1.5 mm equals .059".
.055" is the standard most 1/24 slot car groups use in our area. I would even consider .047" on lightweight 1/32 cars. For now on my track, I'm sticking with .055" as the standard for all cars.
1 mm or even 1.5 mm are odd specs for me. I can get a piece of wire in .055" or .047" to use for tech inspection.
Damage caused by hard parts coming into contact with the track surface are clearly visible on my track. Some of the evidence is years old I'm sure, but I see damage to areas I know I have repainted since the track was moved here. Some marks can't be avoided when caused by de-slots and crashes. However the indications of marks caused by gears coming in contact with the track surface when a car is lapping the circuit can be avoided. The track surface is not perfectly flat in all areas. Please check and verify the clearance you have on your cars between the lowest point of the car and the track surface! On most cars the gear will be lowest point of contact!