How do you tell which brake rotor is warped?

[zxcvbob]

Brakes still work just fine on the truck, but the whole vehicle shakes when I apply the brakes -- especially if I apply them lightly at about 30 MPH.  (brake pedal does not pulsate)  They've been like that for a couple of weeks.  They also make a high-pitched but not very loud squeal when I'm *not* braking.  That just started.  It's worse if I turn the wheel slightly to the left, and goes away if I turn to the right.  No scraping noises.

I just took the left front wheel off, expecting to see a cracked rotor or something.  The front side of the rotor looks good (I'll get to the back in a minute)  Both pads still have plenty of meat on them, but I haven't pulled them off yet because i have to find my caliper wrench.

The back side of the rotor is rusty except for one 1/2" band in the center where the pad is making contact.  And the pad has a ridge that exactly matches the wear band.  Weird.  Not sure which one started wearing funny first.

I don't see any signs that anything is warpped.  Of course, it might be a different rotor...  But I'm not sure what a warped rotor looks like.  When I spin the rotor should I be able to see it wobble?  Or feel a ripple in the surface?

If the other front rotor looks okay (The sun set before I got that far), I might just replace the front pads with new ceramics and see what happens.  If I replace the pads and rotors, I was planning to use semi-metallics because they work better in very cold weather.

Someone who was less of a cheapskate would just replace worn pads and rotors whether they needed it or not (the parts are not that expensive) instead of diagnosing it further, and probably replace all the rubber seals while he was in there...

[dogmush]

Brakes are not the place to skimp.

It's very probably the one with the weird wear,  but still,  you're already there.  Just do both fronts.

[Boomhauer]

If I replace the pads and rotors, I was planning to use semi-metallics because they work better in very cold weather.

No reason not to stick with the semi-metallics, they work fine.

The back side of the rotor is rusty except for one 1/2" band in the center where the pad is making contact.  And the pad has a ridge that exactly matches the wear band.  Weird.  Not sure which one started wearing funny first.

Compare it to the other side but that may be the one right there.

[Fitz]

I've never been able to SEE a warped rotor. Just shaking or pulsing of the pedal.

What vehicle? I've found that sourcing parts online and doing it myself is WAY cheaper than taking it in.

[zxcvbob]

I've never been able to SEE a warped rotor. Just shaking or pulsing of the pedal.

What vehicle? I've found that sourcing parts online and doing it myself is WAY cheaper than taking it in.

Chevy Silverado C1500 pickup.  (the parts are cheap at Advanced Auto Parts, a little higher at O'Reilly's and NAPA but still not bad)  I could probably replace all four rotors and new pads for about $150.

I have never had to replace or turn drums or rotors in any vehicle before.  If they are rusted or have worn grooves in them, I just put on new pads.  Uneven surface means more area once the pads are bedded in.  So this is a new experience.

I also just read that the problem is likely on the back axle because the vibration is felt in the floorboard and not in the steering wheel.

[dogmush]

Chevy Silverado C1500 pickup.  (the parts are cheap at Advanced Auto Parts, a little higher at O'Reilly's and NAPA but still not bad)  I could probably replace all four rotors and new pads for about $150.

I have never had to replace or turn drums or rotors in any vehicle before.  If they are rusted or have worn grooves in them, I just put on new pads.  Uneven surface means more area once the pads are bedded in.  So this is a new experience.

I also just read that the problem is likely on the back axle because the vibration is felt in the floorboard and not in the steering wheel.

this is true.

[lupinus]

General rule of thumb for brake work is to replace both sides. So if it's a mild warping you probably wont see it and should do both anyway.

Dunno if cutting them is an option, depends on how bad the warp is and if they've been cut before. Honestly though, with the cost of replacement vs cutting, you're probably just as well off buying new ones as you are cutting them. Really if you've got a visible groove I'd say cut or replace them along with the pads.

[Brad Johnson]

Markedly different wear inside to outside?  Sounds like your caliper sliders are seized.  Not uncommon, especially if the truck has seen some use.  Easy fix, just takes time, a wire brush, and a tube of moly grease.

Get new rotors.  They aren't expensive so it's good insurance.  Pull the caliper sliders out, thoroughly degrease, clean any surface rust with a wire brush or emory paper, regrease and install.

Probably time for a brake system flush, too. Again, not hard and not expensive.  An hour and a quart of brake fluid.  One man job if you have acess to a vacuum bleeder.

Brad

[Jim147]

Check the inner pad on the right rear side.

jim

[zxcvbob]

Check the inner pad on the right rear side.

jim

I was planning to check that one... last.   So you've piqued my curiosity by mentioning it specifically.  :)

Why that one?  The noise when I turn slightly left?

[Jim147]

Something about the 1500's with four wheel disc. I can replace the right rear twice before i need to o the left rear.

jim

[French G.]

4 rotors, 4 pad sets, 4 sets of caliper slides, please stop being cheap. Go to Rock Auto website, probably cheaper than Advance. So far I have found one modern light vehicle that it made sense to turn rotors on. Newer Mercedes, brakes coulda stopped a tank and new rotors were $70 apiece. About time to do brakes myself, this will be the cheap cycle, rotors from last year are good, stick new pads in. 40K on the brake job and they are still plenty good, a miracle if you add up my driving style and my commute.

[onions!]

Unless specifically labeled otherwise,all pad sets are metallic.They are also all ceramic.There are no industry standards for the percentages either.It's ALL marketing.

When you go online to buy the cheapest rotors keep this in mind.All(hopefully) of the rotors manufactured for a given application will(should)be the same thickness.If the spec is 1.31"new then they'll be that.Very often-and this is true the cheaper you go-the individual plates or panels of the rotor will be noticeably thinner.Thinner rotor.less mass to dissipate heat.Cheap rotors warp and wear faster.

If you're going to be cheap then buy name brand rotors and cheap pads.They won't last as long as good pads and will (probably)dust the wheels something fierce.

+eleventy on lubing the caliper slides.Don't just pick any grease.Don't pick something that says "moly grease"either.There are lubricants made specifically for brake caliper slides.Some look like clear silicone,some look like purple snot.Permatex offers some good stuff.

If they're gone it'd be a good time to replace the dust shields as well.No ryme nor reason but some trucks came with shields that lasted,some didn't.

Try hard not to break the sensor off.

[French G.]

Don't have to buy the cheapest thing online. I significantly upgraded my rotors for about the same price as store. Some don't like them but I put slotted and drilled rotors on which have been wonderful for going to orange and back without warping. Everyday, 6 mountains. If I'm in a mood I'm using the brakes hard on the uphill side too. I specifically chose a pad that would wear out rather quickly but work well while it lasted.

[zxcvbob]

Just from removing the one front wheel and putting it back, the brakes are quieter.    (they are mocking me)  If I stick my head out the window while applying the brakes, I can hear noises coming from the back. 

I think I'm gonna order new rotors and pads for the back and do them first and see how it goes.  I know the back rotors are badly rusted; they've been like that for years.  Might even splurge and replace the emergency brake shoes (13 y.o. originals) while they are accessible.

For the fronts, (I haven't inspected the front right yet so this could change) I'll clean and lube the caliper pins, and swap the inner pads from left to right.  Give it a week to settle in, then do a real brake job on the front if there are any problems.

[Brad Johnson]

What onion said about grease. I said moly grease but should have added "brake" to the description. It's made for high heat applications.

Brad

[Tallpine]

Just from removing the one front wheel and putting it back, the brakes are quieter.    (they are mocking me)  ...

We've had a lot of issues with dirt/mud/rocks in the wheels and calipers.

Could be you inadvertently knocked out an offending object 

[KD5NRH]

Partsgeek.com.

The rear drums were too cheap to justify hauling them even to the guy that turns them for like $8/pair.  I think I paid $12 each for new ones.  about $25/wheel total for new drums, shoes and springs, $12 each for new wheel cylinders and $30 each to replace the hubs.  Worth it to not sound like it's dragging a trash can, not have buggered up studs, and actually have all four wheels stop themselves.  The goo coming out of the rear lines when I replaced the wheel cylinders looked like a cross between diarrhea and toothpaste.  The front bleeders just yielded a couple ounces each of dark fluid followed by clean stuff.  Guess I should have thought of pulling the lines to bleed it when I changed the failed master cylinder; nothing came out the back bleeders at all, so I'd assumed crimped lines somewhere.

Outer tie rod ends were $8 for the ones with grease fittings.  $18 for lower control arms.  Unfortunately, with all the slop out of the front end, I can now feel the warped discr up front.  Going to have to fix that soon.

[zxcvbob]

It's the rears.  I looked at the left rear tonight, and the bright part where the pads are wearing the rotor are not even all the way around.

Also the "brake dust shield" behind the rotor was rotten.  I tore the bottom 2 inches of it off.  The middle part that actually protects the parking brake looks okay, so I haven't decided whether to replace it or just leave it like it is; it's a lot easier to inspect the rotor without it.    If I do replace them I know to get the 2-piece aftermarkets instead of OEM, so I don't have to drain the differential and pull the axles.

[onions!]

If it were my truck and the part that covers the parking brake were still intact and shielding the brake I'd leave it alone.Of course around here most parking brakes are frozen solid by about year six.

Do you have State inspections where you live?If it's something you'd get flagged for...

[zxcvbob]

No inspections here unless the vehicle is "totaled" in an accident.  (insurance company once reported my vehicle to the state as totaled for a door dent they said the damage exceeded 25% of the car's value.  Grrr.)

I think they have emissions inspections up in Minneapolis, but I don't live in Minneapolis.

[onions!]

Agh.Minnesota.

Salt the roads?Splurge for the shields.

[Tallpine]

For us, driving on a lot of unpaved roads, the disc brake shields just seem to trap a lot of mud and rocks 

[zxcvbob]

For us, driving on a lot of unpaved roads, the disc brake shields just seem to trap a lot of mud and rocks 

I think the shields are why my rear disks are so rusty; they trap salt and mud and ice.  And the disks probably didn't really warp, they're just rusted away unevenly and if finally reached the point that it matters.

I ordered a set of new shields; 2 shields cost more than 1 rotor.  That doesn't mean I'm obligated to put them on -- but I think the parking brake actually needs the center part of the shield to work.  Something about the cable linkage.  I won't know until I pull the rotor off.  That will be next week (I wanted to do it this weekend, but the parts won't get here in time)

One could modify the shield so only the center was left.

[Brad Johnson]

You could have them powder coated so they'll stand up to the salt for longer than a couple minutes.

Brad