the larger brakes show their advantage when you do a lot of high speed stops - your E300 is nowhere near the capability of the E320 when it comes to speed and acceleration.

your factory brake setup is more than enough, a good upkeep on them should keep them in good shape for a long time.

I have rebuilt the rear suspension on both W124 and W210 (same parts for both) - buy the whole arms as its easier to do it, and dont forget to get the little metal bushings that are inserted into the rubber bushings and torque at drive height. -those little metal sleeves remove all slop.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)