Nothing at all to do with the testosterone fuelled cerebellum controlling foot/hand/eye co-ordination & 'roid rage egos then?
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Was it indoor / underground / multi-story?
Cars lay rubber in carparks, if they are covered and not washed by the rain this increases the likelyhood screaching when cornering etc.
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Cars lay rubber in carparks if they are covered and not washed by the rain this increases the likelyhood screaching when cornering etc.
Its usually down the surface itself. Dry smooth slippy (but not sufficiently slippy) surface will usually be the cause. Very fine smooth surfaced or painted concrete is worse.
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< Ex RF, Ex TVM >
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The tarmac on the car park of our local Morrisons induces tyre squeal at very low speeds when turning. It is in the open and occurs all over the car park suggesting that it is a different mix or blend of tarmac from the usual.
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P.S: Why Alfa or is that a variety of the new categories?
sorted - PU
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Can also depend on tyre type and size.
Had a Fiesta once on 135s that squealed. As soon as I changed to 155s, albeit with a different pattern, the squealing stopped.
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Car park tarmac (bitmac) is usually a light duty spec to suit light vehicles and low speeds, they use different binders and smaller aggregate, which is cheaper. A main road has to be able to withstand heavier vehicles, but also the dynamic effect of vehicles moving at high speed multiplies the loading, so has to be a heavy duty construction.
Road surfacing uses larger aggregate with usually a more open-faced texture or rougher finish, therefore less surface area contact with tyres.
Perhaps the tarmac in question is quite old and has small surface aggregate which has been polished quite smooth; not slippery smooth but with surface irregularities worn away?
There is a multi-storey car park I used to use in Sheffield and tyres would squeal really easily in there. The surfacing was mastic asphalt, which has a very smooth surface finish.
Also I think tyres can sometimes squeal more readily when surfaces are warmer, ie. have had sun on them all day?
Had a Fiesta once on 135s that squealed. As soon as I changed to 155s, albeit with a different pattern, the squealing stopped.
I read an article years ago that said AFAIR that tyre squeal is caused by the tyre tread blocks "squirming", or oscillating in a circular pattern, when cornering forces are applied. With modern tyres having larger, stiffer tread blocks, they should squeal less readily than old tyre tread designs.
I bet NC will have a definitive answer?
;o)
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>>I bet NC will have a definitive answer?
I would never claim that!
One thing to bear in mind is that the steering of cars is fairly agricultural, and despite the nonsense that is written in basic text books about Ackermann steering geometry, as soon as you turn the steering, there's a tracking error - the tighter the corner, the larger the error. So, on tight corners, you always scrub.
Whether the scrub makes a squeal is a really difficult point - you're right to talk about the local oscillations of the rubber tread blocks. This is linked to a few other motor vehicle troublesome phenomena, namely brake squeal, wiper squeal, wiper judder, and clutch judder. The precise conditions required to promote or diminish the dynamic instability simply aren't well understood.
Among the possibilities which might promote tyre squeal (and brake squeal) is a friction pair that has a negative friction gradient as part of its characteristic - i.e. the friction decreases as rubbing speed increases - this can lead to negative damping, which allows vibrations to build, rather than helping them decay.
Number_Cruncher
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