New tyres are lethal when first fitted!
In very basic terms tyres are made by injecting liquid rubber into a mould, to stop the rubber sticking to the mould the mould has to be coated with a release agent.Some of that release agent gets into the top surface on the tyre, so untill the road has worn away the surface of the tyre on wet roads it can be like driving on ice!
Every new tyre regardless of brand has this problem, from the most expensive brand name to the cheapest budget they all have a coating that needs to be worn off. Even on a dry road the coating and deep tread pattern can reduce grip by as much as 50% over an old bald tyre, think how much of the tyre is actually in contact with the road? it is probably less than the sole of your shoe, the tread pattern reduces that still further. Thats why racing cars use slick tyres in dry conditions so that the maximum amount of rubber is in contact with the road, the tread only helps in wet weather.
You need to drive at least 100 miles before a new tyre will grip as it should and during that time you should be cautious especially in wet conditions, if your car's tracking is out or you have lowered the suspension it will make matters worse.