Whatever the aftermath with the hire company, I'm just pleased you were both able to walk away from it alive!
R40
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I'll wager it's got hardly anything to do with the tyres,
I'll wager that del boy is 100% correct Re: aquaplaning.
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I had a hire car in Spain some years ago that was only around 9 months old, but had 3 nearly bald tyres and 1 with a big lump on the sidewall.
As I picked the car up in a dark airport carpark I didn't notice until the following morning - but as soon as I did I took it back and played merry hell with them. I was amazed how bad the tyres were for a 9 month old car with only around 9,000KMs on the clock!
I ended up with an upgrade (MBenz) and a full tank of fuel for free, but at least, like the OP no one was seiously hurt.
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I'll wager it's got hardly anything to do with the tyres I'll wager that del boy is 100% correct Re: aquaplaning.
So what do you think those groovy things actually do? Just look pretty?
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1. If the tyres were bald it's lucky OP didn't involve the police. 3 points per corner, I believe?
2. "The back left end just started sliding left." Presumably it was the entire back end that started sliding left.
3. A car travelling in a straight line CANNOT just start to slide left. Newton proved this. You must have done something.
4. A 4x4 with pointless fat tyres. Fat tyres are more inclined to aquaplane.
5. You hit a deeper bit of water and aquaplaned. Nothing to do with the car at all.
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I agree with mapmaker and bellboy - sounds like aquaplaning to me.
Tyres also look borderline legal from the photos. 1.6mm across the central 3/4 and tread pattern still visible across the whole width. Hard to say from the photos, looks like its just on the wear indicator. If they are illegal then you should be looking at 3 points a tyre, lucky you didn't kill anyone.
Why do you think you were lucky ot be in a 4x4? A normal saloon may not have crashed in the first place, 4x4s are not known for stability at speed. It that situation I would much rather be in say a mondeo than a 4x4.
The wear on the tyres does look uneven for a rear tyre. Possible suspension wear? Or maybe they have been on the front at some point?
At the end of the day, good to hear no one was hurt. Cars can be replaced, people cant. Good message to anyone hiring a car.
Edited by moonshine {P} on 10/07/2009 at 16:22
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>>3. A car travelling in a straight line CANNOT just start to slide left. Newton proved this. You must have done something.
Once the rear wheels are no longer gripping, the car can lose yaw stability extremely quickly. Even the camber of the road is enough to set it off. Once the ability of the rear wheels to provide lateral grip is lost, this is an unstable situation - this conflicts with most people's common sense based views of the stability of cars, but, it's actually true.
Had it just been the front wheels that had lost grip, besides from the rev counter shooting up, the driver would barely have noticed - losing front wheel grip doesn't lead to instability.
The amount of tread has a direct beaing upon the onset of aquaplaning, and so, the OPs view on the unacceptability of the tread on the vital rear tyres is the important point.
Edited by Number_Cruncher on 10/07/2009 at 16:25
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Once the rear wheels are no longer gripping the car can lose yaw stability extremely quickly. Even the camber of the road is enough to set it off. Once the ability of the rear wheels to provide lateral grip is lost this is an unstable situation - this conflicts with most people's common sense based views of the stability of cars but it's actually true.
I think one of the best things I've learnt from this site over the years is to keep the best tyres on the rear.
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>>> 3. A car travelling in a straight line CANNOT just start to slide left. Newton proved this. You must have done something. <<<
I've only experienced aquaplaning once (thank Goodness !) but that is *exactly* what happend comrade - the rear of the car just started to slide out as if I was on ice ... and it was nothing to do with my tyres.
Edited by Dynamic Dave on 11/07/2009 at 04:54
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Thanks NC. Beautifully put. The "something" in that case is aquaplaning.
A normal car, travelling normally on a road, does not just lose the back left corner that disembodies itself from the rest of the car...
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The OP said the car was doing 60-70mph in the rain.
If you went any slower, you'd probably get rammed from behind.
So how does one avoid aquaplaning?
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Obviously aquaplaning is some kind of unique driving event which quite honestly I don't understand as I have driven at 60, 70, 80 MPH in the rain many, many times and it has only happend to me once in 38 years of driving and is a very frightening experience indeed!
I might add that there was much surface water at the time - which I didn't see until it was too late - so perhaps that is the answer?
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So how does one avoid aquaplaning?
By ensuring an adequate tread depth. It's the job of the tread channels to disperse the 'wedge' of water which accumulates at the leading edge of the tyre contact patch. It's that which causes 'aquaplaning' - and the speed at which it occurs is directly related to the tread depth.
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>>So how does one avoid aquaplaning?
Avoid cars with silly wide tyres.
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Most people aquaplane when they run into a large deep puddle at speed. These are caused by poor road drainage and sudden big downpours. If a drain has become blocked one can come on these puddles in unexpected places when going too fast to avoid them. This has happened to me on various scales in various cars quite a few times over the years.
It can be frightening, as much for the sudden roar of deep water and the tug on the wheel as anything else. It is absolutely essential to pass through the deep water with all the wheels in a dead straight line and without trying to change speed in any way, especially by braking. If you are on a motorway curve when you come upon the puddle, straighten up before you hit it and just hope for the best where the other lanes are concerned. You have to hold the wheel very firmly because the water will give a tug one way or the other. When the wheels are back on land, but not before, you can think about acting fast with the steering or giving a touch on the brakes.
That is the only way to keep it on the island. It's always worked for me so far.
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I've only experienced aquaplaning once (thank Goodness !) but that is *exactly* what happend comrade - the rear of the car just started to slide out as if I was on ice ... and it was nothing to do with my tyres <<
Aquaplaning has EVERYTHING to do with your tyres. It's just that sometimes there is so much water to be displaced by the tyres at a given speed that even the best/newest tyres can't do it.
It is much, much more likely to happen on balder tyres, or those with a poor water dispersing pattern.
There have been dozens of articles on aquaplaning in pretty much all of the motoring journals showing this through experiment.
As N_C alludes to and another poster has mentioned - Best tyres on the rear axle.
This particular point really shouldn't be discussed any more, it is not disputed by any tyre manufacturer or vehicle maker.
Edited by Dynamic Dave on 11/07/2009 at 04:54
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>>> Aquaplaning has EVERYTHING to do with your tyres. It's just that sometimes there is so much water to be displaced by the tyres at a given speed that even the best/newest tyres can't do it. <<<
Yep! I'll go along with that comrade - nuf sed.
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Aquaplaning has EVERYTHING to do with your tyres.
Surely there are 3 factors involved
Your speed
The amount of water on the road
The ability of your tyres to disperse the water.
The first of these is the only factor under your control when driving. You will never aquaplane if driving at an appropriate speed for the conditions.
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Aquaplaning occurs, with a totally smooth tyre, at 9 times the square root of the tyre pressure. So for your average car this is 9 times 6 = 54 mph. Should be higher than this with some tread but it is a figure to bear in mind when driving on a smooth wet road.
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So for your average car this is 9 times 6 = 54 mph
That sure makes you think when most motorway traffic barely drops below 80 in heavy rain.
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Time for a blanket speed limit of 54mph in rain or on wet roads.
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Aquaplaning occurs with a totally smooth tyre at 9 times the square root of the tyre pressure.
Fantastic!
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To those who kindly replied to my post of 1706 (time - not date!) this figure is for a slick tyre and the formula is/was used for aircraft, whose tyres do not have tread as such - just circumferential grooves. Any tread should raise the figure a bit. Also, once aquaplaning has started it can continue to well below the speed at which it commenced, even if you have enough grip/control to steer and slow down which by definition you haven't!
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aquaplaning is basically caused by the inability if the tyre tread to drain the water, thus making the vehicle float on a wedge of water.
the less depth of tread the less depth of water required to aquaplane.
a tyre with 8mm of tread can aquaplane if the depth of water id enough...
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What was it you used to fly AS ?
and did you ever experience aquaplaning - must be quite interesting, being responsible for a couple of million quids worth of Her Maj's hardware without being in control of it ;-)
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I have flown Gnats, Canberras, Phantoms and Jaguars. The deal with many of these was that they had airbrakes and lift dumping devices to help them slow down, plus the latter two had arrestor hooks and all except the Canberra had braking parachutes, which also helped to keep them straight if there wasn't a cross-wind. Also many of them had very seriously high pressure tyres so the square root of the pressure was higher too. I never flew the Lightning but it had very narrow tyres, to fit them into the wing when they retracted, and they were well over 200 psi. Too much thread drift! I shall have a beer or 3 and go to bed!
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I'd appreciate less of the "smart comments" mapmaker.
We are talking about what could have been a serious, if not fatal accident potentially involving other cars too.
My message is one of warning! I had NO CLUE what condition the tyres were in being a passenger! There is without doubt the tyres were the cause of this crash.
I am fully aware of the repercussions with illegal tyres. Firstly as i said i wasn't the driver, wasn't my responibility to check the tyres and the contract stated the car is provided in road worthy condition.
As it turns out, both their inspection unit and an independent deemed the tyres LEGAL. But on the limit.
As i said, the tyres are the FULL cause of this crash. They simply did not have enough tread on them to displace the water, so yes the back end can just give way going straight. If you want to get picky there might have been a slight long right hand bend in the road but as my family could be minus a dad i haven't really got the patience for critical nit picking.
The tyres were practically bald and irrisponsibly kept on a hire car vehicle and it was my bad luck of getting into that car as a passenger.
To HonestJohn,
The tyres were bald on the outer (shown in pic) and inner edges were bald too. This was on both rear tyres.
Also initially we thought there was a blow out on the left rear tyre as there was a big hole in the sidewall. As i wasn't the driver i couldn't tell you how the steering felt but its possible the tyre was ripped as part of the crash.
Here is a pic showing the wear on inner and out edge plus you can see the rip in the tyre (bottom left) : yfrog.com/0791770107j
Edited by OldSkoOL on 10/07/2009 at 20:57
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As I said the tyres are the FULL cause of this crash. >>
I am glad you all survived with no more than a serious fright.
I do not agree with the above statement. The incident was caused by the driver losing control of the vehicle, the tyres may have contributed to this but did not cause it. As you have said the tyres were legal. I change my tyres at 3mm.
Edited by Old Navy on 10/07/2009 at 21:09
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Scary event, glad all survived uninjured.
Not saying this is what happened but.....
About 25 years or maybe more ago I sort of knew a chap who was notoriously dishonest. A bit of a loser actually. Anyway, he had an Austin Princess wedge thing. It needed some tyres. Coincidentally his employer provided him with a hire car for a couple of days for some reason. Again, quite by chance it was a Princess.
Silly fellow switched the worn tyres/wheels from his car for the newish ones from the hire car. He got caught, was prosecuted and lost his job into the bargain.
Maybe, just maybe, this is what happened to your car......
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Quote:...."""A car travelling in a straight line CANNOT just start to slide left. Newton proved this. You must have done something."""
Oh yes it can!
On a wet road with bald tyres, if the car is aquaplaning a bit and then suddenly the front wheels on one side encounter some resistance - like a drier patch or a bump, it's could cause a loss of control.
Edited by Sofa Spud on 10/07/2009 at 21:42
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I meant front wheel, in the singular, of course!
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Crosswinds on motorways are significant too, remember there's almost no friction on an aquaplaning wheel.
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The latest pic shows wear on both shoulders and possibly reasonable-ish tread in the middle 75-80% of the tyre - I'd be suspicious of underinflation but as the tyre is holed it's impossible to know for sure!
Also to say the tyres were 100% the cause of the crash is not possible - as I mentioned, the slick surface of fresh rain on a dusty, smooth road can cause "viscous aquaplaning" (see the wiki link) which is more resistant to tread/tyre quality than the usual dynamic AP.
Edited by Lygonos on 10/07/2009 at 22:22
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Perhaps the pictures are deceptive, but those tyres look fine to me. My car passed 2 MOT's with tyres with worn shoulders - got an advisory on the first MOT but wasn't even mentioned on the second.
How heavy was the rain? I'm dubious about the speed - no-one does 60-70 on the M6 toll. I set cruise at 75 and I don't think I've ever overtaken anyone on it. If the rain was so heavy that is slowed everyone down then that would be the cause of the accident.
I don't think we've been told the make and model of vehicle? If it was one with part time 4WD then perhaps one or more of the wheels aquaplaning caused some change in the proportion of F/R drive split, which could maybe cause the vehicle to become unstable? I don't know, just guessing.
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The other thing we don't know is what the driver did when the car started to wriggle. A lot can depend on that especially with a primitive or defective 4wd...
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Glad all lived to tell the tale.
Were the front tyres appreciably better tread wise than the rears OS?
Also did you notice makes/type even size differences 'tween front/rear.
I am puzzled by the awful wear pattern, usually this type of wear is at the front.
Most unusual to aquaplane from the rear, as the front tyres on most vehicles clear a path for the rears to plough through, just as well as the rear of the vehicle is usually lighter.
I've experienced that lightness that just comes before ''lift off'', a most disagreeable feeling but haven't ended up badly...yet touch wood.
And i wouldn't dream of allowing my own tyres to get so worn as in the photo, which are purchased primarily for their wet grip, wear rate comes a long way down the list.
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We drove into an area that had what looked like a fair amount of rain and it was raining at the time enough for constant wipers but not fast wipe.
I know from my perspective the car certainly did no wiggling, i've had very minor aquaplaning before and this was totally different. The car just literally let go.
1 minute it was straight the next the back end just let go left ways. It happened so quick but from what i remember we held a leftwards slide for a fair distance before the driver couldn't hold it and then continued to do 360's x3 as mentioned.
I was too busy pulling all my limbs inwards and cocooning my head with m hands to notice anything else.
We were at the same speed as all the other cars, we weren't overtaking anyone, just following. Which is why, judging by the circumstances (i.e. no wiggling - just a complete let go) is why i think the tyres are totally to blame. As i said, it just went. Same speed as everyone else.
And what i'm saying is tyres are extremely important and it is defiantly not worth skimping when the tyres starts going bald on the sidewalls. Always check your tyres.
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Yes tyres at the front had sufficient grip, a much bigger improvement over the rears, easily legal with no side tread wear.
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much bigger improvement over the rears easily legal with no side tread wear.
Which makes me think either some crafty so and so did a swap or they put new ones on the front and popped the edge worn fronts onto the rear to get a few more miles out of them, either way i wouldn't have allowed a vehicle so shod out on the road.
(i've had the displeasure of driving trucks that have had similar swap rounds in the past, like driving a bowl of spaghetti..ie 4 wheel steering)
penny wise etc....
If you think about it the huge difference between centre and shoulder tread coupled with a fairly hard pressure tyre may well have given a very small 'footprint' below those dreadful tyres.
A good reminder to us all OS, this would have had a different end result on a really busy motorway as you know only too well.
Will take this further with the rental company?
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@OP: The very nasty scenario you describe happened to me once in heavy rain. In my case the tyres were virtually new but the car still swapped ends. I was fortunate in that I didn't hit anything. The car was a Toyota MR2.
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In my case the tyres were virtually new but the car still swapped ends.
>>
So what did you blame the incident on?
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So what did you blame the incident on?
At the time, unnecessarily wide tyres as fitted as standard on the MR2. Obviously, being perfect, I couldn't have been at fault.
With a bit of hindsight and swallowing of pride, maybe 1 or 2 mph too fast for the conditions.
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@OP: The very nasty scenario you describe happened to me once in heavy rain. In my case the tyres were virtually new but the car still swapped ends. I was fortunate in that I didn't hit anything. The car was a Toyota MR2.
As I said above aquaplaning can happen with new tyres... its the ratio between tread depth, water depth, as well as tyre pressure, road speed, and probably a few other things.......
Ive had it happen twice, once in a Carlton,tyres about 4 mm... country lane 45ish flooded road - clean undies needed!
2nd time Mondeo, 65mph, M25, 5mm on tyres, car seemed happy, till I had to stand on the brakes (2 pickups had spun into centre reservation... ABS cut in - then the wheels locked up! still doing 50+
car stayed straight, I let the brakes off, and Cadence braked to a stop... less than a car length from the car in front.
The ABS got confused because the car was riding on the water - I had a better 'feel' coz I knew the car was still moving!
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What is the purpose of having grooves on tyres? Is it just for preventing aquaplaning by dispersing water or to provide better traction via more friction?
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Grooves in tyres are to clear water to maintain contact with the road.
So without decent tread you can't maintain friction in the wet.
Edited by OldSkoOL on 11/07/2009 at 12:44
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smooth tyres (slicks) give better grip in the dry, plus 'move' less giving more grip in corners.
the grooves allow the parts of the tyre in contact with the road to 'walk' a little....
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Why did the driver hire a 4 X 4 for a motorway journey anyway? Because they are "safe"
If you jack up a car wheel and place a piece of printing paper underneath the tyre before lowering and applying weight you will see that the tread blocks actually grip the paper, the paper needs to be resting on a smooth surface, not gritted tarmac.
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He actually wanted a decent saloon for 2 days for m-way and true to form ended up with a SUV 4x4
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Why did the driver hire a 4 X 4 for a motorway journey anyway? Because they are "safe"
If you're going to have a crash then, for the occupants, they're *much* safer than ordinary cars. So if exactly the same thing had happened in a car, the OP and his colleague may well have been (at least) injured.
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The OP was lucky not to have rolled in the type of crash he was in.
In such a case, the occupants of a 4x4 are *much* more likely to die.
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The OP was lucky not to have rolled in the type of crash he was in. In such a case the occupants of a 4x4 are *much* more likely to die.
I would imagine the wet and slippery conditions helped prevent the car from rolling. A bit of grip at the right moment could have easily tipped it over.
My arguement would be that a 'normal' car would have been more stable than a 4x4 and might not have crashed at all. Surely its safer not to crash at all?
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SFAIK the best grip comes from the largest possible area of 'rubber' on the road - hence the use by F1 and Drag cars etc of vast wide slicks. Grooves are to help clear water and debris off the road and to enable the surface of the tyre to touch the road and grip/drive/steer/brake, if they are the front ones.
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>>SFAIK the best grip comes from the largest possible area of 'rubber' on the road
The area of contact is governed by the tyre pressure, NOT, the tyre size and type.
Fitting wide tyres doesn't increase the area - but, it does change the shape of that contact area.
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As i said the tyres are the FULL cause of this crash.
No. The FULL cause of the crash, is the driver driving at an excessive speed for the conditions - The conditions being wet, standing water, and tyres without much tread (but still legal) - and subsequently losing control of the vehicle.
The tyres are an aggravating FACTOR, but they are not a cause.
Glad nobody hurt.
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