nillvurt Posted March 23, 2017 Share Posted March 23, 2017 So I keep doing my front brakes on my 94 Subaru Loyale. My rear drums are re-lathed so I know they are round. At first I thought it was the crappy aftermarket rotors I was getting, which would go out of round after about 1000 miles. So I bought all new Subaru rotors and pads and the same thing happened, albeit after a bit longer. I am at a loss. One mechanic said that sometimes the splines on the hub will be worn and put play in the system and put it out of wack, so I changed the passenger side hub too, since that is where I have done the most work and had to change multiple axle assemblies (which may be related). I also put high temp grease on the pins/bolts that the brake pad bracket slides on. Is there something which would cause this to happen consistently? I am at a loss and kind of sick of the brake pulsate when slowing down from highway speeds. Thank you for any suggestions! Link to comment Share on other sites More sharing options...
987687 Posted March 23, 2017 Share Posted March 23, 2017 Do your calipers operate freely? I had an issue with the parking brake not releasing all the way dragging the brake pads just a tiny amount. If I hit both sides with a heat gun after a highway run, one brake rotor was a good bit warmer than the other, but not enough to smell like burning brakes. Going from that extra heat to parking the car with the brake on causes hot spots in the rotor warps it. I drove it like that until the rotor actually cracked... A new rotor and caliper fixed the problem. 1 Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 23, 2017 Share Posted March 23, 2017 Get a good brand of rotor and pad. It's probably cheap parts. GD Link to comment Share on other sites More sharing options...
idosubaru Posted March 24, 2017 Share Posted March 24, 2017 More info. How many rotors has this happened too?How long after the new rotors are installed do the symptoms recur? When you "have problems" - what's the condition of all the pads - are all 4 fronts warn, just one corner, or just one pad (inside or outside) on one corner?When one pad is warn - what's the condition of the pads on the opposite side of the car (like new, or also warn)? Is your braking working flawlessly, like new, or are there some characteristics you could describe? I would wonder if the car feels like it's lightly braking even after you take your foot off the pedal. For instance if you're coasting and let off the brakes - maybe they're still dragging. And is it one caliper or multiple? 2 Link to comment Share on other sites More sharing options...
Dee2 Posted March 24, 2017 Share Posted March 24, 2017 Some people on the internet associate this surging problem with not breaking in new pads properly. Not sure how true this is but their recommendation is to get the rotors turned, keep the old pads and go through a break in step again. Worth a shot. Rotors are now need of being turned anyway. 2 Link to comment Share on other sites More sharing options...
nillvurt Posted March 24, 2017 Author Share Posted March 24, 2017 Thanks guys! Much appreciated! Do your calipers operate freely? I had an issue with the parking brake not releasing all the way dragging the brake pads just a tiny amount. If I hit both sides with a heat gun after a highway run, one brake rotor was a good bit warmer than the other, but not enough to smell like burning brakes. Going from that extra heat to parking the car with the brake on causes hot spots in the rotor warps it. I drove it like that until the rotor actually cracked... A new rotor and caliper fixed the problem. It seems to release fully, when I have it up on jacks there is little to no resistance when spinning the wheels. More info. How many rotors has this happened too?How long after the new rotors are installed do the symptoms recur? When you "have problems" - what's the condition of all the pads - are all 4 fronts warn, just one corner, or just one pad (inside or outside) on one corner?When one pad is warn - what's the condition of the pads on the opposite side of the car (like new, or also warn)? Is your braking working flawlessly, like new, or are there some characteristics you could describe? I would wonder if the car feels like it's lightly braking even after you take your foot off the pedal. For instance if you're coasting and let off the brakes - maybe they're still dragging. And is it one caliper or multiple? It has happened to three pairs of rotors, now been driving on the slightly warped Subaru rotors for 15K miles and not getting worse, but pretty annoying when going fast and slowing down. The braking works great, I can't say I ever new what this car braked like when new…but the same as the last 150K miles that I've had it. And I can't feel or hear any dragging on it. I'll inspect the pads when I get the rotors turned…I have never thought to do that, but I'll report back! Link to comment Share on other sites More sharing options...
nillvurt Posted March 24, 2017 Author Share Posted March 24, 2017 Some people on the internet associate this surging problem with not breaking in new pads properly. Not sure how true this is but their recommendation is to get the rotors turned, keep the old pads and go through a break in step again. Worth a shot. Rotors are now need of being turned anyway. I read that also, so I'll try that next. As I understand it, the break in process is to gradually apply consistent even break force at higher and higher speeds. And avoid sudden and heavy braking for the first few hundred miles… Link to comment Share on other sites More sharing options...
idosubaru Posted March 25, 2017 Share Posted March 25, 2017 Okay so it's mainly just front rotors. You mentioned drums and pads for some reason. Rotors - WHICH ones are causing the vibration? One or both? If something is dragging - caliper or failed brake hose - they may not exhibit symptoms every time and be missed? Ive never paid attention to breaking in pads. Clearly it means something but I've never once seen or heard and issue from it and by and large most people like family and friends and myself pad slap cars and drive. Zero issues over hundreds of times, hard to believe it's that big of a deal. Link to comment Share on other sites More sharing options...
ferp420 Posted March 27, 2017 Share Posted March 27, 2017 (edited) Front warped roters almost always shows it self in the steering wheel brake peddle pulsing is a rear drum out of round when a drum is turned your taking off material unevenly in the drum causing thin spots and thick spots this aplifies the warping because the metal cools at different Times thin spots cool faster and heat up faster that's why changing the rotors doesn't help it's your back breaks that is one of the first thing I was taught about breaks some 30 years ago it's not always true but 90% of the time it is Edited March 27, 2017 by ferp420 Link to comment Share on other sites More sharing options...
nncoolg Posted April 14, 2017 Share Posted April 14, 2017 Because our Subies are blessed with such a wide stud pattern, the hubs are quite susceptible to getting bent ever so slightly. This causes lateral run-out in the rotors which in turn will cause disc thickness variation and cause pedal pulsation. Even the way the hubs fit on the car can make a difference - cv stub not straight, centering cone out of shape, etc. The only way to fix this problem completely is to have the rotors 'matched' to the suspension by getting them turned on the car with a ProCut On-car Lathe. If the machine is setup correctly you can guarantee less than .0005" (half a thou) lateral runout on your rotors. Do a google or youtube search and you will see what I mean... 1 Link to comment Share on other sites More sharing options...
nncoolg Posted April 14, 2017 Share Posted April 14, 2017 Because our Subies are blessed with such a wide stud pattern, the hubs are quite susceptible to getting bent ever so slightly. This causes lateral run-out in the rotors which in turn will cause disc thickness variation and cause pedal pulsation. Even the way the hubs fit on the car can make a difference - cv stub not straight, centering cone out of shape, etc. The only way to fix this problem completely is to have the rotors 'matched' to the suspension by getting them turned on the car with a ProCut On-car Lathe. If the machine is setup correctly you can guarantee less than .0005" (half a thou) lateral runout on your rotors. Do a google or youtube search and you will see what I mean... 1 Link to comment Share on other sites More sharing options...
nillvurt Posted April 14, 2017 Author Share Posted April 14, 2017 Because our Subies are blessed with such a wide stud pattern, the hubs are quite susceptible to getting bent ever so slightly. This causes lateral run-out in the rotors which in turn will cause disc thickness variation and cause pedal pulsation. Even the way the hubs fit on the car can make a difference - cv stub not straight, centering cone out of shape, etc. The only way to fix this problem completely is to have the rotors 'matched' to the suspension by getting them turned on the car with a ProCut On-car Lathe. If the machine is setup correctly you can guarantee less than .0005" (half a thou) lateral runout on your rotors. Do a google or youtube search and you will see what I mean... Now that makes sense! Thank you! I will take it in to have that done once I do my front bearings and half shaft which is going out. After I get the rotors matched, should I replace the brake pads? Link to comment Share on other sites More sharing options...
nillvurt Posted April 14, 2017 Author Share Posted April 14, 2017 Front warped roters almost always shows it self in the steering wheel brake peddle pulsing is a rear drum out of round when a drum is turned your taking off material unevenly in the drum causing thin spots and thick spots this aplifies the warping because the metal cools at different Times thin spots cool faster and heat up faster that's why changing the rotors doesn't help it's your back breaks that is one of the first thing I was taught about breaks some 30 years ago it's not always true but 90% of the time it is Actually, I do feel it mostly in the steering wheel Kind of a shudder/shake. But can also feel vibration in the brake pedal. I think it is the front, since when I change the rotors initially there is no pulsation or shudder until a few thousand miles later… Link to comment Share on other sites More sharing options...
l75eya Posted April 15, 2017 Share Posted April 15, 2017 You may have an internally collapsing brake hose. Next time you have your front wheels in the air, pump the brakes a few times, with moderate to strong pressure, and then go check if you're front wheels are both still spinning free. If one of them is locked up you either have a bad brake caliper or an internally collapsed brake hose that's now acting like a check valve only allowing fluid to go one direction. To determine which is the issue there, all you have to do is crack open the bleeder valve on the caliper while the wheel is still locked up. With the bleeder open, if the wheel begins to spin freely again, it's the brake hose. If not, it's the caliper. Also make sure your emergency brake cables and linkage is good, and maybe try disconnecting the hill holder, if equipped. 1 Link to comment Share on other sites More sharing options...
el_freddo Posted April 17, 2017 Share Posted April 17, 2017 My L does the same thing from time to time - it seems to come and go. My theory on this is that with our front hand brake via the caliper, heat is maintained on that part of the disc for a lot longer compared to the other part of the disc. If driving hard, or just slowed from a high speed and the hand brake is applied shortly after, there's going to be a lot of heat held in the caliper. This then warps the disc slightly as different parts of it cool at different rates. I find that applying the brakes firmly a couple of times gets rid of the issue. I have not had this issue for some time now and I haven't replaced or changed anything up front. CheersBennie 1 Link to comment Share on other sites More sharing options...
l75eya Posted April 18, 2017 Share Posted April 18, 2017 It's not actually the metal that warps and the term warped rotors is just a popularly accepted moniker, despite being misleading. In short what happens is that when your brake pads get extremely hot, they can actually transfer friction material from the pad itself and essentially weld it to the surface of the rotor. The vibration you get from 'warped' rotors is the uneven surface of the rotor due to various pad material that has transferred. 1 Link to comment Share on other sites More sharing options...
ferp420 Posted April 19, 2017 Share Posted April 19, 2017 It's not actually the metal that warps and the term warped rotors is just a popularly accepted moniker, despite being misleading. In short what happens is that when your brake pads get extremely hot, they can actually transfer friction material from the pad itself and essentially weld it to the surface of the rotor. The vibration you get from 'warped' rotors is the uneven surface of the rotor due to various pad material that has transferred. Thats called glasing and it dose happen but roters warp like all metal that gets heated and cooled at differant temps ive seen some realy bad ones glazing causes more of a squeek than a shudder a bad or out of ballance tire can cause shaking in the front wheel as can worn parts or if you drill your rims off center lol done that to lol Link to comment Share on other sites More sharing options...
nillvurt Posted May 15, 2017 Author Share Posted May 15, 2017 Thanks for all your suggestions! I finally got time to deal with it and the front right brake pads were worn really unevenly, so it seems like the caliper bracket is being caught on the bottom pin. I'll take that apart and check and lube the crap out of the pins and hopefully that will help them slide better! Link to comment Share on other sites More sharing options...
nillvurt Posted May 16, 2017 Author Share Posted May 16, 2017 I think I found the problem. It seems like the passenger side caliper slide was binding at the bottom and when I tried to move the lock pin sleeve inside the rubber boot, it was pretty stuck. I tried re-lubing with Permatex Ultra Disc Brake Caliper Lube, but it seemed to make it just as sticky and even more bindy. After a bit of research, it seems like that grease makes the rubber swell and the lock pin sleeve bind, which causes it to stick at the bottom of the caliper slide while moving freely up top, which leads to uneven brake pad wear and rotor warp. I cleaned the old grease out as well as I could and replaced it with a silicone based caliper grease (Sil-glyde). Now it slides like butter! Apparently by trying to make it better with the Permatex stuff, I made it worse…we'll see how it goes a few thousand miles down the road! Link to comment Share on other sites More sharing options...
Len Dawg Posted May 16, 2017 Share Posted May 16, 2017 Yeah definetly check back in with us Link to comment Share on other sites More sharing options...
nillvurt Posted May 20, 2017 Author Share Posted May 20, 2017 I haven't got him back on the road yet, but when I put on new rotors and tightened down the axle nut, installed new brake pads and spin the rotor on the car, the rotor is already out of line. I can tell by it getting harder and easier against the brake pad, and also by putting a stationary object against the front surface and when spinning the rotor will get closer and further. Not a lot, but noticeable. I don't know if I have messed up splines or what. I cleaned the surface of the hub where the rotor mounts to make sure it is all in line. My conical washer looks good…but maybe I should change that? Or maybe I'll go get the rotors matched and machined on the car, as that seems the most reliable option… Link to comment Share on other sites More sharing options...
ferp420 Posted May 22, 2017 Share Posted May 22, 2017 Are your roters cast or are they cnc machined cast roters are never true but it shouldent cause a big issue but the cnc are true as there machined out of a solid piece of metal Link to comment Share on other sites More sharing options...
Dee2 Posted May 22, 2017 Share Posted May 22, 2017 Sounds like you replaced everything, hubs, axles, rotors and pads. You might try some thin spacers to get the rotor to spin true. 1 Link to comment Share on other sites More sharing options...
nillvurt Posted May 23, 2017 Author Share Posted May 23, 2017 Sounds like you replaced everything, hubs, axles, rotors and pads. You might try some thin spacers to get the rotor to spin true. So I imagine I would put the shims between the hub and rotor where they bolt on? I may also buy a new cone washer since I keep reusing the same one, but it doesn't look bad. It's just crazy to imagine that the hub is not flat. I guess when hitting a rock, or a curb or something it can bend it…. I was also thinking of pulling a hub from a pick and pull, but I already did that once and didn't change it, but maybe I pulled a bad hub. Link to comment Share on other sites More sharing options...
Dee2 Posted May 23, 2017 Share Posted May 23, 2017 So I imagine I would put the shims between the hub and rotor where they bolt on? Yes I may also buy a new cone washer Never hurts to use new ones, if you can find them I was also thinking of pulling a hub from a pick and pull I would try the shims first... then go from there Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now