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Home > Wheels & Tyres > No grip on ice - vehicle weight?
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DAC364



Member Since: 03 Mar 2014
Location: Norfolk
Posts: 119

United Kingdom 2014 Freelander 2 TD4 XS Manual Orkney Grey

taztastic wrote:
Sorry, it is interesting this and your input is valued, I think our last posts crossed, the databases crashed, can you clarify the 'going faster', to me it suggested simply entering the corner faster will give your more grip, I wouldn't think that was correct, however, a higher speed whilst sliding I can understand from the article as increasing friction.

I imagine that from the data and application of these curves, that much of the data gained is how manufacturers determine how the vehicle safety systems react?


The Stribeck curve indicates that for a given friction coefficient (grip) on a surface, as you increse speed (velocity) the amount of grip initially decreases, but then improves as speed increases. My initial 'the faster you go' comment greatly over simplifies that point - the article I attached explains the interaction between tyre and surface and what goes on.That's the theory.

In the real world however, it's much more complex.

Assuming your speed stays exactly the same as you traverse an icy bend (it doesn't stay exactly the same, throttle inputs and braking) other factors are also constantly changing: The friction coefficient (grip) may well be different microscopically on the surface (thats why braking distances are calculated on averages) - the radius of the bend may tighten (driver input from the steering wheel) - the gradient across the bend (camber) may change. Only gravity is a constant.

Now with all those variables going on, the key factor is at what point does what's going on between driver/car/roadsurface does velocity and centrifugal force overcome gravity and allow slip?

The answer is often what you feel through the seat of your pants or the steering wheel. The Audi A5 will probably have similar section tyres but of lower profile and a lower centre of mass, whereas the FL2 is altogether taller, with slower geared steering and generally more wobbly on its taller tyres.

The greatest variation of all however is the difference between drivers - the OP with greatest respect may have a less well tuned sense of 'seat pants' than the Audi driver and will feel unhappy about the road earlier because the dynamics of the FL2 don't encourage faster driving. Lewis Hamilton, however, may be able to chuck the FL2 into the corner faster than any Audi A5 driver. Physics ultimately have a limit where the forces involved overcome the available grip and you roll into a field, but what's much more difficult to predict is at which point a given driver in a given type of vehicle will realise they've reached the limit!

An 'accident' is "a rare random multi factor event in which one or more drivers fail to cope witjh their environment."

As we say in Norfolk, "slow you down, bor." Td4 XS manual, Orkney Grey, MY2014

Post #287140 14th Jan 2016 11:56 am
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taztastic



Member Since: 03 Feb 2011
Location: North West
Posts: 8652

England 

Thumbs Up Thank you

Post #287181 14th Jan 2016 4:45 pm
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stooby



Member Since: 08 Feb 2011
Location: South Lanarkshire
Posts: 320

United Kingdom 2010 Freelander 2 TD4_e XS Manual Rimini Red

I can confirm that it turns out that on icy roads I'm just a bit of a fanny.

I had several miles of snow covered road today which was much easier to deal with.

Post #287182 14th Jan 2016 5:06 pm
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DAC364



Member Since: 03 Mar 2014
Location: Norfolk
Posts: 119

United Kingdom 2014 Freelander 2 TD4 XS Manual Orkney Grey

Being 'a bit of a fanny' is a good policy. Remember, the Audi driver would be grateful when you catch him hup and use the FL2 to pull him out of the the hedge! Td4 XS manual, Orkney Grey, MY2014

Post #287183 14th Jan 2016 5:20 pm
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hinchy



Member Since: 08 Jan 2009
Location: Stockport
Posts: 777

England 2013 Freelander 2 SD4 HSE Lux Auto Aintree Green

I'm dreading the winter, still on summer continentals and I've had few problems with them at speed on a wet motorway. Sad MY13 HSE LUX Aintree Green
MY57 SE Stornoway Grey. Gone
Nissan X Trail
Discovery V8 LPG
Series II Land Rover

Post #287204 14th Jan 2016 9:25 pm
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taztastic



Member Since: 03 Feb 2011
Location: North West
Posts: 8652

England 

I had (have) Comtinentals on 19" wheels, treads on he limit and they aquaplane woefully, as would any tyre, in bad conditions, superb in the dry.
The car currently has Nokian winter tyres on, amazing difference and feels much better, they don't hold up well in warmer temperatures though, they feel 'squirmy'.
The 19" will be shod with Nokian drummer tyres, they get excellent wet ratings, ideal for our wet summers.
Getting the 18" wheels off an Evoque and swapping the tyres to winters was the best £500 I have spent in a long time, that said, on ice it matters not, your pretty much a passenger.

Post #287207 14th Jan 2016 9:31 pm
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hinchy



Member Since: 08 Jan 2009
Location: Stockport
Posts: 777

England 2013 Freelander 2 SD4 HSE Lux Auto Aintree Green

I'll be sticking with the same size tyre when due for a change, but no way would I go for this tyre again. MY13 HSE LUX Aintree Green
MY57 SE Stornoway Grey. Gone
Nissan X Trail
Discovery V8 LPG
Series II Land Rover

Post #287223 15th Jan 2016 12:11 am
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Lightwater



Member Since: 21 Aug 2014
Location: Sydney Northern Beaches
Posts: 4739

Ukraine 2013 Freelander 2 2.0T SE Auto Fuji White

A long time ago I had a company car. The lease was up & I was to get a spare manager's car who had left. Higher spec but same car but with most of the lease remaining. The tyres on the car were so appalling I ask our fleet manager if they still had my old car. They still had it.

An hour later, two jacks in operation, 8 wheels exchanged, completely exhausted, I the 4 wheels from my old car.

When I had the tyres replaced previously, I had paid an extra $60 out of my our pocket to get better tyres than what the company would pay for. What a world of difference between cheap tyres & a couple of notches up in quality! Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

Post #287229 15th Jan 2016 2:52 am
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