On the OG9-3 (1998-2002+2003CV) and 9-5 (1998-2010) the Tech-2 can program the Main Instrument Unit (MIU) with various tire sizes, so the speedometer is pretty close to right.
SAAB 9-3 MY98-02/MY03 CV or SAAB 9-5 MY98-2010
Tech2 (CANDi module for Saab 9-5 MY06 and newer)
SAAB 1XX.000 PCMCIA card
Gather information of which tire size you are using.
- Select F0: Diagnostics
- Select Model Year
- Select Saab 9-3 or Saab 9-5
- Select F3: Body
- Select MIU (Main Instrument Unit)
- Select Speedometer
- Choose your tire size in the list or press Manual to enter the dynamic tire circumference manually
- Select OK to program the new value