Why Many Electric Vehicles Still Use Drum Brakes: Faults, Repairs and What to Look Out For
By A&E Garage Services – DVSA MOT testing and servicing across the Scottish Borders
If you've recently bought an electric vehicle (EV) and found drum brakes on the rear axle, you may be surprised. Drum brakes feel like old technology, yet several modern EVs and hybrids use them. At A&E Garage Services, we're seeing more of these vehicles come through our doors from drivers in Earlston, Melrose, Lauder, Kelso, Duns, Galashiels, St Boswells and Gordon, so here's why manufacturers choose them and what to watch for.
Why Do Some EVs Use Drum Brakes?
The answer comes down to regenerative braking. When you lift off the accelerator in an EV, the electric motor works in reverse, slowing the car while recharging the battery. In everyday driving, regen does the majority of the slowing down, so the conventional friction brakes are used far less than on a petrol or diesel car.
That changes the engineering priorities. Manufacturers have chosen rear drums for several reasons:
Less corrosion and seizing. Discs that are rarely used can rust and pit, particularly in our wet Borders climate. A drum is enclosed, so the friction surfaces are protected from the weather.
Low drag. Drum brakes don't have the residual contact that disc pads can have, helping efficiency and range.
Less brake dust. The enclosed design keeps dust off the wheels and out of the air.
Cost and weight. Drums are cheaper to manufacture, and they incorporate the parking brake neatly.
Long service life. Because they work so little, shoes can last a very long time.
On most of these cars the front brakes are still discs, as the front axle does the bulk of the braking when the regen system isn't enough, such as in an emergency stop.
Common Drum Brake Faults on EVs
The irony of EV drum brakes is that being used so rarely can cause problems of its own. The most common faults we see are:
Seized or corroded components. Wheel cylinders, adjusters and pivots can stick through lack of use, especially on cars that spend a lot of time parked outside or covered in road salt during winter.
Parking brake problems. Seized cables or a poorly adjusting handbrake mechanism are a frequent cause of MOT parking brake failures.
Leaking wheel cylinders. Brake fluid can contaminate the shoes, causing weak or uneven braking.
Corroded or scored drums. Surface rust is normal, but deep pitting or scoring reduces braking effectiveness.
Glazed shoes. Gentle, infrequent use can leave the friction material hardened and smooth, reducing grip.
Ageing brake fluid. Brake fluid absorbs moisture over time, whether or not the car is used much, and this can speed up internal corrosion.
Warning Signs
Watch for a grinding or scraping noise from the rear, a handbrake that pulls up unusually high or feels weak, the car pulling to one side under braking, a warning light on the dashboard, or a spongy brake pedal. A rear brake issue can also cause an MOT failure on brake imbalance or low efficiency, so don't ignore the signs.
Repair and Servicing
Drum brake repairs are generally straightforward for a trained technician. Depending on the fault, we may need to:
Strip, clean and re-grease the brake assembly
Replace worn or contaminated shoes
Replace leaking or seized wheel cylinders
Replace or machine scored drums
Free off or replace handbrake cables and adjusters
Flush and replace the brake fluid
We always recommend replacing components in axle sets, so braking stays balanced from side to side. As EVs are often heavier than equivalent petrol cars, brakes that are in good order matter just as much as ever.
Keep Your EV's Brakes Healthy
A few simple habits help. Use the friction brakes firmly now and again, so the surfaces stay clean and free. Keep up with brake fluid changes as the manufacturer recommends. And have your brakes inspected at every service, even if the pads and shoes appear to have plenty of life left.
Local Brake Checks and MOT Testing
Here at A&E Garage Services we are a DVSA MOT testing garage, and we're proud to look after drivers across the Scottish Borders. Whether you're travelling in from Earlston, Melrose or Gordon, or from Lauder, Kelso, Duns, Galashiels or St Boswells, our team can inspect, diagnose and repair your drum brakes, and make sure your vehicle is ready for its MOT.
If you've noticed a change in how your EV brakes, or you'd simply like peace of mind, get in touch with us today to book a brake check or MOT.
