Is Recalibration Needed for going to 33’s

[Forshy1075]

My stock jl sport with tires it came with from factory was off by 1mph. My jt sport with 33 falken is off by maybe 1/2 mph at 60mph but still teeters back and forth compared to gps speed. I wonder if they just have the basic calibration set somewhere in the middle for all models.

This has been what I was wondering if Jeep uses a default value out of the factory for all models. When I was doing some research on speedometer laws online this weekend what I could find was federal regulations allowing for up to 5% difference between actual and displayed speed with the expectation that the speedometer will never report a slower speed then actual. So it wouldn't surprise me if the default setting is closer to 33" to hit the sweet spot for all models....I was going to return my Tazer but I think I am going to keep it and see what the default wheel size is over the weekend. Stay tuned!

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[Beowulf85]

This has been what I was wondering if Jeep uses a default value out of the factory for all models. When I was doing some research on speedometer laws online this weekend what I could find was federal regulations allowing for up to 5% difference between actual and displayed speed with the expectation that the speedometer will never report a slower speed then actual. So it wouldn't surprise me if the default setting is closer to 33" to hit the sweet spot for all models....I was going to return my Tazer but I think I am going to keep it and see what the default wheel size is over the weekend. Stay tuned!

This has been what I was wondering if Jeep uses a default value out of the factory for all models. When I was doing some research on speedometer laws online this weekend what I could find was federal regulations allowing for up to 5% difference between actual and displayed speed with the expectation that the speedometer will never report a slower speed then actual. So it wouldn't surprise me if the default setting is closer to 33" to hit the sweet spot for all models....I was going to return my Tazer but I think I am going to keep it and see what the default wheel size is over the weekend. Stay tuned!

Awsome def let us know. On another post about recalibration someone had the directions for mopar recalibration kit that the dealership uses and it can adjust in increments of 1/2. So no matter what the falkens used on a rubicon could never be set to the 32.7 diameter that the tire calls for. You would still be off by a quarter.

 

[Forshy1075]

Well my thought seems to be incorrect, tire size was set to 31” when I installed the Tazer....I went ahead and changed to 32.5 which is what my tires measured. I didn’t notice any change in the speedometer readings but I am seeing my shift points are changing slightly for the better.

 

[Beowulf85]

Well my thought seems to be incorrect, tire size was set to 31” when I installed the Tazer....I went ahead and changed to 32.5 which is what my tires measured. I didn’t notice any change in the speedometer readings but I am seeing my shift points are changing slightly for the better.

Good deal thanks for sharing. I had to drop my gladiator off at the dealer today because my battery was dead when I woke up. After jumping it I had the engine light on and my start stop said it needed to be serviced. Anyway I asked the service guy about recalibration for 33 and he said that jeep is no longer allowing dealerships to calibrate for 33 and 35s. He also told me that 33 on my jeep would not mess with my warranty and that being off by 1mph at 70 wasn't a big enough deal to mess with speedo. So I when I have the extra cash I might just get the tazer lite so I can lower tpms sensors to 30 and set my tires to 32.5 as well.

 

[Beowulf85]

I went ahead and calibrated my truck for 32.79 inch tires with the tazer lite. My truck was set to 32.25 stock which is weird because stock tires are 31.5. My truck is now shifting way better and I can keep my average mpg up alot easier. I also used a mph app instead of my gps, and I was off by 2 -2.5 mph over 60 before tazer. I guess it is worth calibrating for the better drive at least.

 

[Forshy1075]

I went ahead and calibrated my truck for 32.79 inch tires with the tazer lite. My truck was set to 32.25 stock which is weird because stock tires are 31.5. My truck is now shifting way better and I can keep my average mpg up alot easier. I also used a mph app instead of my gps, and I was off by 2 -2.5 mph over 60 before tazer. I guess it is worth calibrating for the better drive at least.

Now that is a head scratcher.....I am an operations guy and would have assumed their was some form of standardization in default settings such as with tire size settings. I would say maybe they measure them and program it in but 32.25 is way over on a 31.5, glad to hear your truck is driving much smoother with the reprogram.

 

[JESmith]

The old school method before GPS was to use a timed mile. IMO this is still the most accurate. Find a flat stretch of highway. Drive EXACTLY 60 mph. At a mile marker sign, start your stop watch and drive for at least 5 miles (use mile marker signs not exits). Your time should be exactly 1 minute per mile. The formula is:

3600 (seconds per hour) / 60 (miles per hour) = 60 seconds per mile
3600 secs / 70 mph = 50.7 seconds per mile

 

[Beowulf85]

The old school method before GPS was to use a timed mile. IMO this is still the most accurate. Find a flat stretch of highway. Drive EXACTLY 60 mph. At a mile marker sign, start your stop watch and drive for at least 5 miles (use mile marker signs not exits). Your time should be exactly 1 minute per mile. The formula is:

3600 (seconds per hour) / 60 (miles per hour) = 60 seconds per mile
3600 secs / 70 mph = 50.7 seconds per mile

Good idea

 

[Fcmalie]

I just got my Gladiator a few days ago, Sport S and dealer put Rubicon tires on. Noticed on the way to work that I sit at just over 2k rpm at 65mph. Checked what gear it was in and was riding in 7th for the 16 mile highway drive. Once I got on a country road and set to 55 it dropped into 8th. Guessing I need to take it in tomorrow for recalibrating?

 

[JeepCares]

I just got my Gladiator a few days ago, Sport S and dealer put Rubicon tires on. Noticed on the way to work that I sit at just over 2k rpm at 65mph. Checked what gear it was in and was riding in 7th for the 16 mile highway drive. Once I got on a country road and set to 55 it dropped into 8th. Guessing I need to take it in tomorrow for recalibrating?

Hi Fcmalie,
I'm happy to see you've recognized this concern and are taking it to your dealer for review. If you ever are in need of additional assistance, don't hesitate to reach out to us privately.

 

[Brahmajoe]

I just got my Gladiator a few days ago, Sport S and dealer put Rubicon tires on. Noticed on the way to work that I sit at just over 2k rpm at 65mph. Checked what gear it was in and was riding in 7th for the 16 mile highway drive. Once I got on a country road and set to 55 it dropped into 8th. Guessing I need to take it in tomorrow for recalibrating?

Did you ever figure this out?

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