The Arithmetic of Hydroplaning a Bicycle ( per NASA )
#76
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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."
For example, on a ride yesterday, I rode through a patch of water on a mountain bike trail then the tire slipped on a rock. The OP of this thread would call that “hydroplaning”. Most others…myself included…would not. It’s simple lubrication and slippage. The rock was dry and my tires were slightly wet. Traction was reduced by the water on the rubber but no bow wave was formed. We use lubrication all the time to reduce the friction between two objects and we understand that the lubricant is filling the interstitial spaces on the surface so that the surfaces can slide past each other. That’s all that is happening in wet conditions except when there is sufficient water for hydroplaning to occur. But the amount of water needed for that to happen is far more than is needed for simple lubrication.
I also realize that the NASA bulletin was written to address hydroplaning in planes on runways and for automobiles and trucks. It doesn’t address width of tire differences and only tangentially addresses tire cross section. However, the results are valid for bicycle nevertheless and the tire differences for bicycles likely increase the advantage that bicycles have over larger vehicles. Our smaller tire contact patch squeezes more water out of the gap leaving us with the inability for that bow wave to form at normal or even abnormal speeds.
That said, bicycles are still prone to the lubricating of the surface issue. And the size of the contact patch…along with a somewhat unstable mode of movement…make us more prone to DFO* on wet surfaces.
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.
*DFO= done falled over
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#77
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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.
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.
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#78
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One reason why this question is of interest is that it comes up when people want to know if slick bicycle tires put them at risk. (The assumption is that treaded tires on cars permit water shedding, thus avoiding hydroplaning, and that this might be relevant to bicycles, so putting that idea to rest is worth the trouble.)
Last edited by Polaris OBark; 06-19-23 at 03:52 PM.
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Uh oh, be careful or someone will bring up how flexible bikes can "plane" and make you go faster using this as evidence.
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#80
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For a clean dry course or a clean wet course, slicks will probably be fine. Out in the real world, roads are seldom clean and having a little bit of tread will keep the shiny side up without as much thought.
It’s not about hydroplaning, however.
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That’s not how I meant it. I do learn some things during these kinds of discussions…like the small amount of water needed to hydroplane a vehicle. I also confirmed for myself why hydroplaning of a bicycle isn’t a thing. My initial statement was meant as a joke because I wanted to be lazy and just skim the paper. Making me read it and explain it was not a useless exercise. I found the paper interesting and enlightening.
*DFO= done falled over
*DFO= done falled over
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Wonder why this comes to mind?
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The central delusion of the OP is that it takes a formula and attempts to derive velocity out of it by using an incident which probably doesn't qualify as hydroplaning. Riding a motorcycle across deep water is arguably riding a bow wave, considering how the tire's leading edge is at an angle that doesn't remotely resemble the flat and horizontal contact patch being discussed with hydroplaning.
If NASA has a single velocity example that we can use as a guide, that would illustrative. But as someone that has landed a 10,000 lbs. plane many times in the rain at over 120 mph, I think the real numbers for narrow bike tires are probably closer to 200 mph.
Keep in mind that there are other effects that can make a narrow bike tire break traction with the pavement other than hydroplaning - impedance, road oils, street texture, durometer, brake chatter, etc.
If NASA has a single velocity example that we can use as a guide, that would illustrative. But as someone that has landed a 10,000 lbs. plane many times in the rain at over 120 mph, I think the real numbers for narrow bike tires are probably closer to 200 mph.
Keep in mind that there are other effects that can make a narrow bike tire break traction with the pavement other than hydroplaning - impedance, road oils, street texture, durometer, brake chatter, etc.
#84
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'...believe that the Sun orbits the Earth...' I think both both orbit their common centre of mass.
#86
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If hydroplaning means skimming across the water without sinking deeper, Like a boat with a planing hull, then I agree with the general consensus it is extremely unlikely on a bicycle as one would have to be going extremely fast, way faster the most cyclist ride, even downhill.
However, there is a much lower speed where the tires will not displace enough water to contact the road for a short time depending on the weight on the tire and its width. One that might be achieved going down hill. So if you make any quick steering adjustments while riding through enough pooling water on the road at speed you could be in trouble. Call it whatever you like.
However, there is a much lower speed where the tires will not displace enough water to contact the road for a short time depending on the weight on the tire and its width. One that might be achieved going down hill. So if you make any quick steering adjustments while riding through enough pooling water on the road at speed you could be in trouble. Call it whatever you like.
Last edited by xroadcharlie; 06-22-23 at 06:16 AM.
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Or a circling the bowl? A redeeming feature of this thread (beyond sending OP back to wherever) is learning that a number of BFers have real knowledge of some complicated stuff. Kudos!
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If hydroplaning means skimming across the water without sinking deeper, Like a boat with a planing hull, then I agree with the general consensus it is extremely unlikely on a bicycle as one would have to be going extremely fast, way faster the most cyclist ride, even downhill.
However, there is a much lower speed where the tires will not displace enough water to contact the road for a short time depending on the weight on the tire and its width. One that might be achieved going down hill. So if you make any quick steering adjustments while riding through enough pooling water on the road at speed you could be in trouble. Call it whatever you like.[/QUOTE]
What you are missing is that this occurs at too high a speed. In post 17, I stole the values that Sheldon Brown has posted. At 40 psi, the bicycle would need to be traveling at 66 mph for hydroplaning to occur. Some people can achieve that speed on a downhill but there’s a couple of problems there. First, it’s downhill. It’s next to impossible to get enough water on the road to hydroplane since water tends to run…well…downhill. Granted the paper says that only 0.1 to 0.4 inches for hydroplaning to occur but that’s a bit hard to achieve when the water flows away. In addition, anyone who could do 66 mph on a downhill is probably not going to be running 40 psi. They are more likely be running pressures closer to 100 psi. That increases the threshold for hydroplaning to just over 100 mph.
The current unpaved speed record is 141 mph on Cerro Negro in Nicaragua so it’s possible to get to over 100mph. However, the grade on Cerro Negro is from 18% to 22%. We are back to that water flowing problem. As has been pointed out many times, it’s possible to hydroplane a bike but it’s not probable. It’s not something mere mortals…nor bicycling gods…need worry about.
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So in summary:
The word "hydroplane" is a compound word of hydro implying water, & the geometry related definition of plane, a 2 dimensional surface that extends indefinitely.
The term, broken into it's constituent parts strongly implies it's not hydroplaning unless there is a complete decoupling from the roadway and subsequent travel upon the waters unbroken surface.
To the Op: TC1 words have definitions. I should think that until the 2 dimensional plane of water the tire rides upon exceeds the depth of the 3 dimensional surface irregularities, the definition of "plane" has not been fulfilled. You have been conflating lubrication, friction coefficients, etc...and all manner of things with an emergent phenomena of a well understood set of conditions. You might do well to lick your wounds and move on to fight another day.
FWIW and as a matter of charity to you, new member, explaining why you are wrong. It's not the tires internal pressure that matters. It is the pressure of the fluid between the tire & the road that does the lifting of the vehicle...and this is why a minimum depth for "bow shock" (ie pressure wave) is necessary to create the plane upon which the tire rides upon. Similar in theory to "ground effect" in airplanes...The fluid underneath simply does not move out of the easily or quickly enough & thus bunches up, lifting the craft. The truth remains: Bicycle tires are too narrow for enough pressure buildup to do the job of lifting the craft within typical bicycle operating norms.
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The word "hydroplane" is a compound word of hydro implying water, & the geometry related definition of plane, a 2 dimensional surface that extends indefinitely.
The term, broken into it's constituent parts strongly implies it's not hydroplaning unless there is a complete decoupling from the roadway and subsequent travel upon the waters unbroken surface.
To the Op: TC1 words have definitions. I should think that until the 2 dimensional plane of water the tire rides upon exceeds the depth of the 3 dimensional surface irregularities, the definition of "plane" has not been fulfilled. You have been conflating lubrication, friction coefficients, etc...and all manner of things with an emergent phenomena of a well understood set of conditions. You might do well to lick your wounds and move on to fight another day.
FWIW and as a matter of charity to you, new member, explaining why you are wrong. It's not the tires internal pressure that matters. It is the pressure of the fluid between the tire & the road that does the lifting of the vehicle...and this is why a minimum depth for "bow shock" (ie pressure wave) is necessary to create the plane upon which the tire rides upon. Similar in theory to "ground effect" in airplanes...The fluid underneath simply does not move out of the easily or quickly enough & thus bunches up, lifting the craft. The truth remains: Bicycle tires are too narrow for enough pressure buildup to do the job of lifting the craft within typical bicycle operating norms.
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Last edited by base2; 06-27-23 at 01:18 AM.
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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.
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.
#95
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To everyone else, I stopped replying in this thread back in June after some of my comments were deleted without explanation. I also went on vacation, and did not attempt to revive it upon my return. I won't do so now, either, since all of the relevant science has been previously posted, and the only remaining question is whether or not some individuals will process it, and realize that bicycle tires can and do hydroplane.
So, if there's anyone who wishes to debate that point, I am game, and this seems like the appropriate place since all other threads on the topic get closed due to the poor behavior of the anti-science zealots here. Please do bring more than insults and weak attempts at comedy.
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Funny to see this old thread. I actually thought he might be gone.
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Well, Pete, that was because your comments on that thread demonstrated precisely that you possess a poor understanding of how tires work. Or do you want to elaborate on the magical non-mechanical traction to which you referred?
So what do you do for a living? What qualifies you to be an authority on tyres? I don’t see anyone really buying into it.
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This is an example of the type of comments this thread, and frankly this entire forum, do not need. We can have a discussion, and we should have a discussion, because a number of people do not understand the topic. But we cannot have an adult discussion with people trying to be funny, or whatever that comment was.
That said, shelbyfv, you know damn well that I wasn't gone, because just last week, you were making-up nonsensical accusations about me.
That said, shelbyfv, you know damn well that I wasn't gone, because just last week, you were making-up nonsensical accusations about me.
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So, if there's anyone who wishes to debate that point, I am game, and this seems like the appropriate place since all other threads on the topic get closed due to the poor behavior of the anti-science zealots here. Please do bring more than insults and weak attempts at comedy.
I genuinely would like to see you ride into a lake and not break the surface, to ride upon a bow wave for any distance.
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I get by on my tyre knowledge thanks. I’m not a tyre engineer/designer, but I’ve overseen hundreds of F1 tyre tests and worked with the best motorsport tyre engineers in the world. I know enough to understand that anyone who claims to know everything there is to know about tyre dynamics is full of bs.
Pete, if you need to attack me personally, rather than debate the point, send a PM, if that makes you feel better -- but that's not what I'm here for, it's not what this thread is here for, and not what this forum is here for, and I doubt that's what many readers are here for.