Brian, you raise some valid points, i don't disagree that the RF option has stood the test of time, just redoing the spot welds will stand the test of time, my issue (not an issue really, because i would not fit it) is that people keep pushing the RF as a better option and more robust, and its not, RF is a car enthusiast not an automotive structural engineer, he looked at the fall out of his torn up car and decided he would weld in something that in his opinion (and thats the cruncher) would be better.
He did not look at the structural calculations and the loading figures, the lateral G etc etc the list goes on to include material grades, strengths, thicknesses etc, and he welded in some profile cut plates. Now if you could present all the figures in the specification of the BMW design and overlay the RF data as a comparison and the data was better, i would agree that his option is better.
What nobody has done when this problem manifests itself (except BMW) is get to the root cause of the failure, they all quote the massive torque and power of the //M and the 6 pot engines, when in fact it has occurred on all versions. Power and torque does not come into it, the rear carrier is held in place by two high tensile bolts of large diameter through the bushes, the carrier is then secured to the body by two plates, it cannot move very far and it cannot twist to the extent to rip the floor the diff is connected to the carrier by 4 bolts, the rear bush on the diff is a damper. The body on all versions shares the same suspension geometry and travel, lowered versions actually travel less through the cycle. If you take this into account the only force that is applied to the boot floor and diff bracket is weight. If you then understand the root cause of the failures is actually poorly supplied product from a supplier and poor process control on welding then the weight is the key factor, because as welds pop the applied force per surface area increases until the majority of welds pop and the floor fails.
If you take this into account the correct course of action is to re-weld the floor as per specification, it will then be to the design and there are 100's of 1000's of zeds that have not failed, they just don't post on a forum that their boot floor is fine, because there is no point, people on post on a forum when they have an issue. Now the next question i deduce from this is that people say well others have had the spot welds repaired and they have failed. I would say i agree that they will, and i will also say that someone with a RF kit fitted will fail also due to welding. The reason is because welding is classed as a special process, as such you cannot guarantee any weld defect free, as it is down to the skill and experience and process that each individual welder applies, now if robots cannot always get it right on a production line, what chance does your mate, the guy in the indie or the stealer have of getting every weld right, now the risk increases by going to seam welding.
Now if i ever experience this I will be going to get it done in line with the BMW repair procedure, the reason is because it will use approved materials and hopefully be done by a qualified welder (coded), i wont be welding in place some angle iron.
How many RF users have informed their insurers of this modification, because it is a modification, it holds no homolgation? i guess none, and if you did you would find they would ask for a structural engineers report, and then you would only get a pass if the installer followed a correct code of welding practice, used specified materials, which included NDT testing of the final weld.
I do not want to influence anyone, but i think people should have all the facts, and then they can make their own decision on what to do.
Waits to watch the fire works............
