"I just had a brake inspection done and a shop told me that I need new brake pads and rotors. Do I really need to replace the rotors?"
If I had a nickel for every time I got asked this question. Rotors have the reputation in the automotive industry that air filters have: always an upsell that I don't need! But, the truth is that rotors are the lawyers of the automotive world in that they may have a poor reputation, but it's essential to have them and they aren't all bad. In fact, given the price they are less the lawyers and more like the paralegals.
First let's think a little bit about why the rotor is such a fundamentally important part of the braking system. What keeps you and your friends and family safe when they are driving with you? Am I correct in saying that brakes play a more important role in that regard than anything else on the vehicle save for seatbelts? After all, airbags would not deploy if brakes stopped you in the first place in so many instances. So why would you skimp on one of the most important safety features of a vehicle?
What the heck are brakes anyway? To simplify: there are rotating discs at every wheel of the vehicle that are then grabbed by pads which are housed in calipers. To visualize this, simply think of the caliper as the hand, the pads as the fingers and the rotor as a rotating plate attached to the wheel. The hand contracts, the fingers grab the plate and the wheel stops moving. This is a very basic description of something that is quite a bit more complex, obviously, but you get the idea.
So, you replace the fingers (pads) - that's a no-brainer - but then imagine the fingers trying to grab onto a plate that is slippery. This is what a rotor that has been "glazed" is: a mirror like surface that lacks the roughness needed to be grabbed by the hand and fingers. As the plate vibrates it creates noise and has an increased stopping distance. Why would you want that? Don't you want a plate that's easy to grab?
We often get the argument that it adds $100 or so to the brake job. Well, consider this: we can "resurface" the rotor for cheap, but that makes the plate (rotor) thinner and easier to heat up. When it heats up, the surface becomes warped and thus results in a brake pedal that jumps or pulsates when you step on it and, again, you are stuck with an increased stopping distance. Now you have step on the brake pedal earlier to stop sooner and is a safety concern. All for $100 savings! Rotors used to be manufactured in the US and were more like $100 apiece in today's dollars. Now, manufactured abroad, they are half the cost. I don't know about you - but my family is worth more than the savings of a couple of rotors. Of course, there are higher end rotors you can buy but that is your prerogative. If you want something that dissipates heat better and lasts longer, then go for it! But at least invest in a brake job that is done the right way. Save up a little and get those rotors replaced. You'll feel much better for having done it.