For those who have 18" wheels, does the offset influence the speedometer reading and if so how much? I use to drive a lowrider (truck), and instead of factory tires I went with low profiles and this messed up my speedometer reading and milage on the car.

Any response would be appreciated

 

If you keep the rolling radius (the length from the center of the wheel to the outside edge of the tire) the same, then no, there won't be an error in speedometer reading.

Phi

 

255/35-18 or
285/30-18
pretty much match the stock 225/50-16 (speedo reads the same)

However, the stock speedo is off about 4-5% so a 265/35-18 in the rear makes the speedo read true (too bad it gears the car higher though).