986 speedometer sensors & oversize rear tires

In an effort to correct the fact that the speedometer reads about 10% higher than GPS speed, I upsized the rear winter tires for 10% greater circumference.  This did not change the speedometer inaccuracy.  Where is the speedometer sensor that greater tire size wouldn't reduce the speedo reading?

Now, when I get up to about 60 MPH, the sensors for the ABS light the ABS and BRAKE lights on the dash.   Is there any solution other than to go back to a smaller tire?

Warren White