Brake System Bedding Log — Documentation

• Green — 0 to 5,000 km after new brake installation

  Without a completed bedding log, you have no baseline. If judder or noise develops, you cannot distinguish between a bedding failure, a defective part, or a mechanical issue. Warranty claims on brake pads (typically 12 months / 20,000 km with major brands like Ferodo, Brembo, or EBC) require proof of correct installation and bedding procedure.

• Amber — 5,000 to 15,000 km, inspection due

  Without a logged start mileage, you cannot calculate actual wear rate. E46 front pads typically last 25,000–40,000 km depending on driving style. Without the baseline, you may change pads too early (wasted money) or too late (disc scoring). The 3 mm minimum pad thickness warning is useless without knowing where you started.

• Red — 15,000 to 30,000 km, untracked wear

  Undetected glazed pads (result of improper bedding) cause disc surface hardening and micro-cracking. On the E46, this accelerates disc warping — a known failure mode on the front vented discs, which are vulnerable to thermal shock. Replacement cost climbs from a pad swap (~€60 DIY parts) to a full axle disc and pad replacement (~€180–280 DIY parts).

• Black — 30,000 km+ without any service record

  Complete loss of brake service history. In the Netherlands and Germany, a BMW E46 without documented brake service history loses resale value and may fail the APK/HU technical inspection if disc thickness is at or below minimum and no measurement record exists. More critically, a brake system operating on unknown wear status presents genuine accident risk on a platform producing up to 343 hp (M3 variant) with no electronic torque vectoring safety net.

• When you perform your first bedding stop sequence, you will smell the pads. This is normal and expected — it is the binding resins in the pad compound curing under heat. First-timers often panic and stop the car immediately, which is exactly wrong: stopping on a hot disc while stationary causes a heat impression of the pad shape into the disc surface, creating the very judder you are trying to avoid. The smell is a process, not an emergency.
• After the bedding cycle, when you examine the discs, you will see a blue-grey iridescent haze on the swept area of the disc face — this is the transfer film of pad material. On a correctly bedded pair of discs, this haze will be continuous, even in colour, and will extend fully across the swept area with no bare silver patches. If you see concentric rings of shiny metal alternating with grey deposits, the bedding was interrupted or done at too low a temperature.
• The first 2–3 applications of the brake pedal after the bedding cycle will feel firmer and slightly different from the last stop of the cycle. This is because the pads and discs have contracted as they cooled and the transfer film has hardened. This is correct. What is NOT correct is if the pedal feels spongy or travels further than before bedding — that indicates air in the system introduced during the pad/disc swap, and you must bleed the brakes before logging the bedding as complete.
• On E46s with more than 100,000 km on the odometer, you will almost certainly find that the brake pad wear sensor clip holes in the front caliper carrier are corroded or stripped. The new pad wear sensor (if included in your parts kit) may not clip in securely. Do not ignore this — a loose sensor will rattle against the disc and be logged as abnormal noise during bedding when it is actually a fitting issue.
• The most common mistake on this exact task is performing the documentation AFTER the bedding cycle without having recorded the starting odometer reading BEFORE the drive. Without the pre-bedding mileage, you cannot calculate the exact km at which bedding was completed, and your wear tracking baseline is offset. Write the starting odometer in the log BEFORE you leave the driveway.

To verify correct parts before beginning: (1) PADS — Compare the new pad's overall width, height, and backing plate thickness against the old pad. E46 front pads should have a backing plate width of approximately 130–132 mm for most variants; M3 front pads are wider at approximately 147 mm. The friction material on a new pad should measure 10–12 mm thick. If it measures less than 8 mm, suspect you have received used or incorrect stock. Check the part number on the pad box against the brand's online fitment guide using your exact chassis code (e.g. E46/4, E46/2C for M3). (2) DISCS — The disc diameter must match: standard E46 fronts are 286 mm (316i/318i) or 300 mm (320i/323i/325i/328i/330i) or 325 mm (M3). Measure with a tape measure across the face. Minimum thickness is stamped on the disc hat — confirm the new disc is at or above that by 6–8 mm (new discs for standard E46 fronts are typically 22–28 mm thick depending on variant). The disc box label should show the vehicle application. (3) SENSORS — If your kit includes a pad wear sensor, confirm the connector colour and shape matches the old sensor. E46 typically uses a 2-pin grey connector on the front left. Common mis-ordering error: buyers of E46 Touring (wagon) variants sometimes receive saloon-spec rear pads; rear pad dimensions differ between body styles on certain build years. Verify body style in your VIN decode before ordering.

• Pen and dedicated service logbook (physical)
  Any waterproof or laminated logbook; alternatively a locked notes app on your phone with date/time stamps
  Physical logbook is preferable — digital logs on phones are frequently lost when phones are replaced. Write in permanent marker or ballpoint, not pencil. A BMW service book (Serviceheft) is the ideal place if your car still has one.
• Digital odometer reader or note of dashboard mileage
  BMW E46 odometer reads in km in NL/DE market; confirm you are reading km not miles if the car was imported from the UK
  Take a photo of the odometer on your phone before the bedding drive and after. This gives you a timestamped, irrefutable record of start and end mileage.
• Smartphone camera
  Any modern smartphone; minimum 8 MP for disc surface detail
  Photograph both disc faces (left and right) after bedding from a 45-degree angle in good lighting. The transfer film pattern is visible in photos and becomes your baseline reference for future inspections.
• Torque wrench (for pre-bedding verification of wheel bolts)
  1/2-inch drive, 0–200 Nm range; calibrated
  Before the bedding drive, re-torque all wheel bolts. Use a 6-point 17 mm socket only — 12-point sockets round E46 wheel bolt heads. Apply torque in a star pattern, not a circle. The click of the wrench should come smoothly as tension builds — if a bolt reaches the click value with very little rotation, the bolt was already at or over torque. If it spins without resistance before clicking, the thread is damaged — stop and assess.
• Nitrile gloves
  Minimum 0.15 mm wall thickness; disposable
  Wear during disc and pad handling. Skin oils contaminate brake disc surfaces and create localised high-friction spots that disrupt even transfer film deposition during bedding.
• Safety glasses
  EN 166 rated
  Required during any inspection of brake components. Disc dust contains iron particles.

• Brake pads (front axle set) — E46 variant-specific
  • OEM / BMW Genuine — Supplied by Textar or Jurid under BMW part number — highest confidence in E46 fitment and bedding behaviour. Most expensive but zero fitment risk.
  • OEM-equivalent (Recommended) — Ferodo DS2500 or EBC Greenstuff for road use; Pagid for standard use. These brands supply to BMW as OEM and are available in NL/DE BMW specialist shops for €35–65 per axle set.
  • Budget — Unbranded or Aliexpress-sourced pads. Avoid — friction coefficient is inconsistent, bedding is unpredictable, and there is no warranty path.
• Brake discs (front axle pair) — E46 variant-specific diameter
  • OEM / BMW Genuine — Brembo or ATE-sourced under BMW label. Correct metallurgy for E46 thermal cycles.
  • OEM-equivalent (Recommended) — ATE PowerDisc (slotted) or Brembo standard discs. Widely available in NL/DE at €45–90 per pair. ATE is the original E46 supplier.
  • Budget — Unknown-brand discs are prone to premature warping on the E46 — the most reported outcome in E46 owner forums after budget disc fitting.
• Brake pad wear sensor — front left (if not reusing)
  • OEM-equivalent — ATE or Bosch sensors for E46 are €8–15 and fit correctly. Always replace if the old sensor shows any fraying or the connector housing is cracked.
• Copper-based brake anti-squeal paste (Kupferpaste)
  • Standard — Liqui-Moly or Würth copper paste. Apply to pad backing plates and caliper slide pins only — never to friction material. €5–10 per tube, available at every German/Dutch auto parts retailer.

• Check
  Pedal feel after bedding cycle cool-down — sitting in the car with engine running, press the brake pedal firmly and hold for 30 seconds
  Expected

  Pedal should be firm within the first 30–40 mm of travel and should not continue to sink toward the floor during the 30-second hold. Pedal height should be consistent between the first and tenth press of the sequence.
  If wrong

  A pedal that sinks during hold indicates hydraulic leakage or air in the system. A pedal that pumps up (gets firmer with repeated presses) indicates a failing master cylinder. Do not drive until diagnosed. Bleed the brakes at the affected caliper first and retest.
• Check
  Disc face visual inspection after 30-minute cool-down — examine swept area through wheel spokes on all four corners
  Expected

  A continuous, grey-blue iridescent haze covering the full swept area of both discs on the same axle. Left and right discs on the same axle should look nearly identical in film distribution. No bare silver patches, no concentric rings, no brown or purple discolouration.
  If wrong

  Bare patches or rings indicate an interrupted bedding cycle — repeat the cycle. Brown/purple discolouration indicates overheating — inspect for seized caliper and check pad compound specification against your usage profile.
• Check
  Wheel bolt torque verification on all four wheels after bedding drive
  Expected

  All bolts accept 120 Nm smoothly and the wrench clicks cleanly. No bolt reaches the click instantly (already overtorqued) and no bolt spins without resistance (thread failure).
  If wrong

  Any bolt that does not accept torque correctly must be investigated before the car returns to road use. An overtorqued bolt: back off by 30 degrees and re-torque. A spinning bolt: remove the wheel, inspect the stud — if the stud thread is stripped, the hub must be repaired before driving.
• Check
  Brake fluid level in reservoir after bedding drive
  Expected

  Fluid level should be between MIN and MAX markings — typically closer to MIN when new (thicker) pads are installed, as the caliper pistons are fully retracted. If the fluid level is above MAX, suspect the pistons were not fully wound back during installation.
  If wrong

  Fluid above MAX: DO NOT remove the cap and siphon — this can introduce air. Instead, re-inspect whether the caliper pistons are fully retracted. If the pads are new and the pistons were correctly wound back, the fluid level should drop to near MAX. Fluid below MIN after bedding suggests a leak — inspect all caliper bleed nipples and hose connections immediately.
• Check
  Log entry completeness check — review the written log against the checklist
  Expected

  Log contains: date, start odometer, end odometer, pad brand/part number, disc brand/part number/diameter/minimum thickness, sensor replacement noted, installation conditions, bedding cycle description, disc face condition, pedal feel rating, any anomalies noted, signature.
  If wrong

  Any missing field should be completed before filing the log. If you cannot recall a specific value (e.g. exact end odometer), note the approximate value and flag it as estimated. An incomplete log is better than no log, but a complete log is the professional standard.