A few possibilities come to mind.
The first is that you're still riding on the new tire, and haven't worn through the very thin "skin" layer which has mold release agent on it. This is the shiny surface
of newly molded tires and can be a bit slippery. When the riding surface has the matte appearance of a used tire the grip should come back to what you're used to.
The other is that you've either made a change in pressure, or changed to a tire with a harder compound.
Discounting the mold skin, tire friction varies among tires within a narrow band. Some makers using a harder compound which offers better tread life, especially on hot blacktop, and others using a softer stickier compound better suited for cooler climates and rain slick roads.
This is part of the reason that experienced cyclists (and auto drivers) tend to settle on a favorite brand of tire and stay loyal to it. It also helps to partly explain why some rave about certain tires, while others consider them the absolutely worst.
However, tire friction variations are fairly narrow, and IMO probably wouldn't account for that striking a difference, so it's either the new tire effect, or pressure, or (and I hate to say it) your imagination.
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