The F1 dictionary: U

Ultrasoft tyre

The new-for-2016 fifth slick compound which will become the fastest tyre in Pirelli's range. Will be marked with a purple stripe and is expected to be used at street track-style venues like Monaco.

Undercut

The term used to describe a car pitting ahead of a rival ahead for fresh tyres in order to take advantage of any subsequent tyre performance drop-off suffered by the latter and take the position. See also: Pirelli; Tyres.

Understeer

The performance characteristic featuring a lack of grip in a car's front wheels when its driver steers through a corner. See also: Oversteer.

Understeering

The performance phenomenon that occurs when a car turns by less than the amount by which it is being steered on account of the front tyres losing their grip before the rears. See also: Oversteering.

Unpredictable

The word used more than any other to describe the start to the 2012 season when seven different drivers won the first seven races. Less so 2015.

Unsafe release

What race stewards investigate drivers and teams for whenever a car leaves its pit box and either collides, or nearly does, with a rival.

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