xaddiction Posted May 14, 2011 Report Share Posted May 14, 2011 Hi, Just a quick question. I have a 2002 E65 BMW 745i and the BMW TIS stated that it must be weighted up when the geometry is set up. Is this really a requirement? What's the negative impact of not doing? Thanks in advance xaddiction. Quote Link to comment Share on other sites More sharing options...
Tony Posted May 14, 2011 Report Share Posted May 14, 2011 Weighting will not help unless you make significant structural changes. What are your intentions for the car? Quote Link to comment Share on other sites More sharing options...
CIH Posted May 14, 2011 Report Share Posted May 14, 2011 I think you misread there Tone Yeah the car needs to be at a specific rideheight when settng to OEM geometry and this entails adding ballast, usually to bring the rear down more than anything. Camber and castor are ride height specific, not so much toe. Quote Link to comment Share on other sites More sharing options...
Tony Posted May 14, 2011 Report Share Posted May 14, 2011 Yep i was having a blond moment.... I thought we was talking corner weighting. Quote Link to comment Share on other sites More sharing options...
xaddiction Posted May 14, 2011 Author Report Share Posted May 14, 2011 I had the geometry set up and the guy decided not to add weight. When I asked why he just said it's not needed. Should I have argued the point and made them weigh it down? Quote Link to comment Share on other sites More sharing options...
Tony Posted May 15, 2011 Report Share Posted May 15, 2011 A few factors here..... If the car is unmodified it would need weight added because the target data assumes this has been done. Adding the weight pre-loads the suspension to a moment in it's dynamic range, but there's another factor.... The loading is a measurement between the unsprung and sprung chassis, the unknown factor is how much the coils have sagged, this is important since the coils are the pick-up points between the unsprung and sprung chassis. Most machines will offer the "desired" trim height or in other words the distance between the unsprung and sprung chassis. By adding weight it's possible to set the suspensions pre-loaded position even if the coils have sagged. In this event some cars need no weight, others might need 190kg? In whatever event for the unmodified car the trim height must be respected or the end results are worthless.... absolutely worthless. If on the other hand the car is modified, let's say lowered then adding weight is not necessary because the chassis will have a bespoke calibration to tune the modification. Quote Link to comment Share on other sites More sharing options...
xaddiction Posted May 16, 2011 Author Report Share Posted May 16, 2011 Ah, right I understand now. My car has a h+r lowering kit on it so that's probably why they didn't weight it down. Also on the camber on the near side was only just in spec. It's adjustable but he refused to do it. He said it don't need doing, you won't notice the difference so I'd rather not take your money. Thing is after it had all been set up and the reflectors were still on the car he climbed on the car lift and leaned in the car to pick something up. When he knelt on the drivers seat his body weight knocked the near side camber into the red. If this happens just from him leaning on the seat won't it be like this most of the time when I'm driving?? Quote Link to comment Share on other sites More sharing options...
Tony Posted May 16, 2011 Report Share Posted May 16, 2011 If the camber is outside of the tolerance then it's along way away from it's tolerance centre point, it should have been adjusted. As for the positions moving with him in the car...... This will happen but remember the car is static so he actually pulled the car body diagonally. Quote Link to comment Share on other sites More sharing options...
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