Speedometer is off after wheel alignment Options

[xxdejavuxx]

Hi guys,

Sorry if this is in the wrong category but i don't know where it should go.
I just changed 2 front tyres and got a wheel alignment done. Now my speedo is about 10-15kms off.
The speedo totally flies now, driving at around 60, it shows 75ish.

What could be the problem? or did the employees decide to throw in a 3sgte for me for free?
Thanks

[jason]

ok wheel size will not effect speed alone... if he has say 14" wheels and with the tires he had on the total diameter of the tire from top tread to bottom tread was say 20" and this place put on tires that from top to bottom are only 18" that would show his car going faster than it really is on the spedometer - likewise if you put larger tires on your car like total top to bottom of say 22" your speedo will show that your slower than you actually are going. my guess is they gave him the wrong tire size. id start by checking the numbers marked on the sidewalls and compare them to your older rear tires. like if the fronts are 215 50 16 and the rears are 215 60 16, then there you have it, they gave you "smaller" tires