Actually,

Years ago I had an Acura that constantly suffered from pulsations from the wheel and pedal when braking. The dealer would "turn the rotors", and then it would go away, for 2k miles or so, then it would be right back to where it started.

Replacing the rotors sometimes got you 3 months or so of trouble free braking.

Were the rotors warped? Maybe? But you know what finally cured it? An on-the car brake lathe.

Take care,

George

 

IF a car doesnt exhibit shimmying in the steering wheel/car when braking new(from mismachined parts) how do they suddenly start shimmying????
Heat and cold cycling as George reffered to, and also impact from curbs and potholes(yes you could call this bent) and as demonstated many times to guys that think torqueing to spec and in a star pattern is not important, I showed another tech how going in a circle instead of star pattern induces warpage in the rotor/hub assemly. Temporary yes unless left this way. I showed him with a dial indicator on a set he was checking for warpage, or out of round,etc... A rotor in specs picked up over .010" when tightned in a circle and with impact gun set on whatever to tighten the lugs for a runout check.
.008" on a fixed caliper on a vette?? try that on a Jaguar with Alcans or Brembo's(fixed calipers) and youll have some pissed off customers. See I deal with customers all day that have cars under warranty that dont accept the compromises you have on a performance setup like Alcans and what you feel with a fixed caliper for what is normal. you know, like brakes that dont fade under heavy braking, brakes that stop you car lengths shorter than standards, and yes there is MORE feedback because of the fixed caliper. As I stated earlier, Jaguar says .008" is acceptable and I know from experiance that youll have a customer now happy saying "well its better than it was, but I still feel the shimmying when braking" thats why I shoot for .000" on the hub and .002" or less on the rotor/hub assemlby. And yes New gets me right there just about every single time. So back to the it was machined correclty leaving the factory, but somewhere along the line it "WARPED" and now has excessive runout. Call it what you want, Jaguar cannot even call a part the same name from shop manuals, to parts, to warranty booking. I just had to help our booker find a part to bill Jaguar that is called 3 differant names from each dept...Youde think that would be TOO easy wouldnt you

 

Yes, I have.. Looked at it on the lathe. Where the cutter touched the high spots.. No, I didn't put them back on the car.. No, they weren't Jaguar rotors... They were 2003 Honda Accord rotors. The Napa guy put them on the brake machine to show me that they had to cut them to much for me to re-use them. I didn't believe they were warped that bad, and only needed a surface "grind" to get any deposits off. He showed me because he took the rotors to resurface but when I came back to get them he told me I needed to buy new ones. I figured he was just trying to "sell" me..

The S Type had new rotors put on by the dealer... I had those warped in a month... Now I'll really pour gasoline on this one.... Against all recommendations I got a set of drilled and slotted rotors for it... They never warped the whole time I had the car.. I am an animal on brakes...They sound like a "buzzing fan" under hard braking, but never warped or cracked.

 

When you are going to tackle that shoot me a PM. I have the special tool and the cube and can come over and give you a hand. During the summer my school schedule is pretty light and now that I'm closer to you can be over pretty quick. Let me know and I'll throw the tool in the trunk and head over so you dont have to go searching and can have an extra set of hands to help. Also we can film it for the channel.

Also on the comments on rotor warpage. Really wish I took pictures but I have warped or gone out of runout spec on my old rear rotors on my STR. Was doing some pretty spirited driving through some mountains and they were definitly ran through some heat cycles. The next day I had pulsing when brakes were applied. Brutal had mentioned to me to check runout on the hub and the rotor and it was determined that my rotors were out of spec. Replaced all my rotors and all way good. If you want Jon I'll throw my dial indicator and mount in with the tools if you want to check yours just for S's and G's.

 

Glad to hear you figured it out Rick, the pics look great, at least the absolut did not give you a shaky paint hand.

 

A carefully machined lightly used rotor can often be superior to a new rotor.

This is because the new machining is performed after any deformation caused by heat cycling.

The new surfaces will then be parallel and on axis.

 

As stated by a few others here, I can't believe that you guys actually turn / machine rotors / discs?

Its not something I've actually really came across here as generally, when a car needs new discs it needs new discsand that what it gets. They're not that expensive and new pads / new discs have to be better.

Usually you'll get 2 sets, maybe 3 sets of pads to a disc / rotor os its not something you're having to replace all that often.....just my 0.2c

 

I've looked over the interesting replies on pulsation and I can say I've experienced all of those issues on my cars. Most were on the open road but some were on the track as well.

The on the car lathe was used on my last brake job on the Suburban but that vehicle also suffers from a PITA issue of pad material deposition when you come to a hard full stop and have to hold the brakes on. Then you get the pulsation. The rotor is not warped but you still get the pulsation.

I also really hate taking my cars in for service because of what Brutal describes with the ignorant Techs and they're improper torquing of your wheels. I'm not a big fan of the slip over the wheel studs rotor design for this very reason.

Another reason is that I've found that when I have tire work done on my 2001 Sable then I can get the pulsation after that because crap gets behind the rotor mount or there's corrosion that needs to be be dressed. Not many places are good enough to properly handle this the first time around.

For the vehicles I've owned the floating calipers never seemed to be able to effectively deal with slight rotor irregularities. I know that's what they're using now on the new Jags but I prefer the fixed mount, multi opposition piston design coupled with proper maintenance. Those sliding posts are subject to corrosion and grease drying out. Then they suck. My STR has been fine thus far.

I've put cross-drilled and drilled & slotted rotors on a couple of street cars and was unhappy with both. The drilled & slotted worked OK but OMG were they noisy. That wasn't very appropriate on a Q45 but it did end my rotor warpage issues. On the Sable the cross drilled rotors were a complete disaster. They might have been better with different pads though. The issue was with the pad material clogging up the holes and then depositing out on the surface of the rotor. I've seen this happen at the track with my race car and a friends Z06 with the stock brakes. Clearing the drilled holes with knitting needles was effective but tedious. A set of slotted rotors cured this issue up on the race car. With heavy track use slotted rotors crack too.

 

On something like a K2500 Suburban it's a lot easier & cheaper to turn them on the vehicle (if they need it) than to replace them. There's a fair amount of labor involved. You still may need to dress the rotors with something even if they don't get turned. I've had mine turned once at 89,000 miles and then again at 140,000.

I didn't even touch them on the STR @ 17K though. It depends ...

 

Vance,

Thanks for your very kind offer to assist with my rear brake job and video it for your Youtube channel. I know your tool collection is far greater than mine, so it would probably make more sense for me to drive to you when it's time to replace the pads. That won't be for another month or two depending upon how much our S-Type gets driven. If that fits your schedule, great. If not, I understand. PM sent. Thanks again, Vance....

 

PM replied.
[/end thread jack]

 

Unfortunately, many garages/owners here do it as part of a routine brake job irrespective of it being either completely unnecessary or the root problem being pad material as described by staatsof below. As stated, true cases of rotors warping due to useage and this being 'curable' by subsequent machining are almost unheard of.

 

Rick, sent you a PM. Let me know. I would really like to get those. Also, have you fixed the issue yet?

 

Sorry guys had technical difficulties yesterday.

I can't believe all the informative information that has become of this "screwed up". Thanks for all the replies! As some missed the screw up is fixed!

Thank you for your input Brutal! The rotors DID NOT fall below tolerance, otherwise I would have replaced.

Jeff, I don't think I can help you out with your clunking.

Jon there is more than 1/4" pad left on the old ones that I have now replaced.Heres a pic of the correct pads for our year:



not these:

 

ajmainevents heres a pic of mine. If you want them PM a shipping address.

 

Rick,

Thanks for the photos of correct vs. incorrect rear pads. My new ThermoQuiet rear pads look like the ones in your correct photo. Since both Advance Auto Parts and rockauto.com say these fit, chances are good that I have the correct set in hand. Guess I'll find out for sure on the day I pull the factory pads off as part of my 60,000-mile service on our S-Type....

 

This is the "pin" I am refering to, that one that did not seat into the caliper piston correctly.

 

Yep, I see that pin on the new rear pad I am holding in my hand. Note to self: make certain those pins get seated properly when new rear pads are installed....

Thanks again, Rick....

 

I don't turn rotors to cure warping... Others may. Once warped; they are not worth the $$ to resurface to only have them warp again sooner...Again, most common cause for warping or wavy rotors is from heat cycles. I do have a shop resurface rotors when changing pads to clear any pad material completely. This is only done when there is no indication of a warped rotor. With my driving habits... I usually waste the rotors before the pads... The only exception in recent years was the set of Centric pads and cross drilled rotors I put on the S Type... In that case both pads and rotors held up great... The fluid was starting to get a bit "toasty" but that is really going off topic... Lets just say.. A soft pedal is not always pads, or a failing brake system...

Oh, Rick, sorry for the "drift".... It's just that brakes do warp with heavy use..saying they don't is crazy...

 

Do you keep on replacing rotors if they go bad for one reason or another while not sufficiently worn?

Not if you have access to a brake lathe, new cutters, and the willingness to cut using multiple light skims. Finish with emery cloth.

No, that's not how most places will do them. But, if you can do them yourself ... then why not.