Definitive explanation: Tramlining

Discussion in 'Wheels, Tyres, Brakes & Suspension' started by wheels-inmotion, Nov 3, 2010.

  1. wheels-inmotion

    wheels-inmotion Hardcore MB Enthusiast

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    Complaint
    1:Involuntary direction changes outside of the drivers command.
    2:Unpredictable changes of direction on different road surfaces.

    What's going on?
    Tramlining is a relatively recent complaint due to...
    1: The road condition
    2: The low profile tyre
    3: The tyre

    1: Motorway troths act like rails with walls
    2: Contact patch deviations and sidewall communication
    3: Some tyres are designed to require yaw in order to deviate the current line of travel.

    To the point....
    It's a combination of factors but really simple to understand.

    Over the years wheels have become bigger/ tyres wider, in order to allow this the tyres sidewall had to become smaller.

    To allow for the smaller sidewall it has to be stronger in order to cope with road irregularity's ( pothole's and alike ) but deviations in the contact patch due to the road condition can no longer be lost between the patch and the wheel due to the reinforced sidewall..... There's no lateral flex.

    A deviation from the contact patch directly communicates to the rim and steers the car.

    Tyres
    1: Symmetrical tread pattern is less susceptible to tramlining
    2: Directional even less, but prone to other issues on the MB
    3: Asymmetrical tyres ( MO ) i might add are the worst but fall way short of the RFT ( run flat tyre )

    What to do?
    You need to minimize the damage, here are the options
    1: Be wise on your tyre choice
    2: Manipulate those tyre pressures
    3: Have the front "toe tendency set?

    To explain
    1: Done that see above
    2: The suggested tyre pressures are just that "suggested", within reason by changing the pressure you can change the flexibility of the tyre sidewall, this in turn changes the "communication".
    3: As the suspension migrates through bump and droop the "toe angle" ( tracking ) moves, it might go from a bit in to a Lot out. Finding the migration values and setting the toe position to it mid-point will minimize tramelining.

    A problem
    Non of the above solutions will work on every car, a combination of solutions would need to be used for each example.

    Well that all reads depressing.... It's not! You have the option on tyre make, you have the option of manipulating the tyre pressure and you know know about "toe migration on bump/ droop".
     
    rf065, markjay, ringway and 12 others like this.
  2. moonloops

    moonloops MB Club Veteran

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    :cool:

    Can you do one of these on bump steer..

    Oh and another one on "counterbalancing" when a standard "garage balance" gets it all wrong but wheel is balanced but still wobbles... as I don't understand this concept (yet) :thumb:
     
  3. OP
    OP
    wheels-inmotion

    wheels-inmotion Hardcore MB Enthusiast

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    Bump-steer and counter balance is another topic if you don't mind. I fully understand your direction but it's another thread.
     
  4. moonloops

    moonloops MB Club Veteran

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    Yep, another thread is what I'm asking for :thumb:
     
  5. moonloops

    moonloops MB Club Veteran

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    p.s.
    - great words from an alignment company :D
     
  6. OP
    OP
    wheels-inmotion

    wheels-inmotion Hardcore MB Enthusiast

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    To much information will keep you awake.... Consume and question the current thread if your interested in this sort of stuff.
     
  7. moonloops

    moonloops MB Club Veteran

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    Definitely interested in the areas I don't have a full grasp of so carry on at your leisure..

    Oh and thanks..
     
  8. OP
    OP
    wheels-inmotion

    wheels-inmotion Hardcore MB Enthusiast

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    Your welcome..... I'll give you a taster to think about in bed.

    Bump Steer is the correlation of the steering arms radius and the wishbone radius, why/ how could this change?
     
  9. moonloops

    moonloops MB Club Veteran

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    All I know is as when the wheel/tyre is on an upward stroke the steering angle changes so you understeer more. I'm just a layman but I know when bump steer is corrected (as on my old Type R impreza) the turn in on medium to sharp corners was fantastic. The front end dug in and pulled the car through the corner....
    p.s. edited to add I suppose it's all about keeping the tyre flat on the road rather than cambered ??
     
  10. OP
    OP
    wheels-inmotion

    wheels-inmotion Hardcore MB Enthusiast

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    The radius of the steering arm and wishbone would change if the sprung body is lowared.

    Imagine your car as a sandwich..... Top layer is above the suspension ( sprung ) and the bottom layer is under the suspension ( unsprung )

    Interactions between the two areas are the dynamic suspension interactions, and the wheels migration during bump and droop, these interactions are geometric interactions.

    A change in the unsprung distance toward the sprung chassis changes the radius of the unsprung pickup points..... Radius is out of sync, consequence of this is the "bump" radii of the suspension acts on the unsprung steering linkage..... Result, bump steer.
     
  11. Minden99

    Minden99 Active Member

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    I kind of get the thread. BUT majority of tramlining is on motorways and fast A roads on the inside lanes caused by 40tonne articulated trucks especially on gradual up hills as their power comes in. It moves the tarmac outwards from the tyre contact patch. Even small trucks in which I'm involved in suffer never mind cars. So cannot see how manipulating tyre type and pressure could ultimately stop tramlining. Do agree though that tyre type and pressures can make massive differences to general handling etc, but to low and tyre wall will generally overheat which in itself is very dangerous. Another impact people don't recognise with tramlining is the effect of the dead spot at straight head steering wheel if too little and too light your always over compensating.
     
  12. zipdip

    zipdip Hardcore MB Enthusiast

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    Nothing wrong with a bit of tramlining ,I never bother to look at the sat nav driving around Paris just get in those tramlines and before you know it you are on the Macon road.
     
  13. optimusprime

    optimusprime Hardcore MB Enthusiast

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    Some tyres are known for this problem of tramlining .And not chepo types ,some well known makes do it . With Volvo V70s it was Pireli 600.
     
  14. Smart320

    Smart320 Hardcore MB Enthusiast

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    This thread is brilliant bedtime reading, am asleep in seconds
     
  15. optimusprime

    optimusprime Hardcore MB Enthusiast

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    Problem with my Volvo V70 was it wanted to go just where it wanted to, once it got in a line on the road . The Volvo forum told me at the time that the tyres i had on would be Pireli P6000. This was right , and i never told them what the were . This was a common fault with those tyres .But after i changed them i still had that go where it wanted to feel , but not so much .Only thing that eliminated it 100% was new control arms .
     

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