calibrating speedo

just changed to some lower profile tires, and now my speedo is way out, i knew it was going to be little bit out, but when i get up to higher speeds its roughly 10mph out, and i've only gone from 60 to 55 profile tires

so anyone know how to calibrate the speedo, or it just a case of taking it to a garage?

cheers nick

1.8 GTi ? Look at the gearbox worm drive on the end of the speedo cable its either

171957821A Natural colour 16Teeth
171957821B Red colour 15Teeth

15 goes teeth goes faster so if you have that swop it for a 16 teeth item , reading will then be slower ! With me so far ? If you already have a 16 teeth item pot luck you have changed the rolling radius of the wheels and faster is what you get .

ah im with you, ill check it out tomorrow, do you know if can you still get the worm drive new? or it just a case of finding a second hand one?

cheers nfor the reply, nick

You can get them new, about 3 pounds a piece at your friendly VW dealer..

don't drop the old one in the gear box !