cyccommute 

I think they understated this problem with regard to roadways. Airports may be different but automobile roadways seldom have much more “texture” than the aggregate put in the bitumen to make asphalt. You can still slide easier on wet pavement in a car…unintentionally or intentionally. That’s why we are told to slow down when conditions are wet. Friction of any kind is reduced when the pavement it wet.

Yes, there is something of a continuum when it comes to water on roadways but the hydroplaning effect is a known phenomenon, can be measured, and can be predicted as shown by the formula for calculating when it happens. But don’t go applying it to everything. That’s not correct nor helpful.

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.

I would say “No, not at all but…you do have to be careful in slippery conditions.” Most anyone who has driven a car or even walked can appreciate that statement. If they want a technical discussion, I can go into that until they DFO* from information overload. I tend to do that anyway but I’ve learned not to be too technical or everyone wants to go talk to the plants.

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

cyccommute 

Well that ‘sa way of saying what I said without murdering millions of electrons

Polaris OBark

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.)

himespau 

Uh oh, be careful or someone will bring up how flexible bikes can "plane" and make you go faster using this as evidence.

cyccommute 

And there I would say “It depends”. Direction of the tread means nothing for road tires. (Different kettle of fish for mountain bikes). Compound of the rubber can mean a lot. If it is too hard, the traction on wet in a slick tire will be bad specifically when cornering. If the compounding of the rubber is soft enough for the wet during cornering, the wear is going to be crap. A little bit of tread on sub-optimal rubber compound for wet conditions changes up that lubrication effect a little bit allowing the tire to provide a less consistent tire surface that interacts better with the inconsistent surface of the pavement. It helps when the road has sand on it as well.

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.

L134 

Sorry, I misunderstood! I've enjoyed the discussion.

Shadco 

Wonder why this comes to mind?

Kontact 

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.

esasjl

'...believe that the Sun orbits the Earth...' I think both both orbit their common centre of mass.

frogman

Pass it around please

xroadcharlie

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.

DiabloScott

The common center of mass is within the sun itself.

FBinNY 

Is there a merry go round emoji?

shelbyfv

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!

GhostRider62

Planing only works with the extralegere tires. Speeds are 0.3 mph higher, one replicate measured with iphone GPS.

mpetry912 

A very good point !

/markp

cyccommute 

I did my part and read the paper. Go read it yourself for more detail. The forward movement of the tire causes the water to pile up under the tire until the tire is actually lifted off the pavement. The speed at which this occurs can be calculated as a function of the square root of the pressure. In other words, we know when it happens. At the typical pressure that bicycle tires use…even today’s lower pressures…we can’t get up enough speed to form this bow wave. The paper points out that heavy vehicles which use higher pressure can’t hydroplane either because the tire pressure is high enough that the truck would have to be traveling at far higher speed than they usually travel.

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.

base2 

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.

base2
(who is just piling on)

PeteHski

I tried to explain this in the other thread but I was informed that I don’t understand the physics or how tyres grip.

TC1

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?

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.

shelbyfv

Funny to see this old thread. I actually thought he might be gone.

PeteHski

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.

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.

TC1

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.

base2 

If you could please demonstrate a bicycle planing upon the hydro all this nonsense could be easily done away with.

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.

TC1

Cite where I claimed to know everything there is to know about tires. I did not. I can cite where you claimed that there exists non-mechanical traction, however, which is a very good indication that someone doesn't understand the topic.

This is another example of the type of comment this thread, and forum, do not need. If you can only judge an argument by the author's credentials, then you aren't capable of judging the argument at all. If a person's argument is correct, it doesn't matter if they are a janitor, a patent clerk, or a principal researcher.

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.

​​​​​​​