Speedometer Calibration/Correction

Ducatislave

Hasn't posted much yet...
42
6
8
Georgetown, TX
Genesis Model Type
1G Genesis Sedan (2009-2014)
Had this posted in the wheel and tires section but had not gotten many views let alone a response. So we shall try General Discussion.

Vehicle: 2013 3.8L Sedan base model. 41,500 mi.

I'm trying to find out if anyone has tried this yet, and if so did the tires fit without rubbing?
My speedometer if off by 6% by my math and confirmed to two different GPS units and a cell phone running simultaneously.
If I am going 100 mph on the speedo I am only actually going 94 mph.

Speedo reading vs. Actual speed
50 47
60 56
80 75
100 94
120 113
140 131
160 150
180 169
200 188

According to my math as well as a tire size calculator I believe that changing from a 225/55R17(which is essentially a 27" tall tire) to a 225/65R17 (a 29" tall tire) will correct the speedo to within 0.3% accuracy. It is only about a 1.5 lb weight increase per tire and a height increase of 1" so handling and braking should not be affected much if at all. Plus I will get the added benefit of clearing most curbs too.
I have spoken to the dealership about the issue and asked if this can be corrected in the computer by changing the number of and ring pings per mile.
I have done this using EFI live on my old 2004 GMC and the math isn't terribly hard to calculate.
According to the book and labels the tires on it now are the correct size. They claim that they are not capable of reprogramming the ECM to alter the speedometer.
My biggest concerns are, #1 it is not accurately recording the real miles on the odometer. If my 6% calculation is correct, then it would mean that the real mileage on my car is not 42.5 k but more like 39.9 k. And #2 it is not correctly calculating my mpg, or more to the point I could get better mpg with large tires.
Has anyone else had this issue of the speedo being this far off? If so did you have it corrected, and how?
 

Rspected

Registered Member
62
17
8
Genesis Model Type
1G Genesis Sedan (2009-2014)
65s would look huge on these cars but if you think that will work then try it... or go with the factory size tires/wheels because the car was designed to work in sync with them. So that's your best bet to get accurate readings
 

Rspected

Registered Member
62
17
8
Genesis Model Type
1G Genesis Sedan (2009-2014)
does Any one even make a 65 series tire for anything other than a truck?
I was surprised when he said he had 55s on there lol. Mine came stock with 45s and I now have 19" aftermarket wheels with 35 sidewalls. 65 is massive
______________________________
 

Mr. Incredible

SUSTAINING MEMBER
1,625
454
83
Genesis Model Type
Genesis G80 Sport
something isn't right..

the correct tire for a 2009 to 2014 Gen 1 is either a 235/50R18 or 225/55R17 depending on the options. both are essentially the same size tire, very minimal difference in overall size (.39" width difference and .52" height) resulting in roughly a .3 to 1.8 mph difference in the Speedo between the 2 sizes.

Either there is an issue with the Speedo, which a dealer should be able to easily recalibrate, as such is required by Federal regulation. Or the OPs math and or GPS readings are seriously off..

The standard deviation is +/- 2mph from a GPS, this is fairly normal for all makes/models because of the different tire sizes offered, anything beyond that requires a recalibration, which again is easily done by a competent dealer, the ability to do so is required by federal regulation.
 

Rspected

Registered Member
62
17
8
Genesis Model Type
1G Genesis Sedan (2009-2014)
something isn't right..

the correct tire for a 2009 to 2014 Gen 1 is either a 235/50R18 or 225/55R17 depending on the options. both are essentially the same size tire, very minimal difference in overall size (.39" width difference and .52" height) resulting in roughly a .3 to 1.8 mph difference in the Speedo between the 2 sizes.

Either there is an issue with the Speedo, which a dealer should be able to easily recalibrate, as such is required by Federal regulation. Or the OPs math and or GPS readings are seriously off..

The standard deviation is +/- 2mph from a GPS, this is fairly normal for all makes/models because of the different tire sizes offered, anything beyond that requires a recalibration, which again is easily done by a competent dealer, the ability to do so is required by federal regulation.
I agree. Although my 5.0 came with 45 sidewalls on the continentals. But I agree that a dealer should have no issues recalibrating the speedometer. They have a seriously expensive tablet tool they can plug into the OBD and run all kinds of calibrations and diagnostic tests. If they said they cant then they are either dumb or lazy
 

Mr. Incredible

SUSTAINING MEMBER
1,625
454
83
Genesis Model Type
Genesis G80 Sport
BTW the faster you go the larger the deviation, it is not consistent.

235/50R18225/55R17Difference
2019.6-.04
3029.3-.07
4039.1-.09
5048.9-1.2
6058.7-1.3
7068.5-1.5
8078.2-1.8
9088-2.0
 

Mr. Incredible

SUSTAINING MEMBER
1,625
454
83
Genesis Model Type
Genesis G80 Sport
I agree. Although my 5.0 came with 45 sidewalls on the continentals. But I agree that a dealer should have no issues recalibrating the speedometer. They have a seriously expensive tablet tool they can plug into the OBD and run all kinds of calibrations and diagnostic tests. If they said they cant then they are either dumb or lazy

agreed
______________________________
 

Mr. Incredible

SUSTAINING MEMBER
1,625
454
83
Genesis Model Type
Genesis G80 Sport
oh the interwebs are a wonderful place.

easily found online:

TESTING SPEEDOMETER OPERATION AND ACCURACY
Model Start Year End Year
All Hyundai Models 2005-2015


PROCEDURE

1. Ensure that your Hi-Scan Pro has the latest SOL Application Software Card.

2. Connect the DLC connector of your Hi-Scan tool to the vehicle's DLC port.

3. Turn the vehicle's ignition to the "ON" position. (do not start the vehicle).

4. Turn the Hi-Scan Pro tool on.

5. On the ‘INITIAL SCREEN', select ‘TOOL BOX (DVOM/SCOPE)'.

6. Next, on the ‘TOOL BOX (DVOM/SCOPE)' screen, select ‘SENSOR SIMULATOR'.

7. After selecting the sensor simulator fuction, a cautionary statement related to the

"Channel B test probe" (not used in the procedure) will be displayed. Press any
key to continue.

8. The ‘SENSOR SIMULATOR' screen will now be displayed. The default function is
VSS, vehicle speed simulation.

9. Enter a target test speed by using the ‘+' and ‘-' keys.

10. A target test speed of 20MPH entered into the Hi-Scan Pro should result in a
readout on the vehicle's speedometer of 20MPH, plus or minus the tolerance
specified in step 13.

11. A target test speed of 100MPH entered into the Hi-Scan Pro should result in a
readout on the vehicle's speedometer of 100MPH, plus or minus the tolerance
specified in step 13.

12. If diagnosing a suspected non-operational speedometer and the target test speed
is displayed, the speedometer is functioning properly and focus should be placed
on testing the Vehicle Speed Sensor, physical connections, and wiring. Refer to
the appropriate Electrical Troubleshooting Manual and Shop Manual for complete
diagnostic procedures.

13. If diagnosing speedometer accuracy, use the following tolerance chart to
determine if the speedometer gauge is within proper specifications.

14. If the speedometer displays target test speeds correctly while connected to the
Hi-Scan, but appears to be out of specification during road speed tests, focus
should be placed on testing the Vehicle Speed Sensor, checking tire pressure, and
tire/wheel rolling diameter. Refer to the appropriate Electrical Troubleshooting
Manual and Shop Manual for complete diagnostic procedures.


---

allows for a tolerance of +/-1.5MPH at 60MPH, and +/-2.5MPH at 120MPH.
 

Ducatislave

Hasn't posted much yet...
42
6
8
Georgetown, TX
Genesis Model Type
1G Genesis Sedan (2009-2014)
65s would look huge on these cars but if you think that will work then try it... or go with the factory size tires/wheels because the car was designed to work in sync with them. So that's your best bet to get accurate readings
As I stated in the original post, it has the factory original tire size currently, as well as the factory original wheels.

----
Mr. Incredible, hows the weather up there on that soapbox?

1.
does Any one even make a 65 series tire for anything other than a truck?
yes actually, with the ever increasing popularity of CUV type vehicles a 225/65R17 is a fairly popular size. Particularly in the Grand Touring and Ultra Touring class.

2.
something isn't right..

the correct tire for a 2009 to 2014 Gen 1 is either a 235/50R18 or 225/55R17 depending on the options. both are essentially the same size tire, very minimal difference in overall size (.39" width difference and .52" height) resulting in roughly a .3 to 1.8 mph difference in the Speedo between the 2 sizes.

Either there is an issue with the Speedo, which a dealer should be able to easily recalibrate, as such is required by Federal regulation. Or the OPs math and or GPS readings are seriously off..

The standard deviation is +/- 2mph from a GPS, this is fairly normal for all makes/models because of the different tire sizes offered, anything beyond that requires a recalibration, which again is easily done by a competent dealer, the ability to do so is required by federal regulation.
Would you mind finding the EXACT federal DOT regulation on that "required" ability, I was unable to find it, since you are apparently a Google wizard. And I am confused here, you are talking about a deviation in a gps unit and then about different tire size options. The two systems are completely unrelated, even if the vehicle has a built in gps unit.
The dealer I went to stated that they could test the speedo, but has no way to PERMANENTLY alter the reading once they exit the test program.

Additionally in regards to both my math and GPS reading; since I originally posted this I have triple checked my readings with the assistance of a friend of mine from the WilCo. sheriffs office and his department issued speed laser. It confirmed that all my previous finding were accurate, and that my speedometer is in fact reading 6.134% off.

3.
BTW the faster you go the larger the deviation, it is not consistent.
No kidding, I already stated that the variation I was seeing was 6% not 6mph, hence the actual vs. speedo reading I posted.


Finally: the original question I had asked, which was only addressed by one person (thank you Rspected), was; If anyone had tried using a taller tire and if it fits without rubbing?
 

Mr. Incredible

SUSTAINING MEMBER
1,625
454
83
Genesis Model Type
Genesis G80 Sport
As I stated in the original post, it has the factory original tire size currently, as well as the factory original wheels.

----
Mr. Incredible, hows the weather up there on that soapbox?

1.
yes actually, with the ever increasing popularity of CUV type vehicles a 225/65R17 is a fairly popular size. Particularly in the Grand Touring and Ultra Touring class.

2.

Would you mind finding the EXACT federal DOT regulation on that "required" ability, I was unable to find it, since you are apparently a Google wizard. And I am confused here, you are talking about a deviation in a gps unit and then about different tire size options. The two systems are completely unrelated, even if the vehicle has a built in gps unit.
The dealer I went to stated that they could test the speedo, but has no way to PERMANENTLY alter the reading once they exit the test program.

Additionally in regards to both my math and GPS reading; since I originally posted this I have triple checked my readings with the assistance of a friend of mine from the WilCo. sheriffs office and his department issued speed laser. It confirmed that all my previous finding were accurate, and that my speedometer is in fact reading 6.134% off.

3.

No kidding, I already stated that the variation I was seeing was 6% not 6mph, hence the actual vs. speedo reading I posted.


Finally: the original question I had asked, which was only addressed by one person (thank you Rspected), was; If anyone had tried using a taller tire and if it fits without rubbing?

dude I spent 20 years working as a tech and in the corporate offices of two major car manufacturers working on vehicle computer systems.

If you learn to comprehend what you read, my statement was very clear, there is a stand deviation of +/- 2mph when using a GPS to calculate your speed, meaning that your Speedometer can be off +/- 2mph from the GPS BECAUSE of different tire sizes offered for the same make and model, in other words, the manufacturers DO NOT calibrate to EACH tire size they offer, but to an average. between them, leaving a margin of error in the cluster between its reported speed and a GPS. I've seen this in many makes/models. My Lexus reported 2 mph faster than my GPS at 50mph with the optional 19" wheels, and the same model with the standard 18" wheels reported 1 mph slower.

The ability to calibrate a speedometer is a federal regulation, all manufacturers must have a way to do it , some can do it on the fly with the manufacturer ODBII tech tool others like Chrysler require the cluster to be sent to the factory for recalibration. But it is a federal regulation by that the speedo and odo must be accurate within 2mph @ 80mph and capable of being calibrated to that margin of error NHTSA DOT 49 CFR § 393.82 -

and Hyundai has the ability to do it, I even found the correct procedure on how it is done with their tech tool for cars up to 2015, just because the "dealer" says they can't do it, doesn't mean it can't be done, simply means they don't know how to do it..

you can do whatever you want to your car, if you want taller tires on it go for it, I for one would be demanding the dealer fix the issue, not putting a Band-Aid on it with bigger tires.
 

edizzle89

Registered Member
111
32
28
Columbus, IN
Genesis Model Type
1G Genesis Sedan (2009-2014)
The ability to calibrate a speedometer is a federal regulation, all manufacturers must have a way to do it , some can do it on the fly with the manufacturer ODBII tech tool others like Chrysler require the cluster to be sent to the factory for recalibration. But it is a federal regulation by that the speedo and odo must be accurate within 2mph @ 80mph and capable of being calibrated to that margin of error NHTSA DOT 49 CFR § 393.82 -
The wording of that section doesn't ever state that the manufacturer must be able to calibrate the speedometer after the vehicle is sold, not that it's impossible but tampering with the speedometer can also affect the odometer over time which is probably a big no-no if anyone's caught doing that for shady resale purposes, like when they rolled back odometers back in the 'mechanical gauges' days.

Per the regulation:
§ 393.82 Speedometer.
Each bus, truck, and truck-tractor
must be equipped with a speedometer
indicating vehicle speed in miles per
hour and/or kilometers per hour. The
speedometer must be accurate to with-
in plus or minus 8 km/hr (5 mph) at a
speed of 80 km/hr (50 mph).


And according to this regulation he is within spec as he's doing 47 mph when the speedo is indicating 50, falling within the +/-5 mph
______________________________
 

Ducatislave

Hasn't posted much yet...
42
6
8
Georgetown, TX
Genesis Model Type
1G Genesis Sedan (2009-2014)
dude I spent 20 years working as a tech and in the corporate offices of two major car manufacturers working on vehicle computer systems.
First off, please refrain from referring to me as "dude". I am not some long haired surfer from the sunny shores of Cali. I address you by your username and expect the same reciprocity.
The ability to calibrate a speedometer is a federal regulation, all manufacturers must have a way to do it , some can do it on the fly with the manufacturer ODBII tech tool others like Chrysler require the cluster to be sent to the factory for recalibration. But it is a federal regulation by that the speedo and odo must be accurate within 2mph @ 80mph and capable of being calibrated to that margin of error NHTSA DOT 49 CFR § 393.82 -
Second...damn... edizzle89 beat me to it. I was going to post the exact wording of that section you quoted. I have seen some state laws regarding the sale of imported vehicles being illegal to sell if the speedometer cannot display in MPH but never a LAW stating that a dealer MUST have the capacity to RE-calibrate a speedometer beyond what is set at the factory. By your own post on the "procedure" it talks about CHECKING the accuracy NOT adjusting it.

oh the interwebs are a wonderful place.

easily found online:

TESTING SPEEDOMETER OPERATION AND ACCURACY
Model Start Year End Year
All Hyundai Models 2005-2015


PROCEDURE

1. Ensure that your Hi-Scan Pro has the latest SOL Application Software Card.

2. Connect the DLC connector of your Hi-Scan tool to the vehicle's DLC port.

3. Turn the vehicle's ignition to the "ON" position. (do not start the vehicle).

4. Turn the Hi-Scan Pro tool on.

5. On the ‘INITIAL SCREEN', select ‘TOOL BOX (DVOM/SCOPE)'.

6. Next, on the ‘TOOL BOX (DVOM/SCOPE)' screen, select ‘SENSOR SIMULATOR'.

7. After selecting the sensor simulator fuction, a cautionary statement related to the

"Channel B test probe" (not used in the procedure) will be displayed. Press any
key to continue.

8. The ‘SENSOR SIMULATOR' screen will now be displayed. The default function is
VSS, vehicle speed simulation.

9. Enter a target test speed by using the ‘+' and ‘-' keys.

10. A target test speed of 20MPH entered into the Hi-Scan Pro should result in a
readout on the vehicle's speedometer of 20MPH, plus or minus the tolerance
specified in step 13.

11. A target test speed of 100MPH entered into the Hi-Scan Pro should result in a
readout on the vehicle's speedometer of 100MPH, plus or minus the tolerance
specified in step 13.

12. If diagnosing a suspected non-operational speedometer and the target test speed
is displayed, the speedometer is functioning properly and focus should be placed
on testing the Vehicle Speed Sensor, physical connections, and wiring. Refer to
the appropriate Electrical Troubleshooting Manual and Shop Manual for complete
diagnostic procedures.

13. If diagnosing speedometer accuracy, use the following tolerance chart to
determine if the speedometer gauge is within proper specifications.

14. If the speedometer displays target test speeds correctly while connected to the
Hi-Scan, but appears to be out of specification during road speed tests, focus
should be placed on testing the Vehicle Speed Sensor, checking tire pressure, and
tire/wheel rolling diameter. Refer to the appropriate Electrical Troubleshooting
Manual and Shop Manual for complete diagnostic procedures.


---

allows for a tolerance of +/-1.5MPH at 60MPH, and +/-2.5MPH at 120MPH.
So it appears that the only thing that your "20 years" in the industry taught you is to never admit your own fault. Not entirely surprising.

And according to this regulation he is within spec as he's doing 47 mph when the speedo is indicating 50, falling within the +/-5 mph
Therein-lies my problem with getting the dealer to do anything about it, because as the law is written the car is legally within spec. Hence why i was seeking an alternative solution.
 
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