Max tire size using OEM wheel

[jlj]

I would like to upgrade the tires on my 2022 Gladiator Overland and utilize the stock wheels. The current tire size is 255 70R 18 mounted on an 18x7.5 5x5 wheel. What is the largest tire I can mount on this wheel, still utilize existing tpms, and have everything operational without voiding the factory warranty. I wanted to put a 275 70R 18 BFG KO2 on that wheel but was told at the tire dealer that may screw up some of the 4x4 functionality. Please help.

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[NachoRuby]

Screw up 4x4 functionality? What a load! 275 70R 18 is a 33" tire (33.16" to be exact). Rubicons and Mojaves come with 33" tires from the factory.

There are plenty of folks running 35s/37s with no drivetrain upgrades. Beyond 37s, you probably would want to beef up your axles. But 33s are fine, and the width you described is even approved for the stock size rim.

The only problem you'll have is with acceleration, possibly, since I'm assuming you have 3.73 gearing. No big deal, and it won't break anything. It'll just burn more gas and go slower.


TPMS doesn't care about tire size. You will want to reprogram your speedometer afterwards.

 

[Rahkmalla]

You will want to reprogram your speedometer afterwards.

Alternatively, don't. Factory speedos are always under because while there is a tolerance for them in either direction in the US (believe it or not 10% plus or minus 49 CFR § 393.82 - Speedometer. | CFR | US Law | LII / Legal Information Institute (cornell.edu) ) other countries like the UK have only a negative tolerance, specifically stating that " For all true speeds up to the design speed of the vehicle, the true speed shall not exceed the indicated speed ".

So if you're designing parts to sell to international auto mnfrs, are you going to set your target to perfect and only accept parts that are perfect or under? Hell no. You'll aim for 3% under and set your tolerances for plus or minus 2%.

Going from a 255/70r18 to a 275/70r18 is a 3.4% increase on your speedo. You're most likely just getting it back to correct. Drive a tad slower than you're used to on the read-out and leave the tire recalibration alone, and enjoy the 3.4% more warranty.

Note: This does not constitute legal advice. Please don't try to convince a cop that some guy on the internet told you this was okay. This is (at best) justifying my own personal laziness, and perhaps yours if you so choose. And while it is all based on truth, none of that will matter because cops clock you based on their radar, not what your speedo says.

 

[jlj]

Alternatively, don't. Factory speedos are always under because while there is a tolerance for them in either direction in the US (believe it or not 10% plus or minus 49 CFR § 393.82 - Speedometer. | CFR | US Law | LII / Legal Information Institute (cornell.edu) ) other countries like the UK have only a negative tolerance, specifically stating that " For all true speeds up to the design speed of the vehicle, the true speed shall not exceed the indicated speed ".

So if you're designing parts to sell to international auto mnfrs, are you going to set your target to perfect and only accept parts that are perfect or under? Hell no. You'll aim for 3% under and set your tolerances for plus or minus 2%.

Going from a 255/70r18 to a 275/70r18 is a 3.4% increase on your speedo. You're most likely just getting it back to correct. Drive a tad slower than you're used to on the read-out and leave the tire recalibration alone, and enjoy the 3.4% more warranty.

Note: This does not constitute legal advice. Please don't try to convince a cop that some guy on the internet told you this was okay. This is (at best) justifying my own personal laziness, and perhaps yours if you so choose. And while it is all based on truth, none of that will matter because cops clock you based on their radar, not what your speedo says.

Will the tams need to be reprogramed?

 

[jlj]

Will the tams need to be reprogramed?

TPMS

 

[Rahkmalla]

Will the tams need to be reprogramed?

I don't think you're asking the question you think you're asking. TPMS don't get reprogrammed per se. They need to recalibrate if you're moving them from one wheel to another, but that's more a plug and play scenario. You swap them from one wheel to the next, drive them around for a bit until the signal is picked up and they just work. None of that is even required if you're keeping the same wheels.

What I think you're asking me is "will my dash yell at me about running a lower PSI with larger tires." And my answer to that is kinda screwy in that I have no way of knowing if my experience is what is to be expected. I switched from 33 to metric 35s, and dropped my psi from 37 to 32 accordingly. My jeep popped the PSI icon and yelled at me for about 2 weeks before it just gave up yelling at me and turned the warning light off. No idea if it's supposed to work that way, but i'd hope it's normal operation.

 

[jlj]

I don't think you're asking the question you think you're asking. TPMS don't get reprogrammed per se. They need to recalibrate if you're moving them from one wheel to another, but that's more a plug and play scenario.

What I think you're asking me is "will my dash yell at me about a lower PSI with larger tires. And my answer to that is kinda screwy in that I have no way of knowing if my experience is what is to be expected. I switched from 33 to metric 35s, and dropped my psi from 37 to 32. My jeep popped the PSI icon and yelled at me for about 2 weeks before it just gave up yelling at me and turned the warning light off. No idea if it's supposed to work that way, but i'd hope it's normal operation.

Thanks. You answered my poorly asked question.

 

[Deleted member 47279]

my spares are 38x13.5x17 on my OEM aluminum 17x7.5 rims. when i sliced a tire i drove 2 of those 38"s for a week so no issues on those stock rims. I did require a hubcentric spacer cause my metalcloak changed the backspace requirements tho. also when i upgraded from the stock 245/75/17 to the 285/70/17 i had rubbing on the sport sway bar. so spacers are gonna be your friend.

 

[jlj]

Alternatively, don't. Factory speedos are always under because while there is a tolerance for them in either direction in the US (believe it or not 10% plus or minus 49 CFR § 393.82 - Speedometer. | CFR | US Law | LII / Legal Information Institute (cornell.edu) ) other countries like the UK have only a negative tolerance, specifically stating that " For all true speeds up to the design speed of the vehicle, the true speed shall not exceed the indicated speed ".

So if you're designing parts to sell to international auto mnfrs, are you going to set your target to perfect and only accept parts that are perfect or under? Hell no. You'll aim for 3% under and set your tolerances for plus or minus 2%.

Going from a 255/70r18 to a 275/70r18 is a 3.4% increase on your speedo. You're most likely just getting it back to correct. Drive a tad slower than you're used to on the read-out and leave the tire recalibration alone, and enjoy the 3.4% more warranty.

Note: This does not constitute legal advice. Please don't try to convince a cop that some guy on the internet told you this was okay. This is (at best) justifying my own personal laziness, and perhaps yours if you so choose. And while it is all based on truth, none of that will matter because cops clock you based on their radar, not what your speedo says.

I checked the speedometer yesterday on the interstate. I used Waze and at 70 mph both the speedo and Waze were the same. That's good enough for me and your advice was dead on. I just wanted to let you know. Thanks.

 

[kevman65]

I checked the speedometer yesterday on the interstate. I used Waze and at 70 mph both the speedo and Waze were the same. That's good enough for me and your advice was dead on. I just wanted to let you know. Thanks.

If whatever device you were using for WAZE was plugged directly through USB to the JT, or connected through blue tooth to the JT, then you were not getting a true GPS speed through the device.

For whatever reason, any GPS speed device connected to the JT will read the speedo display speed

 

[jlj]

If whatever device you were using for WAZE was plugged directly through USB to the JT, or connected through blue tooth to the JT, then you were not getting a true GPS speed through the device.

For whatever reason, any GPS speed device connected to the JT will read the speedo display speed

Is that a published issue or something you personally experienced? What about using a non Bluetooth or USB connected device, Garmin, to check speed? What about using the Uconnect navigation?

 

[kevman65]

Is that a published issue or something you personally experienced? What about using a non Bluetooth or USB connected device, Garmin, to check speed? What about using the Uconnect navigation?

It is something I experienced and others have as well. I used a Garmin GPS and my radar detector with GPS speed after I had it happen using a phone app.

The speedo read 70, the phone read 70, people were passing me like I wasn't moving. Pulled out radar detector and Garmin and found I was doing 64.7 MPH according to them.

Once I made adjustments with Tazer, and redid the calibration run, the radar detector and Garmin were about .25 MPH apart, phone read exactly what speedo did, disconnected phone from JT and it matched the Garmin and was off from radar detector and speedo.

I went with the lower speed to give me a slight cushion.

 

[jlj]

It is something I experienced and others have as well. I used a Garmin GPS and my radar detector with GPS speed after I had it happen using a phone app.

The speedo read 70, the phone read 70, people were passing me like I wasn't moving. Pulled out radar detector and Garmin and found I was doing 64.7 MPH according to them.

Once I made adjustments with Tazer, and redid the calibration run, the radar detector and Garmin were about .25 MPH apart, phone read exactly what speedo did, disconnected phone from JT and it matched the Garmin and was off from radar detector and speedo.

I went with the lower speed to give me a slight cushion.

Thanks. I'll check it using my Garmin and speed app. If I find a discrepancy I'll probably buy an ECRI. Are you familiar with tent brand of programer?

 

[jlj]

Your dealer will tell you anything to sell you something. That said a 7.5 in rim should do fine with a 10.5 or 11 in wide tire. It’ll work with a 12.5 wide as long as sidewall height accommodates. But I would t like to run those aired down if not bead locked.

I did replace the factory all season tires with 275/70R 18 KO2's. What do you think the psi should be for daily street driving? Door plate calls for 38 psi front and back.

 

[AZJT]

I've had 285/75/18s on the OEM Overland wheel for almost 2 years now, with no issues. Calibrated with a Tazer mini, did a 2" level/lift kit. See here: https://www.jeepgladiatorforum.com/...ted-overland-with-35s-and-leveling-kit.35816/

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