The tension that's applied to the wiper blade/rubber insert by the wiper arm needs to be taken into consideration as the car grows older.
I just replaced the drivers side arm on an 11 yr. old 126 car and was impressed by the increased pressure the drivers side now has vs. the pressure on the passenger side.
If the wiper arms are weak, the rubber insert installed in the blade will be far less effective.
1991 300-SEL - Model 126
M103 - SOHC
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