Motorway aquaplaning - an avoidable accident?

[donkmeister]

david-j8694 said:

I was in my aquaplane spec 981 GTS on the M1 last week and the heavens opened and wouldn't relent. I slowed from the usual making progress speeds, to 60mph middle lane, then 50mph left lane, but it was no good. The rain was torrential, wipers were at full speed and barely clearing the windscreen, plus the standing water was increasing rapidly. I knew the greater risks of mid-engine + big tyres, so I crawled the remaining mile or so (at about 40mph, and being flashed by lorry drivers) to a service station and pulled over for half hour.

I felt like a bit of a wimp at the time, but I just didn't fancy being the guy who binned his Porsche for all the passers by.

Still does amaze me the speed people are happy to carry in those conditions, though

The way I've squared it with my conscience in similar situations is that normally they're the ones holding me up 364 days of the year for no reason, so why shouldn't I hold them up on 1 day in 365 (TBH more like 1 day every 5 years!) in the name of safety?

[rallycross]

I’m always amazed when you hit really extreme rain on the motorway and there is always a few morons who don’t slow down, eg you passed them a couple of miles back now everyone has slowed to say 50 - and they car on at 80+ or whatever seemingly oblivious to the risk of hitting deep standing water ( especially in Lane 3 where you can get puddles growing out from the central reservation in extreme rain).
Why not just slow down for a few mins then speed up again ? The reason is they are too stupid to know the risks.

[ATM]

I believe my 2 aquaplaning incidents - both of which wrote off a Boxster - so one in 2005 and one in 2018 - happened where water was travelling across the motorway, like a little stream you can imagine. Both were on slight dips so between a downhill section and then an uphill section and also a slight curve or bend. I don't know if the water was flowing down these surfaced sections to the gully between or if it was draining off the verge or unsurfaced area to the side across the carriageway. I would like to think that these are avoidable with better draining or road design but maybe they are not. And before everyone starts chastising me for driving too fast yes yes yes I was going too fast, I admit that, but that doesn't mean we shouldn't have better roads or road surface designs. Surely if there are no perfectly flat areas on a motorway then water should not stand there. And if we can prevent it flowing onto the carriageway or along the carriageway then there would be none, right?

I believe the newest section of the A5 near Tamworth used some fancy new material for the resurfacing which contained lots of glass which allows it to wick water away from the surface. I cant seem to find any web links about this now.

[DonkeyApple]

Quite a bit of work has gone into creating porous surfaces but it's a problem given freeze thaw plus air pressure erosion caused by air compression by tyres. The end result is that those surfaces don't last as long.

The general policy is that as aquaplaning risk can be very heavily curtailed just simply driving to the conditions that it isn't a brilliant way to spend to tax payer funds to cater for those that either make the personal choice to overtly not drive to the conditions or the even smaller number who get genuinely caught out.

[C.A.R.]

I'd like to 'wade' in with an opinion on the original argument that skinnier tyres are better...

I drive a hybrid company car daily (it's horrible) which has eco tyres on @ 195 section, so "skinny" by todays' standards, especially compared to a sports car.

If you hit standing water in that thing you'll still aquaplane like buggery. Aquaplaning is surely just a point at which the tyre can't disperse enough of the water beneath it quickly enough, so it sails above it? Skinny eco tyres do not help mitigate that danger.

Of course, most people recognise when the wipers are going batsh*t mental and you can't see very well, it's probably best to slow down. Unfortunately this still leaves a lot of very stupid people who will try to go at the speed limit despite the poor conditions.

[Mincey]

I apologise profusely if this has been mentioned already, but this thread reminded me of a story I heard many years ago and was resurrected here last year:

https://www.thedrive.com/news/39529/you-could-buy-...

[samoht]

C.A.R. said:

I'd like to 'wade' in with an opinion on the original argument that skinnier tyres are better...

I drive a hybrid company car daily (it's horrible) which has eco tyres on @ 195 section, so "skinny" by todays' standards, especially compared to a sports car.

If you hit standing water in that thing you'll still aquaplane like buggery. Aquaplaning is surely just a point at which the tyre can't disperse enough of the water beneath it quickly enough, so it sails above it? Skinny eco tyres do not help mitigate that danger.

A wider tyre has to disperse more water per metre travelled, so all things being equal it'll start aquaplaning at a lower speed. So narrower tyres will resist aquaplaning better, all things being equal.

What you're probably encountering is that the eco tyres are designed to minimise rolling resistance, so probably with fewer lateral grooves. This means the better economy is achieved at the cost of aquaplaning resistance. If you had those eco tyres in a wider size, it would be even worse.

Between two tyres with the same tread pattern of different widths, the narrower one resists aquaplaning better.

You can see the aquaplaning section in this test, they had identical Goodyear Eagle tyres in 225, 255 and 285 widths and tested them on the same car. In the aquaplaning section, the 255 scored 5% slower than the 225, with the fat 285s being 13% worse.

[Lexington59]

Standing water is the issue, even then most normal road tyres should clear it unless it is particularly deep. With reasonable tread in my view you’d have to be going quite fast (>70?) to have problems.

[Eyersey1234]

One of our managers at work wrote his Passat off on the A63 when he aquaplaned and hit the central crash barrier at 70mph

[ATM]

Lexington59 said:

With reasonable tread in my view you’d have to be going quite fast (>70?) to have problems.

NO
NO
NO

Different cars with different weight distribution

Mid engine much more susceptible than standard front engine

Lighter sports cars with fatter 'performance' more susceptible - not because performance but because generally these sports cars have really fat tyres - see comment above about wider tyres being worse - and they are lighter than the average car so its a double whammy.

So when you put all that together a standard boring saloon car with average quality skinny tyres with average wear will be much better at dealing with standing water than a lighter sports car with big fat tyres especially if it is mid engined.

My big BMW wears skinny 225 winter tyres. I know people say winter is not necessarily better but I believe that skinny winters gives me the best of both worlds. So I have ice and snow grip plus aquaplaning resistance.

[Dave Hedgehog]

ATM said:

So when you put all that together a standard boring saloon car with average quality skinny tyres with average wear will be much better at dealing with standing water than a lighter sports car with big fat tyres especially if it is mid engined.

and will be even worse if accelerating as even more of the weight will shift to the back

i generally light / moderate brake as i approach a standing puddle / deeper water if travelling at some speed, not so much to knock speed off (although 10-15mph reduction will help) but to put some more weight on the front tyres, if its a bend and safe to do so I keep straight for the water hazard as turning reduces grip even more

[RDMcG]

I aquaplaned a 997 RS with PS Cups many years ago in Germany on an autobahn - was not doing any heroic speeds either ( car had not stability control or nannies). I managed to avoid the median but as I slowed down a VW GTI came by me backwards ,luckily missing me. I had some very hairy moments with that car on Cup tires and eventually changed them for something a bit more suitable for wet conditions,

[Artsy]

I've aquaplaned once when I was a lot younger and in very heavy rain on a motorway.

Felt the car go light just like it would on ice with no grip.

Thankfully didn't attempt to steer or to brake and when car slowed down slightly it got grip again.

Continued the trip at 20kph less than previously travelling and had no further issues.

Learnt a lesson thankfully without having had the accident...

[Lexington59]

ATM said:

Lexington59 said:

With reasonable tread in my view you’d have to be going quite fast (>70?) to have problems.

NO
NO
NO

Different cars with different weight distribution

Mid engine much more susceptible than standard front engine

Lighter sports cars with fatter 'performance' more susceptible - not because performance but because generally these sports cars have really fat tyres - see comment above about wider tyres being worse - and they are lighter than the average car so its a double whammy.

So when you put all that together a standard boring saloon car with average quality skinny tyres with average wear will be much better at dealing with standing water than a lighter sports car with big fat tyres especially if it is mid engined.

My big BMW wears skinny 225 winter tyres. I know people say winter is not necessarily better but I believe that skinny winters gives me the best of both worlds. So I have ice and snow grip plus aquaplaning resistance.

That is an excuse, I drive a Cayman and have done so for many years, I know all about mid engine weight distribution and fat tyres but have never spun
any of them into the central reservation. Most tyres even the dreaded p-zeroes will still clear through the water no problem unless very deep or too fast, or insufficient tread depth.

Fact remains most drivers are unlikely to have an issue unless conditions are really bad with regard to standing water and higher speeds are involved (or poor tread...) Slowing down and driving to the conditions will keep most out of trouble.

Tanking two Boxsters is very poor form in my view, some may say bad luck, but I think you make your own luck by driving to the conditions.

Edited by Lexington59 on Wednesday 12th January 17:04

[phil squares]

Had a quick look at the previous postings and couldn't find anything about the calculation of the speed at which dynamic hydroplaning occurs. It is a function of tire pressure. A quick method is 9 times the square root of the tire pressure. The square root of 36 psi is 6 times 9 is 54 mph at which dynamic hydroplaning will happen. The exact number is 8.73 x square root of the tire pressure.

It's not rocket science to figure it out and the speeds on the M roads are right in the range where hydroplaning will occur. Throw in less than perfect tires and you have a recipe for loss of control.

[ATM]

Lexington59 said:

ATM said:

Lexington59 said:

With reasonable tread in my view you’d have to be going quite fast (>70?) to have problems.

NO
NO
NO

Different cars with different weight distribution

Mid engine much more susceptible than standard front engine

Lighter sports cars with fatter 'performance' more susceptible - not because performance but because generally these sports cars have really fat tyres - see comment above about wider tyres being worse - and they are lighter than the average car so its a double whammy.

So when you put all that together a standard boring saloon car with average quality skinny tyres with average wear will be much better at dealing with standing water than a lighter sports car with big fat tyres especially if it is mid engined.

My big BMW wears skinny 225 winter tyres. I know people say winter is not necessarily better but I believe that skinny winters gives me the best of both worlds. So I have ice and snow grip plus aquaplaning resistance.

That is an excuse, I drive a Cayman and have done so for many years, I know all about mid engine weight distribution and fat tyres but have never spun
any of them into the central reservation. Most tyres even the dreaded p-zeroes will still clear through the water no problem unless very deep or too fast, or insufficient tread depth.

Fact remains most drivers are unlikely to have an issue unless conditions are really bad with regard to standing water and higher speeds are involved (or poor tread...) Slowing down and driving to the conditions will keep most out of trouble.

Tanking two Boxsters is very poor form in my view, some may say bad luck, but I think you make your own luck by driving to the conditions.

Yawn

Tanking two Boxsters gives me the right to tell you that your statement is wrong.

With reasonable tread you don't have to be going quite fast (>70?) to have problems.

So perhaps please accept that I am trying to help people not experience what I have. If people go round believing your rubbish and then crash that's not really helpful is it.

[andygo]

Skinnier tyres increase the weight on the tyre per sq inch. Have you seen how ridiculous WRC cars look in the snow? I realise the tyres are studded, but nevertheless, if they thought fatter tyres were better, they would have them fitted.

The obvious conclusion is that fat tyres behave like skis. Standing water is made out of the same stuff as snow.

Edited by andygo on Wednesday 12th January 20:33

[Lexington59]

ATM said:

Lexington59 said:

ATM said:

Lexington59 said:

With reasonable tread in my view you’d have to be going quite fast (>70?) to have problems.

NO
NO
NO

Different cars with different weight distribution

Mid engine much more susceptible than standard front engine

Lighter sports cars with fatter 'performance' more susceptible - not because performance but because generally these sports cars have really fat tyres - see comment above about wider tyres being worse - and they are lighter than the average car so its a double whammy.

So when you put all that together a standard boring saloon car with average quality skinny tyres with average wear will be much better at dealing with standing water than a lighter sports car with big fat tyres especially if it is mid engined.

My big BMW wears skinny 225 winter tyres. I know people say winter is not necessarily better but I believe that skinny winters gives me the best of both worlds. So I have ice and snow grip plus aquaplaning resistance.

That is an excuse, I drive a Cayman and have done so for many years, I know all about mid engine weight distribution and fat tyres but have never spun
any of them into the central reservation. Most tyres even the dreaded p-zeroes will still clear through the water no problem unless very deep or too fast, or insufficient tread depth.

Fact remains most drivers are unlikely to have an issue unless conditions are really bad with regard to standing water and higher speeds are involved (or poor tread...) Slowing down and driving to the conditions will keep most out of trouble.

Tanking two Boxsters is very poor form in my view, some may say bad luck, but I think you make your own luck by driving to the conditions.

Yawn

Tanking two Boxsters gives me the right to tell you that your statement is wrong.

With reasonable tread you don't have to be going quite fast (>70?) to have problems.

So perhaps please accept that I am trying to help people not experience what I have. If people go round believing your rubbish and then crash that's not really helpful is it.

“Believing my rubbish?”

What part of my suggestion to drive to the conditions is so contentious for you, apart from perhaps you obviously not doing so?

Personally I found a day spent at the PEC on things like the ice hill provided an excellent grounding in the basics of car control, e.g. should anybody lose traction and want to practice how to recover. A bit of additional tuition always a good investment, I do agree with you that mid engined cars can be challenging in certain situations.

The risk of aquaplaning may be increased by several factors but excessive speed for the conditions is usually the main culprit.

Edited by Lexington59 on Wednesday 12th January 21:08

[DonkeyApple]

Lexington59 said:

ATM said:

Lexington59 said:

ATM said:

Lexington59 said:

With reasonable tread in my view you’d have to be going quite fast (>70?) to have problems.

NO
NO
NO

Different cars with different weight distribution

Mid engine much more susceptible than standard front engine

Lighter sports cars with fatter 'performance' more susceptible - not because performance but because generally these sports cars have really fat tyres - see comment above about wider tyres being worse - and they are lighter than the average car so its a double whammy.

So when you put all that together a standard boring saloon car with average quality skinny tyres with average wear will be much better at dealing with standing water than a lighter sports car with big fat tyres especially if it is mid engined.

My big BMW wears skinny 225 winter tyres. I know people say winter is not necessarily better but I believe that skinny winters gives me the best of both worlds. So I have ice and snow grip plus aquaplaning resistance.

That is an excuse, I drive a Cayman and have done so for many years, I know all about mid engine weight distribution and fat tyres but have never spun
any of them into the central reservation. Most tyres even the dreaded p-zeroes will still clear through the water no problem unless very deep or too fast, or insufficient tread depth.

Fact remains most drivers are unlikely to have an issue unless conditions are really bad with regard to standing water and higher speeds are involved (or poor tread...) Slowing down and driving to the conditions will keep most out of trouble.

Tanking two Boxsters is very poor form in my view, some may say bad luck, but I think you make your own luck by driving to the conditions.

Yawn

Tanking two Boxsters gives me the right to tell you that your statement is wrong.

With reasonable tread you don't have to be going quite fast (>70?) to have problems.

So perhaps please accept that I am trying to help people not experience what I have. If people go round believing your rubbish and then crash that's not really helpful is it.

“Believing my rubbish?”

What part of my suggestion to drive to the conditions is so contentious for you, apart from perhaps you obviously not doing so?

Personally I found a day spent at the PEC on things like the ice hill provided an excellent grounding in the basics of car control, e.g. should anybody lose traction and want to practice how to recover. A bit of additional tuition always a good investment, I do agree with you that mid engined cars can be challenging in certain situations.

The risk of aquaplaning may be increased by several factors but excessive speed for the conditions is usually the main culprit.

Edited by Lexington59 on Wednesday 12th January 21:08

'With reasonable tread in my view you’d have to be going quite fast (>70?) to have problems. '

The other poster is correct. There are more variables at play than simply tread.

What you really mean is that in your experience so far, you've not found the tyres, with good tread, that you've run to date to be a risk of aquaplaning on the roads that you e experienced, in the conditions, to date, that you e experienced.

In reality, as the other poster highlights, there is more at play. Type of tyre plays a part, road surface, road topography, depth or water, length of water pool, tyre pressures, weight distribution of car, layout of car even throttle attitude.

I'll bin tyres at 4mm. Always have. Not worth the hassle of keeping them beyond that. The monetary gains of using the last couple of mils just doesn't stack up with the elevated risks. Depth of tread is an important factor but it's not a defining character. I've had cars where it simply doesn't matter what the tread depth is between 7 to 3, the width of the tyres and absence of weight play stronger roles. I remember an '88 Carerra where a full tank of fuel made the biggest difference!!

Best car for grip in the wet was a 2CV. The bicycle tyres gave comedy grip on roundabouts in standing water. Morris Minors we're similarly amusing. With those it was the minuscule contact patch rather than tread.

The reality is that there is a reason why Porsche drivers often bin it on standing water and why TVR owners often bin it joining the motorway and its down to not appreciating the physics rather than purely being a function of tread.

[Lexington59]

DonkeyApple said:

Lexington59 said:

ATM said:

Lexington59 said:

ATM said:

Lexington59 said:

With reasonable tread in my view you’d have to be going quite fast (>70?) to have problems.

NO
NO
NO

Different cars with different weight distribution

Mid engine much more susceptible than standard front engine

Lighter sports cars with fatter 'performance' more susceptible - not because performance but because generally these sports cars have really fat tyres - see comment above about wider tyres being worse - and they are lighter than the average car so its a double whammy.

So when you put all that together a standard boring saloon car with average quality skinny tyres with average wear will be much better at dealing with standing water than a lighter sports car with big fat tyres especially if it is mid engined.

My big BMW wears skinny 225 winter tyres. I know people say winter is not necessarily better but I believe that skinny winters gives me the best of both worlds. So I have ice and snow grip plus aquaplaning resistance.

That is an excuse, I drive a Cayman and have done so for many years, I know all about mid engine weight distribution and fat tyres but have never spun
any of them into the central reservation. Most tyres even the dreaded p-zeroes will still clear through the water no problem unless very deep or too fast, or insufficient tread depth.

Fact remains most drivers are unlikely to have an issue unless conditions are really bad with regard to standing water and higher speeds are involved (or poor tread...) Slowing down and driving to the conditions will keep most out of trouble.

Tanking two Boxsters is very poor form in my view, some may say bad luck, but I think you make your own luck by driving to the conditions.

Yawn

Tanking two Boxsters gives me the right to tell you that your statement is wrong.

With reasonable tread you don't have to be going quite fast (>70?) to have problems.

So perhaps please accept that I am trying to help people not experience what I have. If people go round believing your rubbish and then crash that's not really helpful is it.

“Believing my rubbish?”

What part of my suggestion to drive to the conditions is so contentious for you, apart from perhaps you obviously not doing so?

Personally I found a day spent at the PEC on things like the ice hill provided an excellent grounding in the basics of car control, e.g. should anybody lose traction and want to practice how to recover. A bit of additional tuition always a good investment, I do agree with you that mid engined cars can be challenging in certain situations.

The risk of aquaplaning may be increased by several factors but excessive speed for the conditions is usually the main culprit.

Edited by Lexington59 on Wednesday 12th January 21:08

'With reasonable tread in my view you’d have to be going quite fast (>70?) to have problems. '

The other poster is correct. There are more variables at play than simply tread.

What you really mean is that in your experience so far, you've not found the tyres, with good tread, that you've run to date to be a risk of aquaplaning on the roads that you e experienced, in the conditions, to date, that you e experienced.

In reality, as the other poster highlights, there is more at play. Type of tyre plays a part, road surface, road topography, depth or water, length of water pool, tyre pressures, weight distribution of car, layout of car even throttle attitude.

I'll bin tyres at 4mm. Always have. Not worth the hassle of keeping them beyond that. The monetary gains of using the last couple of mils just doesn't stack up with the elevated risks. Depth of tread is an important factor but it's not a defining character. I've had cars where it simply doesn't matter what the tread depth is between 7 to 3, the width of the tyres and absence of weight play stronger roles. I remember an '88 Carerra where a full tank of fuel made the biggest difference!!

Best car for grip in the wet was a 2CV. The bicycle tyres gave comedy grip on roundabouts in standing water. Morris Minors we're similarly amusing. With those it was the minuscule contact patch rather than tread.

The reality is that there is a reason why Porsche drivers often bin it on standing water and why TVR owners often bin it joining the motorway and its down to not appreciating the physics rather than purely being a function of tread.

You are siding with the Boxster killer now DA? I don’t disagree there are multiple factors at play, but excess speed, (and therefore not driving to the conditions) is the most likely culprit.

What I would say though is that it is quite possible to drive mid engined cars safely on the motorway in the heaviest rain. They are not the death traps some appear to think.