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Old 02-15-2014, 06:08 PM   #31
MrBob
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Originally Posted by troidus View Post
Make sure your lug nuts aren't over-torqued.
This can be problematic. Factory specs for my AWD van call for a hundred pounds on the nuts but I'm convinced that cranking them to spec contributes to warping. What to do?
One study that I read stated that warped discs are more often discs with deposits of brake pad material that cause grabbing.
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Old 02-15-2014, 08:59 PM   #32
SteelJM1
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Originally Posted by MrBob View Post
This can be problematic. Factory specs for my AWD van call for a hundred pounds on the nuts but I'm convinced that cranking them to spec contributes to warping. What to do?
One study that I read stated that warped discs are more often discs with deposits of brake pad material that cause grabbing.
Yeah thats usually the case. Its definitely whats going on on my car. Im going to try different pads for when its Big Overhaul time in 15k miles.

This is the only car ive ever had problems with. And ive done dozens of brake jobs.

As far as your lug specs, do them in stages, preferably with the wheel in the air. 50, then 75, then 100 and see if that helps.

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Old 02-16-2014, 10:09 AM   #33
H96669
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Originally Posted by concours View Post
Thanks for posting the images of crusty rotors... hard to imagine for those not in the salt belt.
I got more if you want....the quite expensive and apparently very good Akebonos brake pads where the rust got between the friction pads and backing plate and then lifted the pads off the plate.

Third set of pads/rotors at less than 40,000 miles. One front wheel bearing last december where the shop commented on the rust/hard to remove bearing and then way overcharged me and returned the car with a rubbing brake shield.

And just yesterday drove it again, forgot to turn on the music only to realize the other wheel bearing is whining. More $$$$ but kind of hoping that one is the source of the "now constantly on" ABS fault lights. Hoping because the shop with the good code reader can't find any fault codes.

I don't have a puller for DIY but the local guy will do the job for about half what them city guys charged me.And unlike the "city" shop will answer my questions on the provenance of them wheel bearings, he recently got me motorcycle wheel bearings that I sent back as they were from China.....and got me some better ones from Bulgaria and Argentina but I do trust SKFs.
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Old 02-16-2014, 10:40 AM   #34
concours
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Originally Posted by H96669 View Post
I got more if you want....the quite expensive and apparently very good Akebonos brake pads where the rust got between the friction pads and backing plate and then lifted the pads off the plate.

Third set of pads/rotors at less than 40,000 miles. One front wheel bearing last december where the shop commented on the rust/hard to remove bearing and then way overcharged me and returned the car with a rubbing brake shield.

And just yesterday drove it again, forgot to turn on the music only to realize the other wheel bearing is whining. More $$$$ but kind of hoping that one is the source of the "now constantly on" ABS fault lights. Hoping because the shop with the good code reader can't find any fault codes.

I don't have a puller for DIY but the local guy will do the job for about half what them city guys charged me.And unlike the "city" shop will answer my questions on the provenance of them wheel bearings, he recently got me motorcycle wheel bearings that I sent back as they were from China.....and got me some better ones from Bulgaria and Argentina but I do trust SKFs.
I had some NAPA "Premium" rotors develop pulsing/thumping, hard spots in the iron.




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Old 02-16-2014, 05:55 PM   #35
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Originally Posted by SteelJM1 View Post
As far as your lug specs, do them in stages, preferably with the wheel in the air. 50, then 75, then 100 and see if that helps.
This. I run the nuts down snug with my fingers, making sure the wheel is seated evenly, then come up to torque in three stages. Then I make one more pass to make sure that final tightening didn't cause any of the others to loosen. The first one will often loosen up as the other four are brought up to spec.
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Old 02-17-2014, 07:50 AM   #36
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Ive had nothing but problems with my subie brakes. OEM ones sharted to shudder, got new replacement ones (i forgot what brand but they were'nt exactly cheap) and good pads that make a lot of goddamn dust. 1000 miles later, the shudder began again. Cut the OEM rotors problem solved... for 1000 miles.

I'm so goddamn tired of shitty quality parts.
This is a classic example of warped rotors,although the term "warped" is misleading.
The problem starts with rotor runout or wobble.The rotors develop thin spots on one side from the pads brushing the same spot each revolution.Then as the pads squeeze the rotor while rotating they hit the thick and thin spots causing the pulsating sensation.
Most mfgs only allow a .0005 variation in rotor thickness all the way around.

The cure is to bolt the rotors to the hubs and check them with a dial indicator to get them to less than .003 runout by cleaning the mating surfaces or rotating the rotors to a different lug position.

worst case you may have to have them trued with an on the car lathe.

I bought one of these http://www.procutusa.com/ when they first came out years ago and it has cured any come back issues.In fact most auto mfgs are requiring their dealerships to have one.
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Old 02-17-2014, 04:38 PM   #37
SteelJM1
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Quote:
Originally Posted by big-t View Post
This is a classic example of warped rotors,although the term "warped" is misleading.
The problem starts with rotor runout or wobble.The rotors develop thin spots on one side from the pads brushing the same spot each revolution.Then as the pads squeeze the rotor while rotating they hit the thick and thin spots causing the pulsating sensation.
Most mfgs only allow a .0005 variation in rotor thickness all the way around.

The cure is to bolt the rotors to the hubs and check them with a dial indicator to get them to less than .003 runout by cleaning the mating surfaces or rotating the rotors to a different lug position.

worst case you may have to have them trued with an on the car lathe.

I bought one of these http://www.procutusa.com/ when they first came out years ago and it has cured any come back issues.In fact most auto mfgs are requiring their dealerships to have one.
Perhaps ill try that, a shop with an on-car lathe. Hopefully its ok to let the subaru AWD system rotate in the air like that.
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Old 02-17-2014, 05:28 PM   #38
showkey
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Quote:
Originally Posted by big-t View Post
This is a classic example of warped rotors,although the term "warped" is misleading.
The problem starts with rotor runout or wobble.The rotors develop thin spots on one side from the pads brushing the same spot each revolution.Then as the pads squeeze the rotor while rotating they hit the thick and thin spots causing the pulsating sensation.
Most mfgs only allow a .0005 variation in rotor thickness all the way around.

The cure is to bolt the rotors to the hubs and check them with a dial indicator to get them to less than .003 runout by cleaning the mating surfaces or rotating the rotors to a different lug position.

worst case you may have to have them trued with an on the car lathe.

I bought one of these http://www.procutusa.com/ when they first came out years ago and it has cured any come back issues.In fact most auto mfgs are requiring their dealerships to have one.
BIGT Wins^^^^^^^^^^^^^^^^^^^ the entire system must be "trued" as an assembly.

Very very common industry wide problem...........and is why the on car lathe was invented.........any other solution is just random luck in parts variation. Variation is not code for quality or lack of it due to tolerance stacking when multiple parts are assembled.

Plus the clown at the tire store with the air gun set at 300 ft lbs is a whole another variable.
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