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Fixing pulsing/"warped" rotors

 
Old 05-08-2019, 10:46 AM
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Fixing pulsing/"warped" rotors

So I've gone through 4 sets of front rotors on this car due to pulsating/shuddering brakes. Five if you count the ones on it when I bought it. That's over the course of about 150K miles. And many of those I kept on for a long time after they began pulsating. Some started pulsing as early as 5K miles. I'm not sure if it's a problem specific to my car or if it's intrinsic to the 4G TL. I'm not a newb when it comes to brakes. I've replaced pads and rotors on several vehicles with no problems whatsoever. My wifes '09 pilot has about 60K on her rotors and pads that I swapped out 4 years ago and they're still smooth as butter.

I've done everything to try to stop it but haven't had much luck:

- Cleaned the rust/debris off the hubs before installing the rotor
- Meticulously followed the bedding procedure (specific to the rotor manufacturer)
- Used a new set of pads for each new set of rotors
- Measured the run-out of my hubs to make sure they were true.
- Made sure all suspension components and wheel bearings are good.
- Made sure the calipers are in good shape - clean, no rust, guide pins were lubed up and freely moving, boots intact, etc.
- Thoroughly cleaned rotors prior to install - first with soap and water to remove the oil usually applied by the manufacturer to prevent rust followed by brake cleaner after install.
- Used anti-seize and brake grease where needed on all contacts of the brake pads.

Also, every set of rotors and pads have been a different brand. Centric (cryo-treated), Stop-Tech, Raybestos, Duralast (autozone) and Wagner. Still - no luck.

Having researched ad-nauseum online, a common consensus among brake experts is that rotors don't generally "warp". They might warp if they're super hot, then cooled very quickly. Such as braking for a long time then running through a deep puddle. However, in general, most pulsating brakes are a result of uneven brake pad material deposited on the rotor. I've always been skeptical of this since I'm unable to visually see any sort of uneven buildup on the rotor surface and I can measure run-out on bad rotors with a dial gauge (whereas they were fine when I installed them). New rotors should have a runout of around 0.002" at most. I've measured runout as high as 0.009" on "bad" rotors that were pulsating. This led me to believe that the rotor was warped. Especially when examining the area where the excessive runout was present and seeing that the surface didn't look any different than the rest of the rotor.

In browsing on the topic, I came across a BMW forum where M3 owners were having similar problems. It seems that it's chronic for them as well. Even worse, their rotors are around $200-$300 EACH . You can get decent rotors for the TL for as low as $40 each. So needless to say, they wanted to figure out a way to prevent or fix the problem. One method to try to remove uneven pad buildup is to repeat the bedding procedure. But that seems to have mixed results. However, one poster on that forum found that if he repeated the bedding procedure with a set of metallic pads (semi-metallic racing pads in this case) that it ground all the old ceramic pad material off the rotor resulting in a relatively smooth surface. After that, he'd replace those with the previous ceramic pads and the pulsating was gone!

https://www.m3post.com/forums/showthread.php?t=1384226

The pads he used were Hawk Blue racing pads which is a semi-metallic pad specifically designed for racing. Semi-metallic typically burn up rotors quicker but have better heat dispersal and more bite. For run of the mill cars, ceramic is most popular since it creates less dust, is quieter, easier on the rotors and lasts longer. But in this case, the whole point was to grind down the rotors to remove the ceramic pad material build up so semi-metallic race pads are perfect

I was unable to find racing pads for the 4G TL. And frankly, I'm not sure I'd be willing to pay the price. They can be well above the $100 mark. So I decided to go the cheap route. I purchased a pair of semi-metallic pads from Autozone then did the bed in procedure. Boom! Pulsing was gone.

Time will tell if the fix is long term. I left the semi-metallic pads on for now but will probably swap the Akebono ceramics back on after a few more hundred miles - just to make sure the old material is fully removed. I'll follow up later to post results.

Last edited by losiglow; 05-08-2019 at 10:50 AM.
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Old 05-08-2019, 11:42 AM
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This is not the first car I have heard of either that has ended up with multiple sets of "warped" rotors!

Typically when I get this phone call, I say something very similar to what you have written out in your third or fourth paragraph. The pad deposits build up in the rotor due to inconsistent braking, cause a vibration, and that is commonly mistook for a warped rotor. I recommend repeating the bed in procedure, as it gets everything hot again and burns off what may have built up on the rotor. This works for the vast majority of the customers, so I would like to think it would benefit you as well! Although it sounds like you are doing better with the new setup so far.

Something to keep in mind moving forward: when you get off the highway on an exit ramp, and are on the brakes, the pads and rotors get hot. When you come to a stop at the end of the ramp the brake pad (somewhat) binds itself to the rotor and leaves a minor deposit. Using the brakes hard, and keeping your foot on the pedal after braking causes pad deposits.

Keeping the rotor moving slightly at a stoplight like this will help minimize the potential for deposits. Leave yourself a little extra room so you can roll forward a bit once you have come to a stop. This way the pad will not sit in one spot on the rotor for too long.

Let us know where you land with the new pads, and don't forget to check us out online for all your braking needs!

Happy modding!
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Old 05-09-2019, 11:32 PM
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having gotten the 4G TL Brakes cherry hot on my TL this past week as an emergency popped up and I was far away from where I needed to be (private land, no one at risk, all is fine). Few minutes of accelerating and hard braking for about 15 miles, speeds of 0-100 varied all over the place due to layout of our grid.

Factory compound and rotors suck, so do most aftermarkets. Key is getting quality (sometimes name does not mean quality IE RAYSBESTOS). Also the factory setup has almost no real brake "ducting" to help cool rotors which is an issue I'm looking to tackle with custom dust shields and piping.

Factory Pads and Rotors are OK for most drivers, for performance oriented your needs require better products:

1. Better brake pads:
Quite a few options out there. I chose EBC YELLOW PADS and they stop great, can get the rotors glowing and will still stop. Was able to stop from 100 to 0 with confidence multiple times. They DUST LIKE CRAZY and SQUEAL a bit but are very good.
EBC has the RED pad also which isn't as good, but perhaps EBC might make blue NDX pads if we can get enough orders. I'd be more than ready for a set as I love my yellows.







2. Rotors:
High carbon rotors will perform better and will be less prone to warpage than standard rotors. I was a fan of Racing Brake Slotted rotors until I found out they no longer offer it for the 4G TL. I love my Racing Brake Rotors on my MDX, 3G TL and 4G TL (front only) and was surprised they no longer offer the 4G even though the ridgeline and ZDX have the same rotor. Either way I've switched to EBC's new V Blade Rotor and am very pleased with them. Less noise and good grip vs traditional slotted rotors. Amazon had the best pricing for the rotors in my case.

https://ebcbrakes.com/product/bsd-disc/

3. Fluid:
Old fluid or fluid with 5% water can make your brakes feel very different! Use a good quality brake fluid and you'll notice a difference. Honda DOT3 is ok and typical brake fluid. You can use something better like a DOT4 fluid. I used Pentosin DOT 4 and it's better than HONDA but certainly not the best. Looking at Motul or another DOT 4 next year as the Pentosin can be boiled with the yellow pads and have vapor lock.

I've done 80-0 stops in all of my cars and managed to warp rotors due to the layout of the highway exit near my home where you have to set at a red light for 5-10 minutes due to traffic after leaving the highway doing 80. Only after getting Racingbrake Rotors in the past did my issues stop. Even with the factory pads I did not have them warp so it seems to me the issue is mainly the rotor not being able to get rid of heat.

Last edited by csmeance; 05-11-2019 at 09:54 PM.
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Old 05-13-2019, 09:30 AM
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Thanks guys. Great advice. XLR8 - I make sure not to keep on the brake pedal after coming to a long or hard stop. I either press them very lightly or keep rolling very slowly. Unfortunately that hasn't helped all that much. Well, I'm sure it has helped, but hasn't eliminated the problem. Thanks for the tips though. Others may not realize that pressing hard on the brakes during a hot stop can cause that buildup.

I've seriously considered EBC brake components but haven't pulled the trigger in the past due to cost. If I experience the same problems (or have the $$$ burning a hole in my wallet and just want to upgrade ), that's the route I'll have to go. I don't care about dust. My wheels are sort of a matte grey so it doesn't show up much. And I wash the car weekly or so, so there's rarely much buildup before it's washed off. I'd happily trade better performance for some brake dust. I also wax my wheels every few months which seems to mitigate dust buildup quite a bit. Thank you for the info. I'm think I'm at least OK on the fluid. It's just the cheapo Walmart brand but it's DOT 4 which I assume is better than the Honda DOT 3. I have no problem with brake response since the fluid it only about 4 months old. If I want to get fancy I might get the Motul DOT 5.1 next time but that stuff is a bit pricey.

Last edited by losiglow; 05-13-2019 at 09:32 AM.
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Old 05-15-2019, 10:13 PM
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I've gone through many sets of rotors and pads. They all do the same thing. I usually just get the cheapest rotors and pads, now, because it hasn't mattered.

One thing I thought about changing... Calipers. I don't know enough to know if will make a difference, but that's the only thing left I haven't changed. If I get my TL running again, this is my next maintenance item. Right front is very annoying to brake... Extreme pulsing.

Oddly enough, I've gone through 2 or 3 sets MORE of rears than fronts. :/ no idea why.
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