At a track day at Brands last year, early in the day I ran over some debris from an incident in front of me, so came straight back in to the pits. There were scuff marks all along the floorpan where the chunk of fibreglass had gone straight under the N/S of my car, front to back but otherwise all seemed ok so I went out again and carried on as normal. It was torrential rain for most of the day and by the end of the session, a knocking noise had developed from the rear. Initially I thought it was the diff. When I got the car home I found that the retaining clip was missing from my N/S outer driveshaft boot, the boot was ripped to pieces, adrift from the tri-lobe and all the grease had been washed out of the CV joint due to the biblical weather conditions. The bearings were trashed and I had to stump up for a complete shaft, as that is how they come. I had just assumed the debris from the morning had dislodged the clip and eventually the boot came away. Fair enough, s**t happens, so onwards and upwards. Fitted my new driveshaft and everything seemed ok. Following a full day at Curborough last week, I was convinced that during my last couple of laps of the day I could hear another knocking noise. I put it down to paranoia. Got my car up on the ramp today for an oil change and spanner check and, lo and behold, my outer N/S driveshaft boot clip is again, missing from my shiny new driveshaft, with grease splattered all over the underside. So my previous debris theory was probably incorrect. I can now see that the blade of the ARB and the joint of the drop link have been impacting the tri-lobe under full compression. The ARB blade has been gouged away. And the drop link is bent and the joint shows signs of heavy impact. So, mystery solved. I had previously checked the possibility of ARB and driveshaft clashing but they did not appear to be moving in the same plane. I checked the drop links and ARB after Brands and they were both unmarked. What I failed to take into consideration was the massive amount of sideways endfloat and lateral flex in the ARB which at full movement to the left, puts it straight under the CV boot retaining clip. It would seem that at Brands, the driveshaft had probably just kissed the ARB mechanism, shedding the clip but not hard enough to leave witness marks whereas at Curborough, the much more brutal rough concrete variegated rumble strips had them smashing into each other. Not ideal but I am glad to have got to the bottom of it and can now see exactly what has gone on. Expensive way to learn though. As it was dry at Curborough, there is still some grease left in the CV and the boot is intact. I probably wont even remove the driveshaft but will back-fill it with grease in situ. I will just have to replace the clip, the trashed rose joint and link. My drop links were set quite short and I am hoping that by adjusting the drop links as long as I can get them will hopefully keep all these parts clear of each other. Otherwise will be in the same position again. Has anyone else had this issue? Andy