HELP--PSI of stock mud tires / chalk test vs. OEM spec

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Lamarsh

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2020 1500 Rebel
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Background: I've replaced the stock OEM tires on all my trucks with a larger AT/MT type tire (been through a few sets of DuraTracs and one set of BFG KO2s) in the 305-315 size. My tire pressure monitoring systems on my old trucks were always set to the stock PSI recommendation, and after doing the chalk test (chalk on tire on flat pavement to see what PSI the tire wears evenly) on these larger tires I always found them to wear the most even at around 33-35 PSI.

Question: I got a new 2020 Rebel 1500, which came stock with DuraTracs in the 275 size (about a 33" tire, quite a bit larger than the normal stock tires that come on Rams). I haven't done the chalk test yet, but I am shocked that the manufacturer has the tire pressure monitoring system set at 45 PSI for front and 50 for rear. I am very confident if I do the chalk test that it will come out the same or similar to all the other DuraTracs I've owned, even though they were a few sizes larger than these.

It just strikes me as way too much PSI for large AT/MT tires like DuraTracs, and makes me wonder whether the manufacturer overlooked that these kinds of tires wear differently than the normal Good Year SRA or whatever other garbage they usually put on the trucks OEM.

Anybody have any insight here?
 

RandomRam

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The TPMS threshold is based on the GVWR of the truck and load rating of the tires. Max load rating is at max PSI only. 35 PSI is fine unloaded but loaded at max GVWR you need what’s listed on the door with stock size tires. Where it gets complicated is upgrading to a larger, high rated tire. An E rated 275/70r18 has about a 3600lb rating at 80 PSI, which is obviously way too much for any 1500.

You can disable the warning with Alfa ODB but will need a security bypass cable. TPMS still works, just no warning light.
 

crazykid1994

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I lowered the threshold on my truck for off-roading purposes. My 35s i run them at 38 front and 35 rear. I run down around 25-30 psi off-roading. Alfa can change the threshold or turn it off
 

ram1500rsm

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Background: I've replaced the stock OEM tires on all my trucks with a larger AT/MT type tire (been through a few sets of DuraTracs and one set of BFG KO2s) in the 305-315 size. My tire pressure monitoring systems on my old trucks were always set to the stock PSI recommendation, and after doing the chalk test (chalk on tire on flat pavement to see what PSI the tire wears evenly) on these larger tires I always found them to wear the most even at around 33-35 PSI.

Question: I got a new 2020 Rebel 1500, which came stock with DuraTracs in the 275 size (about a 33" tire, quite a bit larger than the normal stock tires that come on Rams). I haven't done the chalk test yet, but I am shocked that the manufacturer has the tire pressure monitoring system set at 45 PSI for front and 50 for rear. I am very confident if I do the chalk test that it will come out the same or similar to all the other DuraTracs I've owned, even though they were a few sizes larger than these.

It just strikes me as way too much PSI for large AT/MT tires like DuraTracs, and makes me wonder whether the manufacturer overlooked that these kinds of tires wear differently than the normal Good Year SRA or whatever other garbage they usually put on the trucks OEM.

Anybody have any insight here?
Stock 20 is 275/60/20 P rated, stock Rebel is 285/70/17 E rated i think. at least for 4th gen RAM 1500.

This is the TRA specs for an LT 285/70/17 tire, you truck GAWR at the rear axel is 4100lbs. that means fully loaded up to 4100lbs in the back you will need tires able to withstand 2050lbs each. You can do that with just 35lbs with a 285/70/17 LT. running 40lbs will give you 4630lbs support, 5020lbs at 45psi etc. Way more lbs support than your rear GAWR. the factory will you in theory the best mpg, that doesn't mean you have to have 50psi in the back.


upload_2020-6-27_9-50-12.png
 
Last edited:

olyelr

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Stock 20 is 275/60/20 P rated, stock Rebel is 285/70/17 E rated i think. at least for 4th gen RAM 1500.

This is the TRA specs for an LT 285/70/17 tire, you truck GAWR at the rear axel is 4100lbs. that means fully loaded up to 4100lbs in the back you will need tires able to withstand 2050lbs each. You can do that with just 35lbs with a 285/70/17 LT. running 40lbs will give you 4630lbs support, 5020lbs at 45psi etc. Way more lbs support than your rear GAWR. the factory will you in theory the best mpg, that doesn't mean you have to have 50psi in the back.


View attachment 213364


They dont even put e rated duratracs on the power wagon...doubt they do on the rebel.
 
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