2012 Bigger Tires

[wyosteve]

Well, it looks like I'm going to make the jump to a 4th gen. 2012 3500 SRW. My question is: I'd like to go with a 285/75 Nitto tire which is what I have on my 04. 5, but with all the electronics on the 2012, don't know if I'll set off some type of code or other problem. Any insight would be greatly appreciated.

 

[AH64ID]

The truck would never know, but I would find a way to calibrate your speedo.

 

[mrkstrk]

I went from an 06 3500 SRW 4X4 to a 2012 3500 SRW 4X4. Put 285/70R17 on both. Took the 06 (still brand new) to the dealer and they could program the ECM for the difference in revolutions per mile. Took the 2012 in, to do the same thing, no go, sets off the abs warning, the trans won't shift correctly, warning lights flash, 2 alarms sound. Got online and checked it out, called 6 of the programmer manufactures, found out most wanted to sell a unit for year models up to 2011, won't work on a 2012. Talked to hyper tech, the gentleman was extremely familiar with the 2012 issue (Been thru customers purchasing and returning for the up to 2011 issue), HE told me which programmers would work on 2012, all you have to know is the measured height or revolutions pre mile and it takes about 5 minutes. Checked with a stop watch and GPS.

 

[Cummins12V98]

I went from an 06 3500 SRW 4X4 to a 2012 3500 SRW 4X4. Put 285/70R17 on both. Took the 06 (still brand new) to the dealer and they could program the ECM for the difference in revolutions per mile. Took the 2012 in, to do the same thing, no go, sets off the abs warning, the trans won't shift correctly, warning lights flash, 2 alarms sound. Got online and checked it out, called 6 of the programmer manufactures, found out most wanted to sell a unit for year models up to 2011, won't work on a 2012. Talked to hyper tech, the gentleman was extremely familiar with the 2012 issue (Been thru customers purchasing and returning for the up to 2011 issue), HE told me which programmers would work on 2012, all you have to know is the measured height or revolutions pre mile and it takes about 5 minutes. Checked with a stop watch and GPS.

Probably a stupid question, what programmers did he say worked??????

 

[wyosteve]

Thanks guys. I'm not going to try to re-calibrate the speedo. Once I determine the percentage the speedo is off, I just adapt that to the speed and fuel mileage. Good to know it won't set off any codes, etc.

 

[rscurtis]

Leave it to me to ask a stupid question, but why not just leave the stock tires?

 

[wyosteve]

2 reasons I like the bigger tires. Our speed limit out here is 75 on much of the highway I travel and the bigger tires keeps the engine in the 'sweet spot' of about 1800 to 2000 rpms better than the stock tires. And also, the 265's just look too wimpy in my opinion.

 

[EDankievitch]

I installed 285-70-17's on my 2012 for the same reason you have. The dealer was able to reset the speedo with out any problems or issues. The 285's are one of the choices that come up when the scan tool is hooked up. As for aftermarket programers don't do it the factory has changed the program and will lock up and display a U126 or U162 code voiding your warrenty. Only Chrysler's scan tool can be used.

 

[wyosteve]

Just thought I'd post this interesting phenomenon. I had the 285/75 Nittos installed last week. Before doing so, I checked the speedo with the factory 265 Michelins. I used the gps speed on the nav unit and found the speedometer was dead on. After installing the 285's, I again checked the speedo vs. the gps and it still reads dead on, i. e. 60 or 70 mph on gps reads the same on speedo. Did Ram perhaps build in some type of software that automatically re-calibrates the speedo? On my previous 04. 5, the 285's caused the speedo to read about 6% slow. Just surprised at this result.

 

[mrkstrk]

WYOSTEVE, what model is your new truck that the 285/75s have been installed on?

 

[AH64ID]

Is the GPS speed on the OEM nav really GPS or is it speedo driven? I remember this happening a few years ago, and IIRC it wasn't really GPS speed.

I would take a spare GPS out to confirm.

 

[wyosteve]

The new truck is a 2012 3500 SRW, auto. Good question on the nav. speed. I just assumed it was GPS since it's a Garmin based system. It wouldn't make much sense to me to have it speedo driven, but I'll use my handheld Garmin unit to check and compare.

 

[wyosteve]

Just an update. I checked the truck speedo yesterday with an independent Garmin unit and it shows the truck speedo reads approx. 6% slow with the 285's. So, yes, as AH64ID said, apparently for some reason the in dash Garmin based nav. unit just repeats the speedo reading. Darndest thing I ever expected.

 

[Cummins12V98]

My dually with stock tires reads 1-1. 5 mph fast using the independent Garmin unit. So in reality RAM owes me a bit longer on my mileage warranty. The 2nd gen trucks were off even more.

 

[AH64ID]

I have found that the speedo's read fast, but the odo is much more accurate on several rigs I have owned. I generally set the vehicle to the odo, and learn whatever error the speedo has.

I think they set the speedo fast so you don't get pulled over and blame the rig, but have no clue. I have never owned a rig where is read slow on the dash or odo.