when to replace brake pads

When should you replace your brake pads? How many mm is too few? Some mechanics will make it sound like the sky is going to collapse if you don’t replace your brakes right this second.

But maybe it just doesn’t seem right. I mean, you drove the car in for a routine service. The brakes felt fine. There wasn’t any weird brake noise or grinding sound. Is it possible that your brake pads are worn out and there’s no symptom at all?

Yet now there’s a guy on the phone and he says you need the brake pads TODAY. RIGHT NOW! The car just isn’t safe anymore. If you don’t care about your own safety, at least think of the other motorists on the road! Grandmas in crosswalks! Adorable little puppies! How could you possibly consider driving away from our shop with only 4mm of brake pad left!

How to tell if brake pads are bad

But wait. Brakes aren’t worn out at 4mm. Grandma and her puppies are going to be just fine. Where did this specification come from?

Everybody seems to have their own opinion. The tool on the right is used to measure brake thickness. It turns “red” at 3mm. Is a brake pad worn out at 3mm? Once again, it depends on who you ask. This gauge is yellow all the way up to 6mm, implying that a 6mm brake pad isn’t all that great. I think I’m going to disagree with that pretty strongly.

If only there were a final word. An authoritative source everyone can agree is valid.

A tool to measure brake pad thickness in mm

The ultimate word on how to check brake pads

Who gets to say when to change brake pads? Here are some possibilities.

  • The manufacturer (They designed the car, right?)
  • You (It’s your car and your money)
  • Your mechanic (Maybe he’s stomping his feet and won’t “let” leave without a tow truck.)
  • The State of California (Auto repair is a regulated business.)
  • The City of Berkeley (Well, they have their own health department. Maybe there’s a Minister of Car Brakes too?)

Who get to say when to replace brake pads (mm)- how many mm is worn out? As it turns out, there’s one answer with legal weight. The company that made the car gets to decide the minimum brake pad thickness specification, and they publish this information in their service manual.

If a mechanic says that brakes are “unsafe” or “worn out”, then the brake pads should be at or below the minimum specification published by the manufacturer. For many cars, this is when the pads are 1mm thick.

Everything else is just an opinion. Opinions can be presented as recommendations, but not as fact. Characterizing brake pads as “worn out” or “unsafe” when they aren’t under the mm specification is fraud.

Are opinions brake pad wear valid?

Opinions on when brake pads should be replaced are valid. We recommend you replace your brake pads at 2mm or even 3mm at times. Are we trying to rip you off? No. We have reasons for this and we’re happy to share.

For instance, Honda wear sensors starts rubbing and making a squeaking noise when the pad is 2mm. What if you came in for a brake inspection and your pads were just over 2mm. They aren’t worn out, and we’re not going to say that they are.

But what if your brakes start making noise later that week. You just had the car in. Why didn’t we say anything about the brakes?

Another reason to replace brake pads slightly before they’re worn out is that brake pads are a little more fade resistant when they’re thicker. Most of the time brake fade isn’t an issue, but in extreme conditions it can be.

You could think of it sort of like tires. Tires are “worn out” at 2mm, but don’t work very well in rain under 4mm, and don’t work very well in the snow under 6mm. When you replace them depends a little on the conditions.

The same is partially true of brake pads. If you have a flat freeway commute, it might be fine to run the pads until they’re worn out. Are you Speed Racer? Maybe you should keep a little more pad in reserve.

Fear is an effective sales tool

Nobody wants to be “that guy”. You know, the one doesn’t maintain his car and breaks down on Hwy 80 clogging traffic. Or the guy who doesn’t fix his brakes and causes an accident. Simple work like brake replacement is profitable and doesn’t require a mechanic on the high end of the pay scale. Shops like to sell brakes and struts because they make good money doing those types of jobs. Playing on people’s fears is an effective way to increase sales.

DIY brake pad inspection

Considering checking your brake pads yourself? It’s a bit of a pain doing this type of work without a lift, but as far as DIY car projects go, it’s not very high on the difficulty scale.

A visual inspection of the brake friction material is how brake pads are “measured”. Typically, it’s impossible to directly measure brake pads unless you remove them from the brake caliper. You’ll likely need to hold a ruler or other measuring device near the pads and visually compare.

Also, remember there is more to a brake system than just the pad thickness. I’d recommend having a professional look at the car, especially if you have a low brake pedal or brake fluid leak.

Don’t be afraid to ask questions

So, if you’re told your brakes are “worn out” or “unsafe”, ask what the pad measurement is and what the manufacture’s minimum specification is. Honestly, we don’t often look it up, but we certainly will if you ask.

Most of the cars we work on the minimum brake pad thickness is 1mm. We’ll usually recommend brake pads at 2 or 3mm. However, we’re never going to say that the brakes aren’t safe, or you shouldn’t drive, or any other scary stuff. If you ask if you can wait a month or two, the answer is yes, you’ll likely be fine.

We’d be happy to check your brake pads

If you’re in Berkeley California and own a Toyota, Subaru, Honda, or Mazda we’d be happy to check your brake lining thickness. We bill 1/4 hour for the inspection, but you’ll get an honest assessment with no pressure to buy. Otherwise, I hope this article helps you in communicating with your auto mechanic.