FBinNY 

Folks debating here would do well to heed Mark Twain's very sound advice about these situations.

This is a perfect example of a straw man argument. The OP posits a claim that nobody made, namely that it's impossible to hydroplane on a bicycle, while omitting the legitimately assumed "as a practical matter".

He supports his argument but using motorcycle data points and extrapolating them down to bikes. Then uses videos of bicycles slipping in the rain, and claims them as proof without considering the more obvious reduction of friction.

Even after using his own math with actual tire widths and pressures to show that, bicycles cannot hydroplane within the speed range bicycles actually attain, he simply won't let go.

For my part, it ended yesterday when the OP twice used the phrase "all known laws of physics" which I always take as a cue.

Let's spare ourselves the time and grief and not argue a straw man theoretical position as if it were meaningful in the real world.

L134 

But, some of us may find the topic interesting. If others don't, that's fine. I, for one, have had an experience that I believe defies the generally accepted wisdom and therefore actually read the NASA report to find out why I was wrong in believing that hydroplaning was, in practical terms, possible. Although the science and math were beyond me, the written word was not. I think a careful, skeptical reading of the study leaves plenty of shades of gray to leave open the possibility for the practical implications of partial hydroplaning on a bike. I simply contend the study itself is not nearly as definitive, nor does it even claim to be, as most who cite it characterize it as. There is value in skepticism else we might all still believe the world is flat and the center of the universe. Weren't those that disputed those theories persecuted by the all knowing? Do people really think that 1,000 years from now people won't be laughing at some of the things we accept as the truth? If the topic doesn't interest you, by all means let it go. I usually try to stay out of these things but I am honestly quite puzzled by how this has gone.

SkinGriz

No.

I’ve hydroplaned across short bodies of water on a YZ250 with no “boat” under my motorcycle. Just start out in 5th topped out at around 70mph and losing speed until you get to the other side.

Where I’m from crop dusters will mess around and hydroplane on canals. Around 120mph they say the water under the tires just feels like concrete.

Water likes to stick to water. It’s one of those “life on earth is possible because of…” qualities.

SkinGriz

That said.

I think a skinny tired road bike would need to go insanely fast to hydroplane.

Possible? Yes. Probable? No.

This comes up frequently with my kids. They ask if something is possible. I answer almost anything is possible, but the specific thing they’re asking is highly improbable.

mpetry912 

in real world wet weather riding there are other factors contributing to loss of traction.

namely any presence of dirt, oil, or other contaminants on the pavement surface. Or brand new tires that still have mold release coating on them. Or the paint used for traffic markings - treacherous in wet weather

the point is correctly made that a bike tire's contact patch has a much greater loading in psi than does a car tire. But the other calculations cited are made under very narrow test conditions and not applicable to real world conditions.

but what do I know ?

/markp

shelbyfv

but but but Motorcycles! Lakes!! NASA!!!

jon c. 

So you don't understand the science but you've figured out how to parse the words to arrive at your desired conclusion?

The point of such exercise eludes me.

Mr. 66

But we haven't talked about air friction yet and the varying melting points from that friction. That information is as important to bicycle maintenance as well. I know my bike will melt if I go fast enough.

Omg this is a worthless read, entertaining though worthless.

L134 

The point being I READ the study to find out what it really said rather than accept what somebody who hadn't read it said it said just because somebody else told them NASA said something they didn't actually say. Why did I take the trouble to read it when somebody else already told me what it said? Because my own actual experience made me suspicious that the study didn't actually reach the conclusions stated or that the calculations etc could reasonably be extrapolated out from aircraft landing gear to bicycle tires. Bicycles are not once mentioned in the study. I think it very unlikely the authors would extrapolate their own data and research of aircraft tires to all circumstances without expanding the scope of their research. Presumably they are scientists after all. Therefore, because my own experience makes me question the appropriateness of such extrapolation, I parse the words to better understand the purpose of the study in question and its applicability to my experience.

From the study:
"The hazards of tire hydroplaning to vehicle operation are greatly increased stopping distances, and potential loss of ground directional stability. In order to minimize these hazards, it is most important for the vehicle operator to be aware of the existence of tire hydroplaning and to understand how and when it may occur. Such knowledge being assumed, certain procedures then suggest themselves to minimize hazards of tire hydroplaning where conditions are such that it may be encountered."

I experienced loss of ground directional stability. I am aware of hydroplaning and certain procedures do suggest themselves to minimize the hazards where conditions are such that I have encountered them. I think I am safer in having that awareness rather than dismissing it out of hand based upon formulas applied to landing gear. That is the point of such exercise.

cyccommute 

Okay. You forced me to read through the whole NASA bulletin…thanks a lot

I’m going to quote extensively from NASA bulletin and, for that I am sorry, but it can’t be avoided. You are correct that there is a “partial hydroplaning” as the water layer builds under the tires. Most people experience aren’t really paying attention and only notice the full hydroplaning part when their car goes spinning off the road. It is a continuum but looking at the figures, the partial part doesn’t occur until a substantial proportion speed needed for full hydroplaning has been reached. He also has this to say about speed and inflation

Bicycles typically operate at even higher pressure making full (or even partial) hydroplaning nearly impossible. He also says

Bicycle tires also have a more circular cross section as well as stiffer sidewalls. This study was also done before the era of radial tires which would further soften the sidewalls and make the effect even greater.

The mistake that you and others are making is that you assume hydroplaning where it isn’t present and neglect lubrication where that is predominate. Horne and Dreher address that situation as well (emphasis added)

In other words, what we experience when bicycle tires slip is not hydroplaning but lubrication. They are similar but not the same. Both are due to boundary layers of fluid but lubrication occurs below the point where the tire is lifted off the pavement by a bow wave that slides under the tire. It was pointed out in the other thread that if you are hydroplaning and the underlying surface changes, there is no change in the hydroplaning. Going from pavement to grass (or sand or pebbles or even glass, etc) would have no impact on the traction of the tire. If, on the other hand, the surface is lubricated, changing the surface will have a large impact on the traction. For example, if you were sliding on pavement under lubrication and ran off into gravel, the traction would change. It won’t for hydroplaning.

I will add that the bulletin does point out that smooth tires have more of a problem on wet pavement than ribbed tires. I read something a while back that said that while pavement is smooth, it isn’t consistent. Having a small amount of tread will help break up the boundary layer that causes lubrication. It has nothing to do with preventing hydroplaning and the direction of tread on a smooth tire for smooth pavement doesn’t matter. As to that point the authors say

Adding texture to the tire will also break up this thin-film lubrication. Further they conclude

To extrapolate a bit, thin film lubrication is a much more important phenomena to bicyclist than hydroplaning is. If control is lost on a bicycle in wet conditions, it’s because the surface is slippery. It’s not because there is a build up of a bow wave that is lifting the bicycle off the ground. The light weight of the bicycle/rider (compared to cars and airplanes), the high pressure of our tires, and the very small contact patch give much more weight to lubrication rather than hydroplaning.

squirtdad

this study is from 1963, tire technology has changed hugely for cars and bikes since then, from design to tread compounds

While I am sure a lot of the basics apply, this is far from the holy grail that the OP suggests it is, talk about confirmation bias

Trakhak

Thanks, cyccommute, for doing the work most of us were too lazy to undertake. If I know my fellow Bike Forums habitues as well as I think I do, the formerly earnest "but my bike did hydroplane!" claimants will gracefully acquiesce.

DiabloScott

Exactly -- lubrication is not hydroplaning, even if some of the same principles are involved.

oldukbkr 

This has been one of the most entertaining threads I've seen on here. Mostly pointless as several pointed out most of us are unlikely to experience this. But the back and forth, witty repartee, and mighty indignation well worth the price of admission. Thanks to all who contributed.

mpetry912 

Yeah ! Exactly ! What about Hunter Biden ? Clinton ? 911 ?

Evidence of larger conspiracies at work

/markp

JoeTBM 

Stop feeding the troll

FBinNY 

As noted, this is 40 year old stuff that gets reopened every 10 years or so. An interesting observation about changes since then is that both bicycle and motorcycle tires have moved toward reduced tread, with no negative consequences.

For those who are curious, one may consider the difference in planing and displacement hull design in boats, then compare bike to auto tires.

As one who has ridden in miserable conditions, I can add one other factor.

Hitting deep water (4" or more) at high speed is very similar to hitting deep sand. You get immediate braking and a sudden over steer as the side forces want to swing the front wheel. So there doesn't need to be slippage, it's just that you're normal steering reflexes no longer work.

I feel somewhat guilty because it was my statement in another thread about road tire tread not mattering that set the OP off.

smd4

Speaking of whom, I wonder where he's been.

shelbyfv

Nah, he'd have found something else to carry on about. I hate to tempt fate but he may be gone.

cyccommute 

You are very correct with your analogy. Because the wheel doesn’t form a bow wave, it dives into the water creating resistance that we aren’t used to just like in sand. And, like in sand, the pivot of the fork allows the rear to swing to a side which makes forward progress difficult. The video of the time trial crashes in the other post demonstrate the problem quite well. The riders crash because the rear wheel isn’t tracking and slides too far to the side for recovery.

I was astonished by how little water is needed for hydroplaning to occur. “Hydroplaning requires a critical minimum fluid depth to be present on pave- ment surfaces. This critical depth can range from approximately 0.1 to 0.4 inch depending upon the character of tire-pavement surfaces.”

sweeks

This happened to me on a family ride with my wife and kids. There was a bridge over a stream with a parallel roadway which was covered by about 10 inches of flowing water. The wife and daughter were a bit farther ahead, and I said to my son, "Watch this!" I went ahead a bit then came back downhill and hit the water going about 20 MPH (Mountain bike, ~2" tires). There was a very gratifying splash accompanied by a total loss of control. Of course, I didn't actually hit the ground until I had passed over the water, so I landed on dry concrete. I was able to conceal the missing skin from my wife until I was loading the bikes back onto the car. Then I caught hell!
Was this "hydroplaning"? Even if so, it was so remote from "normal" riding that it is only academic.

Hondo6

FWIW: here are a pair of links to what the late Jobst Brandt had to say about the subject:

https://www.sheldonbrown.com/brandt/slicks.html

https://yarchive.net/bike/slicks.html

This photo of a Goodyear aircraft tire would seem to back his opinion.

https://www.chiefaircraft.com/media/.../gy-tire_4.jpg

FWIW: Brandt worked for many years in the automotive and bicycle industries as a mechanical engineer (for Porsche and Avocet, if I recall correctly - and with Avocet, was as I recall directly involved in tire design). Best I can tell he virtually always knew precisely what he was talking about and was correct when it came to cycling technology and the engineering aspects of same.

L134 

Cool, I'm glad you read it!

"Fortunately, most runway and road pavements in use today are provided with textured surfaces so that thin-film lubrication is probably seldom encountered when vehicles are equipped with tires having adequate tread pattern designs."

So, we can quibble about whether or not my tread pattern was adequate and whether or not I experienced thin-film lubrication or hydroplaning or nothing at all but my take was there is a fine line between all the various things that might be going on and the resultant effects that for purposes of discussion between lay people about practical considerations are largely irrelevant hair splitting. The study in question was conducted and data gathered for the purposes of addressing hydroplaning of aircraft. I don't believe the researches gave any thought whatsoever to bicycles. If my decision process were to lead me to extrapolate their research to a scenario whereby I might dramatically increase the risks of my activity, I might ask the authors if their opinion was that such extrapolation was prudent. My guess is that were they to realize I would be increasing my risks that they would probably say their study was not designed for such a scenario and that they would therefore be reluctant to endorse such an extrapolation. I choose not to assume that their study can be extrapolated to bicycles. Perhaps I am the one nitpicking and the one dismissing scientific research for the sake of being "right," but as it presumably leads me to a more conservative and safer course of action and harms nobody else, it is reasonable rather than a reckless denial of "science."

My question to you then, if asked by a lay, beginning cyclist "do I need to worry about hydroplaning?" are you going to say "no, not at all" and then go into some technical discussion about thin-film lubrication or are you going to say "yeah, you need to be cautious on wet roads"?

If nothing else, I got somebody to actually read the study. I do find it somewhat troubling though that it was an eye rolling exercise to you.

FBinNY 

Having hit both deep water and sand at high speed, I've faced tough split second (liereally) decisions between a sure soft crash now, or try to save it and risk a hard crash later.

The former is probably smarter, but I end up letting nature call it.

Trakhak

cyccommute will likely be along soon. In the meantime, on the basis of the abundant information provided in this thread, this is my takeaway:

No, you do not need to worry about hydroplaning with a bike. Yes, you need to be cautious on wet roads. The two statements are not exclusive.