is pad slapping bad?

[Hall]

and miked the calipers and they were good

I presume you meant rotors, not calipers but you say the parts were good. Why question if it's wrong or bad that you didn't replace "good" parts ? Absolutely nothing wrong with what you did in this case.

As others have said, years ago just replacing the pads was often the norm. Years ago, rotors seemed to cost a lot more too but were thicker and made out of higher quality metals so they lasted a LOT longer. I just bought (4) Raybestos rotors for less than $75. I remember when rotors cost that much EACH.

 

[FordMan59]

I've been driving about 45 years and only remember replacing one set of rotors and that was because one got warped all the rest have just been pad replacements. I also replaced one set of soft lines because they were looking bad. 28K miles on a set of brakes? One of my cars I bought in 2008 with about 80K miles on it now it's got over 210K. It still has the same brake pads/shoes as when I bought it and they have close to 1/8" of meat left on them. I had a front wheel off my Versa with 30K miles the other day and couldn't tell the brake pads from a new set.

 

[blupupher]

A point many here bring up would make a difference as well, the location of the vehicle.

I see youtube vids of vehicles that are ~5 years old and are already covered in rust, pad jacking happening and horrible corrosion on the caliper bolts and rotor mount surface as well as the cooling vanes.

I don't have that issue at all where I am, and that may make a difference on what I did.

As for the definition of a "pad slap", never thought about it, but if I am pulling the tires off and removing the calipers, I am lubing them as well.

Heck, I lubed my daughters Scion @ 30,000 miles just because, and am probably going to do the same on the wife's Santa Fe and mom's Soul.

 

[nthach]

It depends on the situation. Generally speaking, if you are using the exact-same brand/model friction material and the rotor surface is smooth, it is fine. I am also assuming that there was no vibration prior to the brake service.

Pad slaps usually work well for rear brakes, but almost never for fronts.

Yep - pad slapped a friend’s truck. Used the same Wagner QS semi-met pads as before. No problems. Truck braked fine.

I remember installing Raybestos from Kragen a while ago on an Civic - horrible brake judder. I threw on Monroes from the local parts house and it was fine until he sold the car. I would have pad slapped OEM Honda instead.

 

[PandaBear]

If you are charged $2k to do the whole thing vs $300 to replace just the pad, you can do it 6.5 times more often and I can bet you it would be good enough most of the time. I am not saying that's the best you should do all the time but if you have to pay people labor at high cost, it make sense to just slap a new pad on it with some caliper pin cleaning.

This is also the reason why most people don't want to use greasable suspension parts, or rebuild anything, the labor does not make sense financially.

The pros likely also know how to DIY or knows what make sense to them (i.e. a track car) vs what doesn't (i.e. a beater that is driven 1k miles a year). Also for a leased car why do you care?

 

[Hall]

I see youtube vids of vehicles that are ~5 years old and are already covered in rust, pad jacking happening and horrible corrosion on the caliper bolts and rotor mount surface as well as the cooling vanes.

Southwest Ohio here so we get snow, ice, and heavy use of salt on roads. Removing rotors here that have been on for more than 2-3 years (and the underlying surfaces weren't slathered with some type of anti-seize, Fluid Film or similar) will most likely require a hammer (or rubber mallet) and full force swings.

 

[gathermewool]

I wonder how many rotors come close to min thickness right off the shelf.

I would at least use a caliper to check the thickness before doing a pad slap.

 

[ARCOgraphite]

If you have a lip on the rotor surface, the rotor is either near/below minimum specs or will reach that point during the life of the new pads.

Smoother is better for rotor finishes. Roughing up a rotor surface is a dated and incorrect practice. There is zero reason to "rough up" a rotor surface

Boy, you really are the critic ! Depends on pad composition and rotors have been a simple iron alloy for decades.

As I said in one of my posts - don't do this on a customer vehicle, only for cheap and cash strapped relatives and the Wifes car

 

[supton]

I've seen rotors raise a lip due to rust jacking. But once hammered off a good chunk of braking surface is gone, so might as well replace, thickness problems or not.

 

[ARCOgraphite]

I wonder how many rotors come close to min thickness right off the shelf.

I would at least use a caliper to check the thickness before doing a pad slap.

Have you ever seen a disc fail in service due to excessive wear? I haven't. I've had customer cars come in with the surface worn down to the internal cooling fins but the brakes still worked - at least for around town driving.
Many brakes jobs I was doing in the 70's were still drums, though. I recall FWD VW Discs being thin NEW in the 80s, But the rotor hats were cheap and were sacrificial and got replaced every time. Under 20 bucks per rotor at a VW counter.
Those were the brakes that dirtied and dusted up the wheels really bad.

 

[gathermewool]

Have you aver seen a disc fail in service due to excessive wear? I haven't. I've had customer cars come in with the surface worn down to the internal cooling fins but the brakes still worked - at least for around town driving.
Many brakes jobs I was doing in the 70's were still drums, though. I recall FWD VW Discs being thin NEW in the 80s, But the rotor hats were cheap and were sacrificial and got replaced every time. Under 20 bucks per rotor at a VW counter.
Those were the brakes that dirtied and dusted up the wheels really bad.

I’ve only ever done a pad slap once, and that was because the rotor was mostly new-looking with no lip. That side had a caliper seize and wear the pad down within a few months, but not the rotor for some reason. No indication of over-heating either.

Of the other half dozen or so brake jobs I’ve done the rotor always gets replaced with the pads.

I know what you’re saying about the rotor PROBABLY being good for a second service round, but I don’t feel comfortable doing that. I know my STI rotors (Brembos) were below min spec after 60k miles.

 

[slybunda]

What causes the grooves to appear on the rotors? Its annoying when you've just changed pads rotors and calipers only for the grooves to appear 2k miles later.

 

[Snagglefoot]

Pad slaps are ok when the vehicle is your own ( so that you don’t have customers coming back and complaining). Trying to run a financially successful shop doing pad slaps is a non starter.

 

[philipp10]

I wonder how many rotors come close to min thickness right off the shelf.

I would at least use a caliper to check the thickness before doing a pad slap.

Let me ask you this. When was the last time you heard of a rotor exploding due to being too thin?

 

[The Critic]

Let me ask you this. When was the last time you heard of a rotor exploding due to being too thin?

It is a safety issue. Rotors below min thickness do not have enough heat dissipation capacity and the pistons could potentially travel too far.

 

[TiGeo]

If the rotors are in good shape, sure. Slap some new pads, great your slider pins and drive. However with that being said, rotors are so freakin' cheap to replace with freshies.....

 

[andyd]

Over the course of 20 yrs of old BMW maintenance, I learned with every brake and front end job.. Basically, what I learned was to prevent stuff by servicing the brakes every 2 yrs. Mostly lubing and bleeding. If the rotors didn't contact steel I kept them. I just went over the swept surfaces with a knotted wire wheel, to get rid of any pad transfer, If the pads were changed, I went for cheap and dusty pads. Thanks to BIL I knew about banging and grinding ears white grease These were daily drivers, not sports cars. Soft pads dont wear out rotors. Bedding in brakes aint rocket science. The 528e was the ultimate commuter car.But they handled well. That was then. Now I have 2 Camrys that have ~ 50K miles in 5 yrs. So far no brake issues or warning lights....This fall I intend to do a wheels off /tire rotation look see.

 

[gathermewool]

Let me ask you this. When was the last time you heard of a rotor exploding due to being too thin?

That isn‘t the question I asked. Besides, forum rule #17 states that you can’t answer a question with a question. Lol

Since you bring it up: for a group of people who live to spec’s I find it odd that this one would get a pass by any of you. Not for something like this.

Maybe I’m just over-thinking it, but I’ll continue to replace OOS rotors.

 

[Jetronic]

Surface temperature of the rotors determines pad temperature. Excessive pad temperatures can lead to extreme fading or fires. Rotor surface temperaure rises quicker and higher when the mass of the rotor is less. You also don't want heat to travel to the hub and bearings, or to increase tyre temperatures. You also don't need rotors losing their balance

Usually the minimum thickness spec is 1.5 to 3mm less than the original thickness. In case of the rotors on my car, 2mm. These are 28mm thick new, but since they are vented 2mm less means 10% less mass is the disc part of the rotors. VW has some 25mm rotors that can wear to 22mm. this could be close to 20% less mass in the discs and 20% more temp rise during each braking event.

Another aspect is that if the wear occurs mostly on one side, the gap between caliper and rotor face can become large enough to pass a pad. That can ruin your day, and happens frequently. Sometimes the pad is gone, sometimes it gets stuck and locks up the wheel.

When that last happens you are not far from pushing a piston from it's bore and dumping half your brake fluid out. You can read accounts here from people who had a brake line burst, they didn't appreciate the experience. This works exactly the same.

An exploding rotor is the least of my worries....

All this doesn't mean you need to replace the rotors every time you work on the brakes, but keep the minimum thickness in mind and if you are approaching the spec minimum consider replacing pads and rotors.

 

[1 SX]

In the past i did pad swap when i was driving 55K miles a year as delivery, every 6 months new pads. Never replaced the rotors on that 200SX SE-R, or ANY of my past cars now that i think about it. Always just pads, grease, brake in and go!.

Now today, being older my time is worth more now, and i tend to replace EVERYTHING while i'm doing it for the optimal results and piece of mind.