1500 and they have replaced his brakes, his shocks, and his transmission. It surprised me as I thought brakes and shocks were normal wear and tear and not covered. One had a dealer tell them basically what a dealer told you. They called Mopar who was quick to notify the dealer and tell them to honor the warranty. The lifetime warranty is a contract, not a joke.

 

[Neomoritate]

Get AlphaOBD if you use Android, OBD JScan if you use iPhone, and DIY

 

[MOPAR TECH]

IF YOU GET LUCKY ENOUGH SOMETIMES YOU CAN CHANGE THE TIRE SIZE IN TIPM THERE ARE PREPROGRAMMED TO GO UP TO A CERTAIN SIZE I REC YOU GET THE FLASH CAL THROUGH SUPER CHIPS AND THAT WAY YOU CAN PROGRAM THE TIRE YOUR SELF

 

[Dean2]

Get AlphaOBD if you use Android, OBD JScan if you use iPhone, and DIY

Agreed, for the price the dealer charges for one change, you can get the gear yourself, do that summer and winter PLUS a whole bunch more.

Oops, I see I said that already on this thread, oh well, bears repeating.

 

[BlueHemi1500]

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

 

[HarryN]

So do the slightly larger tires improve fuel efficiency any ? Just curious.

 

[Dean2]

So do the slightly larger tires improve fuel efficiency any ? Just curious.

In general, a taller, skimnny tires, if you adjust the speedometer usually give you better gas mileage as you are turning lower revs at each speed. If you dont adjust the speedo you are going further, faster, than what the odo reads so mpg is out by whatever the odo is out.

Wider tires of same height, worse mileage due to increased rolling resistance. More aggressive tread, worse mileage.

These are just general there are exceptions to everything.