With the wheel change around the corner, here is some useful information for those of you who change your wheels yourself! (or let a stressed, underpaid poor guy do it between two c containers in a public parking lot for 250:- (incl. VAT)
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In addition to the obvious horror stories every year with wheels coming loose, warped rims, bolts breaking off or uneven tire wear, incorrect tightening torque of wheel bolts/nuts can permanently deform brake discs through uneven clamping pressure which, together with the heat generated during braking, can lead to warped brake discs over time.
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Which causes a pulsating brake pedal, vibrations in the steering wheel (for front brake discs) or seat (for rear brake discs) and accelerated wear. Both too hard, loose or uneven tightening of wheel nuts can cause these problems.
Always use a torque wrench, and tighten in a star pattern according to the manufacturer's instructions & recommendations.
(Something that many people don't know is that the brake disc is also mounted and in place using the wheel bolts and the clamping pressure that occurs between the rim and wheel hub. The small screws that the brake disc is screwed into during installation are only to hold the brake disc in place until the wheel is mounted)
The limit for lateral runout of a brake disc on passenger cars with disc brakes is usually limited to 0.025–0.050 mm by most manufacturers. (Try to keep that measurement between your thumb and index finger)
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Warped brake discs mainly occur from overheating, hard braking or uneven material transfer and lead to vibrations, pulsating pedal, squeaking or scraping noises.
Other things that further increase the risk of cracked brake discs include cheaper brake discs and/or incorrect installation.
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Regardless of the cause, the first step in fixing this is to have a qualified mechanic inspect the brake system. However, both the brake discs and brake pads will often need to be replaced to restore safe and reliable braking performance.
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and thus becomes an expensive lesson for something that could have easily been avoided.