37" Tire Owners - have a question

[Trunty]

I have not tried this with a TRX, but was able to get my 40's on my 3500 calibrated perfectly using AlfaOBD by using a combo of gear ratio and tire size, focusing on aggregated calc. Not sure if applicable here, but may be worth digging in further on.

 

[10mpg]

Hi Callie,

The case number is 84034205. It’s still open for an AUX switch issue that remains unresolved since the TRX was launched that exists on all 2021 TRX’s.

The inability to adjust tire size on the TRX to accommodate larger tires exists on all TRX trucks and literally all 5th gen Ram 1500’s. It basically came down to my case manager telling me that there is no fix for it and nothing planned. Very disappointing given when the TRX was launched, the fact that it was ready for 37’s was a regular talking point. Oh and by the way, your only competitor, the Ford Raptor, fits 37’s and the truck can easily be adjusted so the speedometer is correct with the larger tires.

Man...if they actually fixed this, they would make a lot of people happy. This issue is super annoying.

 

[ljn21]

So for now, those that have went to 37s are just dealing with the Speedo being off? From the online calculators it’s a fairly significant difference at like 5mph at 70mph). Does the larger size without having the Speedo corrected (and who knows whatever else uses tire circumference or diameter to compute something) mess with shift points at all?

 

[10mpg]

So for now, those that have went to 37s are just dealing with the Speedo being off? From the online calculators it’s a fairly significant difference at like 5mph at 70mph). Does the larger size without having the Speedo corrected (and who knows whatever else uses tire circumference or diameter to compute something) mess with shift points at all?

That's a good question

 

[ljn21]

Seems weird to me that the parking sensors would be affected by tire size/diameter/circumference. Other than maybe needing to calibrate for a small angle change downward, what does the tire size have to do with proximity. It’s not like the truck is calculating the time it will take to hit something, it’s just sensing physical distance. Seems like Tazer and AlphaOBD are saying it’s Rams problem, but feels more like a glitch in their software but I am definitely not an expert. Maybe the parking/prox sensors take info from or input into other systems/modules more than expected. I would expect tire size being off to affect things like DTE calculation, nav turns, etc rather than parking sensors.

 

[Dudebro]

Seems weird to me that the parking sensors would be affected by tire size/diameter/circumference. Other than maybe needing to calibrate for a small angle change downward, what does the tire size have to do with proximity. It’s not like the truck is calculating the time it will take to hit something, it’s just sensing physical distance. Seems like Tazer and AlphaOBD are saying it’s Rams problem, but feels more like a glitch in their software but I am definitely not an expert. Maybe the parking/prox sensors take info from or input into other systems/modules more than expected. I would expect tire size being off to affect things like DTE calculation, nav turns, etc rather than parking sensors.

I would imagine it's more of a liability issue for Ram. If the truck is higher than the OEM spec and your sensors don't work causing an accident and/or hitting a child, someone could find a reason to sue.

 

[DinosaursandJesus]

Couldn’t you argue the opposite way? Ram says these accommodate 37’s, but since I couldn’t recalculate for said tires, it caused an accident. People will sue over anything these days.

 

[10mpg]

I would imagine it's more of a liability issue for Ram. If the truck is higher than the OEM spec and your sensors don't work causing an accident and/or hitting a child, someone could find a reason to sue.

But it works just fine. I have 37's and a 2 inch lift and my parking sensors still operate as intended. I have not noticed any difference.

 

[DinosaursandJesus]

But it works just fine. I have 37's and a 2 inch lift and my parking sensors still operate as intended. I have not noticed any difference.

It’s a recalibration thing. Your speed is showing slower then you’re actually going and I’m not sure we know what else is affected. You can’t recalibrate to 37’s without messing up other functions.

 

[10mpg]

It’s a recalibration thing. Your speed is showing slower then you’re actually going and I’m not sure we know what else is affected. You can’t recalibrate to 37’s without messing up other functions.

Yeah I know that speedo is off but the actual parking sensors are working. It just sucks that you can’t adjust to 37’s without turning the sensors (that still work) off completely. Ram should 100% fix this. Especially if FORD can do it.

 

[Fireman53d]

You can fit 37's but IF you have the parking sensors you cant correct it. I've tried several programmers including Alfa and it was a no go. The only one that did solve this was the Edge Pulsar but for whatever reason my 1500 did not like it and would go into limp mode on all 3 I tried. It may be a day or 6 months but it would happen. Plenty others have them with no issue. Idk if they make one for a TRX but try it out if so. Limp had nothing to do w tire size or sensors. Matter of fact , my local dealer adjusted them for my 35" tires.

 

[Fireman53d]

I have not tried this with a TRX, but was able to get my 40's on my 3500 calibrated perfectly using AlfaOBD by using a combo of gear ratio and tire size, focusing on aggregated calc. Not sure if applicable here, but may be worth digging in further on.

Changing your axle ratio to somthing that its not is going to mess with shift points etc in the tranny. Im not sure I'd want to mess with that without knowing what if any long term damage may occur.

 

[Trunty]

Changing your axle ratio to somthing that its not is going to mess with shift points etc in the tranny. Im not sure I'd want to mess with that without knowing what if any long term damage may occur.

The trans shouldn’t care. I’ll do some more digging to see if it’s a thing.

 

[Cmw1100]

Oh my speedometer is off big time with the amount of speeding fines I received after fixing 37” Nitto’s .
Mopar locally here in Dubai, has got no fix to recalibrate it. For me I think it’s a difference of 7km/h.

 

[TRXforLIFE]

I have the Tyrant with 37 package from Granger and this came with the speedo recalibration. I have not confirmed with GPS if my speed is accurate but I don't seem to be out of the norm with speeds in normal traffic on the highway. My parking sensors still work. Maybe Zach@Granger has some insight on how this was accomplished?

 

[10mpg]

I have the Tyrant with 37 package from Granger and this came with the speedo recalibration. I have not confirmed with GPS if my speed is accurate but I don't seem to be out of the norm with speeds in normal traffic on the highway. My parking sensors still work. Maybe Zach@Granger has some insight on how this was accomplished?

I think we'd all like to hear it because as far as everyone else is concerned, this is not possible today and Ram knows about it.

 

[JBTRXNJ]

I have the Tyrant with 37 package from Granger and this came with the speedo recalibration. I have not confirmed with GPS if my speed is accurate but I don't seem to be out of the norm with speeds in normal traffic on the highway. My parking sensors still work. Maybe Zach@Granger has some insight on how this was accomplished?

@Zach@Granger … thoughts?

 

[Zach@Granger]

@Zach@Granger … thoughts?

We reprogram the speedometer to reflect accurate speeds. I'm not sure on the process they use for parking sensors.

 

[10mpg]

We reprogram the speedometer to reflect accurate speeds. I'm not sure on the process they use for parking sensors.

Can you find out? Everyone here with 37's wants to know, because no one here has found a way to have both an accurate speedometer and parking sensors enabled at the same time.

 

[Cook2kill]

Can you find out? Everyone here with 37's wants to know, because no one here has found a way to have both an accurate speedometer and parking sensors enabled at the same time.

This please. I have money