Brake thump thump thump - 95 Legacy

[Spedtess]

I have 1995 Subaru Legacy Wagon (non-Outback model). About  a year ago I replaced front calipers, all the rotors, and pads to deal with a "thump thump thump thump" when braking down a hill for example. A rotor or rotors must have warped somehow I thought. The new stuff smoothed out the braking. I was happy. A year later the "thump thump thump thump" is back, along with an occasional squealing I notice when I'm rolling around next to walls or other cars. I'm stuck. Why does it keep doing this? I'm pretty sure it's the right front (both times). Do I really need to replace the rotors again? Are the brand new calipers I put in sticking? I'm not that hard on brakes. I don't ride them. When I first picked up the car with 60k, it tore up some tires which cupped badly on the outer edges. I concluded they were just cheap tires and I haven't noticed that on two subsequent replacement sets. I'm bothered that something just seems slightly unbalanced and wobbly about the car and is beating up my brakes. Any thoughts? Thanks in advance.

[heartless]

is the squealing under braking conditions only, or under non-braking conditions?

 

if it is during braking, I would suspect the pads are due for replacement - the little "squealer" tab is making contact with the rotor to warn you.

if it is not during braking - possibly a wheel bearing?

 

the rotors on these cars are not all that heavy and can be warped fairly easily - a few hard braking incidents could potentially warp them, as well as 'continuous' use on downhill grades. far better to downshift and use the brakes sparingly (stab braking) on longer grades. Excessive heat is what causes the warping.

 

 

 When I first picked up the car with 60k, it tore up some tires which cupped badly on the outer edges. I concluded they were just cheap tires and I haven't noticed that on two subsequent replacement sets.

 

What kind of tires are you using / how many miles are you putting on / how long a time frame that you have gone thru two more sets of tires?

There are a number of things that can cause cupping - worn out struts, bad ball joints, bad tie rod ends just to name a few. Any of these items can also cause that "loose, wobbly" feel as well.

a bad wheel bearing can also feel like something is loose/wobbly.

 

Jack the car up and try to wiggle the tires - top to bottom and side to side - any play/slop in either direction is an indicator of something gone bad - it is then a matter of figuring out what part it is.

 

Slop in both directions equally = more than likely a wheel bearing - something like what I posted here: Wheel Bearing Job Fail altho that was a pretty extreme case...

[idosubaru]

i would just have the rotors turned and let us know what happens.  $15 each and you're done. if it's still present you know you have another issue.

 

while doing that, check the calipers and make sure they're sliding properly.

 

as long as the rotor is true and the calipers are sliding - you won't have any thump thump.

 

the aftermarket rotors or pads may have been cheap quality?

 

a loose transverse mount causes mostly knocking on braking in mine, but also when hitting certain bumps.

[86BRATMAN]

Don't forget to sheck out the back brakes.  I had a hell of a thump thump with my brakes, replaced the front rotors twice thinking I had gotten a bad set, thank goodness for parts warranty lol.  But it ended up being the back side of the rears that were absolutley trashed. 

[monk50]

Make certain you torque the lug nuts on your wheels using a cross hatch pattern.  You may already do this but the uneven tightening of the nuts may cause the rotors to warp.

 

I believe the torque specs are 75-80 ft pounds, but check to make certain.  If this is wrong maybe some others will chime in with the proper specs.

 

Monk50 in NC

[Spedtess]

The squealing is noticeable a low speeds, particularly in parking lots and near things that reflect the sound, both while braking or just rolling. It probably does it at higher speeds too but the road noise drowns it out. It's not super loud, just enough to be annoying. The pads are pretty new. I don't think they'd have worn down to squealers yet. The tires I got the car with were a mismatched set of all no-name Chinese brand tires. They wore funny and seemed to have become not quite round anymore. A replacement set of some Japanese brand whose name I forgot wore much better and lasted 30k maybe. Now I have Hercules and I don't notice any unusual wear on them. I plan to check the caliper movement, the pads to see if they've worn evenly. It's just turned bitter cold and snowy in New Hampshire, so I'm going to put it off for a bit. Thanks all for your input.

[Monkeybus]

  First I want to help fix a common misconception about pulsating rotors. The rotors don't "warp" like term implies. Although it happens, it is very rare. Most of the time, the brake pads heat up, and start to break down due to heat long before the rotor does. This also means that a rotor will work properly down to it's machine to specification, you aren't removing enough material to compromise its ability to absorb heat.  The the pad material starts to transfer on to the rotor unevenly. You can resurface the rotor to solve the symptom, but it sounds like you need to switch pads too. I like the Wagner Thermo-quiets and Napa Adaptive One pads. Centric makes a pretty good pad in the 105 & 104 series. These will most likely put up with the heat better, helping to stop the pulsation and squeak that has come back so rapidly. 

[Spedtess]

Thanks for the info Monkeybus. I'll check out the pads you mentioned. I'd like to do it right for once. I thought I'd done it right the last time.

 

I've heard that about warped rotors - not really warped, just heated pad material stuck on. The last time I replaced the rotors I looked at them expecting to see pad material stuck to the rotor, but no. It was nothing but shiny alloy, to the naked eye anyway.