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Alright,
I have two cars… both were purchased new.
2013 Infiniti G37 Jorney G-Sedan (11,200 miles now)
2008 Mazda 3 S Touring Sedan (96,400 miles now)
Basically, I take the car to the dealership for oil changes because it is totally fair! They seriously charge like 0.3 hours labor…Honestly, I am not certain the breakdown, but it’s right at $50… with Mobile 1 Synthetic and OEM filter!
If I buy the synthetic oil oil, OEM filter, and crush washer, the cheapest I can do the oil change $33.
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Anyway, here is the issue.
My girlfriend calls me about the front brakes telling me they are “dangerous” and it needs an urgent brake job for $300… I said, “no, I will look at it and do a brake job if necessary, but I looked at the brakes two weeks ago and they should be fine.”
Girlfriend: The service adviser says it’s not that it has only 4mm left and it can go anytime. It’s not safe to go home.
Me: Did the car stop okay on the way there?
Girlfriend: Yes
Me: Did it make any noises?
Girlfriend: No. You are not listening he said they have 4 mm.
Me: I measured the pads two weeks ago not 300 miles ago and they have 5mm left and are wearing evenly on both the driver and passenger side inside & outside.
Her: Still don’t you think they should be changed. He says it wont’ last long. It’s our safety!
Me: New pads on that car are 10 mm (10.8 before full break-in). They have almost 60,000 miles on them, so that is 1mm per 10,000 miles. Mazda and the State both say 2mm is the minimum, most shops recommend changing them at 3mm or below because they don’t always wear evenly…
Girlfriend: What are you saying it’s not dangerous?
Me: No it is fine. I am saying it will take at least 10,000 miles by their pessimistic measurement of 4mm to get to 3mm, which is when I would first even consider changing them… but even then if they are correct and there is only 4mm it will realistically take 20,000 miles to get to the absolute minimum of 2mm remaining… but my my optimistic measurement of 5mm, that is potentially 30,000 miles more driving to get from 5mm to 2mm. Either way it is good for 10,000 to 30,000 miles depending upon which measurement is right and if you change them at 3mm or 2mm. That is at least a couple oil changes or a tire-rotation away from me even considering worrying about it.
What do you guys (and gals) do on those inspections. When do you recommend pads? Does it depend on the driver? I mean, obviously if the driver is heavy footed and needs pads every 15,000 miles then 4mm or 5mm won’t last long, but someone who already has 60,000 miles on those pads isn’t going to likely smoke them immediately.
My thought process has always been for this particular car (there are 8 usable mm of brake lining):
100% = 10mm (after break-in from 10.8mm)
87.5% = 9mm
75% = 8mm
62.5% = 7mm50% = 6mm (half the usable lining is gone)
37.5% = 5mm <<=== This is where I measure them to be 25% = 4mm <<=== This is where the dealer measures them to be 12.5% = 3mm <<== This is where the dealer SHOULD be selling brakes
0% = 2mm <<== This is where Mazda and the Law actually both stipulate you MUST change the pads -12.5% = 1 mm (This is where the pads may start separating and bad stuff becomes very likely) -25% = 0 mm You hear grinding, see bright orange sparks, and everybody looks at the vehicle... You score the rotors and make a cheap job very expensive! 10mm
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Right or wrong, if we get a car up on the hoist, and notice the pads are thin, we’ll guestimate and ‘judge’ off how thin the pads is, wear etc etc, we don’t know the driver or driving style of the customer and at the end of the day, its our tech # on the Repair order, as a dealership technician cost to customer has very little to do with it, if it needs brakes it needs brakes, eaither sell it, do the job, or report it to be checked for next service, and then off the hoist it goes and onto the next pos
“Urgent” brake job? They make it sound like they are gonna get out the defibrillator (aka “heart jump start thingamabob”)
It would probably be a good time to go ahead and get it knocked out since the pads are wearing thin but haven’t dug into the rotors yet. It doesn’t sound like the sky is about to fall at any moment but more like, “Well, alright, it is getting close”.
However, if you can do the brakes on your own, it won’t cost $300. If you do them soon, not only will the job be out of the way for the next few years but your girlfriend will stop complaining (that is the real motivator here).
With dealers and repair shops, they have two motivations for selling –
1) make money
2) cover their own butts by recommending a service so you don’t go back and be like, “They didn’t tell me it was needing fixed”.
They used a tactic known as “emotional selling”.If you decide to do it yourself, don’t forget the other silly stuff like inspecting how smoothly the caliper pins move in the bores (You wouldn’t believe how often they tend to seize on rear discs), if the boots for them are intact, check out the brake lines, etc…
For something that “might go at any time”. Well for that, anything on a car might go at any time. A brake line “might” break, the timing belt/chain “might” break, the ignition “might” cut off on the highway (especially if it’s a GM), heck the driver door “might” cave in (cause someone was texting and not watching the traffic signals)
The best one can really do is keep an eye on things and act upon it if it’s notably worn.I change mine when they make noise. That is what a squealer was made for. Sometimes I will even bend that back. Other then that if my car is braking good I don’t mess with it. I replace rotors at the same time as new pads because I use aggressive semi-metallic pads. This is because people like to text, do makeup, sleep, shower (truck driver and yes I am serious), and speed. I like to know I can stop when I need too. I also drive a manual so pads last me a long while as I engine brake and having a diesel with high compression makiing it possible in any gear. When I do an oil change I look at my rotors and pads because I am under there I might as well look and I also look at everything else pretty much do a mini inspection. Then when I change pads I clean and relube everything inspect all the stuff in and around the rotor. I also check the brake fluid for floaters, discoloration, the cap seal (most mechanics over look this why I dunno), and debri. I also top it off as I drain the fluid from each caliber and do not push it back into my system. This helps to keep fluid in good workign order. Prevent dirt and debri that got pas the square cut seal from getting into your ABS as easily and keeps bleeders free and clear. It also helps prevent calipers from locking up due to excess dirt in the caliper.
I’m retired but back when I worked we got the use of this pickup some other department didn’t want. They wanted it off their inventory so they could purchase a new one. Well, it came to us with no brakes. It was metal to metal and that is the way we drove it. It had exceedingly good stopping power. Metal to metal makes a very good brake.
So, saying this is a safety issue is silly. You’ll just be ruining rotors you probably will be replacing anyway.
Not to contradict Barney, but running the brakes metal to metal is not a good idea.
Letting the pads wear thin is one thing but grinding MTM produces nasty heat and eventually the brakes could lock up etc. It is begging for serious trouble.
I have done the front brakes before; more specifically, I merely turned the rotors and kept the same pads the summer before last to get rid of a pulsation.
I then cleaned the existing pads washing them in soapy water and spraying brake cleaner followed by sanding the “business end” by doing figure eights with some sandpaper on a flat sheet of glass… Back then the pads had about 7mm on them.
I cleaned the caliper pins and srrubbed everything down with a small brass brush and some Brake Cleaner. I hung the caliper on some zip ties, and cleaned the caliper bracket too.
Finally, I lubed everything that is expected to move with some Sil-Glyde and a dab of the Permetex Purple stuff behind the pads…
Then a break-in procedure… they still feel great!
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This last summer, I changed the rear pads, which had 3 mm of meat left on them. I had to buy a special tool to turn in and compress the rear calipers. Either way, it was more work than the fronts.
Both times, I looked up the torque sects for both the caliper brackets and caliper slide pins. I think the slide pins were measured in inch pounds!
Of course, I always put the metal clip springs back as well as the rubber plugs to keep dirt and debris out.
Right now, the rear has 8mm and the front has 5mm. Everything is silent, smooth, and quiet, so I see no reason to touch it… or rush into it. Maybe next summer, when it is warm outside, I will do a pad slap of OEM pads (why change the type when they are quiet) AFTER first measuring the rotors’ thicknesses.
I need to double-check the spects, but I believe 25mm is new, and 23mm = remove from service immediately (for the front rotors). I believe you need 23.8 mm or more when putting new pads on per factory spec (otherwise, the rotors might not last at least as long as the pads).
[quote=”Summer_Night” post=120549]Not to contradict Barney, but running the brakes metal to metal is not a good idea.
Letting the pads wear thin is one thing but grinding MTM produces nasty heat and eventually the brakes could lock up etc. It is begging for serious trouble.[/quote]
I wasn’t advocating running MTM but just saying if you happened to wear a pad to where some part of its surface was MTM you still will be able to stop.
The amount of heat generated is the same whether running MTM or with new pads. The amount of heat is determined by the weight and speed of the vehicle and nothing else. The brake temperature is determined by the amount of heat, how fast the heat is generated and the size of the brake that absorbs the heat.
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