Tony Posted May 9, 2008 Report Share Posted May 9, 2008 This topic has popped up a few times recently so in true wim fashion lets investigate. What is it?. Tramlining is an unrequested tendency for the steering to deviate from the intended direction of travel. What activates it? The main criminal is the road condition, namely the motorway ruts left by millions of heavy goods vehicles compressing low level depressions in the road. Why is this such an issue nowadays? Tyre pressure, tyre pattern and Geometry owns a share of responsibility but the main culprit is.... The tyres aspect ratio Explanation Over the years the tyres aspect ratio has vastly reduced, 45 or 40 is common place and commanded if the car is to handle as promised by the manufacturer. The problem we have is the lack of flexibility in the tyre sidewall and the tyre width. In the past the higher aspect ratio allowed the sidewall to independently deflect the individual sidewalls contact against the contour of the road ruts. The inflexibility of modern low aspect ratio tyres does not allow conical distortion of the tyre sidewall so this energy is aggressively transported to the steering generating the tramlining phenomenon. What to do? There's no magic fix here but we do have options to belay the effect of tramlining. Tyre pattern The tyre tread pattern does aggravate tramlining. Historically due to a consistency of a the radial pattern Asymmetrical tyres are the worst, followed by directional then symmetrical. Each level is amplified by a progressively lower aspect ratio. Tyre pressure Manipulation of the tyre pressure can regulate the rigidity of the tyre sidewall. Small changes will allow pneumatic distortion and offer a powerful tool to belay tramlining. "WARNING" increments of one or two psi should be used incrementally!! Geometry Changes in the Geometry will help although there is much debate and confusion here. Word on the street is to change the camber position, this is incorrect. Camber being the vertical position permits distortion of the tyre sidewall if the deviation exceeds vertical. In effect the camber positions conical effect agitated by the road rut is the very reason why you have tramlining, so manipulation of this will only aggravate the problem. Other thoughts and theory's are the castor position, again this is wrong. The castor is the longitudinal (fore/aft) position of the steer axis and Geometrically unaware of the road ruts. Our Geometric saviour Toe is the Geometric longitudinal position of the tyres relative to the cars actual centre line. The dynamic goal is 0 but the forces offered by toe is lateral "ah ha" As the image suggests lateral forces and pneumatic distortion can be belayed by changes in the toe position which is also a lateral force. Small changes can deflect "common" tramlining deviations without compromising tyre wear.... Happy days A compilation of all formats can offer resolve for tramlining but needs to be explored in it's varying solutions courtiously and incrimentally to save you time and money. Quote Link to comment Share on other sites More sharing options...
jammy Posted May 10, 2008 Report Share Posted May 10, 2008 Would altering the offset...ie a slightly smaller..also help this??? as noticed with my current wheel's i have very little.and when went to my other set it was more apparent as they were a 40 offset i think and the set i have on car at mo are beleaved to be 35 Quote Link to comment Share on other sites More sharing options...
dazz33 Posted May 10, 2008 Report Share Posted May 10, 2008 Hi Tony......well you know about the tramlining ive had...... since i last left WIM and haveing put Wozza`s tyres on ( thanx Wozza ) my steering has now centred up lovely ( very odd ) and i only have a tiny bit of tramlining which im more than happy to put up with considering the state of the public highways these days.. OFF TOPIC....still need to see lexus about power steering pump/belt sqweeling.. Quote Link to comment Share on other sites More sharing options...
Tony Posted May 10, 2008 Author Report Share Posted May 10, 2008 Would altering the offset...ie a slightly smaller..also help this??? as noticed with my current wheel's i have very little.and when went to my other set it was more apparent as they were a 40 offset i think and the set i have on car at mo are beleaved to be 35 Technically no.. The offset moves the tyres contact patch in or out board of the designed pivotal contact patch. Quote Link to comment Share on other sites More sharing options...
Rich Posted May 13, 2008 Report Share Posted May 13, 2008 I found out last week just how badly my car tramlines on certain roads. Where I work the length of one road had works done on the water pipes, therefore this section has different tarmac on it. In the mondeo with 215/45r17 tyres it tramlines so badly I have to stick to around 25-30mph. In the missus peugeot with 165/65r13 tyres there was no tramlining at all. I suppose this is the price you pay for having bigger wheels! Quote Link to comment Share on other sites More sharing options...
Tony Posted May 13, 2008 Author Report Share Posted May 13, 2008 I found out last week just how badly my car tramlines on certain roads. Where I work the length of one road had works done on the water pipes, therefore this section has different tarmac on it. In the mondeo with 215/45r17 tyres it tramlines so badly I have to stick to around 25-30mph. In the missus peugeot with 165/65r13 tyres there was no tramlining at all. I suppose this is the price you pay for having bigger wheels! It's not the width it's the tyres aspect ratio.... Manipulate the pressure and see what happens. Quote Link to comment Share on other sites More sharing options...
Rich Posted May 14, 2008 Report Share Posted May 14, 2008 I found out last week just how badly my car tramlines on certain roads. Where I work the length of one road had works done on the water pipes, therefore this section has different tarmac on it. In the mondeo with 215/45r17 tyres it tramlines so badly I have to stick to around 25-30mph. In the missus peugeot with 165/65r13 tyres there was no tramlining at all. I suppose this is the price you pay for having bigger wheels! It's not the width it's the tyres aspect ratio.... Manipulate the pressure and see what happens. Well I don't go above 32psi which is what they're on now as I don't like the way the car handles. Tramlines the same when they're on 30psi as well. It's only this bit of road by work that is the worse, everywhere else is ok-ish Quote Link to comment Share on other sites More sharing options...
Tony Posted May 14, 2008 Author Report Share Posted May 14, 2008 I found out last week just how badly my car tramlines on certain roads. Where I work the length of one road had works done on the water pipes, therefore this section has different tarmac on it. In the mondeo with 215/45r17 tyres it tramlines so badly I have to stick to around 25-30mph. In the missus peugeot with 165/65r13 tyres there was no tramlining at all. I suppose this is the price you pay for having bigger wheels! It's not the width it's the tyres aspect ratio.... Manipulate the pressure and see what happens. Well I don't go above 32psi which is what they're on now as I don't like the way the car handles. Tramlines the same when they're on 30psi as well. It's only this bit of road by work that is the worse, everywhere else is ok-ish Then it's time to change the Toe so there's no lateral resistance acting on the tyre sidewall. Quote Link to comment Share on other sites More sharing options...
shortstuff Posted June 10, 2008 Report Share Posted June 10, 2008 I get this loads on severial of the roads I drive. I always thought it was because I have wide tyres now. I too go to 32psi I may try dropping it too 30psi for a while and see what happens Quote Link to comment Share on other sites More sharing options...
Tony Posted June 10, 2008 Author Report Share Posted June 10, 2008 I get this loads on severial of the roads I drive. I always thought it was because I have wide tyres now. I too go to 32psi I may try dropping it too 30psi for a while and see what happens Manipulate the pressure..... This calibrates the rigidity of the tyre sidewall. You are effectively in control of tramlining! Quote Link to comment Share on other sites More sharing options...
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