Speedometers calibrated when bigger wheels are installed by tire shops?

I've noticed a lot of new cars are driven off the lot with aftermarket wheels as well as those purchased from Discount Tire, etc. I know whenever you increase/decrease the overall diameter from the original, it will throw off the speedometer. Are the tire places calibrating them for free? Or are they just "pushing" their products as quicly as possible so nobody notices? I know they sell those gadgets that calibrates it but are they using them?|||Actually NO they don't recalibrate them. I have had several com in wondering how they get such great gas mileage and I say you don't you just get fewer revolutions per mile. tire rack.com actually has rotations per mile of different tires. you can get an idea of the % off by looking at the stock tire and the one on the vehicle now. You can have the VSS recalibrated or get one for the correct size tire from after market suppliers..|||two options, i know for jeeps they sell different speedometer gears that you can replace the stock one with. places like quadratec.com have tables to calculate the correct gear ratio.





you can also use a performance chip or reprogrammer to reset the electronic speedo.





do a search on automotive computer reprogrammer.|||Well, first off it has to be a pretty big difference between the old tires and the new ones. It may only throw your speedometer of by a mile or 2. Second, no...they do not recalibrate speed for free. If you want the bigger tires you pay for the recalibration if necessary. Remember this though, try it out have someone whos speedometer is accurate ride beside you to check it yourself. A lot of places will say they will calibrate when it doesnt need to be done.|||Like just about everything in this world it isn't done for free. The good news is that technology has made it easier for speedometers to be calibrated for tire size. Electronic speed sensors detect pulses that are translated into mph ehrough the ecm. Simple modifications in the ecm configuration can correct the speedometer. If the tire shops are selling products that aren't necessary then they need to be reported to the authorities. Misrepresenting products or services is against the law and should be dealt with appropriately.