Golf mk4 Speedo completely wrong???

[liamcartwright]

I have just bought a Golf MK4 SDI 2002. The dealer who I bought it off put some brand new 17" alloys with 45mm profile tyres on (to help it sell I think). But now the speedo is approx 5 mph out until I get to around 55 mph when my speedo only reads 45 mph. I've drove with a few different friends and family who are in different cars, and it's the say every time.

I've measured the spare wheel (14" wheel with 80 mm profile) diameter and thats approx 62 cm and the wheels on the car are approx 62 cm.

I can't understand why my speedo is so in-accurate!!!! Can anybody please help????

Liam.

[liamcartwright]

Just measured the circumference of the spare and one of the alloys on the the car, and it turns out that the alloy is approx 5cm smaller than the spare.

So the if anything the speedo should be reading faster than I'm traveling not slower.I'm going to take it to VW for a diognostics check and see if it's a faulty speedo (which I think it must be).

Does any body have any other ideas????????