Speedometer Calibration after New Tires

[JohnGow383]

Hi. I've pre-ordered a 2022 RAM Limited Night Edition 5.7 Hemi (no e-torque) and should have it by Novemeber. I am having them fit a lift kit, either a 4inch BDS or the 5inch Rough Country lift. Still undecided which one to go for. I want to fit 35" tires to the stock rims.
The dealer is telling me he is unable to re-calibrate the speedo on the 21s and later without sacrificing either the parking sensors / park assist etc, or, having those work but not having the Sat Nav working.
Is there a way to calibrate this. They used to use the RC calibrator and have tried using tazer but says it can't be done now. I'm in the UK so not many dealers to chose from, bearing in mind this is a US import.
I guess I could live with the speed difference, but then it affects mpg readout, odomoter, oil change notifications etc so would really like to not sacrifice anything on a brand new truck

 

[Mountain Whiskey]

I used the Tazer to adjust mine but there are many kits that will allow you to do this. Look on Amazon. I am positive someone is going to suggest AlfaOBO here too.

Heads up, the stock rims won't fit back on with the BDS kit installed. My plan was to have the lift installed then go to Discount Tire and have them swap out the wheels for something decent with the right offset. The shop called with the news that the plan would not work. They sent someone to go get them for me.

I imagine the budget lift will be the same.

 

[HSKR R/T]

There is something with the programming that causes the park sensors to stop working with when going 35" or taller on tires.

 

[JohnGow383]

There is something with the programming that causes the park sensors to stop working with when going 35" or taller on tires.

Yeah it seems to be only since 2021 or 22 models when they updated the brain.

 

[JohnGow383]

I used the Tazer to adjust mine but there are many kits that will allow you to do this. Look on Amazon. I am positive someone is going to suggest AlfaOBO here too.

Heads up, the stock rims won't fit back on with the BDS kit installed. My plan was to have the lift installed then go to Discount Tire and have them swap out the wheels for something decent with the right offset. The shop called with the news that the plan would not work. They sent someone to go get them for me.

I imagine the budget lift will be the same.

I've been told the Tazer won't work with 2021 models or newer or if it does you lose either Sat Nav or brake sensors (take your pick which you'd want to sacrifice). That's annoying the stock wheels won't fit. I don't want to get my Fuels until I know I can get everything working before I take the plunge.
Still torn whether or not to go with the BDS or the RC The RC is quite a bit cheaper and I'm not planning on taking it off road, more of a pavement princess, but I guess you get what you pay for. BDS has more components, better quality, made in USA and warranty but 1less inch, so torn

 

[JohnGow383]

There is something with the programming that causes the park sensors to stop working with when going 35" or taller on tires.

Is there any solution yet? I really don't want to lose the brake sensors and all that goes with it. I doubt ill use the park assist much but it's a cool show off feature but the emergency braking would be handy, espeically in the UK with tiny parking slots and small roads

 

[Mketch]

I have a similar plan only with stock 20’s. I was of the understanding that backspacing was the issue with stock wheels and the bds 4” lift. My plan was to use the thinnest possible spacer. Maybe 1/4 inch? Order a few sizes then send some back? Cheaper than new wheels plus I’m in the type to prefer oem wheels anyway. Mine is supposed to be built on 10/1.

 

[Shots]

Is there any solution yet? I really don't want to lose the brake sensors and all that goes with it. I doubt ill use the park assist much but it's a cool show off feature but the emergency braking would be handy, espeically in the UK with tiny parking slots and small roads

So if I'm understanding correctly the issue isn't with recalibrating in general, it's the recalibration to account for 35's? That would suggest that if you went with 34's you could recalibrate and retain the Sensors and Sat-Nav. Correct?
If that's the case I'd just have them set the tires at 34" instead of 35". Not a huge difference (only 3%) which some factory spare tires are off that much. This keeps your speedometer pretty close to accurate rather than leaving it unadjusted. For example, if you're on the motorway and your speedometer shows 110 kph, you'd actually be traveling 113 kph (for my SAE bound friends that's only 2 mph difference).
Likewise you're odometer would only be off 3% as well. So if you're changing your oil at 8,000 Km, you'd actually have traveled 8,240 Km. That difference of 240 Km is minimal when changing oil (roughly 150 miles U.S.).

To me, this seems like a good work around. You make the adjustment to keep everything reading pretty close, while also getting to keep the function of your Sensors and Sat-Nav.
Besides, a lot of tire makers 35's physically measure closer to 34" so you may not even be off the full 3% depending on the tires you get. I'd say just recalibrate to 34" (even though they're 35's) and call it close enough.

 

[HSKR R/T]

Yeah it seems to be only since 2021 or 22 models when they updated the brain.

The sat nav thing might be 21/22 model year, but the park sensors are all 5th gens

 

[GKIII]

Is there any solution yet? I really don't want to lose the brake sensors and all that goes with it. I doubt ill use the park assist much but it's a cool show off feature but the emergency braking would be handy, espeically in the UK with tiny parking slots and small roads

The emergency rear braking is the absolute most annoying thing on these trucks. Way over-sensitive to the point it's useless. I disabled mine anyway.

 

[JohnGow383]

So if I'm understanding correctly the issue isn't with recalibrating in general, it's the recalibration to account for 35's? That would suggest that if you went with 34's you could recalibrate and retain the Sensors and Sat-Nav. Correct?
If that's the case I'd just have them set the tires at 34" instead of 35". Not a huge difference (only 3%) which some factory spare tires are off that much. This keeps your speedometer pretty close to accurate rather than leaving it unadjusted. For example, if you're on the motorway and your speedometer shows 110 kph, you'd actually be traveling 113 kph (for my SAE bound friends that's only 2 mph difference).
Likewise you're odometer would only be off 3% as well. So if you're changing your oil at 8,000 Km, you'd actually have traveled 8,240 Km. That difference of 240 Km is minimal when changing oil (roughly 150 miles U.S.).

To me, this seems like a good work around. You make the adjustment to keep everything reading pretty close, while also getting to keep the function of your Sensors and Sat-Nav.
Besides, a lot of tire makers 35's physically measure closer to 34" so you may not even be off the full 3% depending on the tires you get. I'd say just recalibrate to 34" (even though they're 35's) and call it close enough.

Hi,
Thanks for the reply. I will have to investigate and see if it's possible to do this. Are 34s even a standard size tire tho? With smaller tires we are using a different format for the tire numbering ie the tire width in mm, the profile ratio then the internal diameter in inches (315/55/22) for example.

PS - I'm from the UK and we use miles on our roads not km

 

[JohnGow383]

So if I'm understanding correctly the issue isn't with recalibrating in general, it's the recalibration to account for 35's? That would suggest that if you went with 34's you could recalibrate and retain the Sensors and Sat-Nav. Correct?
If that's the case I'd just have them set the tires at 34" instead of 35". Not a huge difference (only 3%) which some factory spare tires are off that much. This keeps your speedometer pretty close to accurate rather than leaving it unadjusted. For example, if you're on the motorway and your speedometer shows 110 kph, you'd actually be traveling 113 kph (for my SAE bound friends that's only 2 mph difference).
Likewise you're odometer would only be off 3% as well. So if you're changing your oil at 8,000 Km, you'd actually have traveled 8,240 Km. That difference of 240 Km is minimal when changing oil (roughly 150 miles U.S.).

To me, this seems like a good work around. You make the adjustment to keep everything reading pretty close, while also getting to keep the function of your Sensors and Sat-Nav.
Besides, a lot of tire makers 35's physically measure closer to 34" so you may not even be off the full 3% depending on the tires you get. I'd say just recalibrate to 34" (even though they're 35's) and call it close enough.

Oh, I re-read what you said. So you're saying put the 35s on but re-calibrate to 34s and live with the slight error? Is that what you mean?
I need to check with him if it's the re-calibration in general thats locked out or if it's that he's unable to enter correct the figure to account for the rolling circumference of the 35s. As I said he said he has tried using Tazer and you no longer get the correct options but it used to work for 2019 and 2020 models.

 

[utlong31]

So this all makes more sense now. I put 35 on my truck right after I got it new and my front and rear sensors haven’t worked. I was planning on taking it in and getting it looked at. Would have felt stupid when they told me this.


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[JohnGow383]

So this all makes more sense now. I put 35 on my truck right after I got it new and my front and rear sensors haven’t worked. I was planning on taking it in and getting it looked at. Would have felt stupid when they told me this.


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These seosnors are kinda important. I mean when you're buying a brand new truck you want everything to work and they are essentially telling me I have 3 options. Put agressive 33s on and have everything working, or, put 35s on and have parking sensors working and lose sat nav or put 35s on and lose parking sensors but have sat nav. I just fear 33s on a 4 or 5 inch lift will look too small and underwhelming, but then at least everthing will still work.

Out of interest, how badly was your gas milage affected after fitting 35s compared to stock? I ask as gas is very expensive here. It has come down to around £1.60 a liter (was around 1.85) which I think is around $7 a gallon. I am prepared to take the hit tho fo smiles to the gallon

 

[HSKR R/T]

These seosnors are kinda important. I mean when you're buying a brand new truck you want everything to work and they are essentially telling me I have 3 options. Put agressive 33s on and have everything working, or, put 35s on and have parking sensors working and lose sat nav or put 35s on and lose parking sensors but have sat nav. I just fear 33s on a 4 or 5 inch lift will look too small and underwhelming, but then at least everthing will still work.

Out of interest, how badly was your gas milage affected after fitting 35s compared to stock? I ask as gas is very expensive here. It has come down to around £1.60 a liter (was around 1.85) which I think is around $7 a gallon. I am prepared to take the hit tho fo smiles to the gallon

Depending on the tire you use, the rolling circumference ofa 35" tire will actually be less than 35" so when you calibrate speedo for tire size change, even though you technically have 35" tires, the size you need to set using calibrator will be 34.x" keeping the sensors happy my "34" in 275/65/20 tires actually required me to use 275/60/20 for tire size to make speedo correct to GPS speed.

 

[utlong31]

Out of interest, how badly was your gas milage affected after fitting 35s compared to stock? I ask as gas is very expensive here. It has come down to around £1.60 a liter (was around 1.85) which I think is around $7 a gallon. I am prepared to take the hit tho fo smiles to the gallon [/QUOTE]

I barely drove it with the stick tires and only around town. I haven’t had my Speedo calibrated yet and it’s off by 6 mh.


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[Av1]

Hi. I've pre-ordered a 2022 RAM Limited Night Edition 5.7 Hemi (no e-torque) and should have it by Novemeber. I am having them fit a lift kit, either a 4inch BDS or the 5inch Rough Country lift. Still undecided which one to go for. I want to fit 35" tires to the stock rims.
The dealer is telling me he is unable to re-calibrate the speedo on the 21s and later without sacrificing either the parking sensors / park assist etc, or, having those work but not having the Sat Nav working.
Is there a way to calibrate this. They used to use the RC calibrator and have tried using tazer but says it can't be done now. I'm in the UK so not many dealers to chose from, bearing in mind this is a US import.
I guess I could live with the speed difference, but then it affects mpg readout, odomoter, oil change notifications etc so would really like to not sacrifice anything on a brand new truck

Remember that 35" sized tires are not actually 35" diameter. Most are a bit under.

Also, you want to re-calibrate the speedo using the rolling diameter of the tire. So, measure center of wheel hub to ground with tires installed on the truck then multiply by two for rolling diameter. It will be quite a bit less than the diameter unloaded.

Finally, as long as you program for 33.75" rolling diameter or below everything works fine on a 2022. It did for me.

Good luck.

Edit: I jumped the gun and overlooked you have a Limited with parking assist. I don't know if parking assist will work or not. I own a Laramie without parking assist, but my parking sensors work fine.

 

[Mountain Whiskey]

I've been told the Tazer won't work with 2021 models or newer or if it does you lose either Sat Nav or brake sensors (take your pick which you'd want to sacrifice). That's annoying the stock wheels won't fit. I don't want to get my Fuels until I know I can get everything working before I take the plunge.
Still torn whether or not to go with the BDS or the RC The RC is quite a bit cheaper and I'm not planning on taking it off road, more of a pavement princess, but I guess you get what you pay for. BDS has more components, better quality, made in USA and warranty but 1less inch, so torn

The Tazer has no issues on mine.

Look into the ride quality of the RC lift. Most do the 3.5 because it uses stock springs. I would imagine you are replacing them with 5. RC has a poor reputation in the Jeep world. I don't know about the 5 inch for trucks though.

 

[JohnGow383]

The Tazer has no issues on mine.

Look into the ride quality of the RC lift. Most do the 3.5 because it uses stock springs. I would imagine you are replacing them with 5. RC has a poor reputation in the Jeep world. I don't know about the 5 inch for trucks though.

Thanks. I've heard the 5" lift kit isn't too bad at all. That's if you don't intend to take it off-road.

 

[JohnGow383]

Remember that 35" sized tires are not actually 35" diameter. Most are a bit under.

Also, you want to re-calibrate the speedo using the rolling diameter of the tire. So, measure center of wheel hub to ground with tires installed on the truck then multiply by two for rolling diameter. It will be quite a bit less than the diameter unloaded.

Finally, as long as you program for 33.75" rolling diameter or below everything works fine on a 2022. It did for me.

Good luck.

Edit: I jumped the gun and overlooked you have a Limited with parking assist. I don't know if parking assist will work or not. I own a Laramie without parking assist, but my parking sensors work fine.

Yeah I guess the 35s are actualy more like 34¼ or thereabouts and setting it to 33¾ as you say should work albeit have a small error.
I'm going to have to run all this past the dealer. Thanks