Speedometer discrepancy

[JFBours]

Hi, I live in Mexico and have a Thailand built ROW 24 Ranger Raptor. Has anyone else experienced a noticeable speed discrepancy? I have verified it several ways. Pacing my wives 23 Navigator, GPS and chronograph. All three methods give me about a 5% discrepancy. If my speedo says 100 kph, I'm actually doing 95 kph (or very close to). By doing some quick math, it seems like my truck is adjusted to 35" tires rather than the factory 33"

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[SolarWinds]

You should be able to adjust the tire diameter in forscan, which I assume would correct your speedometer

 

[Texas Ranger]

I’m stateside and my Speedo always seems to be off by -1 mph , all stock+ tune.

 

[CACTUSGREYFX4]

Mine's off by 2 kph all stock Lariat FX4. At least I know if I set it for the speed limit I not going to get a speeding ticket.

 

[JFBours]

I’m stateside and my Speedo always seems to be off by -1 mph , all stock+ tune.

Mine is off by 3mph @60

 

[stuartmunto]

Mine is off by 3mph @60

This is completely normal. Speedos can not read slower than what the actual speed is, so car manufacturers intentionally make sure it’s a few percent over reading. Mine is reading 4kmph faster at 100kmph (actual speed via GPS 96kmph)

Totally normal and I would 100% leave it as is

This was the same as my old VW and also my partners Hyundai. They all read 4kmph faster at 100kmph

 

[JFBours]

Mine's off by 2 kph all stock Lariat FX4. At least I know if I set it for the speed limit I not going to get a speeding ticket.

That is the only upside to this situation. My biggest concern is that I am racking up the mileage at a 5% higher rate than what I am actually traveling

 

[stuartmunto]

That is the only upside to this situation. My biggest concern is that I am racking up the mileage at a 5% higher rate than what I am actually traveling

Is that how it works? I thought Speed is only speed. Distance is set no matter what speed you’re doing

Speed is only how fast you travel over the distance, the distance remains the same no matter how fast or slow you cover it

 

[JFBours]

Speed is only speed. Distance is set no matter what speed you’re doing

Speed is only how fast you travel over the distance, the distance remains the same no matter how fast or slow you cover it

When the speedo is out of calibration, you not only get an erroneous speed measurement, you also get a bad mileage record. It can go either way, where in my case, I may be only traveling 1000 geographical miles, but the car will have 1,050 miles on the odometer. That means that at 100,000 miles, my odometer will read 105,000

 

[Blowndodge]

Speed is only speed. Distance is set no matter what speed you’re doing

Speed is only how fast you travel over the distance, the distance remains the same no matter how fast or slow you cover it

I don't think that's how it works. Mileage is a math function of speed X time. When I changed my 31 inch tires on my last truck to 33's the mileage to work was less and I drove that route 5 years.

 

[JFBours]

This is completely normal. Speedos can not read slower than what the actual speed is, so car manufacturers intentionally make sure it’s a few percent over reading. Mine is reading 4kmph faster at 100kmph (actual speed via GPS 96kmph)

Totally normal and I would 100% leave it as is

This was the same as my old VW and also my partners Hyundai. They all read 4kmph faster at 100kmph

This is the first time I've had such a big discrepancy. On road trips, I need to set cruise control 5kph over my desired travel speed

 

[JFBours]

I don't think that's how it works. Mileage is a math function of speed X time. When I changed my 31 inch tires on my last truck to 33's the mileage to work was less and I drove that route 5 years.

Exactly to your point, if you do the math, from the 32.8 inch diameter tires RR's come from factory, I would need 34.4 inch tires to be closer to the actual mileage. When you went from 31 to 33, your vehicle now needs less tire revolutions to cover the same distance due to the larger circumference of the new tire. Likewise, had your vehicle been calibrated for 33s, and you went to 31s without recalibrating, even if you knew it is only a 20 mile commute, you would be adding 21+ miles to your odometer

 

[Arsenall11]

So I have the F150 LED heads up, reads off the obd2 port and reads 2 mph different than the speedo. Reads the same as my max3 and Garmin Treadmill, both are gps based.

 

[JFBours]

Is that how it works? I thought Speed is only speed. Distance is set no matter what speed you’re doing

Speed is only how fast you travel over the distance, the distance remains the same no matter how fast or slow you cover it

The Odometer gives you distance based on the number of revolutions the tire makes. If it is calibrated wrong, it will display the wrong distance.

 

[Satex]

I’m stateside and my Speedo always seems to be off by -1 mph , all stock+ tune.

My speedo seems to be about 2% to 3% optimistic. 50 mph indicated tends to be 48 to 49 mph actual. My wife's Subaru is optimistic, but is within 1%. My previous Tacoma was in between.

I'm a motorcycle guy, and have had lots of them from lots of manufacturers. The most accurate speedo I've had on a m/c is 5% optimistic. My current Aprilia and KTM are both about 8% off.

The more important issue related to this is the odometer. I have rarely had a vehicle more than 2% off, and they've been low and high. I haven't carefully measured the Ranger yet, but it SEEMS pretty close.

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