Hydroplaning
Any vehicle can hydroplane with tires that are new to well worn ... just a few facts to share ....also, as someone who used to work selling and installing tires ... wetter weather always brought in a slew of customers for new tires because they had experienced this sensation even though they had plenty of wear left on their tires but the insisted on new tires.
The risk of hydroplaning increases with the depth of standing water and the sensitivity of a vehicle to that water depth.[SUP]
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[h=3][
edit] Water depth factors[/h]
Ruts in a road.
- Depth of compacted wheel tracks and longitudinal depressionsHeavy vehicles can cause ruts in the pavement over time that allow water to pool, negatively impacting draining.
- Pavement micro and macrotexture[SUP][3][/SUP]Concrete can be preferable to hotmix asphalt because it offers better resistance to rut formation, though this depends on the age of the surface and the construction techniques employed while paving. Concrete also requires special attention to ensure that it has sufficient texture.
- Pavement cross slope and grade[SUP][4][/SUP]Cross slope is the extent to which the cross-section of a road resembles an upturned U. Higher cross slopes allow water to drain more easily. Grade is the steepness of the road at a particular point, which affects both drainage and the weight of the vehicle. Vehicles are less likely to hydroplane while traveling uphill, and far more likely to do so at the trough of two connected hills where water tends to pool. The resultant of cross slope and grade is called Drainage gradient or "Resulting grade". Most road design manuals world wide require that the drainage gradient in all road sections must exceed 0.5 %, in order to avoid a thick water film during and after rainfall. Areas where the Drainage Gradient may fall below the minimum limit 0.5 % are found at the entrance and exit of banked outer curves. These hot spots are typically less than 1 % of the road length, but a large share of all skid crashes occur there. One method for the road designer to reduce the crash risk is to move the cross slope transition from the outer curve and to a straight road section, where lateral forces are lower. If possible, the cross slope transition should be placed in a slight up- or downgrade , thereby avoiding that the drainage gradient drops to zero. The UK road design manual actually calls for placing the cross slope transition in an artificially created slope, if needed. In some cases, permeable asphalt can be used to improve drainage in the cross slope transitions.
- Width of pavementWider roads require a higher cross slope to achieve the same degree of drainage.
- Rainfall intensity and duration
[h=3][
edit] Vehicle sensitivity factors[/h]
- The driver's speed, acceleration, braking, and steering
- Tire tread wearWorn tires will hydroplane more easily for lack of tread depth. Half-worn treads result in hydroplaning about 3-4 MPH lower than with full-tread tires.[SUP][5][/SUP]
- Tire inflation pressureUnderinflation can cause a tire to deflect inward, raising the tire center and preventing the tread from clearing water.
- Tire tread aspect ratioThe longer and thinner the contact patch, the less likely a tire will hydroplane. Tires that present the greatest risk are small in diameter and wide.
- Vehicle weightMore weight on a properly inflated tire lengthens the contact patch, improving its aspect ratio. Weight can have the opposite effect if the tire is underinflated.
- Vehicle typeCombination vehicles like semi-trailers are more likely to experience uneven hydroplaning caused by uneven weight distribution. An unloaded trailer will hydroplane sooner than the cab pulling it. Pickup trucks or SUVs towing trailers also present similar problems.
There is no precise equation to determine the speed at which a vehicle will hydroplane. Existing efforts have derived
rules of thumb from empirical testing.[SUP]
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[6][/SUP] In general, cars hydroplane at speeds above 53 MPH (72 km/h), where water ponds to a depth of at least 1/10 of an inch (2,5 mm) over a distance of 30 feet (9 meters) or more.
[h=3][
edit] Motorcycles[/h]
Motorcycles benefit from narrow tires with round, canoe-shaped contact patches. Narrow tires are less vulnerable to hydroplaning because vehicle weight is distributed over a smaller area, and rounded tires more easily push water aside. These advantages diminish on lighter motorcycles with naturally wide tires, like those in the
supersport class. Further, wet conditions reduce the lateral force that any tire can accommodate before sliding. While a slide in a four-wheeled vehicle may be corrected, the same slide on a motorcycle will generally cause the rider to fall. Thus, despite the relative lack of hydroplaning danger in wet conditions, motorcycle riders must be even more cautious because overall traction is reduced by wet roadways.
