I have a 05 bcp xB with 18's and need to know if the speedo has to be adjusted for larger
wheel size.

Wheels go up, tires go down. Should be damn near the same.

no adjustments...

just make sure your tires are the correct size...speedo might end up 2-3% off. its no big issue.

goto one of the tire calculator sites (google it) to figure out the percentage you are off....

There's not much you can do to adjust the speedo on a Scion. I looked into myself and there aren't any devices on the market that allow you to do this. There's shops that will physically cahnge the gears on the spedo to correct it but it'll run over a thousand to do it.

first thanx for the info the calc shows about a +3% diff,
will this just affect speedo or odom too- just don't want it to add more miles than i already put on it. the box is 3 days old and 300 miles so far

both, speedo and odo...