FAQs—Lexus Brake Disc
- Do I always have to replace the brake discs/rotors when changing the brake pads? I’m considering buying a complete pad and disc set if this is the case.
This is not always the case; the brake disc can also be refinished. The process is known as turning. The mechanic or technician will first check if the thickness of the disc is still within the requirements or minimum specs. If it’s not yet too thin, then the brake disc can be turned or refinished. However, if the damage on the disc goes beyond minor surface cracks and the disc is already severely warped or hollowed, then it’s best to have the disc replaced instead.
- How can I measure the thickness of the brake disc? Why do some people prefer rotor turning instead of replacing the discs altogether. What are the benefits?
When measuring the thickness of the brake disc, you have to use a micrometer. You have to check the minimum thickness allowed for the rotor/disc of your vehicle. If the disc is still within the safe measurement, then it can be turned or refinished using a brake lathe. This will leave behind a smooth disc surface, which will improve braking performance. A turned or refinished disc/rotor will help minimize noise and vibration, extend the life of the brake pad, and ensure longer braking distance. The reason people have their rotors turned or resurfaced is to save money. This is less expensive than buying a new piece right away.
- Why is brake disc resurfacing/turning usually done by a technician or brake mechanic? My friend advised against a DIY. What’s with the fuss about turning the rotors on your own?
When resurfacing a disc or turning a rotor, precision machining is needed. You have to be sure that the disc will have a smooth and even surface and that the disc will still be within the minimum thickness required. The refinishing process is usually done with a brake lathe. If you don’t have the tool, automotive background, or technical know-how, then turning this into a DIY project is not advised. A technician can skillfully make accurate measurements of the disc thickness and can also take note of the side-to-side variance and runout. This is best done by a pro.
- When I installed new brake pads, I got the chance to take a closer look at the discs. Some of them have minor cracks, although they’re not that noticeable. Should I replace the discs right away?
Surface cracking is not really unusual. Heat and wear are what cause minor cracks on the disc surface. However, if the cracks are deep or big, measuring more than an inch or so, it’s a cause for concern. The cracks may eventually lead to rotor failure, poor disc condition/performance, and damage. If they have deep cracks, then the discs should be replaced or at least checked by a brake mechanic.
- I had to change my Lexus brake disc because of uneven wear, as advised by the mechanic. What causes this type of wear on rotors/discs?
Excessive runout is one of the reasons for uneven wear. This type of damage may also be triggered by hard spots. The discs may be distorted or warped as a result of unevenly torqued lug nuts and/or rust/dirt buildup between the hub and rotor. Variations in thickness may be caused by uneven wear, and this may be manifested through pulsations in the brake pedal.
- Is there a way to avoid excessive runout on the brake discs/rotors?
Re-indexing the disc/rotor’s position on the hub is one way of minimizing runout. Basically, the rotor is moved from its position and should be measured using a dial indicator for adjustments. This should be within the specs or should aim at the least runout. A correction plate may be wedged in between the rotor and hub flange if runout is still over the limit.
- Why do most mechanics suggest complete disc replacement instead of resurfacing the disc if uneven wear is caused by hard spots on the rotor?
The disc/rotor may be resurfaced in case of uneven wear. But if this is due to hard spots, changes in the disc/rotor may get deep into the surface and beyond. As such, the hard spots may re-emerge after thousands of miles. Resurfacing the disc will be a quick fix at best but won’t be a long-term solution.