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Apart from the headline, what makes you think that i3 was aquaplaning? I would have thought that with its skinny tyres it would have been safe.
 

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9 times the square of the tyre pressure: 2.5 bars = 36 psi = 9 x 6 = 54 mph. Not many cars travel in the outside lane at less than 54MPH - and there is only so much that narrow tyres can do! It looks like the driver might have been a passenger for a while. I bet it gave the guy behind quite a shock as well.
 

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9 times the square of the tyre pressure: 2.5 bars = 36 psi = 9 x 6 = 54 mph.
I have no knowledge here...but intuitively that looks like a random number generator...(even assuming square root ;))
What has tyre pressure got to do with aquaplaning that means contact patch area, size/shape/volume/direction of cuts, weight of car, and no doubt other stuff makes no impact on?
 

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Don't know about the maths but common sense says when the road is flooded, whatever tyres you have, slow down if you don't fancy aquaplaning.

A21 in Kent is another poorly drained road that has seen many a car swap ends in heavy rain.
 

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Well that i3 is the “S” version so has wider tyres so will aquaplane sooner than the standard i3 with narrower tyres, my experience in heavy rain and standing water has been the normal i3 is much less effected than others. In fact very stable in the rain.
 

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Total width of the tyre is pretty much irrelevant for aquaplaning resistance compared to the tread pattern design.

This is why aquaplaning resistance is one of the metrics measured when testing different tyres - of the same size against each other. Sure, if the tread pattern is identical a narrower tyre will do slighty better but not much, and the difference is smaller than staying with the same size tyre with a different tread block design more optimised for removing water.

Tyres with tall tread blocks with sipes and wide gaps between blocks tend to be best for aquaplaning reistance as they give the water a lot of room to displace within the tread of the tyre before aquaplaning can initiate.

So winter/all season tyres can do quite well here as they tend to have tall tread blocks with sipes and have a lot more water channels and less rubber than a summer tyre. Most summer tyres have large flat areas of tread with no sipes that can't displace large amounts of standing water.
 

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9 times the square of the tyre pressure: 2.5 bars = 36 psi = 9 x 6 = 54 mph. Not many cars travel in the outside lane at less than 54MPH - and there is only so much that narrow tyres can do! It looks like the driver might have been a passenger for a while. I bet it gave the guy behind quite a shock as well.
I don't know where those numbers come from, but surely, weight of the car, depth of water, as well as the design pattern of the tyres play a HUGE role. You can't seriously mean that 54mph is some sort of magic speed you can keep, regardless of the other data...
 

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Total width of the tyre is pretty much irrelevant for aquaplaning resistance compared to the tread pattern design.

This is why aquaplaning resistance is one of the metrics measured when testing different tyres - of the same size against each other. Sure, if the tread pattern is identical a narrower tyre will do slighty better but not much, and the difference is smaller than staying with the same size tyre with a different tread block design more optimised for removing water.

Tyres with tall tread blocks with sipes and wide gaps between blocks tend to be best for aquaplaning reistance as they give the water a lot of room to displace within the tread of the tyre before aquaplaning can initiate.

So winter/all season tyres can do quite well here as they tend to have tall tread blocks with sipes and have a lot more water channels and less rubber than a summer tyre. Most summer tyres have large flat areas of tread with no sipes that can't displace large amounts of standing water.
All that doesn’t change the fact that the i3 with narrow front tyres has better aquaplaning characteristics than many other vehicles I have driven/tested over the years.

And to be accurate the tread pattern on the front tyres of the i3/i3S are effectively the same being the same tread design and construction, so there should be a difference.
 

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I don't know where those numbers come from, but surely, weight of the car, depth of water, as well as the design pattern of the tyres play a HUGE role. You can't seriously mean that 54mph is some sort of magic speed you can keep, regardless of the other data...
54mph is a calculated/approximate speed based on the lower of the two tyre pressures for an i3. In truth, the calculated speed is slightly higher as the actual calculation is:

Vp = 10.35 Square Root of the Tyre Pressure in PSI

There is science underpinning the aquaplaning/hydroplaning formula.


The possibility of aquaplaning is instilled into all pilots from day one of their training. Weight alone will not stop a machine from aquaplaning. I have experienced it twice on very wet (debatably, flooded runways) with an aircraft landing weight well in excess of 100 Metric Tonnes. Modern runways are now grooved but not all airports and runways can be considered modern. It will not surprise you know that crews carry out some very detailed calculations before landing. In the case of a very wet runway, the maximum landing weight of the aircraft would be markedly reduced below that of the same aircraft on a dry runway.

It happens to small aircraft as well:

 

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I fail to see how a simple equation like Vp = 10.35*sqrt(pressure in psi) can give any meaningful insight into the aquaplaning characteristics of a car/tyre when it takes nothing about the tyre into account except the pressure. Where does the 10.35 come from ? I also notice this equation is lifted directly from the Wikipedia article and the section of the article says "This section does not site any sources". So I call BS on this dinky formula. It might as well say that red cars aquaplane more easily than blue ones. Tyre pressure is a minor factor relative to tread depth and pattern.
 

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I fail to see how a simple equation like Vp = 10.35*sqrt(pressure in psi) can give any meaningful insight into the aquaplaning characteristics of a car/tyre when it takes nothing about the tyre into account except the pressure. Where does the 10.35 come from ? I also notice this equation is lifted directly from the Wikipedia article and the section of the article says "This section does not site any sources". So I call BS on this dinky formula. It might as well say that red cars aquaplane more easily than blue ones. Tyre pressure is a minor factor relative to tread depth and pattern.
Fair enough: I will put my hand up to one basic school boy error. For 54 mph read Knots, so the speed for an i3 is just over 60mph.

Might I respectfully suggest that you search for Horne's Formula. I chose Wik as it a source that many people are familiar with. Here are other sources that you might not have seen before (there are many others with lots of scientific references):


The original research into aquaplaning tyres was carried out by NASA in the 1960s. I suggest that you look at page 5:


Of course, it is entirely up to you whether you think what I have posted is BS. All I am saying is that when I am driving on very wet roads, it is at the back of my mind that at high speeds on wet roads there is the possibility of aquaplaning. Sadly, from experience, many drivers on wet Motorways have a different opinion.
 

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Bottom line is if you don't want to aquaplane - (in any car) - reduce speed according to the conditions.

And if you do aquaplane that tells you that you are going too fast.
 

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54mph is a calculated/approximate speed based on the lower of the two tyre pressures for an i3. In truth, the calculated speed is slightly higher as the actual calculation is:

Vp = 10.35 Square Root of the Tyre Pressure in PSI

There is science underpinning the aquaplaning/hydroplaning formula.


The possibility of aquaplaning is instilled into all pilots from day one of their training. Weight alone will not stop a machine from aquaplaning. I have experienced it twice on very wet (debatably, flooded runways) with an aircraft landing weight well in excess of 100 Metric Tonnes. Modern runways are now grooved but not all airports and runways can be considered modern. It will not surprise you know that crews carry out some very detailed calculations before landing. In the case of a very wet runway, the maximum landing weight of the aircraft would be markedly reduced below that of the same aircraft on a dry runway.

It happens to small aircraft as well:

Perhaps quoting Wikipedia is not the best scientific evidence and is not the best answer to my question... :( Anyway, I guess that the calculation is still wrong, because as I said, it doesn't take all the parameters into account. Weight plays a role, just like the tire pattern. I know very well what aquaplaning is and what causes it, as well as the fact that weight alone is not protecting you from it, but ALL parameters must be used in a calculation, INCLUDING weight, if you want to come up with such precise figure. So, I strongly question your calculation, as it is far too generic. In fact, what you don't quote is that even the Wikipedia reference is warning you, saying that:

Wikipedia said:
However, the above equation only gives a very rough approximation. Resistance to aquaplaning is governed by several different factors, chiefly vehicle weight, tyre width and tread pattern, as all affect the surface pressure exerted on the road by the tyre over a given area of the contact patch - a narrow tyre with a lot of weight placed upon it and an aggressive tread pattern will resist aquaplaning at far higher speeds than a wide tyre on a light vehicle with minimal tread. Furthermore, the likelihood of aquaplaning drastically increases with water depth.
So be careful spreading that as absolute facts, because it isn't.

Regarding landing an aircraft ... it is totally irrelevant here and is not comparable. I have never landed an F16, but landed a few others, and also learned about how to perform emergency landing on water, where forcefully causing aquaplaning is to your benefit, since it increasing the chances of survival and may reduce damages. So you may say that I have some limited knowledge about the subject... :) Never the less, you can't compare what's happening when the main gear touches the surface of the wet runway, because it is a totally different situation compared to a car on the road hitting some water, the major problem being water braking the plane too fast for a proper flare so your nose gear will hit the runway too early and too fast, which may cause bouncing, or may cause a nose gear collapse (i.e. snap it off), the second problem is that you may not be able to stop if the plane started aquaplaning the runway may not be long enough for you, the third issue is the wind, a crosswind may blow you off the runway (remember that now you are acting like a boat with poor floating ability and control), especially if you are sliding on water, and I think the quoted pilot's biggest mistake was not to listen to the controller about the conditions. He shouldn't have landed. Period. Landing on wet runways is not rocket science, planes do that all the time, and even the article says that:

Military.com said:
"Contributing factors to the accident included: environmental conditions affecting vision, misperception of changing environment, and failure to follow procedures," .
"We land in rain all the time."
Meaning that visibility was too bad, the pilot did not pay attention to warning signs and lost contact with runway, landed using only instruments, had no visual reference before touching the surface, so he had too high speed. Simply put it, he should have aborted the landing in time, and should have followed procedures, landing elsewhere or whatever routines they have. The wet runway was NOT the cause of the accident, planes land on wet runways every day somewhere on this planet and they don't crash.
 

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Fair enough: I will put my hand up to one basic school boy error. For 54 mph read Knots, so the speed for an i3 is just over 60mph.
Applying common sense is better than applying that formula, even if it comes from NASA. It is also different if you hit the water at high speed and you have tires which don't rotate yet (landing plane), compared to tires which rotate already (car).

Even your very own reference says that:

"skybrary" said:
"Aquaplaning is also highly relevant to cars at speeds as low as 40 mph."
It does NOT mention knots, it says mph. Reducing speed is the only sensible think you can do when you drive a car. You can't reduce the speed of the landing plane because you will crash. Leave out the aviation issues, the problems are different.
 

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Bottom line is if you don't want to aquaplane - (in any car) - reduce speed according to the conditions.
And if you do aquaplane that tells you that you are going too fast.
Can't disagree with that!
Vp = 10.35 Square Root of the Tyre Pressure in PSI
I'm not sure that is correct - if you look at the derivation of the formula it is based on the weight /surface area expressed in psi. This may be similar to the tyre pressure in aircraft but not on cars, and certainly not EVs. In my case I'm running at 45 rather than the recommended 36 (which may be based on weight/surface area), but increasing tyre pressure for a given mass of car will make no difference to aquaplaning.
 

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Might I respectfully suggest that you search for Horne's Formula. I chose Wik as it a source that many people are familiar with. Here are other sources that you might not have seen before (there are many others with lots of scientific references):


The original research into aquaplaning tyres was carried out by NASA in the 1960s. I suggest that you look at page 5:


Of course, it is entirely up to you whether you think what I have posted is BS. All I am saying is that when I am driving on very wet roads, it is at the back of my mind that at high speeds on wet roads there is the possibility of aquaplaning. Sadly, from experience, many drivers on wet Motorways have a different opinion.
Driving faster increases aquaplaning risk, I have no argument with that. If it's wet, slow down.

What is BS is taking an over simplified formula that is used as a rule of thumb on aircraft tyres and only takes one input variable - tyre pressure, and extrapolating it to car tyres. Totally different scenario and totally different kind of tyre.

From the very article you just posted above:

V = 9 x √P

This formula is based upon the validation of hydrodynamic lift theory by experimental evidence. For many modern tires the constant maybe closer to 6 or 7 rather than 9.
In other words the fudge factor at the front depends on the type of tyre and isn't just some magic number. What a surprise, this is exactly what I already said...tyre design is the most important factor.

Another thing to keep firmly in mind is that car tyres are not balloons. It's a common fallacy to think that if you halve the tyre pressure in a car tyre that the contact patch area must automatically double or vica versa. Nope, doesn't happen. This is because most of the strength of the tyre in supporting the weight of the car comes from the relatively rigid tyre carcass not the air in the tyre. Pressurising the tyre serves mainly to convert compression loads into tension loads, and a reinforced rubber wall is of course weak under compression but strong under tension. But ultimately the majority of the load carrying ability of a car tyre comes from the tyre carcass under tension loads not the air inside. As a result tyre contact patch size changes much, much less with pressure than the balloon model proposes.

About the only thing useful from that formula above in relation to car tyres is that the faster you go the more risk of hydroplaning you have. Trying to calculate a specific speed from a tyre pressure though is non-nonsensical when the "fudge factor" at the beginning is specific to a class of air-plane tyres and not car tyres, and would have to be redetermined (empirically) for every different tyre.
 
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