[Leica] Question for anybody using R lenses on Nikon body

[Aram]

I have been using my R lenses for quite some time, first on Canon and 
then on Nikon.  They never metered well on Canon, but were fine on my 
D7000.  But on my D600 and now D750, they never meter fine.  They are 
always overexposed, and get more overexposed as I stop the lens down.  
Has this been experienced by others an if so, what is your solution.  
They do meter just fine in LiveView, but when using the optical 
viewfinder (my preferred method), they are totally unpredictable.

One thing of perhaps importance, I have converted the lens mounts with 
non-chiped adapters from China.  My understanding is that on the D600 or 
D750 they do not need the chip to meter correctly. Maybe that is my problem.

Any help would be appreciated.

Aram