When I put my tire size of 25.5 in and gear ratio of 3.42 in It says my calcualted tire is 27in . Anyone know Whats up with that? and when driving my speedo says i am doing 60 mph when I am actually doing 65.
I am swaping gears and rims and tires this week and I would like to know how to fix this. The new setup will be a 26 in tire and a 3.73 gear.
thanks for your help
teh best way to get your true height is to physically measure it..
take a string or a fabric tape measure and go around the tire....
circumference/pi = diameter or tire size...
enter tire size in the speedo table
enter gears(3.73) in the appropriate box..and click commit...
let the software do the calculating for everything else...
how did you test the fact that your car is doing 65 and reporting 60 on the speedo??
-Scott -
what i did was measure teh tire on the ground for height. i just put a flat piece of steel on the top of the tire and measured to it. with weight down on the car it will make the radius slightly smaller. plus as speed changes the radius will slightly change so there is really no good way to do it.
Sulski Performance Tuning
2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB
thats why I go around the tire while its up in teh air...
so you get the middle of squished and expanded
-Scott -
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