....been a while but there is a range from (96mm-88) this all depends on how your tracks are set up.with the escalator running up.you should being able to have 3/8-1/2 pullout from the bottom newels..this vintage has gone through some handrail drive upgrades..Otis sells the Cog traction belt which..will give you a more traction to drive the rail..also i have seen mechanics tighten up on the 19mm studs which slotted to allow the drive sheave spring assemble to float freely.with No spring tension on belt one person shopuld be able to spin the rail without to much resistance.again this all depends on how clean and how you tracks arte setup..and also If someone had replaced the handrail and made it too short..506,s do not like friction..
