Here’s the latest reader question, along with my reply!
Meg asks: This is a “girl” question, so forgive me – but why are disc brakes better than drum brakes? What’s the difference?
My Reply: They aren’t necessarily better! It depends on the criteria.
Disc brakes dissipate heat better and (usually) have more surface area, so they have more resistance to fade under heavy braking and offer better overall braking performance. Plus, they’re simpler – in general – and easier to maintain. There is a disc, caliper – the thing which squeezes the caliper, to apply braking force – the pads inside the caliper and not many small parts.
Drum brakes are much more rugged and usually last longer, especially the drum (equivalent to the caliper) which is reusable several times (it can be machined, or “turned” during a brake job) while the rotors used in many newer cars are made of comparatively thin/comparatively fragile steel that is more easily damaged (e.g., “warpage” due to heat, overtorqued lug nuts – a common problem – and inept brake service) and frequently have to be replaced to be repaired. This can get expensive.
Same with regard to the calipers in a disc bake system. These are expensive to replace when they fail; in a drum system, there is no caliper – wheel cylinders perform the function of the caliper in a disc system – and wheel cylinders are more durable and much cheaper to rebuild/replace when needed.
In my opinion, it is debatable whether disc brakes are that much of a real-world advantage in a street-driven car. On the track – or in a high-performance car driven fast on the street, discs win hands down. This is why discs are so common – the test performed on the track tout the superior performance of discs … but much of that is just talking points, like the 130 MPH “sustained safe speed” rating some performance tires tout. How often do you sustain speeds of 130 MPH? Or even 90?
The truth is almost all new cars are overbuilt in terms of their capabilities – relative to the way almost all people actually drive and in the context of what the law allows as regards driving.
In my opinion, some of this overbuilding – ABS is a good example – has encouraged poor driving by giving people the idea that they can afford to be less careful and so do things like tailgate and fail to pay full time and attention to the road.
If we were allowed to drive at even two-thirds the pace that modern cars would easily allow safely – assuming competent drivers – then discs all around (and 130 MPH tires) make absolute sound sense.
But in the real world, as it is? I dunno!
Got a question about cars – or anything else? Click on the “ask Eric” link and send ’em in!
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