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Treaded car tires are said to be better at avoiding hydroplaning than smooth tires (slicks) in the rain. In particular, directional treads are thought to be the best.

The following is an example of that claim:

Hydroplaning: the Role Tires Play

Directional tread designs (sometimes called Unidirectional tread designs) are frequently used on tires intended to better resist hydroplaning. Their multiple tread grooves are aligned in a repeating "V" shape to increase the tire’s ability to channel water from between the tire’s footprint and the road. Somewhat like the vanes of a water pump continually pushing water in one direction through the engine, the grooves of a directional tire are designed to push water in one direction through the tire (forward on an angle to the sides). Directional tread designs are especially helpful in increasing hydroplaning resistance when relatively wide Plus Two, Plus Three or Plus Four tire and wheel applications result in fitting a much wider tire to a vehicle than its Original Equipment size.

Note that there is a difference between directional tires and asymmetric tires.

Do directional tires (not asymmetric tires) give measurably better performance in the rain?

If you mount them with a contrary rotation, does it matter?

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    This question might go better over on the Motor Vehicle Stackexchange. There's an answer to the second half of your question already there. – Compro01 Mar 6 '14 at 2:46
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    @Com The answer linked above is a repetition of the claim, not an answer according to our standards. – Sklivvz Mar 6 '14 at 8:09
  • I added the word "car" to your question (e.g. because some people say that bicycle tires, for example, don't hydroplane). Because you mentioned "slicks" in your question does that mean you're asking about auto racing rather than passenger-car tires? – ChrisW Jun 27 '15 at 8:28
  • What's the difference between 'directional' and 'assymetric' in this context? I'd this just a language confusion by the OP? – Oddthinking Jun 27 '15 at 8:38
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    @ChrisW: items_learnt_today_count++; Thanks. – Oddthinking Jun 27 '15 at 10:11
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A combined tire tread pattern lowers hydroplaning risk in different modes of vehicle movements.

Researchers have concluded in 'Effectiveness of Tire-Tread Patterns in Reducing the Risk of Hydroplaning' 2009 that combined groove pattern would help in lowering hydroplaning risk sufficiently in different modes of vehicle movements.

The following six forms of tire-tread groove patterns are considered: (a) longitudinal groove pattern, (b) transverse groove pattern, (c) V-groove pattern with 20° V-cut, (d) V-groove pattern with 40° V-cut, (e) combined groove pattern consisting of longitudinal grooves and edge horizontal grooves, and (f) combined groove pattern consisting of longitudinal grooves and 20° V-cut grooves. The analysis shows that a parameter computed as the groove volume per tread area of the tire is a useful performance indicator to assess the effectiveness of various tire-tread groove patterns in reducing vehicle hydroplaning risk. The significance of V-shape grooves is discussed. For vehicular operations involving both forward and lateral movements, the analysis indicates that a combined pattern would provide a good compromise in lowering hydroplaning risk sufficiently in different modes of vehicle movements.

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