Larger tires - Speedometer correction

Haufski762 · January 16

Gents,

Is there a way to correct the speedo for larger tires? The dealership says they can't.

Jus Cruisin · January 16

I used to go with lifts and significantly bigger tires. Long before all this computer/electronic stuff. I never messed with changing speedo gears. Now with all the GPS available to you just compare it to speedo readings and adjust in your head. Plus....now you're staying in warranty longer by showing fewer miles than actual.

newdude · January 16

11 hours ago, Haufski762 said:

Gents,

Is there a way to correct the speedo for larger tires? The dealership says they can't.

GM will only calibrate to factory authorized sizes for things like GM accessory wheel/tire packages.

Vincej138 · January 16

Unless you went from stock to like 40's, your only gonna be off 1-3mph. Stock to 35's on the idash is 2mph diff at 70mph. And my drive safe and save app doesnt yell at me when im doing 71 in a 65. It does when im 8 over... so ya

Went from stock to 315/70/17's

Haufski762 · January 16

I'll have to check the tire size but I had the speedo set at 82 and I was passing people like crazy. According to my GPS I was doing 90.

Edited January 16 by Haufski762

Vincej138 · January 16

https://tiresize.com/speedometer-calibration/

Its pretty accurate. Give you a good idea of what your off

Edited January 16 by Vincej138

Zeker · January 17

I went with this. It seems to be pretty accurate based on Google Maps GPS speed. You put in vehicle info, rim size and tire size if I remember correctly.

https://www.roughcountry.com/product/speedometer-calibrator-90045

Steve-2019 · January 17

5 hours ago, Zeker said:

I went with this. It seems to be pretty accurate based on Google Maps GPS speed. You put in vehicle info, rim size and tire size if I remember correctly.

https://www.roughcountry.com/product/speedometer-calibrator-90045

This shows only for 2021 models and older. The OP has a 2023 which is newer technology.

newdude · January 17

Some food for thought for the 19-22 pre-refresh folks. MC-10202392-9999.pdf (nhtsa.gov)

Problems are arising and growing from aftermarket speedo inline calibrators and warranty is grounds for blocking if its found and causing one or more of the listed concerns. They also can interfere with programming done at the dealership.

916TrailBoss · January 18

I put my Ram Rebel wheels on my TB and they're just slightly larger than the OEM wheels. Here's a screen shot of the calculator I used to get the difference.

Zeker · January 18

19 hours ago, Steve-2019 said:

This shows only for 2021 models and older. The OP has a 2023 which is newer technology.

Correct. I figure if he was interested he could contact Rough Country and see if they would be releasing one for the 2022 and newer models.

Transient · January 19

On 1/17/2024 at 4:00 PM, newdude said:

Some food for thought for the 19-22 pre-refresh folks. MC-10202392-9999.pdf (nhtsa.gov)

Problems are arising and growing from aftermarket speedo inline calibrators and warranty is grounds for blocking if its found and causing one or more of the listed concerns. They also can interfere with programming done at the dealership.

So, stay away from dealerships. Got it. Glad I didn't buy the SCA Black Widow edition.

Ironically, this is counter to what GM says it would be doing for dealers -- get people into the service department to generate revenue for the dealer. You'd think they'd create ways to assist customers as an enticement to get them into the service department. If only they offered speedometer calibration services. I digress and I'm well off topic now, so I'll move along.

newdude · January 19

7 hours ago, Transient said:

So, stay away from dealerships. Got it.

Ironically, this is counter to what GM says it would be doing for dealers -- get people into the service department to generate revenue for the dealer. You'd think they'd create ways to assist customers as an enticement to get them into the service department. If only they offered speedometer calibration services. I digress and I'm well off topic now, so I'll move along.

My point is more that these devices are causing problems either from just being installed or they cause problems during any type of ECM, BCM, TCM, etc. programming. So even if you avoid a dealership and have some repair shop work on the issue, that device can still be the cause of whatever is going on.

They do offer calibrations, but again only for factory authorized sizes. If GM offered a 35" wheel/tire package, they'd have a calibration.

The Raven · January 19

6 hours ago, newdude said:

My point is more that these devices are causing problems either from just being installed or they cause problems during any type of ECM, BCM, TCM, etc. programming. So even if you avoid a dealership and have some repair shop work on the issue, that device can still be the cause of whatever is going on.

They do offer calibrations, but again only for factory authorized sizes. If GM offered a 35" wheel/tire package, they'd have a calibration.

It is almost impossible for an inline speedometer calibrator, that simply intercepts and translates the VWSS pulse, to cause any real issue. But even if that were the case, all one has to do is remove the device, and see if the issue goes away. If it doesn't, take it to the dealer. No problem.

To add to the subject of this thread - there is not yet any way to calibrate the refresh trucks for tire size changes, or for that matter, anything at all...not even any inline translator boxes. There is no guarantee that there ever will be either - just hope. The Corvette and Tahoe/Yukon have been on this architecture since 2020 and 2021 respectively, and there's no progress there either.

Edited January 19 by The Raven

Transient · January 20

12 hours ago, newdude said:

My point is more that these devices are causing problems either from just being installed or they cause problems during any type of ECM, BCM, TCM, etc. programming. So even if you avoid a dealership and have some repair shop work on the issue, that device can still be the cause of whatever is going on.

They do offer calibrations, but again only for factory authorized sizes. If GM offered a 35" wheel/tire package, they'd have a calibration.

I got your point, which is why I said "avoid the dealership". It's my point I think you missed. GM isn't serious about getting customers into the service departments at their franchise dealerships. Something as simple as speedometer calibration could go a long way in customer service, customer retention, and generated revenue/increased profits for their dealerships. By your admission they have the technology and means. They just need to stop being so narrow minded.