Tire Calibration

[Hoorah77]

Sorry if this has been covered but I did not see a thread…

Just put 35s on and drove from FL to GA.The difference between Waze and the speedometer was consistently 3-4 mph the entire trip. Today I put a couple of hours on the highway driving to ATL. Now they match perfectly. There and back.
Bought the truck used and the stock 33s looked almost new. Several upgrades to the stock version including exhaust and other minor replacements to the engine. Is it possible for the previous owner to have added 35s previously and changed the settings?

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[Gvsukids]

Sorry if this has been covered but I did not see a thread…

Just put 35s on and drove from FL to GA.The difference between Waze and the speedometer was consistently 3-4 mph the entire trip. Today I put a couple of hours on the highway driving to ATL. Now they match perfectly. There and back.
Bought the truck used and the stock 33s looked almost new. Several upgrades to the stock version including exhaust and other minor replacements to the engine. Is it possible for the previous owner to have added 35s previously and changed the settings?

Possibly. You could use a scanner like Tazer or jscan. Maybe your dealership would check for you.

 

[ShadowsPapa]

Just put 35s on and drove from FL to GA.The difference between Waze and the speedometer was consistently 3-4 mph the entire trip. Today I put a couple of hours on the highway driving to ATL. Now they match perfectly. There and back.

So you are saying with the 35s on it was off 3 to 4 mph, then today you drove it and it was a perfect match.
With the same tires?
OR are you saying you had 33s on it and it was off, THEN you put 35s on and it was fine?
The way you worded it you put 35s on and it was off, then it wasn't off.
That's not possible.
If it was off on one trip unless YOU changed tires or changed settings, it can't be wrong one trip and ok the next.
They are either always wrong or always right.

 

[mtudb24]

What Papa said. Its either going to be always off or always on. The ECM doesn't learn new tire heights. Factory 32" going to 35's is about a 10% change depending on true diameter of old and new tires, so at 50mph, a 5mph diff (reading slow going to larger tire). 40mph is 4mph and so on.
My dealer used their MVP calibration when I bought my jeep as I brought them my 35's before I even took delivery of the truck. It was $125.

Here is Interco's calibration tool on their website for reference

https://www.intercotire.com/calculator_speedometer_adjustment_tire_size_change

 

[Main Line Willys]

If my phone is plugged in and I am using waze through carplay, the speedometer matches waze.
If I am not plugged in or connected through BT, they will read different speeds.

 

[jcarbs]

Using Waze and now having upgraded to 35's, I am consistently off 3 to 4 miles per hour when going 65 or faster on the freeway. Below 60, Waze and my speedometer aren't that much off. I wonder if the OP is seeing something similar.

 

[SargeDiesel]

It changed because your phone was plugged in, it was mirroring the vehicles calibration.

 

[Hoorah77]

Ok. Yes the phone was plugged in on the second trip and I honestly don’t remember if it was plugged in the first time but based on these answers it sounds like I should check it again without directly connecting.

Thanks everyone.

 

[AmosMoses01]

Hmmm... I've had a bit of oddity going on that may (or may not) be similar to what you're seeing. I put 37's on in mid-summer last year, and as part of that process used the Tazer Mini to reprogram my tire size. Speedo matched what Waze said.

In the past several months, however, the speedo disagrees with what Waze says - by about 2 mph in the 30 - 50 mph range, scaling to more with higher road speed. (I.e. Waze says I'm going 47, speedo says 45). When this first happened, I thought that perhaps it was tire pressure variances with the weather changing. Ever since, though, I've checked the tire pressure whenever Waze and the speedo disagree. I haven't found any rhyme or reason to it, but there are some days they are in agreement and other days they're slightly off from one another, all whilst having the same tire pressure. I've wondered if Selective Availability could be in play causing Waze to be off - but figured if that was the case a lot of others would be noticing it. It's a mystery...

 

[SargeDiesel]

Ok. Yes the phone was plugged in on the second trip and I honestly don’t remember if it was plugged in the first time but based on these answers it sounds like I should check it again without directly connecting.

Thanks everyone.

This has been covered and the conclusion was the connection caused the issue. Definitely unplug/no Bluetooth... go fully analog and I bet you will see the difference again. Sorry I don't remember/have a link to previous post about it. Good luck with it !

 

[BAT]

I just put new tires on Toyo 34's and had Falken Wildpeak 33's on before. When I used the Tazer to set the Wildpeaks I set it at around 32 or something like that to get my speedometer to match correctly. I took my truck down the road from my house with the new tires and there is a radar sign my speedometer currently is a bit off so will have to go in with the Tazer and make adjustment. I was doing 35 MPH in the truck and the radar sign was showing that I was doing 37. Previously this sign was spot on with me speedometer before the tire change.

 

[BAT]

Oh a thought just crossed my mind and wonder if it makes a difference. I rant the Wildpeaks at 37 psi and had asked Discount Tire to set the new Toyo 34's at 37 but when I checked the tires were all set to either 34 or35 psi. I think tomorrow I will bring them to 37 and then check the speedo again

 

[ShadowsPapa]

Oh a thought just crossed my mind and wonder if it makes a difference. I rant the Wildpeaks at 37 psi and had asked Discount Tire to set the new Toyo 34's at 37 but when I checked the tires were all set to either 34 or35 psi. I think tomorrow I will bring them to 37 and then check the speedo again

37 is high.
Why not use a GPS or speedometer app on your phone?
I used GPS and drove several miles, then compared the truck odometer to the GPS trip tracker and got it spot-on.
Heck, even the stock 33s on a Rubicon are only 36 psi, I'd not run a larger tire with more PSI.

 

[BAT]

Toyo didn’t really give any information on what PSI to run them at from what I saw other than max was 65 psi. The wild peaks seemed to run best for me at 36-37 psi. Jeep dealership had them at 41 but I dropped them down as it was not handling well at 41 psi. Since these tires are similar in size (Toyo has them listed as 34’s) but everything I have seen points to them really just being 33’s.

 

[BAT]

37 is high.
Why not use a GPS or speedometer app on your phone?
I used GPS and drove several miles, then compared the truck odometer to the GPS trip tracker and got it spot-on.
Heck, even the stock 33s on a Rubicon are only 36 psi, I'd not run a larger tire with more PSI.

I'll look at the speedo some more this evening along with Waze. Yesterday I just ran it against the radar by my house. Guess I will have to find the sweet spot with these new Toyo's and the PSI to run them. Maybe 34 is going to be it.

I did a tire calculator deal to get an idea and below is what it came back with for the tires. Previous Tires were the Falken Wildpeak and New are the Toyo's

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