01 t and c front wheels/alignment question

I have the Michelin Hydroedge tires. In the center of the tires there are two even grooves. I pull a measurement on the back and the front of the front tires to get both tires centered straight. It has worked and the van drives so much better. However I have notice it drive different sometimes so I recheck the measurement and have noticed that sometimes both sides are 64 inches and sometimes its 64 1/4 inches, like the whole tire moves in or out. What is causing this? The bushings? Strut mounts? Thanks

anyone know about alignment specs? are the front wheels supposed to be dead straight, toed in or out alittle? Thanks