The aquaplane

[Batmonster]

Yello,

Riding home during the "showers" that resembled an indian monsoon I began to wonder about aqua planing. I'm assuming it can happen on a bike, any advice on how to ride it out? Any one care to share their experiences?

Batmonster

[slick]

Highly unlikely to happen on a bike due to the small contact area of the tyres which lets them cut through surface water.

Only happened to me once in 24 years of riding in all weathers, first time around Pukekohe on a drying track, large puddle at the end of the front straight, must have been doing at least 220kmh on a 'blade and just about to brake for turn 1 when it all went very 'vague' by the time I realised what was going on I had 'flown' over the puddle and back onto dry land, it's very useful having the reaction times of a slug sometimes!!

If it happens, which is unlikely on a 250, keep pointing it straight ahead and don't try and do anything until you're back on 'drier' land! There is probably a really high tech physics equation for it...

[vifferman]

I also read a few years back about someone who "lost it in a big way" on a motorway (in the UK, IIRC) because he aquaplaned on standing water. Mind you, he was going very fast.
The thing to do is slow down if you see big puddly bits. The bike aquaplanes because the tyres can't push the water out of the way through the stipes (grooves/treads) fast enough, and you get a wedge of water betwen the tyre and the road. Slow down, and the tyres should be able to pump the road dry(ish).

[avgas]

never mind the aqua plane, bloody hovering diesel that gets me.......

[unhingedlizard]

my old VW in britian used to stall if you went through water. trick was to boot it and control the slide over the puddle/flood! Wont like to try on a bike though....
Got a great picture of Mick Doohan at home sliding his knee through a puddle.

[car]

Riding home during the "showers" that resembled an indian monsoon I began to wonder about aqua planing. I'm assuming it can happen on a bike, any advice on how to ride it out? Any one care to share their experiences?

It happened to me once, caught in a sudden downpour, trying to make it home late one night on the RVF. I was doing a customary 95mph on empty motorway and the skies opened. Before I knew it the rear wheel was slithering all over the place. It wasn't helped by the squared-off rear tyre -- not enough tread to shift the water.

I'm not sure what the correct procedure is, but from that small experience I'd say "don't touch the front brake". In fact, don't shut off the throttle with any great haste either. Just gently roll off the throttle, doing your best not to take weight off the rear tyre. Oh, and don't go out on squared-off tyres if it's going to rain.

[terbang]

Its a real issue and aeroplanes have issues with it all the time. Its related to tyre pressure and we use the formula (the square root of the tyre pressure in pounds multiplied by nine) to give us a hydroplaning speed in knots. In real numbers a Gulfstream that has tyre pressures of 190 psi will aquaplane at 124 Knots, 229 K/hr. We typically rotate at around 150 knots and touch down at similar, so it can be tricky as the water between the tyre and the tarmac actually boils and damages the tyres.
A typical car or bike tyre at say 30 psi would hydroplane at 49 knots, being 91 Kph.

[Edbear]

Its a real issue and aeroplanes have issues with it all the time. Its related to tyre pressure and we use the formula (the square root of the tyre pressure in pounds multiplied by nine) to give us a hydroplaning speed in knots. In real numbers a Gulfstream that has tyre pressures of 190 psi will aquaplane at 124 Knots, 229 K/hr. We typically rotate at around 150 knots and touch down at similar, so it can be tricky as the water between the tyre and the tarmac actually boils and damages the tyres.
A typical car or bike tyre at say 30 psi would hydroplane at 49 knots, being 91 Kph.

Interesting post, terbang! Always good to get some techie info!

So if I wuz ter pump my C50T tyres up ter 190psi she'll be fine up to 229km/h...

[terbang]

Interesting post, terbang! Always good to get some techie info!

So if I wuz ter pump my C50T tyres up ter 190psi she'll be fine up to 229km/h...

Yup, but best to use nitrogen though.

[Edbear]

Yup, but best to use nitrogen though.

Soooo...! Dat'll stop der water boilin' under der wheels, then...

[rainman]

Highly unlikely to happen on a bike due to the small contact area of the tyres which lets them cut through surface water.

Maybe I'm not getting the difference between hydroplaning and just common or garden skidding, but I've had a brief moment during torrential rain when there wasn't a lot of traction going on. I just kept as straight up as possible, let go of the throttle, and tried to gently steer to the side of the car in front. Fortunately I was going fairly slow (not 91kph?) so got traction back before the bumper of the car ended up as a front wheel ornament... After several biker Hail Mary's (also known as OhShitOhShitOhShit's) I got my following distance back to where it shoulda been in the first place, mentally kicked myself for being such a dick, and resolved to be waaaaay less keen on the front brake when riding in the wet...

Or is that something different?

[Batmonster]

Thanks for all those replies. When it rains hard here in the Hutt there is a whole lot of deceptive surface flooding. I've aqua planed many times in a car, but I don't really want to try it on a bike, so thanks for all the advice... though I may leave the nitrogen filled tyres to the aeroplanes, lol.

Batmonster

[idb]

It's happened to me on the open road.
I got caught in a rain storm and the shallow wheel track just inside the centre line filled up and I got in it. Turning the bars had no effect ... very un-nerving.
My general philosophy in times like that is 'no sudden movements'.
No sharp braking, snapping off the throttle or steering input until everything comes good.

[MarkyMark]

Its related to tyre pressure and we use the formula (the square root of the tyre pressure in pounds multiplied by nine) to give us a hydroplaning speed in knots. In real numbers a Gulfstream that has tyre pressures of 190 psi will aquaplane at 124 Knots, 229 K/hr.

I'm pretty sure this rule of thumb won't work everywhere. It would be specific to the shape of the tyre, the tread pattern, and how much weight you've got on it.
A large contact patch, like big wide racing slicks, will hydroplane way before a small contact patch with a lot of weight on it, like a fat dude on knobblies.

[Mikkel]

Its a real issue and aeroplanes have issues with it all the time. Its related to tyre pressure and we use the formula (the square root of the tyre pressure in pounds multiplied by nine) to give us a hydroplaning speed in knots. In real numbers a Gulfstream that has tyre pressures of 190 psi will aquaplane at 124 Knots, 229 K/hr. We typically rotate at around 150 knots and touch down at similar, so it can be tricky as the water between the tyre and the tarmac actually boils and damages the tyres.
A typical car or bike tyre at say 30 psi would hydroplane at 49 knots, being 91 Kph.

Lemme guess that this applies to any wet runway and doesn't take into account the amount of water that actually is standing on the runway as well. In that case it would most likely rely on the evaporation of water and the ensuing expansion (~1->1400) produced during the hard braking during touchdown to cause a loss of traction.

I haven't tried aquaplaning on a bike - but for cars it's very dependent upon the depth of the puddles you drive through and your velocity. Although with todays tires it's become a fairly rare phenomenon - even in heavy rain. It's the exact same mechanics as those that will life a speed boat out of the water and allow it to skip across the water at high speeds.

And yes there are some very very nasty equations that describes the mechanics of fluids (Navier-Stokes equations) - however solving them analytically is not an option since the system is too complex. Fluid mechanics are largely black magic to this day - even the best guys are quite happy if they only get an error factor of 2. (Just calculating the trajectory of an ideal football (plain sphere) flying through the air while spinning is bloody difficult and there isn't necessarily an analytical answer since the problem is non-linear - you need a big computer and a couple of hours.) Think about that for a second and then consider Joe Average being able to catch a ball in the blink of an eye - even with a sidewind. Pretty cool eh