Motorway aquaplaning - an avoidable accident?
Discussion
This discussion arose from ATM kindly sharing his rather nice 996 CSR and his car history on Reader's Cars.
As part of that, he mentioned he'd suffered a couple of cases of aquaplaning on motorways
Mine is on semi slicks and I haven’t had a problem (so far)Generally front engined cars less prone due to weight over the front wheels. These should cut through the standing water and leave a channel for the rears to use.
Light weight
Fat Tyres
Speed
Tread depth
Tire design for getting through water
The above are your enemies when it comes to standing water. So generally I would say all Porsche sports cars are more risky than your average city car due to their lowish weight, fat tyres and less weight over the front.
I have never aquaplaned in any other cars. Little video showing what can happen. The car just goes light, rotates, then grips and spits you off in whatever direction it is pointing.
I dont want to say I a a brilliant driver. But you would need to be seriously good to catch this and save it.
The belief that anyone who encounters aquaplaning must have had bald tyres or been driving badly is not only unfair on the OP, but it's also a dangerous misconception.
Firstly it has nothing to do with the speed differential between the front and rear wheels, and as I and Samoht have said, you don’t need to have the throttled pinned heavily to experience aquaplaning, because aquaplaning occurs when the depth of surface water on the road is such that the tyre driving through it, is incapable of clearing sufficient water to enable the tyre to remain in contact with the road.
When this happens the tyre will effectively be raised up by the bow wave formed in front of it, and onto the plane” ie it will be riding on the surface of the standing water.
At this point you’ll experience the horrible feeling the OP felt, that being the steering going extremely light (as if driving on ice) the car feeling unstable, and if you were to lift off/brake, you’d find the brakes ineffective, and the car would most likely start to rotate, by the time most drivers have established what’s going on, it’s too late and the car will more than likely have sufficient momentum that the ensuing spin will be all but uncatchable in the space available.
As Samoht and I have stated, this can happen at as little as 45mph, or on the motorway/autobahn at much higher speeds.
All too often the driver won’t even see the heavy surface water at all, or until it’s too late.
Whilst I agree one should drive to the weather conditions, all too often aquaplaning can occur because of poorly drained/designed roads or blocked drains and gulleys.
As part of that, he mentioned he'd suffered a couple of cases of aquaplaning on motorways
ATM said:
In the long and distant past my first Porsche was a 986 Boxster gen 2 facelift.... In the first 2 or 3 weeks of buying it I aquaplaned on the motorway and destroyed the car.
ATM said:
My next Porsche was a 2012 981 Boxster S with PDK gearbox.... I had another Aquaplaning incident.
Yes I destroyed another Boxster by Aquaplaning but this time I knew the car was properly aligned and I had good matching tyres.
This lead to a discussion of aquaplaning, which I've moved here to allow further discussion without derailing the OP's threadYes I destroyed another Boxster by Aquaplaning but this time I knew the car was properly aligned and I had good matching tyres.
ATM said:
Bright Halo said:
TheJimi said:
As for the aquaplaning - are Boxsters particularly susceptible? (and I'm not being facetious either - I genuinely don't know!)
I don’t think so.Mine is on semi slicks and I haven’t had a problem (so far)
Light weight
Fat Tyres
Speed
Tread depth
Tire design for getting through water
The above are your enemies when it comes to standing water. So generally I would say all Porsche sports cars are more risky than your average city car due to their lowish weight, fat tyres and less weight over the front.
I have never aquaplaned in any other cars. Little video showing what can happen. The car just goes light, rotates, then grips and spits you off in whatever direction it is pointing.
I dont want to say I a a brilliant driver. But you would need to be seriously good to catch this and save it.
DuncanM said:
Sorry OP, but writing off two cars, in the exact same way, and not acknowledging that your driving needs to change in the conditions that both incidents occurred?
Skinnier tyres won't help you, driving to the conditions will.
Skinnier tyres won't help you, driving to the conditions will.
ATM said:
You're absolutely right. I do blame myself. But even driving to the conditions with skinny tyres will be safer than fat tyres. Surely we can agree to that?
DuncanM said:
I guess so to a point, but for me, driving fast in those conditions, in a sports car = recipe for disaster.
Best just to pootle around and get home safely when it's that wet - both incidents must have been scary?
I hate motorways for fast driving, dangerous places at the best of times + unmarked cars etc.
Best just to pootle around and get home safely when it's that wet - both incidents must have been scary?
I hate motorways for fast driving, dangerous places at the best of times + unmarked cars etc.
ATM said:
I wasn't speeding. I can say this for definite.
But even at 70 [not sure if I was actually doing 70 because of poor visibility] you can still spin off in a light sports car with fat tyres.
But even at 70 [not sure if I was actually doing 70 because of poor visibility] you can still spin off in a light sports car with fat tyres.
DuncanM said:
Both crashes would be due to acceleration - asking the rear wheels to go faster than the front. You will hopefully know this though.
You own and have owned some serious metal, and they need a delicate right foot in the sopping wet.
You own and have owned some serious metal, and they need a delicate right foot in the sopping wet.
Slippydiff said:
You don’t need to be accelerating to aquaplane ... Sure if you’ve got the accelerator nailed it’ll exacerbate the problem, but you can aquaplane at 80mph on the lightest of throttles (or indeed no throttle at all) on a motorway with 8mm of surface water, when you’ve got 7mm of tyre tread. That’s not to suggest that lack of tread depth is always a major factor, as if there’s sufficient surface water and the tyre is incapable of moving it despite having plenty of tread, the car will still aquaplane.
samoht said:
Evo Tyre test said:
In a straight line we measured the maximum speed each tyre attained in 7mm of water before it overspeeded by 15 per cent.
7mm isn't a very deep puddle, and 45mph isn't very fast - pootling speed, I'd say. This was the best-performing available brand-new premium tyre, on a nose-heavy Audi.- Dunlop Sport Maxx ... 45.5 mph
The belief that anyone who encounters aquaplaning must have had bald tyres or been driving badly is not only unfair on the OP, but it's also a dangerous misconception.
DuncanM said:
This is dangerous rubbish, anyone blaming these crashes on anything other than not driving to the conditions is enabling poor driving, and will learn absolutely nothing.
I'm astounded tbh, it'd be nice if someone else would like to chime in on this? I didn't want to derail the thread, but this is utterly nuts?
I'm astounded tbh, it'd be nice if someone else would like to chime in on this? I didn't want to derail the thread, but this is utterly nuts?
Stegel said:
I’ve experienced aquaplaning in a months old, <5k mile (stated re tyre wear) E class estate - as far from the OP’s car as you can get. 75mph on cruise control on M74. Brilliant sunshine after heavy rain. The front end stepped out dramatically, but fortunately the car’s systems, and it finding dry tarmac, sorted it all out before I really knew what was happening, even so I was in a different lane by then.
Not a driving God, but I’d certainly say my driving was appropriate to the conditions. It’s in the “sh#t happens” category in my view, and bumbling along at 40mph in the same conditions would be far more dangerous.
Not a driving God, but I’d certainly say my driving was appropriate to the conditions. It’s in the “sh#t happens” category in my view, and bumbling along at 40mph in the same conditions would be far more dangerous.
Bright Halo said:
I believe you can theoretically experience aquaplaning above 45mph.
However there are many factors. Speed, tyre pressure, tyre size, depth of tread, depth of standing water etc.
There is a complicated equation that calculates aquaplaning speed but even this is flawed.
The real risk factors where possibility of losing traction grows exponentially are the combination of Tyre tread depth below 3mm, speed above 65mph and standing water greater than 10mm.
Vehicle weight not so much a factor although does play its part.
Lowering tyre pressures is a bad idea when surface water is present as the tyre can be more concave in the centre and prevent water from being pushed away.
I think a mod should move the aquaplaning posts away to form a separate discussion so we don’t clutter up this thread.
However there are many factors. Speed, tyre pressure, tyre size, depth of tread, depth of standing water etc.
There is a complicated equation that calculates aquaplaning speed but even this is flawed.
The real risk factors where possibility of losing traction grows exponentially are the combination of Tyre tread depth below 3mm, speed above 65mph and standing water greater than 10mm.
Vehicle weight not so much a factor although does play its part.
Lowering tyre pressures is a bad idea when surface water is present as the tyre can be more concave in the centre and prevent water from being pushed away.
I think a mod should move the aquaplaning posts away to form a separate discussion so we don’t clutter up this thread.
Slippydiff said:
DuncanM said:
Both crashes would be due to acceleration - asking the rear wheels to go faster than the front. You will hopefully know this though.
You own and have owned some serious metal, and they need a delicate right foot in the sopping wet.
It would appear your understanding of what aquaplaning is, and what causes it, maybe somewhat lacking.You own and have owned some serious metal, and they need a delicate right foot in the sopping wet.
Firstly it has nothing to do with the speed differential between the front and rear wheels, and as I and Samoht have said, you don’t need to have the throttled pinned heavily to experience aquaplaning, because aquaplaning occurs when the depth of surface water on the road is such that the tyre driving through it, is incapable of clearing sufficient water to enable the tyre to remain in contact with the road.
When this happens the tyre will effectively be raised up by the bow wave formed in front of it, and onto the plane” ie it will be riding on the surface of the standing water.
At this point you’ll experience the horrible feeling the OP felt, that being the steering going extremely light (as if driving on ice) the car feeling unstable, and if you were to lift off/brake, you’d find the brakes ineffective, and the car would most likely start to rotate, by the time most drivers have established what’s going on, it’s too late and the car will more than likely have sufficient momentum that the ensuing spin will be all but uncatchable in the space available.
As Samoht and I have stated, this can happen at as little as 45mph, or on the motorway/autobahn at much higher speeds.
All too often the driver won’t even see the heavy surface water at all, or until it’s too late.
Whilst I agree one should drive to the weather conditions, all too often aquaplaning can occur because of poorly drained/designed roads or blocked drains and gulleys.
DuncanM said:
Oh how strange, I honestly thought people would chime in on my side 
I still believe acceleration would make the crashes much more likely, I didn't state that acceleration causes aquaplaning in my post, but was trying to nudge the OP towards looking at his driving.
Cars are inanimate objects.
Single vehicle accidents are (typically) the fault of the driver.
Having two exact same crashes should make you question your driving, and not hunt for skinnier tyres as a solution.
Blaming xyz instead of driving inappropriately for the conditions is a concerning mindset, I'd hate for the OP, or anyone else to be hurt due to not changing said mindset.
So.. in the case of driving down a sopping wet motorway, assuming tyres with a reasonably deep tread, how much would you slow down? And would you be confident that would be slow enough to avoid the risk of aquaplaning?I still believe acceleration would make the crashes much more likely, I didn't state that acceleration causes aquaplaning in my post, but was trying to nudge the OP towards looking at his driving.
Cars are inanimate objects.
Single vehicle accidents are (typically) the fault of the driver.
Having two exact same crashes should make you question your driving, and not hunt for skinnier tyres as a solution.
Blaming xyz instead of driving inappropriately for the conditions is a concerning mindset, I'd hate for the OP, or anyone else to be hurt due to not changing said mindset.
DuncanM said:
Oh how strange, I honestly thought people would chime in on my side
I still believe acceleration would make the crashes much more likely, I didn't state that acceleration causes aquaplaning in my post, but was trying to nudge the OP towards looking at his driving.
Cars are inanimate objects.
Single vehicle accidents are (typically) the fault of the driver.
Having two exact same crashes should make you question your driving, and not hunt for skinnier tyres as a solution.
Blaming xyz instead of driving inappropriately for the conditions is a concerning mindset, I'd hate for the OP, or anyone else to be hurt due to not changing said mindset.
As a general rule I agree with your last statement. Any time one has an accident, or narrowly avoids one, one should always be asking 'what could I have done differently to avoid that situation?'.I still believe acceleration would make the crashes much more likely, I didn't state that acceleration causes aquaplaning in my post, but was trying to nudge the OP towards looking at his driving.
Cars are inanimate objects.
Single vehicle accidents are (typically) the fault of the driver.
Having two exact same crashes should make you question your driving, and not hunt for skinnier tyres as a solution.
Blaming xyz instead of driving inappropriately for the conditions is a concerning mindset, I'd hate for the OP, or anyone else to be hurt due to not changing said mindset.
I do however believe that some cases of aquaplaning are an exception to this general rule.
The reason is that in scientific tests like the evo tyre test I posted above, using brand new premium tyres, they were aquaplaning at 45mph in 7mm of water.
So I suppose the question is, given a situation where you're on a motorway in or after heavy rain, and you're aware of a risk of aquaplaning, how do you judge how many mm of water are on the road, and how do you judge how slowly you need to go with your vehicle and tyres to avoid the risk of losing touch with the tarmac?
How long did that post take to create OP 
Anyway - yes - totally avoidable. As the poster above I drove at 15mph only the M5 once (this September) when a freakish rain storm occurred - I doubt I was alone in praying we were all going to do the right thing without someone barrelling through and then taking us all out like skittles. But thankfully all was good and 10 mins later we were back to a normal speed.
Anyway - yes - totally avoidable. As the poster above I drove at 15mph only the M5 once (this September) when a freakish rain storm occurred - I doubt I was alone in praying we were all going to do the right thing without someone barrelling through and then taking us all out like skittles. But thankfully all was good and 10 mins later we were back to a normal speed.
POIDH said:
I would drive to the conditions and my vehicle.
There is no definitive.
I've done 10mph on motorway before, on ice.
HtH
Exactly this. There is no definitive.
I've done 10mph on motorway before, on ice.
HtH
I’ve heard before “I was doing the legal limit for the road, so no, not speeding..” which is a foolish statement of the highest order.
There are obviously scenarios where 150mph is safer than 15mph.
The spinner of plates said:
POIDH said:
I would drive to the conditions and my vehicle.
There is no definitive.
I've done 10mph on motorway before, on ice.
HtH
Exactly this. There is no definitive.
I've done 10mph on motorway before, on ice.
HtH
I’ve heard before “I was doing the legal limit for the road, so no, not speeding..” which is a foolish statement of the highest order.
There are obviously scenarios where 150mph is safer than 15mph.
Anybody who defends driving at the posted limit because that's what they're entitled to do is an utter Bellend.
There's a lot of it [url=https://www.pistonheads.com/gassing/topic.asp?h=0&f=23&t=1706855&i=0]about.[url]
Looking at the Evo tyre test, standing water on an A road will yank the steering around quite noticeably whether you're about to overwhelm your tyre's tread or not. If you ignore the car telling you to "stop doing this silly thing," you'll find yourself picking bits of scenery out of your car sooner or later although luck can save or damn you quite easily.
Looking at the Evo tyre test, standing water on an A road will yank the steering around quite noticeably whether you're about to overwhelm your tyre's tread or not. If you ignore the car telling you to "stop doing this silly thing," you'll find yourself picking bits of scenery out of your car sooner or later although luck can save or damn you quite easily.
jjones said:
Often see cars way on the verge on the A46 as it exists Coventry to the south after aquaplaning. Heavy rain always leaves large patches of standing water in the outside lane. If you don't know (or don't care) it is a recipe for disaster.
I used to drive that section every day. You could tell the regular users of the road because if it was raining they'd stay well away from the outside lane until Kenilworth. It's the worst section I've ever seen for standing water, and it's been like that for at least 20 years. It baffles me why the drainage hasn't been fixed in that time.
I've had one incident of aquaplaning on the motorway (although more through luck than judgement I didn't crash). I was doing about 40mph in the left-hand lane when it happened to me (despite there being other vehicles doing 60+ in the other lanes); it was entirely avoidable and entirely my fault... I was driving too fast for the conditions.
Bill said:
kambites said:
I was driving too fast for the conditions.
I can't see how there's any argument otherwise. The speed that becomes "too fast" will vary with the car so a lighter car with wider, "sporty" tyres will aquaplane sooner, but it still boils down to driver error.Another one for drive to conditions,summer 2019 was a crazy hailstorm coming down from Aberdeen on a Saturday afternoon,all traffic just pulled over n stopped,felt sorry for the bikers,hail stones were hammering down road was covered wasn't a safe speed to drive
Have aquaplaned on motorway few occasions,driven through it,but that's up on the emptier parts of M6 in Cumbria
Have aquaplaned on motorway few occasions,driven through it,but that's up on the emptier parts of M6 in Cumbria
legless said:
jjones said:
Often see cars way on the verge on the A46 as it exists Coventry to the south after aquaplaning. Heavy rain always leaves large patches of standing water in the outside lane. If you don't know (or don't care) it is a recipe for disaster.
I used to drive that section every day. You could tell the regular users of the road because if it was raining they'd stay well away from the outside lane until Kenilworth. It's the worst section I've ever seen for standing water, and it's been like that for at least 20 years. It baffles me why the drainage hasn't been fixed in that time.
Bill said:
kambites said:
I was driving too fast for the conditions.
I can't see how there's any argument otherwise. The speed that becomes "too fast" will vary with the car so a lighter car with wider, "sporty" tyres will aquaplane sooner, but it still boils down to driver error.Motorways here in the UK are generally very well engineered and maintained, which means that the conditions are usually very predictable and safe. However, I have seen situations where the drainage has failed so the road goes from no standing water to significant standing water. In some situations that flooding isn't visible until you see someone ahead hit it, or until you are about to hit it yourself.
So, the driver can be travelling at a safe speed for the prevailing conditions, only for a change in conditions to become apparent that means a much lower speed would be safer but at the precise time where braking becomes unsafe. The catch-all is to assume the drainage has always failed when it rains, and that there is always black ice when it's cold, so do 30-40mph whenever it rains and 10mph when it's cold. But that would be silly.
donkmeister said:
Mostly, but I think there is a caveat to this: conditions can change more quickly than your speed.
Indeed. Which is why your speed should reflect the worst that conditions are realistically going to change to in the time in which you can react. Aquaplaning is the classic example of this; if you're not pretty damned sure the road isn't flooded in front of you, you have to assume that it is. Obviously there are situations where this isn't realistic (black ice, oil spills, etc.) but aquaplaning really isn't one of them.
Edited by kambites on Saturday 4th December 11:21
All I'll say is I can see at least 6 other vehicles in that photo, none of them embedded in the scenery. Yet the driver of the Porsche has written off two in similar circumstances.
Either this is a scandal of Mk1 TT proportions, or there's some other common factor. And I'm not entirely sure which.
Either this is a scandal of Mk1 TT proportions, or there's some other common factor. And I'm not entirely sure which.
Three instances from me:
(1) Driving along the M25 near J6 at 55mph, a speed where my tyres where occasionally being overwhelmed by the rain/water. Got overtaken by a Sprinter travelling at 85-90mph. About 2 junctions on I encountered him stuffed into a barrier. He was dazed, and I helped him out of the van to a safe place behind the barrier. He then blamed the Sprinter for losing grip.
(2) Driving home from Scotland in the new Shed in Storm Katie and the fastest I went was 55mph - most of the time I was travelling at 40mph.
(3) Gym Dad arrives in a hire car one evening. Explains that he was in Lane 3 and the car spun. Obviously not his fault as there was "too much water on the road."
In (2) I'm in full control of my right foot. What the hell do (1) & (3) think they are doing? What happens when it snows and they can't do 90mph in Lane 3?
For most drivers, you get that horrible sound in the wheel arches when the tread is overwhelmed and you back off. There's part of me that thinks that drivers in premium cars, with premium tyres think they should perform "premiumly" in all situations. And lease car bashing alert: Most lease companies won't change tyres until they hit the 1.6mm limit. I routinely bin mine at 2-3mm. Could it be non-maintenance leases on Wan King ditchfinders making up a significant %?
(1) Driving along the M25 near J6 at 55mph, a speed where my tyres where occasionally being overwhelmed by the rain/water. Got overtaken by a Sprinter travelling at 85-90mph. About 2 junctions on I encountered him stuffed into a barrier. He was dazed, and I helped him out of the van to a safe place behind the barrier. He then blamed the Sprinter for losing grip.
(2) Driving home from Scotland in the new Shed in Storm Katie and the fastest I went was 55mph - most of the time I was travelling at 40mph.
(3) Gym Dad arrives in a hire car one evening. Explains that he was in Lane 3 and the car spun. Obviously not his fault as there was "too much water on the road."
In (2) I'm in full control of my right foot. What the hell do (1) & (3) think they are doing? What happens when it snows and they can't do 90mph in Lane 3?
For most drivers, you get that horrible sound in the wheel arches when the tread is overwhelmed and you back off. There's part of me that thinks that drivers in premium cars, with premium tyres think they should perform "premiumly" in all situations. And lease car bashing alert: Most lease companies won't change tyres until they hit the 1.6mm limit. I routinely bin mine at 2-3mm. Could it be non-maintenance leases on Wan King ditchfinders making up a significant %?
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