Tony Posted May 30, 2006 Report Share Posted May 30, 2006 The car: BMW 535I E39 Series The Tyre: 225/55-16 The Position: Rear The Driving Environment: 90% Fast Motorway This is the second pair of rear tyres to wear in this fashion... Pressure: Actual 30psi Stock 36psi So why the wear? Quote Link to comment Share on other sites More sharing options...
discount tyres dan Posted May 30, 2006 Report Share Posted May 30, 2006 did you know it was low tyre presure that caused ayrton senna's death? Quote Link to comment Share on other sites More sharing options...
Tony Posted May 30, 2006 Author Report Share Posted May 30, 2006 did you know it was low tyre pressure that caused ayrton senna's death? As i recall a few caution laps on new tyres kept them under-inflated, then on a bend the weight transfer moved the camber curve and allowed the floor pan to 'sledge' the car off the track.....A tragic loss to the entire World. Quote Link to comment Share on other sites More sharing options...
discount tyres dan Posted May 30, 2006 Report Share Posted May 30, 2006 thats right, his last words.. "the car feels ok" Quote Link to comment Share on other sites More sharing options...
Tony Posted May 30, 2006 Author Report Share Posted May 30, 2006 thats right, his last words.. "the car feels ok" Some sentences send shivers down my spine... 'The car feels ok' and another one 'Huston we have a problem'. Back to the wear issue..... Any thoughts? Quote Link to comment Share on other sites More sharing options...
jon Posted May 30, 2006 Report Share Posted May 30, 2006 Isn't that backwards? I thought over inflation would result in that, not under?! Quote Link to comment Share on other sites More sharing options...
Tony Posted May 30, 2006 Author Report Share Posted May 30, 2006 Isn't that backwards? I thought over inflation would result in that, not under?! Yes that assumption seems reasonable... This particular customer reading the wear as over inflation lowered the psi from 36 to 30, and this actually accelerated the wear This logic is flawed as is air for inflation.... I'm not playing games here only making people think before the answer arrives..... Go again Quote Link to comment Share on other sites More sharing options...
discount tyres dan Posted May 30, 2006 Report Share Posted May 30, 2006 maybe he should raise the presure to maybe 40 psi, could be the heat from all that motorway driving playing havoc with his air presures. i take it he is using 'normal' air Quote Link to comment Share on other sites More sharing options...
jon Posted May 30, 2006 Report Share Posted May 30, 2006 My only other guess without going to a book would be the obvious. Way, too, much, toe. maybe he should raise the presure to maybe 40 psi, could be the heat from all that motorway driving playing havoc with his air presures. i take it he is using 'normal' air How does that work? Air expands with heat so by your logic he'll probably be running close to 45psi once he's underway Quote Link to comment Share on other sites More sharing options...
Tony Posted May 30, 2006 Author Report Share Posted May 30, 2006 My only other guess without going to a book would be the obvious. Way, too, much, toe. maybe he should raise the presure to maybe 40 psi, could be the heat from all that motorway driving playing havoc with his air presures. i take it he is using 'normal' air How does that work? Air expands with heat so by your logic he'll probably be running close to 45psi once he's underway Yep. Rolling resistance generates heat, the moisture in the air expands over inflating the tyre... So the science is to reduce the contact patch belaying the build up of temperature. Most car manufacturers suggest psi for Town/Loaded and Motorway, this particular car should have had 44psi in the tyres not 30psi.... Another factor is centrifugal force... If the tyre is running under pressure then the casings resistance to the 'centrifugal pull' is low, allowing distortion, whereas if the correct pressure was inflated the rigidity of the casing suppresses distortion. Historically tyre centres would correctly explain the problem is due to over inflation but fail to explain the exact reason... The customer then has no option but to react uneducated and deflate the tyres accelerating the wear.... this customer was a perfect example. Quote Link to comment Share on other sites More sharing options...
jiberjaber Posted May 30, 2006 Report Share Posted May 30, 2006 Wow.... I was thinking that there was a link to the heat=>expansion, but never would have guessed it was down to the x-sectional area increasing the rolling resistance, resulting in a quicker build up of heat that could not bedisapaited hence the expansion. It certainly is the missing piece in the jigsaw! Quote Link to comment Share on other sites More sharing options...
Tony Posted May 30, 2006 Author Report Share Posted May 30, 2006 Wow.... I was thinking that there was a link to the heat=>expansion, but never would have guessed it was down to the x-sectional area increasing the rolling resistance, resulting in a quicker build up of heat that could not bedisapaited hence the expansion. It certainly is the missing piece in the jigsaw! Like most things technical a true understanding speaks volumes..... Most times simple reasoning's resolve the entire problem, but only if this is transmitted to the customer.... Unfurtunately is not always the case. Quote Link to comment Share on other sites More sharing options...
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