DJ_AS Posted August 23, 2006 Report Share Posted August 23, 2006 First of all - hello to everyone in the forum and thank you to Tony for checking the geometry of my Mondeo. Tony - the front-rear tyre swap seems to have done the trick. Funny how much of an effect tyre drift can have. Anyway, my Mondeo seems to follow road camber and bump steer more than the old Ka. The Mondeo has wider tyres (though not huge at 205), and is a lot heavier. Also the power steering is lighter. Could these factors contribute to this phenomenon? Can the tyre pressures be adjusted so that the car stays straighter on lumpy country roads (i.e reduce bump steer?) My first instinct would be to lower the pressure but I assume that if you lower the pressure too much the sidewalls lose integrity and the front may be difficult to control. Not sure of the current pressures - my portable tyre compressor should arrive in the post the next couple of days. Quote Link to comment Share on other sites More sharing options...
Tony Posted August 23, 2006 Report Share Posted August 23, 2006 First of all - hello to everyone in the forum and thank you to Tony for checking the geometry of my Mondeo. Tony - the front-rear tyre swap seems to have done the trick. Funny how much of an effect tyre drift can have. Anyway, my Mondeo seems to follow road camber and bump steer more than the old Ka. The Mondeo has wider tyres (though not huge at 205), and is a lot heavier. Also the power steering is lighter. Could these factors contribute to this phenomenon? Can the tyre pressures be adjusted so that the car stays straighter on lumpy country roads (i.e reduce bump steer?) My first instinct would be to lower the pressure but I assume that if you lower the pressure too much the sidewalls lose integrity and the front may be difficult to control. Not sure of the current pressures - my portable tyre compressor should arrive in the post the next couple of days. Welcome in ... Bump steer is unusual on an unmodified car.... Could it be more the case of tram lining? Quote Link to comment Share on other sites More sharing options...
DJ_AS Posted August 23, 2006 Author Report Share Posted August 23, 2006 Well, if I drive down a bumpy road I can feel the steering wheel wanting to wriggle left and right according to the road surface. Its not awful by any means but a bit more than I expected. It feels different to torque steer, and I would assume tramlining feels like torque steer to the driver. Assuming it is tramlining, can tyre pressure changes reduce that affect? Maybe increasing pressure to reduce contact patch? I do quite a bit of motorway driving so its probably not a bad idea anyway. Quote Link to comment Share on other sites More sharing options...
Tony Posted August 23, 2006 Report Share Posted August 23, 2006 Well, if I drive down a bumpy road I can feel the steering wheel wanting to wriggle left and right according to the road surface. Its not awful by any means but a bit more than I expected. It feels different to torque steer, and I would assume tramlining feels like torque steer to the driver. Assuming it is tramlining, can tyre pressure changes reduce that affect? Maybe increasing pressure to reduce contact patch? I do quite a bit of motorway driving so its probably not a bad idea anyway. Tyre pressure changes the rigidity of the tyre sidewall denying tram steer, but the manipulation of the pressure needs to be reasonable. Quote Link to comment Share on other sites More sharing options...
discount tyres dan Posted August 24, 2006 Report Share Posted August 24, 2006 have you checked the lower arms on the front of the car? at the point where they bolt into the sub-frame there are 2 bushes, these have a tendency to work them selves out of the arm itself causing a floaty feeling in the steering as the front wheels 'move about' you may need the car on a ramp to check properly. Quote Link to comment Share on other sites More sharing options...
DJ_AS Posted August 24, 2006 Author Report Share Posted August 24, 2006 Dan - haven't checked but the car was only just serviced and MOT'd before I bought it, so I assume that the bushes would have been checked. Heck, its probably just me being paranoid or just getting used to the car! Despite having driven lots of Mondeo class cars before, its always been on the motorway or A-roads. Its not until you get onto the winding lanes that you really get to know the handling nuances of a vehicle. I don't think there is a 'problem' with the car. I just wanted to know if it was possible to change the handling characteristics a bit more to my taste by adjusting the tyre pressures. I think in terms of the compromise between ride and comfort, the Mondeo is pretty much sorted. I'm a big fan of the way Ford set up their chassis. Quote Link to comment Share on other sites More sharing options...
kev7117 Posted August 25, 2006 Report Share Posted August 25, 2006 Tony's just sorted out my Mondeo - it drove like a pig with a misaligned steering wheel and a pull as well. Now that the geometry is sorted I do notice a tendency for the car's steering to go left and right as I hit bumps and lumps in the road. I thought that's what you call 'feedback'. If you don't feel the road at all then the car would feel totally lifeless?? Just my thoughts..... Quote Link to comment Share on other sites More sharing options...
DJ_AS Posted August 28, 2006 Author Report Share Posted August 28, 2006 I agree Kev, but there was something not quite to my liking. My portable tyre inflator arrived the other day and I checked and adjusted the pressures. The recommended pressures are 34-35 psi at the front and 31-41 at the rear. The pressures as measured by my inflator were 25psi at the front and 30psi at the rear. I've adjusted these to 35 psi all round and I'm happier with the handling I'm having to assume that my portable inflator's guage is calibrated accurately - I'll check the pressures against a petrol forecourt inflator if I can find one that actually works. Amusingly, the car's handbook also lists pressures for continous road speed over 100mph Quote Link to comment Share on other sites More sharing options...
Tony Posted August 28, 2006 Report Share Posted August 28, 2006 I agree Kev, but there was something not quite to my liking. My portable tyre inflator arrived the other day and I checked and adjusted the pressures. The recommended pressures are 34-35 psi at the front and 31-41 at the rear. The pressures as measured by my inflator were 25psi at the front and 30psi at the rear. I've adjusted these to 35 psi all round and I'm happier with the handling I'm having to assume that my portable inflator's guage is calibrated accurately - I'll check the pressures against a petrol forecourt inflator if I can find one that actually works. Amusingly, the car's handbook also lists pressures for continous road speed over 100mph Out of curiosity why do you think the pressure needs to be modified for continuous speeds over 100mph... This is not a test so don't feel 'pressured ' Quote Link to comment Share on other sites More sharing options...
DJ_AS Posted August 29, 2006 Author Report Share Posted August 29, 2006 I agree Kev, but there was something not quite to my liking. My portable tyre inflator arrived the other day and I checked and adjusted the pressures. The recommended pressures are 34-35 psi at the front and 31-41 at the rear. The pressures as measured by my inflator were 25psi at the front and 30psi at the rear. I've adjusted these to 35 psi all round and I'm happier with the handling I'm having to assume that my portable inflator's guage is calibrated accurately - I'll check the pressures against a petrol forecourt inflator if I can find one that actually works. Amusingly, the car's handbook also lists pressures for continous road speed over 100mph Out of curiosity why do you think the pressure needs to be modified for continuous speeds over 100mph... This is not a test so don't feel 'pressured ' I think I read somewhere that increasing the tyre pressure will reduce contact patch and therefore also the friction between tyre and road surface. This is turn should reduce heat build up in the tyre which would otherwise occur at high speed. However - I would have thought that a hot tyre would increase in pressure anyway; sort of a self regulating system ?? Quote Link to comment Share on other sites More sharing options...
Tony Posted August 29, 2006 Report Share Posted August 29, 2006 I agree Kev, but there was something not quite to my liking. My portable tyre inflator arrived the other day and I checked and adjusted the pressures. The recommended pressures are 34-35 psi at the front and 31-41 at the rear. The pressures as measured by my inflator were 25psi at the front and 30psi at the rear. I've adjusted these to 35 psi all round and I'm happier with the handling I'm having to assume that my portable inflator's guage is calibrated accurately - I'll check the pressures against a petrol forecourt inflator if I can find one that actually works. Amusingly, the car's handbook also lists pressures for continous road speed over 100mph Out of curiosity why do you think the pressure needs to be modified for continuous speeds over 100mph... This is not a test so don't feel 'pressured ' I think I read somewhere that increasing the tyre pressure will reduce contact patch and therefore also the friction between tyre and road surface. This is turn should reduce heat build up in the tyre which would otherwise occur at high speed. However - I would have thought that a hot tyre would increase in pressure anyway; sort of a self regulating system ?? You are wise indeed... Quote Link to comment Share on other sites More sharing options...
DJ_AS Posted August 29, 2006 Author Report Share Posted August 29, 2006 So I'm correct?? But then why DO they tell you to raise the pressure if it is a self regulating system?? My head hurts... Quote Link to comment Share on other sites More sharing options...
Tony Posted August 29, 2006 Report Share Posted August 29, 2006 So I'm correct?? But then why DO they tell you to raise the pressure if it is a self regulating system?? My head hurts... Sorry, what is a 'self regulating system?' Quote Link to comment Share on other sites More sharing options...
DJ_AS Posted August 30, 2006 Author Report Share Posted August 30, 2006 I agree Kev, but there was something not quite to my liking. My portable tyre inflator arrived the other day and I checked and adjusted the pressures. The recommended pressures are 34-35 psi at the front and 31-41 at the rear. The pressures as measured by my inflator were 25psi at the front and 30psi at the rear. I've adjusted these to 35 psi all round and I'm happier with the handling I'm having to assume that my portable inflator's guage is calibrated accurately - I'll check the pressures against a petrol forecourt inflator if I can find one that actually works. Amusingly, the car's handbook also lists pressures for continous road speed over 100mph Out of curiosity why do you think the pressure needs to be modified for continuous speeds over 100mph... This is not a test so don't feel 'pressured ' I think I read somewhere that increasing the tyre pressure will reduce contact patch and therefore also the friction between tyre and road surface. This is turn should reduce heat build up in the tyre which would otherwise occur at high speed. However - I would have thought that a hot tyre would increase in pressure anyway; sort of a self regulating system ?? You are wise indeed... So I'm correct?? But then why DO they tell you to raise the pressure if it is a self regulating system?? My head hurts... Sorry, what is a 'self regulating system?' I'll try explain my thinking. A tyre running at high speed along a motorway for a while will gradually get hotter due to friction. The heat in turn causes the pressure within that tyre to increase. The increased pressure causes the contact patch between tyre and road to decrease. This is turn reduces the friction between road and tyre and therefore also the rate of heat build up. Eventually, the tyre should reach an equilibrium where heat and internal pressure remain stable. Further increases in friction mediated heating cause further increases in pressure and there is a resultant reduction in contact patch which stops any further heating. more heat --> higher pressure --> smaller contact patch --> less friction --> no more heating Yes? Quote Link to comment Share on other sites More sharing options...
Tony Posted August 30, 2006 Report Share Posted August 30, 2006 I agree Kev, but there was something not quite to my liking. My portable tyre inflator arrived the other day and I checked and adjusted the pressures. The recommended pressures are 34-35 psi at the front and 31-41 at the rear. The pressures as measured by my inflator were 25psi at the front and 30psi at the rear. I've adjusted these to 35 psi all round and I'm happier with the handling I'm having to assume that my portable inflator's guage is calibrated accurately - I'll check the pressures against a petrol forecourt inflator if I can find one that actually works. Amusingly, the car's handbook also lists pressures for continous road speed over 100mph Out of curiosity why do you think the pressure needs to be modified for continuous speeds over 100mph... This is not a test so don't feel 'pressured ' I think I read somewhere that increasing the tyre pressure will reduce contact patch and therefore also the friction between tyre and road surface. This is turn should reduce heat build up in the tyre which would otherwise occur at high speed. However - I would have thought that a hot tyre would increase in pressure anyway; sort of a self regulating system ?? You are wise indeed... So I'm correct?? But then why DO they tell you to raise the pressure if it is a self regulating system?? My head hurts... Sorry, what is a 'self regulating system?' I'll try explain my thinking. A tyre running at high speed along a motorway for a while will gradually get hotter due to friction. The heat in turn causes the pressure within that tyre to increase. The increased pressure causes the contact patch between tyre and road to decrease. This is turn reduces the friction between road and tyre and therefore also the rate of heat build up. Eventually, the tyre should reach an equilibrium where heat and internal pressure remain stable. Further increases in friction mediated heating cause further increases in pressure and there is a resultant reduction in contact patch which stops any further heating. more heat --> higher pressure --> smaller contact patch --> less friction --> no more heating Yes? Yes! Another area within this topic: Can you say what in the compressed air causes this problem... and it turn suggest a solution? Quote Link to comment Share on other sites More sharing options...
DJ_AS Posted August 30, 2006 Author Report Share Posted August 30, 2006 I agree Kev, but there was something not quite to my liking. My portable tyre inflator arrived the other day and I checked and adjusted the pressures. The recommended pressures are 34-35 psi at the front and 31-41 at the rear. The pressures as measured by my inflator were 25psi at the front and 30psi at the rear. I've adjusted these to 35 psi all round and I'm happier with the handling I'm having to assume that my portable inflator's guage is calibrated accurately - I'll check the pressures against a petrol forecourt inflator if I can find one that actually works. Amusingly, the car's handbook also lists pressures for continous road speed over 100mph Out of curiosity why do you think the pressure needs to be modified for continuous speeds over 100mph... This is not a test so don't feel 'pressured ' I think I read somewhere that increasing the tyre pressure will reduce contact patch and therefore also the friction between tyre and road surface. This is turn should reduce heat build up in the tyre which would otherwise occur at high speed. However - I would have thought that a hot tyre would increase in pressure anyway; sort of a self regulating system ?? You are wise indeed... So I'm correct?? But then why DO they tell you to raise the pressure if it is a self regulating system?? My head hurts... Sorry, what is a 'self regulating system?' I'll try explain my thinking. A tyre running at high speed along a motorway for a while will gradually get hotter due to friction. The heat in turn causes the pressure within that tyre to increase. The increased pressure causes the contact patch between tyre and road to decrease. This is turn reduces the friction between road and tyre and therefore also the rate of heat build up. Eventually, the tyre should reach an equilibrium where heat and internal pressure remain stable. Further increases in friction mediated heating cause further increases in pressure and there is a resultant reduction in contact patch which stops any further heating. more heat --> higher pressure --> smaller contact patch --> less friction --> no more heating Yes? Yes! Another area within this topic: Can you say what in the compressed air causes this problem... and it turn suggest a solution? Would that be the water thats in the air (and therefore the tyre)? I have noticed that some tyre places now inflate tyres with nitrogen instead of compressed air. Is the rubber of the tyres permeable though? Would air (and moisture assuming it is the culprit) eventually find its way through the rubber and replace the nitrogen? Quote Link to comment Share on other sites More sharing options...
Tony Posted August 30, 2006 Report Share Posted August 30, 2006 Quote: DJ AS Would that be the water thats in the air (and therefore the tyre)? I have noticed that some tyre places now inflate tyres with nitrogen instead of compressed air. Is the rubber of the tyres permeable though? Would air (and moisture assuming it is the culprit) eventually find its way through the rubber and replace the nitrogen? ................................................ Yes the criminal is water!.... Dry Nitrogen will be the assassin of compressed air in the near future... This inert gas used in Aircraft and racing for many years in different levels of chemical mix is not subject the the variants of heat (almost) The Nitrogen molecule is to large to seep through the tyre inner liner so retains pressure for longer.... The only obligation by the driver is to increase the pressure if the cars load is increased, not general speed, so the maintenance is more 21st Century.... wim centres would only use Nitrogen inflation at no additional cost to the owner.... setting an acknowledged example! Quote Link to comment Share on other sites More sharing options...
Mark H. Posted August 31, 2006 Report Share Posted August 31, 2006 If you had nitrogen filled tyres, and one was a bit low, how would you fill it up without going to a shop with a nitrogen tank? Quote Link to comment Share on other sites More sharing options...
Tony Posted August 31, 2006 Report Share Posted August 31, 2006 If you had nitrogen filled tyres, and one was a bit low, how would you fill it up without going to a shop with a nitrogen tank? If this example happened then you would use compressed air... the result would only dilute the benefit if Nitrogen.... This transition to Nitrogen will take time, but not much since the evolution is so cheap now in delivery terms....... So says wim Quote Link to comment Share on other sites More sharing options...
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