Rep Power: 954

How do I measure the height of my tires? I need to know the exact height of my tires (or within a 1/4 of an inch) and I'm coming up with two different numbers here. My tires are coming to be 24.5 inches tall if I just measure from the ground to the top of my tires. However when I use the roll test (mark a spot on the ground and tire and do one full rotation and measure distance between marks then divide by pie (3.1416)) I'm coming out to around 25.156 and 25.0668. My question is should their be this much between the both forms of measuring?

 
Rep Power: 1121

height is relly variable even 2 psi difference will change it

 
Rep Power: 954

True, I might just say 25 inches as an average and it call it done. When it comes to the tires being bigger or smaller, which one would make the speedo show faster then what the car is actually traveling? If I'm wrong on my guess I rather have the speedo show I'm going faster anyway.

 
Rep Power: 1121

smaller makes it show faster

 
Rep Power: 954

I have some work to do in the afternoon then.

 
Rep Power: 800

u using the hypertech programmer? I went with the lowest number at first and i guess it was about 5 under lol. i moved it up a little and haven't driven it with someone to compare yet, but i think it's right.. 25 should work for u. there was much more of a diff for mine lol like more than an inch between the two measurements.

 
Rep Power: 0

275/40/18

275mm tread width
40% of the tread width is side wall (110mm)
18in wheels

18in + 220mm (8.661417322834646in) = height of tires (26.661417322834646in)

It's also dependent on if the required amount of air is in there. Obviously if you have 3lbs, it won't measure the same as 30lbs.

 
Rep Power: 845

I used this site to get the computerized estimate of my tire height:

http://gs.tolan-hoechst.com/tirecalc.htm