I would say that the shim have to be made out of steel.It's all about friction factor called mi.The coke can is made out wit an aluminium thin.So in your torque limiter you will have steel-aluminium-steel friction couples.It has got different characteristic than steel-steel.And the important figure is that type of lubrification or it absolutely absence doesn't make an influence for friction factor is a feature of fricting couple.If the manufacturer set steel-steel couple, the only way to get it reconditioned is keep the same factor.The shim gives you bigger pressure at surfaces in your torque limiter what causing higher rate of torque once it starts slip.Notice that torque limiter has got a torque, when it beginn slip, but when it started slipping, the torque need to keep it slipping can be a bit less! That effect is happening, because of certain number of friction factor.The higher torque for "breake"the contact, and the lower torque to just keeps it slipping is related to friction factor.I would recommend use steel washer, made out with higher-carbon steel, not just soft anykind steel( like standard washers for bolts ).Try made it from body repairer's filler knife.It's a hard steel, and you can get different thicknesess.Or made it from old type of razor blade.
