Speedometer shows 2 MPH faster than actual speed

[windmilljumper]

My speedometer is 2 miles per hour fast. The dealer says there is no way to adjust it. I have a Level V 2010 with the 16" wheels. Does anyone know anything to do about it. Is this a common problem with this model?

[BDDave]

Originally Posted by windmilljumper

My speedometer is 2 miles per hour fast. The dealer says there is no way to adjust it. I have a Level V 2010 with the 16" wheels. Does anyone know anything to do about it. Is this a common problem with this model?

2 miles per hour fast compared to what?

[hampdenwireless]

Originally Posted by BDDave

2 miles per hour fast compared to what?

The actual speed.

Almost every car speedometer reads a higher number then the actual. This is normal and is across all mainstream car brands.

[a priori]

Originally Posted by windmilljumper

My speedometer is 2 miles per hour fast. The dealer says there is no way to adjust it. I have a Level V 2010 with the 16" wheels. Does anyone know anything to do about it. Is this a common problem with this model?

Ken@Japan provided a great resource in Post #2 of the thread Accuracy of Speedometer for TCH. He links us to the UN requirements which bias all speedometers on the high side. I believe the purpose would be so that people do not unintentionally exceed speed limits.

BTW, is it only on the 2010 Prius V with Package #8 that you get those 16" wheels?

[cpatch]

Originally Posted by a priori

BTW, is it only on the 2010 Prius V with Package #8 that you get those 16" wheels?

They're a special dealer option to help close the sale for those people who can't decide between the 15" and the 17".

[windmilljumper]

Originally Posted by BDDave

2 miles per hour fast compared to what?

Compared to 2 different GPS's at steady speed and speed radar sign.

[LRKingII]

Mine reads 1 mph high at 35 mph and 65 mph when gps says 34 and 64. No biggy to me.

[RodJo]

Originally Posted by windmilljumper

My speedometer is 2 miles per hour fast. The dealer says there is no way to adjust it. I have a Level V 2010 with the 16" wheels. Does anyone know anything to do about it. Is this a common problem with this model?

I had read somewhere recently that Toyota claims that their odometer logic computes the distance/speed without error. I will see if I can find that again.....

In the meantime, what is your tire size? I assume the V is calibrated for the stock 17" tires. If the 16" tires have a larger circumference than the standard 17" tires, then you will travel farther than expected per wheel revolution.

With that said, 2 mph seems like a lot unless you drive at > 100 mph. For comparison, dropping down to the stock 15" tires (195/65R15) would also make you cover more ground per revolution (adding about 1 mph at 70 mph). But the stock 15" and 17" are not particularly well matched. It turns out that 185/65R15 would be a closer match to the 215/45R17 and that was what I was planning to get for snow tires.

As an aside, I had assumed that those that change wheel/tire sizes just had the dealer reprogram the odometer to compensate. Is that not the case?

[Judgeless]

My Prius is 1 MPH off. My GPS and my radar detector with GPS for photo/speed cameras shows the MPG. I just went on a 3,200 trip. I watched all three. My Prius IV with 15" rims is 1 MPH off 100% of the time.

[cwerdna]

Speedometer Scandal! - Feature - Auto Reviews - Car and Driver

Related chart: http://www.caranddriver.com/var/ezfl...32f82a5a71.pdf