How it works

1. Read the laps

   Garage61 records iRacing's telemetry 60 times a second: speed, pedals, steering, gear, revs, ABS, g-forces, yaw and position.

2. Line them up metre by metre

   Both laps are put on the same 1 m grid around the track, so every point of your lap has a matching point on theirs. The time gap is known at every metre.

3. Find the corners

   Corners are found from where the faster lap brakes or lifts and where it's slowest. They're named from real track maps where known (48 layouts so far), otherwise numbered.

4. Measure each corner

   Brake point, peak brake, how long you brake, turn-in and apex speed, coasting, when the throttle comes back, how fast you get to full throttle, exit speed and gear.

5. Turn differences into findings

   Only differences above set thresholds count (10 m in brake point, 3 km/h in speed, 15 m in throttle), and only in corners that cost time. The corners losing the most come first.

6. Write the tips

   Each finding has a plain-English template with its numbers: what you did, what they did, what to try.

iRacing's position data is exact to the simulation, not real-world GPS, so lines can be compared to within centimetres. For every point of your lap, the app finds the nearest point of their line and measures the distance across the track. Per corner it takes the typical gap at turn-in, at the apex and on exit, and whether you're towards the inside or the outside.

The path the car takes (its yaw rate divided by speed) needs a certain amount of steering. On the lap's gentle bends, where the tyres have grip to spare, the app learns how much steering this car needs for a given path: that's the car's neutral. Under load, using more steering than that for the same path is understeer, and less, or opposite lock, is oversteer.

Because it calibrates on your own lap, it works for any car. It's relative, though: it finds where the car is looser or pushier than elsewhere on the lap. A car that's equally loose everywhere looks balanced, which is why the wizard asks how the car feels.

Being slower on a straight has two causes: leaving the corner before it slower, or more drag. Comparing top speeds can't tell them apart, because a better exit carries on all the way down the straight. So the app looks at the top end only: how many metres each car needs to gain the same 50 km/h below its top speed. Drag decides that part, whatever the exit was.

A tow also gains speed in fewer metres. That's why the app uses your typical lap over a session and flags laps that look towed.

Fuel per lap:

the typical (median) fuel used on your clean, full-speed laps, and the safe figure that 90% of laps stay under.

Stops:

fewest stops that cover the race, with the formation lap on the first tank and the spare on the last.

Many circuits are mapped in OpenStreetMap with their track sections named after the corners (“Eau Rouge”, “Druids”). iRacing's positions match the real map to a few metres, so each corner is named after the section its apex lies on. Circuits with no names in the map were named by hand. Corner names © OpenStreetMap contributors (ODbL).