Siping can
help with water evacuation (and storage). I don't disagree. But neither Michelin or Cooper specifically state that it helps with hydroplaning resistance. They both note it improves wet surface traction, snow traction and ice traction by virtue of keeping the tread blocks more uniform; from deforming, while allowing water to displace into the voids (sipes). This is not the same thing as hydroplaning resistance. This is why performance summer tires, with no siping whatsoever, can have absolutely incredible wet weather performance and hydroplaning resistance. The circumferential grooves allow for water evacuation, while the soft compound doesn't require siping to achieve optimal contact.
Large voids and channels in the tread, as well as grooves, are for water evacuation and hydroplaning resistance, which is why these are common features across all types of tires, with and without sipes.
I don't see a reference to it being called a 3D sipe, but it very well could be. And yes, its structure is such that by opening up as the tire wears, it maintains the same void to contact ratio, keeping performance consistent.
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I recall something similar back when Michelin first started revising their siping technology. They implemented "Y" shaped sipes on tires like the LTX so that once the tire had worn down, decreasing the sipe void area, that this was offset by doubling the number of sipes, keeping performance consistent.
So, back to the main claims here:
- The angled grooves on the Platinum are grooves, not sipes (they are too large to be sipes)
- Hydroplane resistance is not an advertised feature of siping
Anecdote:
The Goodyear Eagle Sport Touring tires that came on my wife's 1500 had lots of siping and lots of grooves, including large circumferential ones:
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They were absolute crap in wet weather, because even with the siping, the compound itself was just hot garbage. They were never prone to hydroplaning, having lots of void area, but they were downright dangerous on even slightly wet surfaces, because you simply had no traction; the compound had no bite, regardless of the siping. It was like gold plating a turd, because even though the tread blocks were able to make better contact, the compound couldn't provide traction.