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Offline lambert

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maths
« on: December 15, 2011, 07:19:02 »
Hi clever peeps,

Whilst I was getting my tracking done yesterday I was reading a poster from michelin that was telling me how many miles of sideways a tyre feels per rotations per mile when the tracking is off. It did not however give the formula so I could do it for my tyres.

So can anyone tell me how to work it out.

Cheers.
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Offline dxmedia

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Re: maths
« Reply #1 on: December 15, 2011, 08:19:08 »
It was on the poster I was reading the tyre place yesterday ;)

If your aliment is out buy say 3mm and the tyre is a 29" - it rotates something like 950 times every mile (simple to work out accurately) and multiply 950 x 0.003 to get how many meters of scrub per mile.

It's a bull [!Expletive Deleted!] calculation though. It's presuming that the whole tyre is moving sideways which it isn't. If the car only traveled in a dead straight line then one side of the tyre would be effected by this, but you move the tyre around on the road which will effect this. It's a case of use shocking (ly bad) maths to scare people.
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Offline LandRoger

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Re: maths
« Reply #2 on: December 15, 2011, 16:35:01 »
There is an easy way over this useless information ,dont read makers blurb there is no better indication of wear than the human eye so when you see wear change the wheels around and if its the tyre edge thats worn then have the tracking done,simples!
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Offline tack43

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Re: maths
« Reply #3 on: December 15, 2011, 21:03:06 »
Is this like tyre manufacturers insisting we NEED winter tyres?
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Rich

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Offline lambert

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Re: maths
« Reply #4 on: December 16, 2011, 06:24:36 »
I think that is down to people mistaking grip for handling and then needing over wide tyres to feel in control of their car. What that means is that they then can't see how those same tyres don't work properly in winter and they need to be force sold the right tyres to keep the rest of us safe.
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Lambert Coverdale.

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Offline Range Rover Blues

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Re: maths
« Reply #5 on: December 19, 2011, 01:39:22 »
Tyres only generate sideways force when they are slipping anyway, so every corner you drive rund the tyres are not going "straight on", the lateral force is proportional to what's called the slip angle.
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Offline dxmedia

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Re: maths
« Reply #6 on: December 20, 2011, 11:52:32 »
Seems to also neglect to mention tow in / out as well.

OK permi 4x4's should be 0, but nothing else.
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Offline Range Rover Blues

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Re: maths
« Reply #7 on: December 27, 2011, 03:35:50 »
zero to 3 degrees negative on a LR.  I always used to get p***ed off when tyre fitters tried to set my old RWD Escort to toe out, becuase the wall chart said so, even when the wall chart said it was for a 1980s Escort, they just don't understand some of them.
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