What metric do you use to estimate remaining brake pad life on a typical economy sedan?

[Arlen Holder]

What metric do you use to estimate remaining front brake pad life on a typical economy sedan (assuming normal driving under normal conditions)?

A neighbor's kid was heading off to college where her mother asked me to take a look at her vehicle, where I found a few things to warn them of such as this rack and pinion steering boot badly torn for some reason:

I told her that I had never replaced steering boots before so I wasn't even sure how to diagnose whether she needed just a boot or the whole rack:

One of the things I simply noted was they had "x" miles left on their front brake pads (where there is only one mechanical wear sensor per rotor):

If you look closely, the pad is about the thickness of the backing plate:

The owner asked me how many miles those pads had left under normal driving:

I wasn't sure, so I guessed wildly at roughly about 5 thousand miles to go:

But what metric do you use to estimate a pad's remaining life given only the thickness of the front pads, and the fact that you are told the vehicle is driven by a typical owner under typical driving on typical roads?

[Ed Pawlowski]

What is normal? Nothing a teenager does is normal. What I use does not apply unless you are in the same situation. When I lived in the city, it was a stretch to get 12 to 15,000 miles from a set of pads. Stop sign on every corner, traffic lights on the main streets, even the highway would have some stop and go at a couple of spots.

When I moved to another state and did a lot of highway driving, I got

50,000 miles from pads.

You could measure them now and in 3000 miles to see how much wear and make a decent calculation from that.

[trader_4]

The brake pad wear sensor indicator light and/or message.

[Arlen Holder]

Hi The Real Bev,

Thanks for that information about the front pads, which is what I seek. o Personally, I get about one thousand miles per millimeter of pad

The goal is to get those who have done the calculation to help out with an estimate of the number of miles per (whatever) thickness of pad, on average, that others would get (as I drive on mountainous roads a lot).

People either know how many miles they get, or they don't know it. o So I thank you for that datapoint of another average'ish driver,

If you get 40K per pad, and if new pads are, oh, hmmmm... how thick?

I happen to have a few sets of "Centric Premium Ceramic" pads lying around, P/N 301.09080, marked "CEN30109080 31AC9101 GG 02 B19" (i.e., cold/hot friction rating of G/G, which is a friction coefficient of 0.45-0.55)

The backing plate is 6mm & the pad, brand new, is an additional 12mm:

At 40K miles, that's about 40,000miles/12mm = about 3K miles per pad mm.

Given the worn pads are about as thick as the backing plate, that's: o 6mm times about 3K miles/mm = about 18,000 miles left on those pads

This is what they come with, apparently:

Regarding not asking how you know this, I know that steel on steel has almost the same cold/hot friction coefficient as many brake pads people buy (e.g., EE pads) where I've seen rotors worn down to the ribs and the brakes "still work".

You get three times the miles I get, where I get around one thousand miles per millimeter of pad, or thereabouts, on my bimmer (OEM Textar/Jurid pads, with cold/hot friction ratings of F/F), looking at my records, but I live in hilly country, where people would likely get more on flat land.

If we don't get further data, an average of two thousand miles per millimeter might be our starting point, in which case that's about twelve thousand miles left on those worn pads.

[Scott Dorsey]

Teenagers can go through a set of brake pads in ten miles on the track. assuming they make it ten miles before the clutch wears out.

--scott

[Arlen Holder]

This is a college-aged girl who probably has never left skid marks on the road even once, as I've seen her drive - and it's verrrrrry sloooooow.

Nonetheless, without an actual miles per millimeter of pad, it's not helpful to tell me everyone is different, and every car is different, and every road is different, as everyone knows that and so it isn't useful.

It's like claiming there is no such thing as a statistical average. o There is a statistical average - but it takes data to arrive at it.

All I'm asking for is the data in miles per pad (or miles per millimeter).

I'm leaning toward 1000 miles per millimeter for those who brake hard, and double to quadruple that (see The Real Bev's response) for normal driving.

All I want is number of miles per pad, where I can do the math (assuming 10 mm of pad is worn away in that time period, leaving 2mm of pad on average).

So far we have only two suitable responses:

1. I get 1,000 miles per millimeter of FF pads (Jurid/Textar)
2. The Real Bev gets about 4,000 miles per millimeter of pad

How many miles per front pad do others get?

[Arlen Holder]

On average, how many miles is that for you per front pad?

[gfretwell]

OLD school dating from the start of disk brakes was a metal tab that hit the rotor and made a horrible sound when the pads were worn down too far. I had that on my 67 Chevelle.

[Xeno]

I'm up to 100,000 kilometres on my Toyota front pads and I expect many more.

[Arlen Holder]

Thanks Xeno for understanding the question (which some who posted clearly didn't) and for purposefully helpfully adding another datum to the solution set (where the more good data we get, the better that average estimate).

Assuming new pads are 12 mm with a margin of 2 mm when replaced, that means you attain at least 10,000km per millimeter (at least 6,000 miles per mm).

So far, we have the following decent datapoints: o Jurid/Textar FF front pads at ~1,000 miles per mm (10,000 miles per pad) o The Real Bev at about 4,000 miles per millimeter (40,000 miles per pad) o Xeno front pads at about >6,000 miles per mm (>60,000 miles per pad)

One question is how much meat is left on the pad when you replace them. o I'm assuming 2 mm out of the 12 mm in toto & of course, linear wear

Does that sound about right?

[The Real Bev]

That's a memory from long ago. I don't actually KNOW if those are good numbers.

That looks too complex. I seem to remember (from the 1983 Sentra) just a little thin metal tab that stuck out and contacted the rotor at a chosen point. I bent it more to give me more wear, but I sent the car to the knackers long before that point.

That would be me. The rotors looked like a beginning lathe project -- proof that they're made of softer stuff than the pad's backing plate nubs. I could feel and hear the grinding, but the braking was just as good as before it started. When I had to brake carefully to avoid hogging in I figured I needed to deal with the problem. At the time the rotors (Pep Boys, used) cost only $10 each. The cost wasn't the problem, just the time.

I wouldn't let it go that long now. I love my little Corolla and don't want to hurt it. Rear drums, but I've never noticed a problem with insufficient brake power from the rear. OTOH, how would I know?

[Arlen Holder]

Hi The Real Bev,

I've worn _plenty_ of pads down to the rotors, where the grooving limit on rotors is huge when you can find the spec. The limit that most people check is the thickness, which, depending on factors, is usually two sets of pads in my experience (but I sometimes get three sets of pads out of a rotor).

It's interesting that the cold/hot friction rating for steel on steel is very similar to E/E pads, which I find a lot of people buy who don't know anything about brake pads but what the MARKETING people tout (e.g., "ceramic" on the package could mean no more than a few spec of clay dust, based on my personal talks with the Axxis marketing team).

Basically, the only valid data you have is what's printed, by law, on all US pads sold for passenger vehicles, which is the cold/hot friction rating.

Anything else, IMHO, is marketing bullshit.

Drums are different, and more of a pita, IMHO, than disc brakes. o The drums have an inspection port, but I always found it rather useless.

While you "can" hurt a caliper by metal on metal heating up things, going to the point of a millimeter or two of that is safe, as far as I know.

In my situation of mountainous driving causing inboard wear on the front tires, I rotate the wheels every few months anyway, so for disc brakes, I inspect them at every rotation.

That's where the calculation of miles remaining can be of use. o Given current data, something around 4K miles per millimeter seems ok.

That means I'll tell her she has likely at least 20K miles to go.

[Vic Smith]

You probably wouldn't unless your front pads were wearing fast. The self-adjusters on rear drums are usually the weak point. Some adjust when you brake in reverse gear, others when you use the E-brake. Since I never (or seldom) use the E-brake here in the flatlands, my back shoes weren't even applying on one car I had. Wondered why my front pads were wearing out so fast. As I recall there was no mention of using the E-brake to adjust the rear shoes in the owners manual.

[trader_4]

Every pad I've installed for decades has had them, including the ones that use electric wear sensors.

[The Real Bev]

I remember about braking backwards, but I've never heard of using the handbrake. I think they discourage calling them 'emergency brakes' now, on the assumption that you'll think they protect you in an emergency. Like 'safety belts' instead of 'seat belts'. I'll try to find something about it in the manual.

The E-brake on the 1976 monsterhome (or some other elderly vehicle, it was decades ago that I saw this) had nothing to do with the brake, it was a clamshell that tightened on the driveshaft.

[rbowman]

I don't know how many years it spanned but a '60 Plymouth with a TorqeFlite had a drum on the tail of the tranny for the e-brake. When i dropped in a manual, I didn't have an emergency brake. No big deal until a state trooper asked me to demonstrate the effectiveness. Next step was replacing the rear axle with one that had one and kludging up the linkage. The car wasn't exactly factory stock when I got through with it.

[Clare Snyder]

I've seen slow drivers get as little as 10,000km on a set of pads because their foot was never off the brake

[Xeno]

Yes, that or more. I don't wear pads right down to the legal minimum either.

Previous car's pads were replaced at 80,000 kilometres and had more than

4mm remaining. This current car does mostly country highway running so brakes last a long time whereas the previous was used in heavy city commutes.

[Arlen Holder]

The last time I looked at this vehicle, as I recall, the metal tab was about 2mm (or so) from the brake pad backing plate.

Hence, given the datapoints so far in this thread, I'm going with a calculation of miles per millimeter (yea, I know, I'm mixing units) of around 4,000 miles per millimeter (tentatively).

That's assuming a 12 mm pad when new, and 2 mm left when replaced. o More data is always welcome so that we can hone those figures.

[Arlen Holder]

How many miles do you get per front pads, in general?

As for mechanical sensors, my bimmer has only one wear sensor per axle o No mechanical sensor; only electronic (front left and rear right).

Although electronic is essentially mechanical, since it's a stub of plastic that wears on contact, exposing the wires embedded inside that plastic.

One issue is removing the sensors often breaks them if you're not careful.

Since we rotate so frequently, checking brakes are easy; but this question was for estimating miles for someone else who doesn't rotate as frequently as I do (due to mountainous terrain causing specific "camber scrub" wear to the inboard corners of the front tires).

At the moment, with the data we have, it's about 4,000 miles per pad mm.