Tony Posted November 19, 2010 Report Share Posted November 19, 2010 Vehicle BMW X5 Index 2007 Complaint Inner rear tyre wear History We see many X5's with the same complaint but i don't think i've documented this before in HOTW. The chassis The X5 rear camber/ toe positions are unremarkable since we are talking 4X4 The problem The problem is the RFT ( Run Flat Tyre ) these tyres cannot adopt the rear camber position suggested by BMW simply because the camber position needs to distort the tyres inner sidewall, the RFT sidewall remains the same circumference inside and out and loads the inner wall with the vehicles weight. The evidence The data The data images displayed are not to distant from the BMW idyllic positions The solution We don't use BMW's positions, over time and research we have developed new positions that allow the contact patch to be undistorted, this stops the Tyre wear and although the camber positions are reduced it increases the grip coefficient because the contact patch is undistorted. Quote Link to comment Share on other sites More sharing options...
Rich Posted November 19, 2010 Report Share Posted November 19, 2010 Excellent, that's another example of WIM doing it right and the manufacturer wrong! Quote Link to comment Share on other sites More sharing options...
Tony Posted November 19, 2010 Author Report Share Posted November 19, 2010 Scary stuff when you poo poo BMW. Quote Link to comment Share on other sites More sharing options...
hms Posted November 19, 2010 Report Share Posted November 19, 2010 So that tyre was seperated from the bead, and the driver was still driving? Were there no pressure sensors? h Quote Link to comment Share on other sites More sharing options...
Tony Posted November 20, 2010 Author Report Share Posted November 20, 2010 The bead hasn't separated, the tyre is intact and correctly inflated. Quote Link to comment Share on other sites More sharing options...
dazz33 Posted November 21, 2010 Report Share Posted November 21, 2010 So in other words what you are saying is that run-flats are pants as they cant adopt BMW`s geo positions.? would it resolve the inner tyre wear if the tyres were NON run-flats.? so letting the tyre wall compress.? to allow for the geo positions.? :bananapopcorn: Quote Link to comment Share on other sites More sharing options...
phipck Posted November 22, 2010 Report Share Posted November 22, 2010 or more importantly BMW choosing to use run flats should have made considerations in the geometry Quote Link to comment Share on other sites More sharing options...
Tony Posted November 22, 2010 Author Report Share Posted November 22, 2010 So in other words what you are saying is that run-flats are pants as they cant adopt BMW`s geo positions.? would it resolve the inner tyre wear if the tyres were NON run-flats.? so letting the tyre wall compress.? to allow for the geo positions.? It would be fine. Quote Link to comment Share on other sites More sharing options...
Tony Posted November 22, 2010 Author Report Share Posted November 22, 2010 or more importantly BMW choosing to use run flats should have made considerations in the geometry In many countries run-flats will be mandatory, so BMW are compiling, but seemingly they are not making geometric considerations..... we are. Quote Link to comment Share on other sites More sharing options...
HighlandPete Posted November 22, 2010 Report Share Posted November 22, 2010 or more importantly BMW choosing to use run flats should have made considerations in the geometry In many countries run-flats will be mandatory, so BMW are compiling, but seemingly they are not making geometric considerations..... we are. Don't forget BMW suspension is designed for run-flats..... often quoted by BMW. Nah, they can't be wrong. :lmaosmiley: I've seen pictures like above, where the tyre has seperated. Get the warning 'bong' and 5 miles further on, total tyre failure. So looks like the X5 had a very close call before failure. Also seen pics where it looks the same as above, but with a flat and the owner was praising the run-flat as it 'probably saved his life'. Don't think everyone using the run-flat is getting, that without very close inspection, run-flats are contributing to premature tyre failure. HighlandPete Quote Link to comment Share on other sites More sharing options...
Tony Posted November 23, 2010 Author Report Share Posted November 23, 2010 We are told the suspension is softer to accommodate the RFT but when normal tyres are fitted the ride improves Pre/ post RFT tyres the sport geometry positions remain the same, although this savage tyre wear issue only exists with the RFT. Quote Link to comment Share on other sites More sharing options...
parthiban Posted November 23, 2010 Report Share Posted November 23, 2010 Aren't we unfairly bashing the run-flat though then in this case? Where the fault actually lies with BMWs lack of geo adjustment to take the lack of flex into account? As WIM has fixed it, the actual RFTs aren't the problem, it's BMW Quote Link to comment Share on other sites More sharing options...
Tony Posted November 23, 2010 Author Report Share Posted November 23, 2010 I don't like runflats period. Quote Link to comment Share on other sites More sharing options...
parthiban Posted November 23, 2010 Report Share Posted November 23, 2010 I don't like runflats period. Fair point Quote Link to comment Share on other sites More sharing options...
TheBoy Posted December 23, 2010 Report Share Posted December 23, 2010 Scary stuff when you poo poo BMW. I'm slowly bringing people around to the fact BMW designers leave a lot to be desired... Quote Link to comment Share on other sites More sharing options...
Tony Posted December 23, 2010 Author Report Share Posted December 23, 2010 It's just not something you would expect from a top builder. Quote Link to comment Share on other sites More sharing options...
TheBoy Posted December 23, 2010 Report Share Posted December 23, 2010 It's just not something you would expect from a top builder. They are no better than any other manufacturer from a design standards point of view. Probably no worse than most though. My bro has an X5, I will, of course, get him to check him tyres - was this fronts or rears? Quote Link to comment Share on other sites More sharing options...
Tony Posted December 23, 2010 Author Report Share Posted December 23, 2010 It's just not something you would expect from a top builder. They are no better than any other manufacturer from a design standards point of view. Probably no worse than most though. My bro has an X5, I will, of course, get him to check him tyres - was this fronts or rears? Rears, historically the fronts are fine. Quote Link to comment Share on other sites More sharing options...
aussie aligner Posted February 7, 2011 Report Share Posted February 7, 2011 Vehicle BMW X5 Index 2007 Complaint Inner rear tyre wear History We see many X5's with the same complaint but i don't think i've documented this before in HOTW. The chassis The X5 rear camber/ toe positions are unremarkable since we are talking 4X4 The problem The problem is the RFT ( Run Flat Tyre ) these tyres cannot adopt the rear camber position suggested by BMW simply because the camber position needs to distort the tyres inner sidewall, the RFT sidewall remains the same circumference inside and out and loads the inner wall with the vehicles weight. The evidence The data The data images displayed are not to distant from the BMW idyllic positions The solution We don't use BMW's positions, over time and research we have developed new positions that allow the contact patch to be undistorted, this stops the Tyre wear and although the camber positions are reduced it increases the grip coefficient because the contact patch is undistorted. sorry did i miss something, no specs were changed? did you just toe it in 3mm? Quote Link to comment Share on other sites More sharing options...
Tony Posted February 7, 2011 Author Report Share Posted February 7, 2011 Stock rear camber would be -1 degree 50' and toe +18', we have not used those values. Quote Link to comment Share on other sites More sharing options...
eclipse Posted August 16, 2011 Report Share Posted August 16, 2011 Stock rear camber would be -1 degree 50' and toe +18', we have not used those values. Sorry to bring this after a while but can you share with number of toe values you set on this one? Quote Link to comment Share on other sites More sharing options...
Tony Posted August 16, 2011 Author Report Share Posted August 16, 2011 Yes, it was + 5' each side on the rear and stock toe on the front. Quote Link to comment Share on other sites More sharing options...
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