Every serious sim racer eventually has the same moment: you know you're half a second off your best lap, you can feelthat it's somewhere in the middle sector, and you have absolutely no idea what you're doing differently. You drive another twenty laps changing random things. Sometimes it gets better. You don't know why.
The delta trace answers that question in one glance — if you know how to read it.
What a delta trace actually is
A delta traceplots the running time difference between two laps at every point around the circuit — usually your current lap against your best. Above zero means you're slower than the reference at that point; below zero, faster. The line's value tells you the damage so far; the line's slope tells you where the damage is happening right now.
The three shapes that matter
1. The cliff before the corner.The delta jumps sharply in the braking zone. You braked earlier (or softer) than your reference lap. This is the easiest time to find on any track — it's pure commitment. If the line jumps 0.3s in one braking zone, that's 0.3s that requires no new skill to recover: same brake pressure, a few metres later.
2. The slow bleed through the corner. The delta climbs gently from turn-in to exit. Your minimum speed is lower — you over-slowed the car. Counter-intuitively, this often happens on laps where the braking felt great: you braked late and hard, upset the car, and paid through the whole corner. A late brake point that costs you apex speed is a bad trade almost every time.
3. The long shallow ramp on the straight. The delta creeps up for hundreds of metres after a corner. This is an exit problem: you got to full throttle later, and the gap compounds all the way down the straight. Exit losses look small in the corner and enormous by the end of the straight — which is why the classic advice holds: fix the corner that leads onto the longest straight first.
A real example
Here's the kind of read this makes possible. In one of our own Spa sessions, the delta showed a 1.59-second loss concentrated in a single corner — but the braking point was later than the reference lap and the throttle came earlier. Cliff shape? No. Bleed shape? Yes: apex speed was down and the car was unsettled mid-corner. The fix wasn't the brake marker; it was calming the entry so the middle of the corner worked again. Twenty laps of guessing, replaced by one look at one chart.
Reading it without doing the homework
You can do all of this by eye — or you can have it done for you. MyRacingData captures your laps at up to 120Hz, draws the delta against your best automatically, breaks every corner into braking point, apex speed and throttle commitment, and then its AI race engineer writes you the plain-language version: where you lost time, why, and what to try next lap.
There's a real session with a real debrief you can poke at, no account needed: see a live example — or start free and see your own.