BMW: 1998 BMW 320i Speedometer, bmw 320i, size tires

Question
I was driving at 100km with a friend following in another car, later he said I was doing 110km. I do have some problems with my auto transmission (sticks in first gear when cold & won't change down from top gear sometimes). Is it likely my speedo is wrong and can it be checked for accuracy?
Thanks

Answer
Keith,
 What size tires are you using?  If you went to a wider/taller tire, it can affect the speedometer.  195/65/14's should be the factory size.  So go out and check you're tire size and if they are different then that's your problem.  Otherwise your friend might have the faulty speedo!
 Good luck,
 Josh