sntheticdelusion1

find out what gear size and your tire size and use a a gear calculater to figure out what rpms you will be running at a certain mph and just go off the tach its kinda ghetto but its what i have to do due to tire size and gear

wildstang87

that only helps if you know your car really well, he just bough his, and thats a pain to go through, i say buy the speedcal, and keep changing the gear ratio until you get the speedo right.