90 Vette tire sizes and speedo

[jwn4854]

Hi, i recently changed the wheels and tires from the original p275/40 zr-17 to 93 wheels and tires w p255/45 zr-17 on the front and p270/40 zr-17 on the rear. as i find out, my speedo is off 2 mph and i was welcomed by the patrol in cheyenne with a greeting card for 72 in a 65 zone. i talked to the chevy dealer and he says that the speedo is controlled by the front wheels. does any one have an answer and some advice for me? i had thought the rear wheels as in rear wheel drive drove the speedo. thanks so much Joe

 

[-=Jeff=-]

Hi, i recently changed the wheels and tires from the original p275/40 zr-17 to 93 wheels and tires w p255/45 zr-17 on the front and p270/40 zr-17 on the rear. as i find out, my speedo is off 2 mph and i was welcomed by the patrol in cheyenne with a greeting card for 72 in a 65 zone. i talked to the chevy dealer and he says that the speedo is controlled by the front wheels. does any one have an answer and some advice for me? i had thought the rear wheels as in rear wheel drive drove the speedo. thanks so much Joe

My advice, find a new dealer.

The speedo is calculated from the rear wheels and the VSS (vehicle speed sensor0 is located in the tail housing of the trans.

I am not sure if you will be able to fix the 2mph difference unless you use a conversion box. I would just suggest keeeping a mental note that it is 2mph off at 70.

 

[Tom73]

Just wondering, why did you go to the smaller (width) tires?

Your current tires are about 1/10th inch shorter in diameter then the original rear tires. Given that your speed should have been slower than indicated :confused

tom...