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Tire size calibration question

djevox

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Later today or tomorrow I’m going to use the taser dt to calibrate my tire size. For all you guys who have already done this with any calibration tool, are you measuring all four tires with the truck sitting on the ground and averaging that, or are you just measuring the front tires and using that measurement since those tend to be a smaller number with the extra weight of the front?
 

JBowman

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I took the average after measuring all four. I used the Rough Country calibration tool and that method worked out great. The speedometer reading is spot on with the indicated speed on several of the GPS apps that I compared it against.
 

Shots

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You're fine by simply using the manufacturer's stated size. But lets say you're off a hair. For example a 35 x 12.5 may actually measure 34.6".

Even if you use 35" you're still close enough for a speedometer. We're talking about an actual size difference of 1.15%. With that minimal of a difference you'll only be driving 80.9 mph when your speedometer reads 80. The difference is less apparent as slower speeds, so you'll be driving 25.2 mph when the speedometer reads 25.

I don't think 1 mph at the high end is going to change anything, and the low end won't even register it. Don't stress it. Either measure 1 tire and call it good, or go off the manufacturer's size.
 

XmikeX

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I took the average after measuring all four. I used the Rough Country calibration tool and that method worked out great. The speedometer reading is spot on with the indicated speed on several of the GPS apps that I compared it against.
The RC tool that you have is it the inline model or is it the handheld model with front display? I have seen several models stating it will work with 19+ ram. Did you have to plug into the back of the cluster or just the OBD port under the dash?
 

Tgryphon

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Tazer DT, then used 'Waze' app to check against GPS speed, and calibrated. 35" in Tazer was off for my tires, ended up going down a couple 'clicks' from there and it was spot on.
 

JBowman

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The RC tool that you have is it the inline model or is it the handheld model with front display? I have seen several models stating it will work with 19+ ram. Did you have to plug into the back of the cluster or just the OBD port under the dash?
I have the handheld model with display. PN: 90019. Works fine on my 2021. Should be good as long as you do not have the Park Assist feature. Those that have Park Assist claim that the RC handheld model will screw with that feature.
 

Tgryphon

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"I have the handheld model with display. PN: 90019. Works fine on my 2021. Should be good as long as you do not have the Park Assist feature. Those that have Park Assist claim that the RC handheld model will screw with that feature."

I have no problem believing that...I had made the change with TazerDT and then messed with the sixe using AlfaOBD...ParkSense went haywire and it took some doing getting it straightened out
 

XmikeX

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I have the handheld model with display. PN: 90019. Works fine on my 2021. Should be good as long as you do not have the Park Assist feature. Those that have Park Assist claim that the RC handheld model will screw with that feature.
Awesome thank you, I wanted the model that you ae using since you can simply plug it in under the dash and use the GUI to calibrate. The Inline model seems to be a pain since you have to plug it into the back of the cluster and program it from a computer.

The parksense issue hasn't been resolved yet from RC? I'm still new to Ram but when you say park sense you mean the front and rear sensors that beep when you get to close to something? Is this an issue for all Ram's or just some, unfortunately if it is the park sense that beeps my truck does have it. I wonder if turning it off before tuning will help negate the issues.

Did you need to use a security bypass or just the tuner?
 
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JBowman

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Awesome thank you, I wanted the model that you ae using since you can simply plug it in under the dash and use the GUI to calibrate. The Inline model seems to be a pain since you have to plug it into the back of the cluster and program it from a computer.

The parksense issue hasn't been resolved yet from RC? I'm still new to Ram but when you say park sense you mean the front and rear sensors that beep when you get to close to something? Is this an issue for all Ram's or just some, unfortunately if it is the park sense that beeps my truck does have it. I wonder if turning it off before tuning will help negate the issues.
No. we are talking two different things. Parallel/Perpindicular Park Assist w/ stop is basically where the truck will "self park" once a spot is located. Park Sense - Front and Rear sensors with stop system provides visual and audible indications as you approach an object. I have park sense just as you listed and the RC handheld tool will work completely fine with that feature. Feel free to shoot me a message if you have more questions on it.
 
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djevox

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I’ve been thinking about this a lot over the last few days, and I’m over complicating things. The front tires have no affect on the speedometer reading, it’s just the rears. That being said, Toyo tires says that I have a 33.0 inch outer diameter and I had to set 33.73 on the tazer dt to make it match my gps.
It ended up being a very painful process of getting a nice stretch of road and pulling over just to adjust the tire size over and over again to get it just right.
 

Idahoktm

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No. we are talking two different things. Parallel/Perpindicular Park Assist w/ stop is basically where the truck will "self park" once a spot is located. Park Sense - Front and Rear sensors with stop system provides visual and audible indications as you approach an object. I have park sense just as you listed and the RC handheld tool will work completely fine with that feature. Feel free to shoot me a message if you have more questions on it.
I was going to buy the RC calibration tool, so I sent RC a message and this is their reply.

Q: Will your Speedometer Calibration tool work on a 2021 Ram 1500 with ParkSense® Front and Rear Park-Assist with Stop? This feature detects objects near the front or rear and will stop the truck if contact is predicted. In your "Notes", it says...Does not fit 20+ models with parking assist. I believe that is referring to Parallel and Perpendicular Park-Assist that automatically parks the truck, but I want to make sure before I purchase your tool.

A: No sorry it will not
 

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I was going to buy the RC calibration tool, so I sent RC a message and this is their reply.

Q: Will your Speedometer Calibration tool work on a 2021 Ram 1500 with ParkSense® Front and Rear Park-Assist with Stop? This feature detects objects near the front or rear and will stop the truck if contact is predicted. In your "Notes", it says...Does not fit 20+ models with parking assist. I believe that is referring to Parallel and Perpendicular Park-Assist that automatically parks the truck, but I want to make sure before I purchase your tool.

A: No sorry it will not

I have had several members here DM me stating the same thing. RC is indicating that it will not work and they suggest purchasing the in-line unit instead. While I am not certain, I assume RC is just telling everyone that it doesn't work because people with the self parking feature were experiencing issues. Rather than indicate which 2019+ models it does or does not work with, I think they are just stating to buy the inline tool to eliminate any potential confusion altogether. I'm not speaking on their behalf nor am I suggesting that you should go against what RC is telling you, but I can confidently say that this tool worked completely fine on my 2021 Bighorn. It goes through all prompts without issue, and also supplies a "calibration successful" message at the end of the process. Like said above, My speedometer is also dead on the money now when it originally was quite a bit off at highway speeds after adding my 35's. I've tested the parking sensors and even the auto brake feature several times since recalibrating, and it all still works perfectly fine. To my knowledge, the self parking feature is the only thing that is giving people trouble when using the unit on the 21+ models.

I included a link below of another member that also used this tool without issue.
 
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JBowman

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I’ve been thinking about this a lot over the last few days, and I’m over complicating things. The front tires have no affect on the speedometer reading, it’s just the rears. That being said, Toyo tires says that I have a 33.0 inch outer diameter and I had to set 33.73 on the tazer dt to make it match my gps.
It ended up being a very painful process of getting a nice stretch of road and pulling over just to adjust the tire size over and over again to get it just right.

Trial and error! At least you got it dialed in!
 

JBowman

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I was going to buy the RC calibration tool, so I sent RC a message and this is their reply.

Q: Will your Speedometer Calibration tool work on a 2021 Ram 1500 with ParkSense® Front and Rear Park-Assist with Stop? This feature detects objects near the front or rear and will stop the truck if contact is predicted. In your "Notes", it says...Does not fit 20+ models with parking assist. I believe that is referring to Parallel and Perpendicular Park-Assist that automatically parks the truck, but I want to make sure before I purchase your tool.

A: No sorry it will not
I recently got back from my first service and had returned the truck to the stock tire size prior to the appointment. While recalibrating, I originally set it at 33.75” when it should have been 33.25”. Figured I’d record the process while I updated it back to the correct tire size. Not really a how to, just wanted to show that the tool works okay on my 2021.
 

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I recently got back from my first service and had returned the truck to the stock tire size prior to the appointment. While recalibrating, I originally set it at 33.75” when it should have been 33.25”. Figured I’d record the process while I updated it back to the correct tire size. Not really a how to, just wanted to show that the tool works okay on my 2021.
It's pretty sad when a company like Rough Country doesn't even know their own products compatibility. I probably would have bought their tool if they had answered differently or if I watched your video. I guess it worked out because I got mine programmed with AlfaOBD for $150 less.
 

JBowman

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It's pretty sad when a company like Rough Country doesn't even know their own products compatibility. I probably would have bought their tool if they had answered differently or if I watched your video. I guess it worked out because I got mine programmed with AlfaOBD for $150 less.

Yeah, I’m not sure where the process breakdown occurred but I agree whole heartedly. It has caused a ton of confusion for a lot of members… Myself included. I also think they are missing out on potential sales due to the confusion as once many find out that the RC team says it is incompatible with their truck, they look elsewhere for another recalibration solution similar to how you did opposed to opting for the inline unit like they suggest.
 
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HSKR R/T

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I used my Pulsar to change mine. 275/65/20 Kenda Klever M/T. Set it to that size to start. Speedo read 2mph faster than GPS speed. Tried 265/65/20 and noticed no change in speedo error. Ended up at 275/60/20 and speedo is within 1mph with cruise set at 70mph. Whe initially changed to actual tire size, the 2mph error started at 40mph.

Easier to just do trial and error starting with the manufacturer tire size, than trying to measure a tire. I messed with mine over several days. Wasn't something I felt the need to stop and change immediately until I got it right. Set it, noticed the error. Next time I started the truck, I adjusted it. Still noticed error. Then kept forgetting to try a different size. Pretty simple process with the Pulsar other than you use the gas pedal to change the numbers. Idle is 0 and full throttle is 9.
 

HSKR R/T

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It's pretty sad when a company like Rough Country doesn't even know their own products compatibility. I probably would have bought their tool if they had answered differently or if I watched your video. I guess it worked out because I got mine programmed with AlfaOBD for $150 less.
Due to liability reasons, they can not market, or recommend a device for anything they haven't done the R&D testing in. Which in the Rams cases they have to test it on every model year, and engine/drivetrain configuration. If they don't list it for your vehicle, you could always ask about being used as a test vehicle for them. Back in 2007, I got a free AEM intake for my Dodge Caliber because I reached out to AEM, about using my vehicle for their testing. They had the car for four days, provided us a rental, and we got to keep the prototype intake they used on the car.
 

XmikeX

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Big shoutout to JBowman on helping me with the process and dropping some knowledge on me. I too can confirm that the part number 90019 does work for new gen rams, 2019 at least. I called RC and was told that model would not work and I needed an inline model which was $100 more. Bowman said his worked so pulled the trigger on one from amazon for $150 and successfully recalibrated my truck yesterday. Had a little difficulty eyeballing the tape measure to see how big my tires actually were but took a stab in the dark and got lucky and guessed right the first time. Truck is dead on with two different GPS applications and my MPG has gotten a little better since shift points were adjusted. Before adjusting, at certain cruising speeds my truck wouldn't shift and seemed to hang out in a higher RPM range than it needed to.

Running 275/60/20 which are stated to be 33's but needed to calibrate for 32.50
 

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