Most EV owners go days without really using their brake pedal. Lift off, the car slows, the battery gets a little back. So it's fair to ask whether the brakes on an electric car even matter. They do, and in a couple of ways they matter more than on a petrol car. Here's what's actually going on under the wheel arches, written for someone about to buy one in Australia.
Key Takeaways
- Regen is the everyday brake, not the emergency brake. Volkswagen, Bosch and ZF quote roughly 0.25 to 0.3 g from regen alone. The legal minimum for a cold-brake stop from 100 km/h works out to about 0.66 g.
- The law keeps friction brakes in charge. ADR 31/04 adopts UN R13-H, which requires the friction brakes to stay connected and do the job alone, and tests them with the battery at or near full so regen can barely help.
- Speed is the big number. Kinetic energy rises with the square of speed. Going from 100 to 110 km/h adds 21% more energy to get rid of.
- A full or cold battery limits regen. Plan big descents, especially when towing, around that.
- EV brakes rust from disuse. Use the pedal properly now and then, and follow your logbook for fluid and inspections.
Rules referenced here are current as of 1 October 2026
ADR 31/04 is quoted from the Federal Register of Legislation and Euro 7 from EUR-Lex. Check the current version before relying on either.
Start with the physics: speed is the thing
Braking is energy disposal. A moving car carries kinetic energy, which is half its mass times its speed squared. That squared bit is the whole story.
Take a 2,000 kg EV. At 60 km/h it carries about 278 kilojoules. At 100 km/h it's about 772 kJ, nearly 2.8 times as much, even though the speed only went up by two-thirds. To hit that same 772 kJ at 60 km/h, the car would need to weigh around 5,560 kg.
Put another way: add 10% more mass and the energy goes up 10%. Add 10% more speed and it goes up 21%. EVs are heavy, and that matters, but speed is the bigger lever.
All that energy has to go somewhere. Regen turns some of it back into electricity. Whatever regen doesn't take, the friction brakes turn into heat.
What regen does, and where it runs out
When you lift off or press lightly, the motor switches to generating and slows the car. Bosch describes it simply: when you need more braking torque than the generator can give, the friction brakes add the rest.
How much can regen do alone? Volkswagen says the ID.4's motor handles braking by itself up to around 0.25 g, which covers most everyday braking. Bosch and ZF both quote about 0.3 g for regen with their systems. That's plenty for traffic, and nowhere near an emergency stop.
There are four situations where the friction brakes carry the load:
- Hard and emergency stops. Bosch lists very rapid deceleration as one of the times the friction brake is used. The regulation's pass mark for a cold-brake stop from 100 km/h is a mean deceleration of 6.43 m/s², about 0.66 g, more than double what regen offers.
- A full or cold battery. Volkswagen puts it plainly: if the battery is fully charged, it can't store any more recovered energy. Tesla's Australian manual says regen may be limited if the battery is cold or full, and that the car then applies the regular brakes automatically so lifting off still feels the same.
- Very low speed and standing still. Bosch also names very low speeds and stationary as friction-brake territory.
- Stability control. The brake rule defines "selective braking" as automatic braking of individual wheels to change how the car behaves. ADR 31/04 also requires cars certified to it to be certified to the ESC and brake assist rules.
One nice detail: regen that slows you firmly has to light your brake lights. Under the rule, if lifting off decelerates the car by more than 1.3 m/s², the stop lamps must come on. At 0.7 m/s² or less they must not.
Why the law won't let regen replace friction brakes
Australia's passenger-car brake rule is ADR 31/04, which has applied to new models since 1 July 2019. Its technical content is UN Regulation 13-H, printed in full as Appendix A. Three parts of it settle the question:
- The service brakes must act on all wheels.
- Where regen is part of the service brakes, it may drop out, but only if the friction brakes stay permanently connected. In all cases, the friction side must keep the service and secondary brakes working to the prescribed standard.
- The standard stopping test is run with the battery at the maker's maximum recommended charge or at least 95% full, or with regen switched out. In other words, the car must pass on friction brakes, because a full battery gives regen almost nothing to do.
So a road car here can't legally rely on regen to stop; it's written into the rule. The same rule also says the anti-lock system must control the electric braking, so ABS manages regen too.
How your pedal talks to the brakes
"Brake blending" is the job of splitting each stop between motor and friction brakes so you can't feel the seam. Volkswagen says on the ID.4 the handover from generator to hydraulic braking goes almost unnoticed. How a car does that depends on its actuation hardware. Broadly, there are four types:
| Type | How it works | Supplier example |
|---|---|---|
| Hydraulic with electric booster | Pedal still pushes a master cylinder; an electric motor provides the boost instead of engine vacuum | Bosch iBooster |
| Integrated electro-hydraulic | Brake boosting and stability control combined in one electro-hydraulic unit | Bosch Integrated Power Brake, ZF IBC |
| Full brake-by-wire (hydraulic at the wheels) | Pedal is decoupled from the brake circuits and feeds a pedal-feel simulator; a controller sets the regen and hydraulic split | Bosch IPB, which Bosch describes as brake-by-wire |
| Dry electromechanical | No brake fluid at all; an electric motor at each wheel makes the clamping force | ZF electromechanical brake |
You'll see these names in Australian spec sheets. Hyundai lists an "active hydraulic booster (regenerative braking)" for the Hyundai IONIQ 5 RWD and an "Integrated Electronic Brake (IEB)" for the Hyundai IONIQ 5 N (N AWD). MG's IM6 spec sheet lists a "Brake-By-Wire Cooperative Regenerative Brake System" across the range, including the MG IM6 Premium 75 RWD. Polestar's Australian spec page lists a brake-by-wire system with Brembo brakes on the Polestar 3 Rear Motor and its siblings.
Is by-wire a worry? It has to pass the same rule. R13-H adds requirements for brakes with an electric control transmission: a single temporary failure of up to 40 milliseconds must have no distinguishable effect on braking, failures must trigger a red or yellow warning, and if the service braking can't be met, the secondary braking level must still be there through the pedal. ZF's pitch for the dry version is that pads barely drag when released, so there's less wasted energy and less brake dust, and no brake fluid to change.
The hardware: discs, drums and calipers
Disc materials
- Cast iron. The conventional disc. Porsche describes its carbon-ceramic brakes as an alternative to the cast iron used in conventional discs.
- Coated cast iron. Porsche's Surface Coated Brake is a cast-iron disc with a tungsten-carbide coating. Porsche says it produces 90% less brake dust than a grey-iron brake, lasts 30% longer and doesn't rust.
- Carbon-ceramic. Porsche says its ceramic composite discs save around 50% of the weight of cast-iron brakes and hold stable friction through repeated high-speed stops.
Floating versus fixed calipers, and why piston count isn't a score
A floating (or sliding) caliper has its piston on one side; the body moves to bring the outer pad in. ZF's workshop guidance literally refers to the "piston side" of floating calipers. A fixed caliper stays put and has opposed pistons on both sides. Brembo says opposed pistons give even brake force distribution, greater stiffness and uniform pad wear.
That's the real point of more pistons: spreading the clamp evenly over a bigger pad and keeping things stiff. It isn't a stopping-distance rating. A four-piston badge tells you how the clamping load is spread, not how quickly the car stops. In a real emergency stop the ABS is modulating pressure to the grip the tyres have, as Tesla's manual describes, so the tyre and the whole system decide the result. Hyundai's own IONIQ 5 N sheet mixes both: four-piston monobloc calipers at the front and single-piston sliding calipers at the rear.
Why some EVs have rear drums
Volkswagen's Australian ID.4 and ID.5 spec brochure lists ventilated discs at the front and drums at the rear for both the Volkswagen ID.4 Pro and the Volkswagen ID.5 GTX. VW's reasoning: the pads are designed to last the life of the car, and corrosion isn't an issue even though the brakes are rarely used in everyday driving. Brake supplier HELLA adds that drums cost less to make, save weight and, thanks to a self-reinforcing effect, give more braking for less actuation effort.
What do you trade away? The drum is enclosed, so you can't eyeball its friction surface through the wheel the way you can a disc. And the design leans on regen doing most of the work, which is exactly what you lose with a full battery at the top of a long hill. They still have to pass ADR 31/04 like anything else.
How common are they in our data? Of the 307 electric rows we list as on sale, only 29 record a rear brake type at all. Five of those say drum: the ID.5 GTX and four Hyundai Mighty Electric light-truck rows. That's a gap in our data, not a count of the market, so check the spec sheet for the exact variant.
What the makers' own Australian documents say
| Car | Actuation | Front | Rear |
|---|---|---|---|
| Hyundai IONIQ 5 RWD | Active hydraulic booster | Ventilated disc, 345 x 30 mm | Ventilated disc, 345 x 20 mm |
| Hyundai IONIQ 5 N (N AWD) | Integrated Electronic Brake | Ventilated disc, 400 x 34 mm, 4-piston monobloc | Ventilated disc, 360 x 20 mm, single-piston sliding |
| Volkswagen ID.4 Pro | No data | Ventilated discs | Drums |
| MG IM6 Premium 75 RWD | Brake-by-wire (CRBS) | Ventilated disc, Continental 4-piston fixed | Ventilated disc |
Sources: Hyundai Australia IONIQ 5 and IONIQ 5 N specification sheets, Volkswagen Australia ID.4/ID.5 MY25 spec brochure, MG Australia IM6 specifications sheet.
Heat and fade
Fade is what happens when brakes get hot enough to lose bite. The Australian rule tests for it directly: the Type-I test heats the brakes with 15 stops, one every 45 seconds, from 80% of top speed (capped at 120 km/h) down to half that. Hot performance must then be at least 75% of the required figure and at least 60% of the car's own cold result.
EVs can help themselves here. Hyundai lists "Regen Brake Maximisation" on the IONIQ 5 N to minimise brake fade, and Tesla's manual describes hydraulic fade compensation that adds brake pressure if it detects reduced performance from fade or cold, wet conditions.
Rust, dust and Euro 7
The weird EV problem is brakes that don't get used enough. Tesla's Australian manual says the pads are used less often because of regen, and recommends pressing the brake pedal frequently to dry the pads and rotors and stop rust building up. Several cars now automate this: Tesla has brake disc wiping in cold or wet weather, Hyundai lists a brake disc cleaning function on the IONIQ 5 N, and MG lists Brake Disc Washing on the IM6.
Tesla's yearly or 20,000 km caliper clean applies only where roads are salted in winter. Disuse rust applies everywhere.
Brake dust is where Europe has moved first. Euro 7, Regulation (EU) 2024/1257, sets brake particle limits for cars. Until the end of 2029, the PM10 limit is 3 mg/km for pure EVs and 7 mg/km for other passenger cars, and from 2035 it's 3 mg/km for all of them. It applies from 29 November 2026 for new EU car types and from 29 November 2027 for all new cars registered there.
That's EU law. It doesn't apply to cars certified for Australia, and our ADR 31/04 is about stopping performance, not dust. Don't assume an Australian car meets a Euro 7 brake-dust number unless the maker says so for the car sold here.
Heavy EVs and towing: our numbers
Here are the heaviest cars from one slice of our data: on-sale electric passenger vehicles (vans, cab chassis and trucks excluded) that hold both a kerb weight and a braked towing figure. That's 165 rows, sorted by kerb weight.
| Car | Kerb weight | Braked towing |
|---|---|---|
| Volvo EX90 Ultra Twin Motor Performance | 2,880kg | 2,200kg |
| Volvo EX90 Plus Twin Motor | 2,858kg | 2,200kg |
| Volkswagen ID. Buzz Pro LWB | 2,739kg | 1,000kg |
| BMW i7 M70 xDrive Sedan | 2,715kg | 2,000kg |
| BMW i7 xDrive60 Sedan | 2,680kg | 2,000kg |
| Mercedes-Benz EQE Mercedes-AMG EQE 53 4MATIC+ | 2,670kg | 2,000kg |
| Mercedes-Benz EQS SUV EQS 450 4MATIC SUV | 2,665kg | 2,000kg |
| Mercedes-Benz EQS AMG EQS53 4MATIC+ | 2,655kg | 2,000kg |
| Porsche Cayenne Electric Turbo Coupé | 2,650kg | 3,500kg |
| Porsche Cayenne Electric Turbo | 2,645kg | 3,500kg |
| Kia EV9 GT-Line AWD | 2,636kg | 2,500kg |
From our database; about a third of on-sale EV rows have no kerb weight yet, so this isn't a ranking of the whole market, and one row is left out because its towing figure needs re-checking against the maker. Confirm figures with the maker before you tow.
Two things jump out. Weight and towing rating barely line up: rows within about 100 kg of each other are rated anywhere from 1,000 to 3,500 kg. And hitch a trailer at its 3,500 kg rating to the Cayenne Electric Turbo and you're moving about 6.1 tonnes. Even with the trailer's own brakes doing their share, the energy maths above applies: shave your speed and you cut the energy far faster than shaving weight would.
What to inspect, and how often
Your logbook rules. As a worked example, Tesla's Australian Model Y manual says:
- Brake fluid health check every 4 years, replaced if necessary.
- Towing, mountain descents or performance driving, especially in hot and humid conditions, may mean more frequent fluid checks.
- Brakes must be periodically inspected visually by removing the tyre and wheel.
- Pads have wear indicators that squeal when they reach the end of their life.
The rule helps too: R13-H requires pad wear to be easy to check from outside or underneath the car without taking the wheels off, through inspection holes or a wear sensor that warns the driver. Handy for discs, less so for how much you can learn about a drum at a glance.
What to check when you're buying
- Front and rear brake type for the exact variant. Discs or drums, ventilated or solid, disc size. The Australian spec sheet is the source, not a global press release.
- Actuation type. Booster, integrated or by-wire. It changes pedal feel more than stopping power, so feel it on a test drive.
- Regen settings. Can you choose the level, and is there a strong setting you can hold on a descent?
- Towing plans. Check the braked rating for the variant, not the model, and the maker's brake fluid advice for towing.
- Long descents. If you're heading down from the alps or off a range with a trailer, don't start the descent at 100% charge. Leave room in the battery for regen to do its job, and use the strongest regen setting if the car lets you choose, so the friction brakes stay cooler for when you need them.
- Where the car sits. Coastal, garaged, rarely driven? Disuse rust is the EV's version of worn brakes. Ask what the car does to keep its discs clean.
Want to compare brake hardware and towing figures side by side? Browse every electric car on CarSorted or read our towing capacity guide before you hitch up.
Sources
- Vehicle Standard (Australian Design Rule 31/04, Brake Systems for Passenger Cars) 2017, incorporating UN R13-H/01 as Appendix A
- Regulation (EU) 2024/1257 (Euro 7), EUR-Lex
- Bosch: regenerative braking systems, iBooster, Integrated Power Brake
- ZF: Integrated Brake Control, ZF: dry brake-by-wire, ZF Aftermarket: brake pad installation
- Brembo: GT kit guide (fixed, opposed-piston calipers)
- Volkswagen: ID.4 recuperation, Volkswagen: ID.4 chassis
- Porsche: PCCB explained, Porsche Christophorus: Surface Coated Brake
- HELLA: brake drums
- Tesla Model Y Owner's Manual (Australia): maintenance, braking and stopping
- NASA Glenn Research Center: kinetic energy formula
- Hyundai Australia IONIQ 5 (2026) and IONIQ 5 N specification sheets; Volkswagen Australia ID.4/ID.5 MY25 spec brochure; MG Australia IM6 specifications; Polestar Australia Polestar 3 specifications.
Disclaimer: This is general information, not advice for your specific vehicle. Brake specifications vary by variant and model year; confirm with the manufacturer's Australian documents and follow your vehicle's logbook. Car-specific figures come from our database and the manufacturer documents named above.