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KCF3712 09-17-2010 08:28 AM

Speedo calibration for tire size change
 
My 2007 Kia Spectra came from factory with 195/60/15 tires. To save a little cash, I went with 195/65/15 tires. Does anyone know if there is an inexpensive way to reprogram for tire size change. I know how to calculate for the change, but would like for the speedo an odo to be correct.

gone-ot 09-17-2010 03:48 PM

...don't believe it's possible to "re-calibrate" the factory ECU.

...only under 'secondary' calibration--such as via SGII, etc.--can this be accomplished, but those results are not reflected on the instrument panel odometer or speedometer.

MaxiBoost 11-01-2010 03:01 AM

when you change tires to 195/65/15
overal tire diameter increase %3.17

than, when you drive car 200km speed (124.2 mile)
you see on the your speedometer 194km (120.5 mile)

your choice

azaviator 11-01-2010 12:50 PM

Quote:

Originally Posted by KCF3712 (Post 194507)
Does anyone know if there is an inexpensive way to reprogram for tire size change.

Since this post is a couple of months old, this info may be too late for you. Could be helpful to others, though.

On most (all?) OBDII cars the dealer can flash the computer with the adjusted info to correct the odometer and speedometer for tire size and gearing changes. Call the dealer and ask their price, it should be reasonable (I've seen anywhere from $15 to $100).

If you would like to do it yourself, you can use products from Hypertech(not an endorsement, as I haven't used it personally) or other programmer companies, but you'll pay a bit of a premium (online price is ~$170).

Either way, if you want to have an accurate reading, it is easily done and somewhat reasonably priced.

gone-ot 11-01-2010 10:31 PM

...uh, which dealership(s) can do that?

...I ask because both of our Toyota-made, defunct-GM Pontiac, Vibes' ('04 & '09), show a consistent "+2 mph" high reading on the speedometer, but NOT when read through the OBD-II connection via ScanGauge-II from the ECU.

...hence, at least for our Toyota/GM hybrids, it appears the "+2 mph" offset is being "added" at the dashboard display and NOT within the ECU...which would seem to rule out subsequent dealership reprogramming capability...but who knows?

...but, I'm curious to learn otherwise.

tumnasgt 11-02-2010 04:57 AM

The +2 MPH thing could be in either the ECU or the instrument panel, as there's no reason the ECU couldn't just give a different speed value to the instrument panel, and then store the correct one for the odo. I doubt it can be corrected by a dealer either way, as the ECU does actually know how fast it is going.

gone-ot 11-02-2010 03:00 PM

Quote:

Originally Posted by tumnasgt (Post 202074)
The +2 MPH thing could be in either the ECU or the instrument panel...

...that's what the evidence, so far, seems to indicate. The Pontiac serviceman said it was a "cushion" against speeding (ie: an intentional 'error').

euromodder 11-02-2010 03:05 PM

Quote:

Originally Posted by Old Tele man (Post 202056)
...I ask because both of our Toyota-made, defunct-GM Pontiac, Vibes' ('04 & '09), show a consistent "+2 mph" high reading on the speedometer, but NOT when read through the OBD-II connection via ScanGauge-II from the ECU.

Same here.

Dash reads 2-3 kph fast, but ScanGauge value matches GPS-speed


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