I put my Garmin GPS in WAAS mode and did some speed testing to see how accurate the speedo is.
It looks like the speedo is 2mph optimistic. So a steady indicated 70 mph on the speedo is actually 68mph.. pretty accurate. So now I know I can go a bit faster in speed traps.

 

I use Microsoft streets and trips 2006 for GPS and noticed a similar discrepancy. The speedo on the xB is off by 2 (no more than 3 though) miles an hour. Although, since the speed is determined by gps satellites and not by a guage on the car, there is also room for error.
- sh00k

 

A GPS vs. Speedometer test on my 2005 xB on a lengthy near-straight segment of interstate highway (using an assistant to minimize driver distraction and using cruise control for speed maintenance) shows a similar 1.5 to 2 MPH difference at around 60mph. The speedometer seems to run a little bit high, which is just fine with me. Oh, and my wheels are the stock steelies - that's pretty important to note in this test.

Also, I can make a mileage accuracy adjustment of approximately -3% to my fuel economy figures, which adds about 0.9 mpg to the odometer/fuel usage calculation.

 

Same thing here. I have a Garmin I2 and the speedometer is off by about 2-3 mph.

 

good point.. Stock wheels and tires on my test also..

 

I was just about to run the same test! Maybe I still will this weekend just to add some more data points.

Wholeflaffer, who installed your cruise? And if I may ask, how much did it cost?

 

I got the cruise with the new car from the dealer here in Pa., but it wasn't a factory or port install - it was a dealer install. I think it was just over $300. The other local Scion dealer around here absolutely refused to entertain any thoughts of installing a cruise control for me, even though the southeast port (not the port for Pa.) offered it as an option. They actually claimed that legal reasons prevented it! So the sale went to their cross-town competition.

The unit I got is the same as the "factory" unit that the southeast port used, and is apparently meant for installation in the xB. It's made by Rostra, and there's an entertaining thread about it at https://www.scionlife.com/forums/viewtopic.php?t=102894.

 

I also got the cruise control, port install.. It works.. but its slow to respond and varies up to 5 mph when in use.
Too bad the xB doesnt use a drive by wire system. It makes things much easier to implement and its much cheaper.
I have drive by wire in all my other cars.. It makes the cruise control work seamlessly. It functions smooth and accurately and is less complex and more reliable..
I'm sure Scion will eventually move to this sometime in the future... also makes for less of a mess under the hood... no cables or cruise module.

 

I can't say I have had your direct experience with "drive by wire" (my previous car was a '79 Mercedes 300SD), but I should think that implementing cruise control on such a car would be trivial. I would guess that any car with "drive by wire" already comes standard with cruise control, unless the manufacturer was very serious about gouging the consumer on accessories.

 

Haha.. good points! It was std on the Z06 and the Honda... but it was an option on the mini.. Not a gouging option. When you order cruise on the mini, you get a new steering wheel with buttons for the cruise and radio controls along with a blue-tooth control. All for $220

 

The speddo is calibrated to what Japan uses as stock tires, not what is put on here in America. 195/85/15 is what the speddo is set to I believe. It might be 195/80/15 though.

 

when i have the stocks on mine is about 4mph of with my 17" it is only 2mph off

 

Does the cruise you had installed take the pedal away as it adjusts the gas? My tC didn't and that was a little disturbing after my Golf which let me know exactly how far down the pedal was.

Sorry to turn this into a cruise thread, I promise to post my observations on the speedometer when I mess with it this weekend!

 

Yes, it does. Although it does take a couple of seconds to kick in, I don't find it objectionable because I've grown used to keeping my finger on the "speed set" button and my foot on the accelerator until the cruise control (physically) takes over the pressure on the pedal.

I should think that "drive by wire" cars might not be able to do this unless some sort of servo-motor is attached to the pedal for feedback.

 

I have noticed that MY speedo is reading LESS than what my GPS is reading. It is off 5 miles per 100 miles driven (distance, not speed). This figure really helped with explain a low MPG problem I was having (well, it didn't help with it, but it made the numbers look better). This was done over a 2 week 5000 mile trip and the GPS is dead on with the mile markers AND mapquest figures....so I would like to say the GPS is pretty accurate.

Just my $.02

BTW...I am running 17" and my tires are within 1/2" of stock height (stock is like 23.7, mine are 24.2)

 

If your tire measurements are accurate, then your tires give you about 1.25% more distance per rotation, not nearly enough to account for your rather large difference. I would assemble your data and present it to the dealer.

Bring a GPS and ask the dealer rep to take a quick ride on the nearest highway...show how different the speedometer reads compared to the GPS in his or her hand.

You may want to ask your salesperson to do this ride with you...Unlike a service tech who must account for every minute, the sales rep will usually be able to take a few minutes to keep (or make) an existing customer happy. If the speed difference is objectionable, he or she would likely be on your side in dealing with the service department.

 

That makes no sense.. I doubt they would not have it calibrated for the tires used here in the states... If that were the case.. Toyota would be liable for speeding tickets. wrong odo mileage for warranty and sale issues..
Its not hard to re-calibrate the speedo for the tires being used.

 

how do you do it?

 

This has been documented in a few threads in the past. The speedo is about 3% high on stock wheels and tires.

 

I read an in depth test in different makes and models of cars and this is common. If you wanted to go 70mph (actual), you would have to drive 72-74mph (varies by car).