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Water displacement?

Old 06-13-20, 06:55 AM
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venomx
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Water displacement?

What does that term mean in regard to bike riding ?
i heard that the tyre has to be fitted in the right direction for water displacement.

my back tyre is facing the wrong way according to the arrow so Iíll be getting it changed this week
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Old 06-13-20, 07:23 AM
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It has to do with the ability of a tire to move water from under the tread to avoid hydroplaning; at the speeds and tire pressures usually encountered in cycling hydroplaning is not a worry.
Approximately, where is hydroplaning speed in mph and is pressure in psi; even at 25psi the hydroplaning speed is over 50mph.
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Old 06-13-20, 07:30 AM
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If it bothered me, I'd wait until I had a flat that needed changing and flip the tire over then.
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Old 06-13-20, 07:37 AM
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That directional arrow has to do with tread design and generally applies to MTB tires to get the best traction on loose surfaces. It has nothing to do with "water displacement". As dsbrantjr demonstrated, you will never hydroplane a bicycle.
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Old 06-13-20, 07:54 AM
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Originally Posted by dsbrantjr View Post
It has to do with the ability of a tire to move water from under the tread to avoid hydroplaning; at the speeds and tire pressures usually encountered in cycling hydroplaning is not a worry.
Approximately, where is hydroplaning speed in mph and is pressure in psi; even at 25psi the hydroplaning speed is over 50mph.
Interesting equation. But wouldn't tire width play a role as well? And system weight? I assume a 5 pound system would hydroplane before a 300 pound system with given tires and speed.
and tread design changes water displacement as well. So the equation should include many more variables.
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Old 06-13-20, 08:34 AM
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Originally Posted by HerrKaLeun View Post
Interesting equation. But wouldn't tire width play a role as well? And system weight? I assume a 5 pound system would hydroplane before a 300 pound system with given tires and speed.
and tread design changes water displacement as well. So the equation should include many more variables.
Note the first word in the sentence, "approximately"...Besides the variables you state, water depth, surface condition, roughness and treatments (grooving, etc.), whether the tire is driven or just rolling, tread depth and wear and a host of other conditions come into play.
My point was to illustrate that hydroplaning is generally not an issue with cyclists.
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Old 06-13-20, 09:24 AM
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About the only way you can hydroplane with a bike is to drive it off a pier.
You have to keep pedaling until you hit the bottom though.
Bring scuba gear.
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Old 06-13-20, 09:33 AM
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So the rotational arrow is just for aesthetics?
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Old 06-13-20, 09:37 AM
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the contact patch of a bicycle tire is too small to hydroplane.. and if its a slick surface, steel plates or paint, you will still need to be careful..
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Old 06-13-20, 04:03 PM
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Originally Posted by venomx View Post
So the rotational arrow is just for aesthetics?
The sipes on the tire tread are generally angled so that water, if encountered, will be directed towards the edge of the tread as the tire rolls over it, rather than towards the center of the tread where there is theoretically no place for it to escape. As noted above, this will not lead to hydroplaning under virtually any conceivable circumstances. Putting the tire on backwards is a "D'oh!" moment (I've done it), but as suggested above, it's perfectly OK to wait until the tire is removed for other reasons.

Heh... (afterthought!)... think of the arrows as a test to see if you're paying attention!
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Old 06-13-20, 05:55 PM
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Originally Posted by venomx View Post
So the rotational arrow is just for aesthetics?
For a road tire, yes. For an MTB tire, it can indicate the direction the tread works best on loose, muddy or sandy terrain.
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Old 06-13-20, 06:12 PM
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The arrow points towards the label, and we all know how important the label is.
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Old 06-13-20, 08:25 PM
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Bike tire marketing borrows from what many consumers already know, car tires. But the dynamics of car and bike tires are pretty different so what cars require is not completely transfered to bike tires. However the average consumer doesn't know this and as such can be manipulated by advertising (and labels are this to a large degree) claims.

I explain the hydroplaning possibilities as this. A car tire rolling along is a squeegee that builds up a wall of water in front of it. It needs channels to route that wall of water around it to prevent it from being lifted off the road by that wall of water. Much like a flat bottomed boat will plane on top of a lake. Now a bike tire is like a canoe on that lake. It's cigar like shape is very "hydrodynamic" and the water will readily flow around and past it's shape.

Having said that there's still the unmentioned issue of lessened friction/traction from the water acting like a lubricant. Much like oils on the road will increase a tire's ability to slip so to will water. Just not from hydroplaning. Andy
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