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Thread: Traction.......the grip issue :)

  1. #49
    F.A.S.T. Butuz's Avatar
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    Well all i know is my 225 wide Eagle F1's are sooooooooooooooooooooooooooooooooooooooooooooooooooooooooo much more grippy both in a straight launch, and round corners than my 205 wide Eagle NCT5's were - but then thats down to tyre compound rather than width i am sure.

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    Great thread Zak…

    There are in fact three tire to road interactions that comprise of what we are calling "grip", its not just friction * normal force. Material deformation over the road-surface (this is why softer compound increases grip), also there is hysteresis of the rubber compound as it slides across the road-surface. This is why it is possible to get a coeffecient of grip higher than 1 because the three components add together. So its a bit misleading to say "wider types don’t increase grip", you can say "wider tyres do not increase the component of grip which is generated by the normal force * the coefficient of the tyre" although that would be a bit long winded! The other two components are severely affected by tyre width, and as has been mentioned heating effects are more problematic on a small tyre purely because of the amount of rubber that is able to dissipate the heat. Also as a tyre reaches its limit all sorts of funny affects start to occur as the tyre deforms and loses grip, this characteristic (breakdown) is also affected by the width of the tyre.

    Without being provocative I would actually have to claim that "the total grip a tyre can generate in real world situations is heavily dependant on width"
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  3. #51
    Looser Konan555's Avatar
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    In the case of magnesium alloy wheels, doesn't the increased rim and decreased amound of rubber lower the unspung weight?

    Just asking as I've never picked up a mag rim to see how light it is.

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    Looser Konan555's Avatar
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    Oh, and to further the initial 'wider isn't more'

    All you're changing is the footprint, not the contact area.

    There's quite a few cases of Cars having totaly the wrong footprint relative to their design (thanks to some over zealous 'modz') and causing some nasty accidents 'cause they're not doing their job right.

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    Quote Originally Posted by Konan555
    All you're changing is the footprint, not the contact area.
    I think the contact area does increase (area = width * height)
    its just that you are reducing the force/m2 so the effect is cancelled.
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    Quote Originally Posted by Konan555
    In the case of magnesium alloy wheels, doesn't the increased rim and decreased amound of rubber lower the unspung weight?

    Just asking as I've never picked up a mag rim to see how light it is.
    Yes alloys are noticably lighter (mine are anyway) than steels. But most are bigger than steels because they are larger diameter and wider, so the effect is somewhat reduced.
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    Mac's Just Work BroadbandPlacey's Avatar
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    hmmmm can i ask one thing? if this is true WHY when i went dune riding in the dessert in 4 x 4 toyota landcruisers, they let the tyres down to give them a larger surface area hence more grip?

    and surely if you have more rubber touching the ground (wider tyres) the frictional forces that act on that larger surface area will be larger.... more friction = more grip

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    Looser Konan555's Avatar
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    That's down to a deformable surface. If you where on 'English farm mud' you'd want thin nobbley tyres for better grip.

    Friction is also related to the pressure between the two surfaces. Since you've increseded the surface, you've decreased the presure at any one part of it.

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    Konan is right, the tyres are let down to spread the force over a larger area. This means more grip is attained because the loose surface is having less force/m2 and so therefore it does not "give way" as much.
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    Senior Member Tumble's Avatar
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    Quote Originally Posted by Konan555
    That's down to a deformable surface. If you where on 'English farm mud' you'd want thin nobbley tyres for better grip.

    Friction is also related to the pressure between the two surfaces. Since you've increseded the surface, you've decreased the presure at any one part of it.

    I tend to use fat knobbly tyres for 'English Farm Mud' actually.. like driving on sand.. you want to spread the weight over as much tyre as possible... bloke in the club runs inner tubes, with 8 psi in them.. and wins most comps if his beasty doesn't pop it's axles (common)

    Quote Originally Posted by The Quentos
    "My udder is growing. Quick pass me the parsely sauce." Said Oliver.

  11. #59
    Looser Konan555's Avatar
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    Quote Originally Posted by Tumble
    I tend to use fat knobbly tyres for 'English Farm Mud' actually.. like driving on sand.. you want to spread the weight over as much tyre as possible... bloke in the club runs inner tubes, with 8 psi in them.. and wins most comps if his beasty doesn't pop it's axles (common)
    Depends on yer mud

    Good old norfolk clay mud likes tyres that cut down to the firm layer under it.

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    Senior Member Tumble's Avatar
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    this is our mud :


    Quote Originally Posted by The Quentos
    "My udder is growing. Quick pass me the parsely sauce." Said Oliver.

  13. #61
    Looser Konan555's Avatar
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    Well yer bound to get stuck Bloody Defender! But it won't be the mud..... it'll be an overheat or a broken gearbox it a trashed axle.

    Raw nerve..... I got lumped with the defender from hell one year.

  14. #62
    Senior Member Tumble's Avatar
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    naa it was put in there on purpose - see the stake next to the passenger window? got a clipper on it.. like an orienteering course.. had to drive down into the hole to get it, then get pulled back out by your team mate, then he had to get the clipper too - that was a helluva fun day out

    Quote Originally Posted by The Quentos
    "My udder is growing. Quick pass me the parsely sauce." Said Oliver.

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