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Pedagogy: Ross Bentley Speed Secrets

The coaching system is grounded in Ross Bentley's driving curriculum. Coaching is not ad-hoc — every message traces back to a specific pedagogical concept with a telemetry trigger.

Sonoma research applied (2026-04-28)

The pedagogical vectors below are the framework. The applied voice for our Sonoma field test is grounded in three additional sources, all in this docs tree:

  • Sonoma Track Intelligence — per-corner brake refs, gears, common mistakes, and Bentley-flavored technique tips compiled from public sources (Kanga Motorsports, Blayze, lapmeta, Sonoma Raceway).
  • T-Rod Sonoma Coaching Session — verbatim transcript of a T-Rod (pro coach) session at Sonoma in a BMW M3, with structured per-corner extraction. T-Rod's canonical phrasings ("Distance is king", "Just go 100", "Trust the curb", "Wait, you're not at the apex yet") are folded into the intermediate-pod system prompt in src/pitwall/features/coaching/prompts.py (Sonoma track lore lives in src/pitwall/features/track/sonoma.py:SYSTEM_PROMPT_LORE).
  • Track Markers — 16 named landmarks across 8 Sonoma corners ("the bridge", "the bump where the road widens left", "the K-wall bend", etc.) authored from the intel doc and surfaced in CoachContext.next_brake_marker_label. Verified to fire in 42 % of Sonoma pace notes per lap.

Per ADR-005, the vectors below are the schema; per ADR-011, the markers are the surface vocabulary; per ADR-012, LitertCoach (Gemma 4 E2B via MediaPipe Genai) consumes both.

Pedagogical Vector Retrieval

Each coaching concept is encoded as a pedagogical vector: a structured mapping from telemetry conditions to driving knowledge, calibrated for each skill level.

graph LR
    FRAME[Telemetry Frame] --> MATCH[Vector Matcher<br/>find applicable concepts]
    VECTORS[(Pedagogical Vector DB<br/>Ross Bentley curriculum)] --> MATCH
    MATCH --> CANDIDATES[Matched Vectors<br/>ranked by relevance]
    CANDIDATES --> LLM[Gemma 4 E2B / LitertCoach<br/>generate coaching using<br/>matched concepts as context]
    LLM --> MSG[Coaching Message<br/>grounded in curriculum]

Vector Schema

{
  "id": "trail_braking",
  "concept": "Trail Braking",
  "category": "vehicle_dynamics",
  "source": "Ross Bentley, Speed Secrets",

  "trigger": {
    "conditions": "brake > 10 AND abs(g_lat) > 0.4",
    "confidence_required": {"brake": 0.70, "g_lat": 0.80},
    "corner_phase": "entry_to_apex"
  },

  "physics": "Maintaining brake pressure while turning transfers weight to the front tires, increasing their grip. This allows higher corner entry speeds and a tighter line to the apex. The key is a smooth, progressive release of the brake as steering angle increases.",

  "coaching_by_level": {
    "beginner": "Keep some brake on as you turn in. It helps the car turn.",
    "intermediate": "Trail brake to the apex. Smooth release — the front tires need that weight.",
    "advanced": "Trail to apex, {brake_pct}% at turn-in. AJ holds {gold_brake_pct}% here."
  },

  "anti_patterns": [
    {"condition": "brake == 0 AND abs(g_lat) > 0.6", "message": "You released the brake before the corner. Keep some pressure to load the fronts."},
    {"condition": "brake > 50 AND abs(g_lat) > 0.8", "message": "Too much brake in the corner. You're overloading the fronts. Ease off."}
  ],

  "gold_standard_reference": {
    "corner": "Turn 3",
    "aj_brake_at_apex": 15,
    "aj_trail_distance_m": 45
  }
}

Core Pedagogical Vectors

Vehicle Dynamics

Weight Transfer and Traction

Concept: Every input (brake, throttle, steering) causes weight transfer. Weight transfer changes grip per tire. Smoother inputs = less weight transfer = more total traction.

Telemetry trigger: Sudden gLong or gLat spikes (>0.3G change in <200ms) indicate abrupt inputs.

Coaching: - Beginner: "Be smoother with your inputs. Smooth is fast." - Intermediate: "That brake application transferred too much weight. Squeeze the brake, don't stab it." - Advanced: "Load rate {g_dot} G/s. Target <0.5 G/s for smooth transfer."

Traction Circle (Friction Circle)

Concept: The total grip available is a circle in the gLat/gLong plane. You can brake OR turn at maximum, but not both. Trail braking and corner exit throttle trade braking for cornering and vice versa.

Telemetry trigger: sqrt(g_lat^2 + g_long^2) relative to max observed G.

Coaching: - Utilization < 50%: "You're leaving grip on the table. Push harder." - Utilization 80-95%: "Good, using most of the grip available." - Utilization > 100%: "Over the limit — tires are sliding."

Understeer Detection and Correction

Concept: Front tires have less traction than rears. Car pushes wide. Caused by too much speed, too much steering input, or too much throttle transferring weight rearward.

Telemetry trigger: yaw_rate < expected_yaw_from_steering AND steering > 30°

Coaching (from Ross Bentley): - Look where you want to go, not where the car is headed - Ease off the throttle (transfer weight forward) - Straighten the steering slightly (reduce front tire slip angle) - Be patient — wait for weight transfer to take effect

Oversteer Detection and Correction

Concept: Rear tires have less traction than fronts. Car rotates more than intended. Caused by too much throttle (RWD), too much braking, or lift-off mid-corner.

Telemetry trigger: yaw_rate > expected_yaw_from_steering * 1.2 AND speed > 60

Coaching (from Ross Bentley): - Look and steer where you want to go (counter-steer naturally follows vision) - Gently modulate throttle to transfer weight rearward - If power oversteer: ease off throttle smoothly (don't lift abruptly — makes it worse)

Cornering

Reference Points: Turn-in, Apex, Exit

Concept: Every corner has three reference points. Turn-in (start steering), Apex (closest to inside), Exit (use all the track). Late apex is almost always faster than geometric line.

Telemetry trigger: GPS position relative to defined corner geometry.

Coaching: - Early turn-in detected (steering input before turn-in point): "Wait for the turn-in. Patience." - Early apex (car at inside before apex point): "You turned in early. Late apex lets you accelerate sooner." - Not using full track on exit: "Use all the road on exit. The car should track out to the edge."

Exit Speed Over Corner Speed

Concept: Speed on the following straight matters more than speed through the corner. Sacrificing 2mph in the corner to gain 5mph on exit is always worth it.

Telemetry trigger: throttle < 50% at exit point AND speed < gold_standard_exit_speed * 0.95

Coaching: - Beginner: "Get on the throttle earlier as you exit." - Intermediate: "Exit speed matters more than corner speed. Sacrifice entry for a better exit." - Advanced: "Exit speed {speed} vs AJ's {gold_speed}. Throttle pickup is {distance}m late."

The Mental Game

Vision: Look Ahead

Concept: Look as far ahead as possible. Look where you want to go, not where you don't want to go. Turn your head around corners.

Telemetry trigger: This can't be measured directly from vehicle telemetry. Inferred from: - Late braking reactions (reaction time tracking) - Inconsistent turn-in points - Steering corrections mid-corner (suggests the driver is looking at the apex, not the exit)

Coaching: - "Look further ahead. Your eyes should already be on the exit." - "Think through the corner as you look through it."

Gold Standard Integration

Each pedagogical vector can reference the Gold Standard (AJ's reference lap) for concrete comparisons:

graph TB
    FRAME[Driver's Current Frame] --> COMPARE[Compare to Gold Standard<br/>at same track distance]
    GOLD[(AJ's Reference Lap<br/>per-corner telemetry)] --> COMPARE
    VECTOR[Matched Pedagogical Vector] --> GENERATE[Generate Coaching]
    COMPARE --> GENERATE

    GENERATE --> MSG["Turn 3: you braked 15m earlier than AJ.<br/>Trail braking transfers weight forward —<br/>try holding brake to the 2-board."]

The Gold Standard provides concrete, measurable targets. These are real numbers from the Sonoma track definition, auto-generated from the dataset:

Corner Entry km/h Apex km/h Exit km/h Brake Zone Brake Bar Elevation Coaching Focus
Turn 3 104 87 102 50m 12 bar +11m uphill Uphill braking — zone is shorter than expected
Turn 6 92 77 105 86m 29 bar -11m downhill Downhill into corner — brake earlier. Key safety corner.
Turn 9 121 116 132 66m 25 bar -16m downhill Long 288m corner, fast exit onto straight
Turn 10 106 73 108 124m 47 bar flat Heaviest braking corner on Sonoma. Trail brake training ground.
Turn 11 88 64 95 134m 34 bar flat Final corner — exit speed onto main straight is critical

Coaching with real numbers: "Turn 10: typical brake zone starts 124m before entry at 47 bar peak. You braked at 132m — 8m early. Hold to the 124m marker next lap."

Vector Testing

Each pedagogical vector includes test cases (from Pitwall ADR-008 rule testing, adapted):

{
  "id": "trail_braking",
  "tests": [
    {
      "input": {"brake": 25, "g_lat": 0.6, "brake_confidence": 0.95},
      "should_match": true,
      "expected_category": "vehicle_dynamics"
    },
    {
      "input": {"brake": 0, "g_lat": 0.8, "brake_confidence": 0.95},
      "should_match": false,
      "note": "No brake = not trail braking, but should trigger anti-pattern"
    },
    {
      "input": {"brake": 25, "g_lat": 0.6, "brake_confidence": 0.15},
      "should_match": false,
      "note": "Derived brake confidence too low — vector should not activate"
    }
  ],
  "reference_sessions": {
    "sonoma_aj_reference": {"expected_triggers": 8, "tolerance": 2}
  }
}