Originally Posted by Robb
Why do they crack ?
Too much power or poor choice of metal used in building the car?
Power has nothing to do with it. 323s been reporting failures as early as 50k kms.
Its a mystery, well not really but much so. First , the design of the rear subfloor hasnt changed much from the E36 which had a bad bad design to start with. And then its the sheet metal suppliers at certain years. 98-02 have THE most damage , 03+ cars rarely are seen with damage because BMW physically changed the rear subfloor design after 03. M3 will all have damage because they havent got the new updated subfloor as standard.
Originally Posted by Slow36
What are the symptoms of a damaged subframe?
Cracks in the rear subfloor sheet metal. Those are the symptoms.
Poor maintenance also leads to this. Reaplce your diff bushes, subframe bushes and in general keep your car in good shape if you wish to enjoy it.