Is it necessary to replace the brake discs when changing brake pads?
3 Answers
The replacement time for brake discs is related to the vehicle's driving environment and personal driving habits. The specific details are as follows: 1. Front brake discs should be replaced approximately every 60,000 to 80,000 kilometers, while rear brake discs need replacement around 100,000 kilometers. 2. The replacement of brake discs is significantly influenced by the driving environment and habits. Driving in urban or mountainous areas with high braking frequency leads to faster wear and shorter replacement cycles. Conversely, frequent highway driving with low braking frequency extends the replacement cycle. 3. Replacing brake discs does not necessarily require replacing the brake pads. If the brake pads still have sufficient thickness, they can be retained when replacing the brake discs. Generally, brake discs need replacement only after two sets of brake pads have been used. It is advisable to replace the brake discs promptly when the combined groove depth on both sides exceeds 3 millimeters or when the edges of the brake discs become sharp.
Just helped my brother replace his brake pads a couple of days ago, and I asked the repair shop technician while at it. He said brake discs and pads don't necessarily need to be replaced together. It mainly depends on the wear level of the disc—generally, a new disc can last through two or three pad changes. But don't skimp if you notice these danger signs: if the disc surface has grooves deeper than 1mm, feeling like a washboard; or if the edges protrude significantly; or if a micrometer shows the thickness is below the MIN value marked on the disc's side; or if the steering wheel shakes like a phone vibration when braking—in these cases, you must replace the disc along with the pads. Also, new pads paired with old discs will have a break-in period, and braking distance might slightly increase for the first few hundred kilometers.
Last time I got my brake pads replaced, I was asked if I wanted a 'disc resurfacing', which essentially means treating the brake discs. The mainstream approach now is to check the thickness and runout of the brake discs when replacing pads. For example, German cars generally require thickness tolerance within 0.02mm, with most OEM discs having a minimum thickness around 20-22mm. Here's a real case: my Corolla had driven 80,000 km with front disc grooves worn about 0.5mm deep, and the mechanic suggested waiting until next replacement for new discs. Many wheel maintenance packages now include free brake disc inspection - you can request the actual measurement report before deciding. A reminder: pay extra attention to disc conditions for models with thin-disc designs like the Sylphy or Fit when replacing pads.
