odometer counting to fast

[HawkeyeSierra]

Using these same numbers. You would be looking at around 100,011 actual miles on a truck that's odometer showed 100,000 miles.

That makes me feel better. The amount of difference is of no real consequence. At least not to me.

[Terp84Alum]

For me, the variance will be about 1400 miles at 100k. No big deal.

[RhinoGuy]

For me, the variance will be about 1400 miles at 100k. No big deal.

I may have calculated wrong. I was using memory on feet per mile and my phone for a calculator.

That makes me feel better. The amount of difference is of no real consequence. At least not to me.

You may want to check my math just in case.

[HawkeyeSierra]

I may have calculated wrong. I was using memory on feet per mile and my phone for a calculator.

You may want to check my math just in case.

I'd rather take your word for it. I don't enjoy math that much.

[TJay74]

275/55-R20 = 31.91" height

 

265/65-R18 = 31.56" height

 

GM uses the same calibration for all of the trucks for all of the tire sizes from what I have seen in the calibrations. There is nothing the dealer can do to re-calibrate the ECM due to how GM has the calibration set up in the ECM.

 

Here is how to calculate tire height.

 

275/55-R20 as the example

 

275 x .55 = 151.25mm

 

151.25mm / 25.4 = 5.9547" (This converts from mm to inches)

 

5.9547" x 2 = 11.91" (This is both sides of the tire only)

 

11.91" + 20" (wheel) = 31.19" total height.

[sk]

Everything so far is correct. I would just like to add that on these newer vehicles the diameter (actually circumference) of the tire/wheel combo affects a lot of other things, especially ABS and traction control. On small differences like the ones you guys have been talking about it isn't a big deal but if you go to a significantly larger tire you NEED to get your BCM recalibrated or you could have safety issues even if you don't care about the speedometer/odometer readings.

 

That is why if you compare all the tire sizes available from the factory no matter what wheel/tire size you have most of them come out to right around 32" diameter -- that way they are designed to work with the other electronic systems without GM having safety issues to worry about. Then if you go with an "unapproved" size they can argue that they are not responsible. This is why GM only approves certain tire sizes and why some dealers won't do a recalibrate on sizes that aren't in the computer (it has more to do with the safety systems than with the speedo/odometer not being correct).

[TJay74]

Everything so far is correct. I would just like to add that on these newer vehicles the diameter (actually circumference) of the tire/wheel combo affects a lot of other things, especially ABS and traction control. On small differences like the ones you guys have been talking about it isn't a big deal but if you go to a significantly larger tire you NEED to get your BCM recalibrated or you could have safety issues even if you don't care about the speedometer/odometer readings.

 

That is why if you compare all the tire sizes available from the factory no matter what wheel/tire size you have most of them come out to right around 32" diameter -- that way they are designed to work with the other electronic systems without GM having safety issues to worry about. Then if you go with an "unapproved" size they can argue that they are not responsible. This is why GM only approves certain tire sizes and why some dealers won't do a recalibrate on sizes that aren't in the computer (it has more to do with the safety systems than with the speedo/odometer not being correct).

 

 

 

To correct you and to re-iterate once again, no dealer nor GM can or will re-calibrate the BCM for any tire sizes other than the stock sizes. So if any owner decides to go with something larger/smaller than the stock tires you are on your own and will have to seek out custom tuning to change the tire sizes. As long as the tire sizes are in the same ratio as stock the ABS wont have any issues at all, transmission shift points are another thing, but ABS is fine. Coming from owning a C6 Corvette that runs different size tires front to rear when we would change tire sizes we had to keep the plus size in the same ratio as stock so to not trip up the ABS computer.

[Bully.207]

Okay went to the dealer they say they may have to replace the the front instrument panel but the odometer has to be out 4% which mine is at 4.5% they have to talk to the service manager on Monday won't find out till then exactly what they're going to do all the software was up-to-date just the odometer is off badly make sure you check your odometer

[oneandzero]

Interesting topic. I've recently noticed the digital display vs the speedo needle are off in my truck. My speedometer reads about 2kph faster than the digital display. I wonder what the odometer is referenced to, the analogue gauge or the digital one and which one is right.

[fondupot]

download a speedometer app on your iphone or android and compare to what your speedo says.

 

Mine is dead on....

[MK4TDI]

Interesting topic. I've recently noticed the digital display vs the speedo needle are off in my truck. My speedometer reads about 2kph faster than the digital display. I wonder what the odometer is referenced to, the analogue gauge or the digital one and which one is right.

I've noticed this as well with my truck both before the Blackbear tune and after. However, when I switch the units over to "US" the indicated speed on the needle and the digital read out are bang on in MPH. Switch back to metric and the needle will read a touch higher.

 

Going back a few years to my VW, I recall reading that there was some legislation that stated a speedometer had to read/indicate that the vehicle was travelling just slightly faster than it was to avoid speeding ticket issues. In Canada on single lane highways a lot of people set their cruise at 110 when the speed limit is 100. When traffic cops are running radar that keeps most people under the 10 km/h grace window with most vehicles travelling around 108/109.

 

 

Sent from my HTC One M9 using Tapatalk

[oneandzero]

I've noticed this as well with my truck both before the Blackbear tune and after. However, when I switch the units over to "US" the indicated speed on the needle and the digital read out are bang on in MPH. Switch back to metric and the needle will read a touch higher.

 

Going back a few years to my VW, I recall reading that there was some legislation that stated a speedometer had to read/indicate that the vehicle was travelling just slightly faster than it was to avoid speeding ticket issues. In Canada on single lane highways a lot of people set their cruise at 110 when the speed limit is 100. When traffic cops are running radar that keeps most people under the 10 km/h grace window with most vehicles travelling around 108/109.

 

 

Sent from my HTC One M9 using Tapatalk

Interesting. I checked mine with a speed app and found the digital display is correct and the needle is off.

Not sure what the speeding tolerance is now for years if you stayed below 120 you were ok. Now I think its more 130ish.

[dave07]

How does varying tread depths through wear and different tires play into all of this .

 

 

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[SouthernSilveradoGuy85]

I don't use the digital speed in the DIC, but it seems to be that the analog gauge shows maybe a 1/2 mph above which isn't a big deal. That's at about 60 mph so the slower you go the less it will be off. I'm going off of when I set the cruise control which I assume goes with the digital speedometer.

[Bully.207]

Sorry i haven't got back to everyone on this but i did contact gm and open up a case, So this is documented. Because i really don't want the dealership to pull apart my dash to replace instrument panel.This is a leased truck, but i am going to be buying the truck anyway. I have put to much money into this truck to trade it in 2.5 years from now and pay that ridiculous tax on new vehicles. So far so good no issues except this and the quirky 8 speed trans.