Tire/Speedo issue 2014 Ram 1500

[hudgenja]

Hey guys,

Asking for help, I know this is a noob topic but, I do not claim to be a mechanic. From my research I believe I need something like a bully tuner but I do not want to drop the cash if this will not fix my issue. I purchased a 2014 Ram 1500 5.7 Hemi 8sp auto 4x4 crew cab tradesman a few weeks ago. It came equipped with one of the mopar lift kits (unsure if it's the 2" or 4") the owner the dealer got it from had put Nitto Trail Grapplers Mt's 37s/12.5/20 on it. I just noticed tonight on the highway that I appeared to be flying by everyone on the road. I had the cruise set to 68, I pulled out my phone and GPS said I was doing 75. The difference it is off varies from 5-7 depending on speed. Also, I believe the tires are under-inflated to the factory 38 psi as to not set off the TPMS light , I will verify that in the morning. I'm looking to fix speedo and get the tpms light not to come on when I put the correct amount of air in it. Will a tuner fix this? If so which should I buy? Sorry for the lengthy post and for my ignorance.

 

[Stu4x4]

I'd have the dealer fix the speed since you purchased it there, they usually won't change it for larger tires past a certain point but maybe since you bought it that way. The tpms won't go off if you put more air in, you can jack up the psi all you want, it's only if you are below the 35psi threshold (I think it's 35). Though you may want to look into it more before taking the pressure up, 40 may be just fine for those tires on the ram, even if the tires say max pressure is much higher. I run my 35's at 40 psi but they are max 65ish on the tire.

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