hifi engine

Akai M8/Gx27) Tape Recorders

I am servicing my two recorders and I need to know what type of tape to use for the clutch/brake band adjustment on each of my units.
I have the Akai manuals for each but they only mention 60mm of tape on a 5inch reel and nothing about tape thickness. The weight varies according to said thickness hence change in inertia.
Would appreciate any recommendations on this before I try hit or miss.

Many thanks in advance.

johnso