You need a fairly wide open area for this and it helps to have a helper.
1) Use some shoe white to put a white mark on the rear tire and the front tire on one side where you can easily see it as it passes a reference.
2) Drive forward slowly with the 4wd dis-engaged and count the front to rear tire rotations. Do at least 3 rear tire rotations, 10 is better, but you need some room for that! You must go dead straight.
3) Repeat with the 4wd engaged the same distance. You will get a different number of front wheel rotations. You want the 4wd engaged number to be 3-7% more than the dis-enaged. The ideal is when in 4wd, the front tires rotate 5% farther than the rear tires. Acceptable is 2-10%. You never want it to be negative.
So, if you do 10 rear wheel rotations and get 35 front wheel rotations with the 4wd dis-engaged, you would want to repeat in 4wd and get 36.75 front tire rotations. That would be 5%.
Use those numbers with the current tire rolling circumference to order up new tires that get you into the 3-7% range with a 5% target. (2-10% is acceptable, but higher than 5% will wear the rubber faster)
1) Use some shoe white to put a white mark on the rear tire and the front tire on one side where you can easily see it as it passes a reference.
2) Drive forward slowly with the 4wd dis-engaged and count the front to rear tire rotations. Do at least 3 rear tire rotations, 10 is better, but you need some room for that! You must go dead straight.
3) Repeat with the 4wd engaged the same distance. You will get a different number of front wheel rotations. You want the 4wd engaged number to be 3-7% more than the dis-enaged. The ideal is when in 4wd, the front tires rotate 5% farther than the rear tires. Acceptable is 2-10%. You never want it to be negative.
So, if you do 10 rear wheel rotations and get 35 front wheel rotations with the 4wd dis-engaged, you would want to repeat in 4wd and get 36.75 front tire rotations. That would be 5%.
Use those numbers with the current tire rolling circumference to order up new tires that get you into the 3-7% range with a 5% target. (2-10% is acceptable, but higher than 5% will wear the rubber faster)