Brake Pads: Six Friction Rating Bands, Not a Stop Test in Canada
A two-letter friction rating classifies a brake pad’s friction behaviour across a normal (low) temperature band and a high-temperature band, using letters that correspond to specific friction coefficient ranges. The code tells you what the material does under controlled test heat, not how your vehicle will stop in traffic. Use it to match a pad’s temperature profile to your driving style, and treat fitment and vehicle-specific data as the final word on performance.
TL;DR:
- The first letter rates cooler friction and the second hotter friction; EF rises from 0.25–0.35 to 0.35–0.45, while FF stays midrange.
- Choose a higher second letter for towing or mountain descents, but wet or winter driving requires moisture clearing, which the friction code does not measure.
- SAE codes come from controlled Chase machine tests, not vehicle stopping tests; rotor design, airflow, hydraulics, bedding, and batch variation can alter real world torque.
- Bed new pads with the 30/30/30 process, then inspect thickness during routine service; 4 mm remaining has no universal mileage estimate, and fitment is vehicle specific.
Table of Contents
- How to read the two-letter friction code
- Coefficient of friction and temperature behaviour in real driving
- Why testing limits mean edge codes are not a stopping-distance guarantee
- How to choose a pad rating for your driving
- Our HydroAdaptive formulation and where each product line fits
- Three things worth remembering before you buy
- Weather-adaptive pads and rotors built around your driving needs
- FAQ
- Sources
How to read the two-letter friction code
Every disc brake pad sold with an SAE-style edge code carries two letters stamped or printed on its edge, backing plate, or packaging. The first letter describes the pad’s friction coefficient in the normal, or lower, temperature range. The second describes friction behaviour once the pad has heated up under sustained or hard braking. SAE J866 (2019) defines this two-letter system and ties each letter to a specific coefficient of friction band, derived from Chase machine testing under SAE J661.
The letter-to-mu mapping under SAE J866 runs as follows:
- C: friction coefficient of 0.15 or less, rarely used in modern passenger pads.
- D: above 0.15 up to 0.25, a lower-friction band common in some OE light-duty applications.
- E: above 0.25 up to 0.35, a moderate band found in many commuter pads.
- F: above 0.35 up to 0.45, a widely used mid-to-high friction band.
- G: above 0.45 up to 0.55, a higher-friction band favoured in performance and towing applications.
- H: above 0.55, rarely used for street pads due to aggressive bite.
The test temperatures behind “normal” and “hot” readings are sampled points on a Chase machine, not a full simulation of your brake rotor’s heat cycle, which is why two pads with the same letter pair can still feel different on the road. Beyond the two-letter code, you will often find a longer edge-marking string that includes a manufacturer identification code, a formulation number, a batch code, and environmental markings such as low-copper designations. These extra marks help technicians trace a specific production run, but they do not change what the two main letters tell you about friction behaviour.
Coefficient of friction and temperature behaviour in real driving
Coefficient of friction, or mu, is the ratio of stopping force a pad generates relative to the clamping pressure applied to it. Peak friction coefficient (PFC) describes the highest friction value reached during a test cycle, a concept that Transport Canada’s Technical Standards Document uses when evaluating braking performance at the vehicle level rather than at the pad level alone.
A pad coded GG, for example, sits in a high mu band at both normal and high temperatures, according to the SAE J866 letter-to-mu table, meaning it holds a strong, consistent bite whether cold or hot. A pad coded EF starts in a moderate 0.25 to 0.35 band when cool and climbs into the 0.35 to 0.45 band once hot, giving gentler cold bite with firmer response as the brakes build heat. FF pads hold a steady mid-range bite across both conditions, which suits drivers who want predictable pedal feel without an aggressive cold grab.
Different driving patterns call for different letter pairs:
- Daily commuting in city traffic suits balanced mid-letter pads like EF or FF, where cold bite and everyday stopping power matter more than sustained high-heat stability.
- Towing or carrying heavy loads benefits from a higher second letter, such as FG or GG, since sustained braking under load pushes pads into the high-temperature band more often.
- Spirited or mountain driving favours pads with strong hot-band stability to resist fade on long descents.
- Winter and wet-weather driving calls for pads engineered to clear moisture quickly, since a technically correct letter rating does not account for how fast a pad sheds water film.
Why testing limits mean edge codes are not a stopping-distance guarantee
The letter code comes from a Chase machine test, a small-scale friction test described under SAE J661 that measures material friction under controlled, repeatable conditions. It is useful for comparing formulations, but SAE J866 (2019) itself cautions that these edge codes classify a friction material and are not a substitute for vehicle-specific performance testing. A more complete picture comes from dynamometer procedures such as SAE J2522, which measures friction behaviour across a range of temperatures, pressures, and speeds rather than at isolated sample points.
Real-world variability compounds this gap. Industry reporting on brake lining friction documents that torque output between formulations and even between production batches of the same formulation can vary considerably, so two pads sharing an edge code will not always deliver identical stopping torque. On top of material variability, several vehicle-level factors shift real-world results:
- Rotor design and mass affect how quickly heat dissipates from the friction surface.
- Cooling airflow around the caliper and rotor changes how fast a pad moves between temperature bands.
- Hydraulic system layout and brake-proportioning valves affect how much clamping force reaches each pad.
- Proper bedding-in and ambient environmental conditions both influence the friction surface a pad presents to the rotor.
Pro Tip: When torque or dynamometer data is available from a supplier, use it alongside the letter code rather than in place of it, since torque figures reflect tested performance rather than a material classification alone.
How to choose a pad rating for your driving
Matching a rating to your driving style starts with an honest look at how you use your vehicle, followed by a short bedding-in process and ongoing wear checks.
- Match the letter pair to your driving profile: choose balanced mid-letter pads for city commuting, a higher second letter for towing or mountain driving, and moisture-clearing pads for wet or winter climates.
- Bed the pads in properly: the commonly recommended 30/30/30 burnish process, 30 stops at low to moderate speed, 30 at moderate speed, and 30 with gradually increasing load, helps transfer an even friction layer onto the rotor before you rely on full braking force.
- Track remaining pad thickness: pad life to a 4 mm wear point depends heavily on driving style, rotor condition, and climate rather than on the letter rating alone, so check thickness during routine service rather than by mileage alone.
- Confirm vehicle-specific fitment: check which brake pads suit your car before buying, and plan for a professional rotor and pad match if you tow or carry heavy loads regularly.
Pro Tip: If you are unsure whether your driving qualifies as heavy-duty, err toward a higher-stability hot-band rating rather than the lightest option available.
Our HydroAdaptive formulation and where each product line fits
We built our HydroAdaptive ceramic technology to address a gap the friction letter code does not cover: how quickly a pad clears moisture from its surface. A letter rating tells you about dry friction bands, but it says nothing about wet-weather lag, which is the delay between pedal application and full friction engagement when water sits on the rotor surface. Our formulation is designed to clear that moisture rapidly and maintain consistent friction through rain, humidity, and snow.
Within our lineup, each product line maps to a different driving need:
- Type 03 Brake Pads suit everyday commuting and light-duty driving where balanced, predictable friction matters most.
- Type 07 Brake Pads are built for winter-ready and higher-moisture conditions where rapid water clearing counts.
- Some rotors pair with brake pads to support even bedding and resist corrosion across seasonal conditions.
If you want the material science behind how coatings and formulations affect friction behaviour, our piece on brake pad friction, test codes, and mu behaviour goes deeper into the chemistry.
Three things worth remembering before you buy
Read the code first, then match that rating to how hot your brakes actually run given your driving style, not the other way around. When towing, driving mountain routes, or facing persistent wet weather, lean toward a higher-stability hot-band rating and confirm pad-to-rotor compatibility rather than assuming any pad with a matching letter will perform the same. If you remain unsure which rating fits your vehicle, a guide to choosing the right brake pads or a conversation with a qualified technician beats guessing.
— AAA
Weather-adaptive pads and rotors built around your driving needs
Choosing a friction rating tells you how a pad behaves on a test bench. Choosing the right AAA Frictions product tells you how it behaves on your actual commute, in your actual weather. Our Type 03 Brake Pads suit everyday driving where balanced bite and quiet operation matter most, while our Type 07 Brake Pads are engineered for winter and high-moisture climates where rapid water clearing keeps your pedal feel consistent. Pair either line with our SC Type Rotors or GC Type Rotors for corrosion resistance and even bedding across seasons.
For readers finishing a brake job and wondering how to keep wheels looking clean afterward, our partners at Diamondbrite explain safe brake dust removal with a short dwell time that will not strip wheel coatings.
Browse our vehicle-specific brake kits to find the pad and rotor pairing built for your climate and driving style.
FAQ
What does the friction rating on brake pads mean?
The two-letter friction rating classifies a pad’s coefficient of friction in a normal temperature band (first letter) and a high-temperature band (second letter), based on SAE J866 test standards. It identifies the friction material, not a guaranteed stopping distance for your specific vehicle.
How long will 4 mm last on brake pads?
Remaining pad life at 4 mm thickness depends on driving style, rotor condition, climate, and how the vehicle is used rather than on the friction letter alone. There is no single mileage figure that applies across vehicles, so checking thickness during routine service gives a more reliable answer than estimating by distance driven.
What is the 30/30/30 rule for brakes?
The 30/30/30 rule is a commonly recommended bedding-in process for new pads and rotors: 30 stops at low to moderate speed, 30 stops at moderate speed, and 30 stops with gradually increasing load. It helps transfer an even friction layer onto the rotor surface before the brakes are used at full force.
Are AAA Frictions brakes good?
Our HydroAdaptive ceramic pads are engineered to clear moisture rapidly and maintain consistent friction across rain, humidity, and snow, addressing a gap that standard friction ratings do not cover. Our Type 03 and Type 07 lines are built for different driving conditions, from everyday commuting to winter-ready performance.
Do higher letter ratings always mean better brake pads?
A higher letter indicates a higher coefficient of friction band, not an automatic performance upgrade for every driver. The right rating depends on your vehicle, driving style, and operating temperatures, which is why matching the code to your use case matters more than chasing the highest letters available.
Sources
- SAE J866 (2019) — Friction coefficient identification and environmental marking system for brake linings
- Technical Standards Document No. 135 (Revision 5) — Canada
- The break shop: Brake linings – Fact and friction | Truck Parts & Service