Defending makes an overtake harder without blocking. What the DMSB allows, how to close the inside line before the braking zone and what is not allowed.
Defending means: you make an overtaking attempt harder by closing the inside early, without obstructing or pushing the other driver. The honest answer to "What may I do?": less than many think. The DMSB regulations are clear here, and violations can be punished with a scoring penalty [1].
The rule in brief: a kart may use the whole width of the track. Any driving that could obstruct others is forbidden, for example more than one change of direction on a straight to defend a position, pushing a kart off, or any unusual change of direction. In the braking zone before a corner a change of direction to prevent an overtaking move is not permitted [1]. "Zigzagging" or a line change against an overtaking move already begun is forbidden [1].
From research comes a frame: a paper on training racing drivers names "defend-ability" as one of three basic possibilities of racing next to cornering and overtaking. It is constrained by rules, condition of kart and tyres, track condition, the speed of both karts and the type of the next corner [2].
Good defending is leaving room, not taking room.
Entry criteria (practice standard):
The first step is not about driving. You know the regulation passages on overtaking, pushing off and braking zone by heart [1]. The DMSB has scoring penalties for this and, for unsporting behaviour, the black-and-white flag [1].
Milestone: You name the three prohibitions (more than one change of direction, pushing off, change in the braking zone) from memory.
A defence begins before the braking zone, not in it. The line with which you close the inside you choose on the straight before, in one single movement. After that you stick with it. That also matters for feel: whoever changes line twice on the straight shows uncertainty to the attacker and tempts him into risky attempts. That is coaching practice.
Milestone: You make the decision on the straight and carry it out without a second change of direction.
The research paper on training racing drivers stresses that defenders should perceive the attacker's possibilities: his speed, his position, the next corner [2]. You see where he lines up and act accordingly.
Milestone: In a defending situation you name which line the attacker might choose.
If two karts drive side by side, each must leave at least one kart width to the track limit [1]. That is not an option but an obligation.
Milestone: In a side-by-side situation you leave enough room on the outside and stay on the track.
Duels are stressful. In a field study heart rate in a kart race averaged 168.8 beats per minute, clearly above the solo value of 140.9 [3]. Whoever is under pressure makes poorer decisions. Breathe, look ahead, stick to your plan. After a duel you give yourself a review: what did you decide, when, and what was the price? A video of the race helps more than your memory.
Milestone: You drive a duel over three laps without changing line frantically.
Most accidents happen in duels: in a US analysis of emergency departments, collision with another kart was the most common injury mechanism overall (29.6%), and 43.7% of those collisions involved the head [4]. So for duels:
This guide explains and motivates, it does not replace training with a coach on the track.
Practise defending with a trusted partner and a clear agreement: he attacks fairly, you defend fairly, then you swap and review on video where there was room. That way you learn to read the attacker's line without risking penalties. That is coaching practice, not a study finding.
Under the DMSB regulations not more than one change of direction on a straight to defend a position [1].
No. In the braking zone before a corner a change of direction to prevent an overtaking move is not permitted [1].
If two karts drive side by side, each must leave at least one kart width to the track limit [1].
For caused contact the race director can impose a scoring penalty, and the stewards can impose further penalties [1].
A paper on training racing drivers describes defending as one of three basic possibilities and names rules, tyre condition, track condition, speeds and the next corner as constraining factors [2].
Karting for Beginners: How to Start, What Rental and Your Own Kart Cost — and Why It Is a Real Sport