Pulsing/wobbling brakes: Pads? Rotors?

[Martinjmpr]

So the new-to-me '02 Pathfinder has an issue where if I hit the brakes at higher speeds (say 40mph or more) I get a strong pulsing or wobbling. Am I right in thinking this may be warped rotors? Is this a known issue? How difficult is it to replace the rotors on these? Something I can do in a driveway?

 

[jschmidt]

This is often caused by a caliper that is seized on its slide pins

 

[dstn2bdoa]

The warped rotor myth. Stoptech's white paper, a good read.

http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

 

[Hawairish]

I wouldn't say that's a good read. He wrote all that over a technicality?

In fact every case of "warped brake disc" that I have investigated, whether on a racing car or a street car, has turned out to be friction pad material transferred unevenly to the surface of the disc. This uneven deposition results in thickness variation (TV) or run-out due to hot spotting that occurred at elevated temperatures.

It doesn't matter whether it bends or acquires material. If it's not consistent in thickness, "warped" is an acceptable term.

Martinjmpr: check the run-out on your rotors. Spec limit is 0.1mm/0.004". At limit, it will cause the symptoms you described. Duke90 had this exact issue earlier this year. You may need to check the bearing races, reseat the hub, or swap hubs/rotors to see if run-out improves. Otherwise, might need new rotors. Do the pads appear to be wearing evenly?

 

[Nd4SpdSe]

I'd say rotor. I had the issue with my girlfriend's Avenger (which is known for poor brake life) and they were vibrating BADLY under braking. I tried looking at them, but they seemed fine. I checked with my favorite mechanic and he said even with a serious vibration caused by a warped rotor, it's not visible to see the wrarpage with the naked eye, where it doesn't really take that much to do it. To test, I swapped to new rotors, the cheapest I could get from NAPA (considering her "Dodge Dealership" brake job, before we met, only lasted a year before this problem arose) I figured they used cheapies as well...that or Dodge has cheap rotors, or the dealership got screwed by the supplier. Anyway, swapped the rotors, kept the pads (they were wearing evenly) and the problem went away, and it's been a few years since.

 

[Burb One]

I wouldn't say that's a good read. He wrote all that over a technicality?



It doesn't matter whether it bends or acquires material. If it's not consistent in thickness, "warped" is an acceptable term.

Martinjmpr: check the run-out on your rotors. Spec limit is 0.1mm/0.004". At limit, it will cause the symptoms you described. Duke90 had this exact issue earlier this year. You may need to check the bearing races, reseat the hub, or swap hubs/rotors to see if run-out improves. Otherwise, might need new rotors. Do the pads appear to be wearing evenly?

Agreed^

Every time this has happened to me, on a racecar or truck (whether or not the disc was actually warped, or if there was uneven wear or deposits,) replacing the rotor has usually fixed it. Moreso, it's the cheapest and easiest first option, so i would go with that first.

it's entirely possible that a bearing, etc., has worn as well, but again, start with cheap easy likely, and move up from there. (When replacing the rotor do check for seized pistons though)

 

[Chili]

One reminder that many people forget (or don't know).. When / if you replace pads and rotors, when you're bedding in your new stuff and they are nice and hot, do not sit at a stop sign / light with your foot pressed on the brakes. It can transfer more pad material to the rotor in that spot and cause similar issues. Once cooled down it's fine, but even then, I am usually cautious for the first week or so, especially if the brakes have gotten really hot.

 

[Chili]

BTW.. Sometimes just going through the bedding process again can help... That is where I always start on brakes with issues like this. Just make sure you are in a safe area to do it, and not near any cliffs or anything.

 

[Martinjmpr]

So let me ask this: I've never done a brake job on a car before, but I've removed brake rotors. Is it pretty simple? IOW could I just buy a set of new rotors, a set of new pads, and then just bolt them on? Assuming I'm not replacing calipers, I wouldn't even need to bleed the brakes, right? Are the rotors and pads easy to remove? Any tricky spots? Also, any good YouTube videos of brake replacements you would recommend?

I just know a shop is going to sock me for at least $300 - $500 or more to do a simple brake job and I'm thinking that I can turn a wrench and I have a garage, how difficult can it be?

 

[Martinjmpr]

Found this online:
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https://www.youtube.com/watch?v=UcSHy4qmFb0
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Says it's for a 1999 - am I right in assuming that this information should still apply to my 2002? Particularly since mine has the conventional part-time 4wd?

 

[Burb One]

Found this online:
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https://www.youtube.com/watch?v=UcSHy4qmFb0
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Says it's for a 1999 - am I right in assuming that this information should still apply to my 2002? Particularly since mine has the conventional part-time 4wd?

I am 99% sure A1 auto has a youtube video online to replace suburban brakes (also look up silverado ,becuase it's the same.

It is SUPER easy. If you can do pads, you can do rotors.

Doing the pads is the hard part (compressing the pistons etc.) Basically the only extra step is the two bolts that hold the caliper guides on. (They are two big bolts, sometimes a little stubborn, but if you have trouble PB blaster and a big breaker bar can handle it no problems) Depending on your year, there may be a single small bolt holding on the rotor to the hub. You don't need it, just makes installing the stuff easier by holding it in place, I don't put them back on as it's another point to get stuck or strip. Also, make sure the mating surfaces are all clean between the caliper, hub, and wheel.

You do not have to bleed the brakes, however I'd recommend it if you have an extra person around or a pressure bleeder as it's not difficult while you have it all open. If you don't replace the fluid but are replacing rotors and pads, be careful that because the pads and rotors are now "thicker" the extra room in the system will cause the fluid level in the brake reservoir to rise and overflow. I keep an eye on it and turkey baste extra out when going from corner to corner. Also make sure you take off the cap while compressing the pistons.

 

[Burb One]

Front Video https://www.youtube.com/watch?v=nPohZtD8zlA
Rear Video https://www.youtube.com/watch?v=RRnGAiGuvK4

It's really simple. Sometimes the sockets are different than in the video. Also sometimes the caliper slide pins are a torx bit. other than that no special sauce needed

 

[Martinjmpr]

I am 99% sure A1 auto has a youtube video online to replace suburban brakes (also look up silverado ,becuase it's the same.

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Just to be clear, this isn't for the 'Burb (brakes on the 'Burb are fine.) This is for my DD which is a 2002 Nissan Pathfinder (R50.)
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It is SUPER easy. If you can do pads, you can do rotors.

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That's what I'm thinking. Looking at the video I said "hell, I can do that!" When I lived in Washington State I had a 1984 Mazda B2000 pickup that seemed to go through wheel bearings every 6 months due to the wet weather. I got very good at taking my truck down to the Fort Lewis auto craft shop, putting it on the lift, removing the wheels and brakes and replacing the bearings.
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From the video I can only see three tools I'll need to get: One of those double-cone bearing greasers (I had one for the Mazda but it's long gone - that was more than 25 years ago!), the special pliers for the C-clip on the axle and a grease gun. And I think I may actually be able to borrow a grease gun from O'Reilly.
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The only other requirement is time. I figure a half day in the garage should be sufficient.

 

[Martinjmpr]

Dumb question, but do you generally replace wheel bearings when you do brakes? I know the bearings have to come out anyway.

 

[Burb One]

Ah, It should be pretty similar though! I would youtube search your model and year, and add A1 to the end, they have a ton of vehicles and are very thorough in their instructions.

In my experience, no, you do not need to replace wheel bearings. For every disc brake system I have worked on, you do not have to take out the wheel bearings to do them so I don't have any experience with whteher you would replace them or not, maybe other can chime in?

I would say, if it's been 100k+ miles on the bearings and it's not a beater, I'd place them. The only trouble I have had with wheel bearings was when I added my lift kit, I had to take the wheel bearings out becausethe lift had a new knuckle, and by removing the bearing, I must have accidently cleaned out the grase, or damaged it and it failed upon the first 10 miles of driving. Now, those bearings had 200k on them when they failed, so YMMV