Delaminating Brake Pads
For reasons I don’t understand the brake pads delaminate on my Audi A4 after several years use. It happened to the OEM pads and now the replacement Mintex Red Box pads are doing the same thing. The friction material separates from the steel back plate. The friction pad is captive within the caliper cage so the brakes still function, but if you brake going backwards and then brake going forward you can hear a clunk/click as the friction pad moves back and forth and hits against the caliper cage. I probably have 6 or 7 mm of friction material remaining. So I’m wondering if I can just re-cement the friction material to the metal backer plate again. When I looked at the OEM pads after this happened before it appeared that the original adhesive didn’t fail. Rather, some of the friction material tore out of the body of the friction pad, so I was left with a few divots pulled out of the friction pad (and matching bumps of friction material on the steel back plate). Does anyone know what kind of structural adhesives are used in brake pads and if it’s available on the open market? Obviously it needs to have high shear strength and good temperature handling capability. I figure if I try this and it fails I’m no worse off than I am right now. The friction pad will still be captive in the caliper cage and I’ll hear the clunk again when braking after changing directions. Then I’ll know my little experiment failed and I’ll have to buy new brake pads. I don’t see much risk in trying this. Has anyone tried this? How did it work? What adhesive did you use? Don't most pads have a Lifetime warranty on this kind of failure? I can't imagine you will find any adhesive available to you that will perform as required. As Gunguy 45 suggests, I would first check with th manufacturer, since you have the name. To properly apply an adhesive, you are going to need to remove the calipers to get the pads out. If I was going that far, I would just drop in a new set of pads. This assumes that the disc is still running true and without heavy scoring. There are many wonderful adhesives developed and used in the engineering market. Unfortunately, few of them are available to the DIYer. I wouldn't bother salvaging the pads with adhesive. The practical solution is to replace the pads with new ones. Either claim a warranty on this set or buy new ones. Hawk makes a good brake pad (model HPS)... pricey, but good. No one has mentioned anything to the fact that this is the second time this has happened. I'm curious as to what's going on here. It seems as if maybe the caliper isn't bolted onto the car's body properly. This is just conjecture on my part, but it seems almost reasonable to me this is the problem. When the brakes are applied, the calipers give (just a little play) in the opposite direction and tear at the pads. I guess one test would be to see if both sets are bad. Then maybe it's a caliper defect and I would see if this is common with your model car. There could potentially even be a recall. Else not, bring it to the car manufacturer's attention. There's NO reason you should have to keep prematurely buying brake pads. Good point. But I find it hard to imagine what condition would cause delamination. The only time I've read of this problem is when an automaker was field testing for corrosion in the Maritime Provinces and found corrosion to undermine the pad to backing interface. The OP didn't mention where he's from, so I refrained from making such a suggestion. Looking at the brand the OP mentioned, it appeared to be a UK/European brand. Plus he used metric measurements. I'm pretty sure they use the metric system in Canadian Maritime provinces... but who's to say corrosion doesn't occur in Europe? Help us out here, OP. What's going on? Also, do your neighbors share your issues? I stepped away from this forum for a few days as I wasn't seeing any new postings. But it seems this has caught the attention of a few of you. Here are some answers to your questions. I live in northeast Massachusetts. For the past year we've been only 6 miles from the Atlantic. Prior to that, we were about 20 miles from the ocean. But our prevailing winds come from the west and surprisingly our climate isn't all that humid. We do, of course, get winds from the east, northeast, and southeast at times. But if saline air or salt is the issue then the biggest problem by far is the salt our road crews spread on our roads during the winter. On those sloppy/snowy days I'm sure the brake pads are basically marinated in a saline solution, with some sand and grit thrown in for good measure. I went back to check my repair log and the last time I had this problem with the OEM pads was January, 2004. Three of the four front pads delaminated at that time. Now I've got at least one delaminated pad. I haven't pulled the pads so I could have more. The fact both incidents have happened in the winter would suggest salt corrosion. But if that were the case they you'd think all kinds of northern cars would be experiencing this problem. As far as how the calipers are attached it's pretty straightforward. As I recall it's just two bolts. When it comes to things like brake calipers I torque those bolts pretty snug. And I'm pretty conscientious about putting things back together the way I found them so I don't think the calipers are incorrectly installed. I always use anti-squeal compound on the backs of the pads so they're not vibrating themselves to death. My neighbors aren't the kind to fix their own vehicles so I can't add any anecdotal evidence from them. So I'm still mystified as to why I have this recurring problem. One thing I will do is to contact the brake pad manufacturer to see their warranty policy. I would not have thought of that. If anyone has more questions or another insight please let me know. I would also say an Internet search is in order for your model car and this brake pad problem. Maybe it's in the formulation of the OEM pads. Is the latest incident with aftermarket pads? Do you have aftermarket rotors? The corrosion is a great start, but everyone in your part of the world would have a similar issue. I still think it might be a defect in the caliper function. Not that you didn't properly reconfigure it, that the design is off. Hence, the Internet search. Butttttt, I'm probably way off base here. 5 years on pads? That doesn't seem too bad...how many miles though? Does the car get driven often or occaisonally? And when it is driven, is it hard, moderate, or granny style? Garage kept, under cover, or in the weather? All these factors could add up to something...to someone..not me..lol. I'm just curious. You could always call Click and Clack...they're in your area. btw...you'd be surprised at the actual torque value on caliper bolts...it may not really be all that high. For instance..my caliper bracket bolts are 111 ft lbs, but the caliper bolts are only 26 ft lbs. A good torque wrench (or 2) is a necessity. There's no such glue that will hold the friction puck to the backing plate, don't even try. I would bring those pads back to the place of purchase and either buy a new set or see if they can be warrantied. If there is a defect, the manufacturer would be interesed in seeing them. If there is an issue with the brakes and this vehicle is involved in an accident, it would not be a good situation, regardless if it was this vehicles fault or not. OK. Front rotors are original (!) and have 174 K miles on them. Front pads are aftermarket and have 96 K miles on them. Both OEM and aftermarket pads have shown this problem. The car is always garaged overnight, save for a few trips a year when it's parked at the airport. The car has been driven, moderately, mostly in suburban and rural areas. I checked one of the Audi forum websites and other people report this problem, but not in what I'd call alarming numbers. But clearly I'm not the only one that sees this. The brakes are made by one of the typical European manufacturers, either ATE or Girling, I can't remember which. But they're strictly OEM not something I added. Mightymanb, when is the last time you saw brake pads with rivets? For me, it's been about 30 years. Most brake pads use some kind of adhesive to attach the friction material to the metal backer. As Kestas says, there are some wonderful adhesives out there. I was just interested in repeating that process on my partially worn pads. There's a new technology I've seen advertised in the engineering journals, where during manufacture, the backing pad is gouged in such a manner that curly slivers of base metal stick up to provide a machanical interlock with the pad material. There's no way that can delaminate. Rivets have lost favor for two reasons -- adhesive technology has improved, and rivets reduce the amount of usable thickness in the pad. Ok..if I'm reading all the info correctly...you have 96K miles on the aftermarket pads. Which I assume to mean the factory pads had about 80K when replaced. Uhhh how long do you want them to last? I don't have anything to compare yours to, of course, but how thick was the pad material initially? 6 mm isn't really that thick, seems like the new ones on mine were probably about 18mm thick or so, but its been a while since I did the brakes. As they wear, there is less and less material to absorb the heat generated. If I was getting almost 100k on pads, I'd feel lucky, and not look for a way to save a few bucks. Not being rude, just that I think you are asking for quite a bit from a componant designed to wear out. Psscht! Really. 100K? I have changed mine about 4 times and I barely have 60K on the car. Of course, I suspect I might have a faulty caliper. The last set might have given me another 10-15K easily if not for the one inside pad. I think they're delaminating from heat exhaustion (think of how many times you've applied the brakes over the last 96K times, they constantly cool, sit, heat up have friction applied). Seems to me to be very normal wear and tear for a pair of pads that's braked more than the bible's got pages. Hey, no problem. I'm cheap and I know it! But the real point of interest to me here is the cause of the delamination. I spent a chunk of my career doing failure analysis of microelectronic devices so I'm particularly interested in failure mechanisms and their kinetics. I thought someone might already know what's going on here. If I do decide to try reattaching the friction pads to the backers I'll post back in several months and let you know how it worked out. I too have done failure analysis my whole career. Have you closely examined the pads to get a clue what's going on? Corrosion should be obvious. since i live in a area with moderate winters the freeze thaw cycle may be the culprit, I used to be a professional wrench and saw quite a few brakes, I have never seen delamination other than once on my snap-on truck after driving in slush for a day then parking overnight the next morning when I tried to take off it would not without a significant amount of throttle and then gave a big lurch accompanied by a sharp bang sound when I looked for the cause the pads on the left rear had broken free from the rivets causing the noise the only cause i could think of was that the slush had frozen the pad to the rotor and when I tried to take off it broke the rivet bond. I agree take these back to the parts house and see if there is any type of warrenty. you either use the trans to engine brake or your system ballanced perfectly for the type of driving you do to get that kind of milage out of your pads. if we're not supposed to eat animals why are they made out of meat? i would suggest not buying a taurus. i replace rotors and pads every other year with maybe 40g on them. the pads wear and by then the rotor is warped because the dealer torques the damn lugs too tight. Kestas, I haven't yet pulled the pads out so I haven't had the opportunity to check them over. Last time this happened there were four spots of friction material about the size of a nickel that basically pulled out of the friction pad. So there were divots in the friction pads and corresponding bumps on the metal backer where the adhesive was. So the adhesive didn't fail, the friction material itself pulled apart. I'm assuming this is the same situation this time but won't be able to confirm until I pull the pads. Speedwrench, This car is always garaged overnight. It's spent most of its life in a garage that never dropped below 40 degrees. So the freezing slush problem you mention really isn't a factor here, but I know exactly what you're talking about. This car has a 5 speed manual tranny and I do practice engine braking, but not excessively. Brakes are a lot cheaper to replace than clutches. Also, these new ceramic brake pads are great--very good stopping ability and long wear.
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