Quick question. There is supposedly a forumla out there that helps you determine if you should stock a subcomponent or not. ie Do I want to stock break shoes or should we just stock the whole break assembly, as an example.

The forumla, to the best of my knowledge, contains the following variables:

Cost of subcomponent
Carry cost (taxes, interest, facilities, etc.Instrumentation Ball Valves)
install time
est. use
quanity assembly cost

Supposedly one should be able to plug numbers into a formula that would let you know quickly if stocking the subcomponent would be a good/bad idea.

Ring any bells?

Way too simple.

Add supplier dependability and availability of alternate suppliers at least.

Other than that - calculate inventory turns.  

As it is now you are mixing dollars and lead times.  They do relate but they can also be entirely separate.    

Make sure customer goodwill is in the formula somewhere.  I loathe automakers and their parts suppliers who continue to take us hostage with ridiculous practices regarding replacement parts.
Root cause on historical failures/service issues should drive how a part or assembly is handled on the spare parts end of things.
I just really appreciate (not) the idiots who decided it was better to sell an entire fuel pump assembly unitized into a neat plastic housing that contained the pump, check, valve, filter, etc, when all I really needed was a stinking check valve.  Who doesn't like to pay $500 for a $15 part, I always say!!!
Consumers are not all as stupid as corporate thinks they are!

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