[DURBANPOIZIN]

so iv had the car for over a year now (2016 Mazda 6 sport) and approximately 5 months ago I started to develop an issue with the brakes. The car will shake at speeds of 35-50 mph when slowing down. Iv had the rotors changed about 4 months ago in the front(they said pads were like new, but I changed them today to ceramics to make sure) I’m going to check the back pads and rotors today. Is there anyone having this issue or anything recommendations. Like I said the front rotors are like new and I just did the pads today please help it’s shaking pretty bad now probably going to go out of service until fixed.

 

[Archerfish]

Are you braking hard? If yes, it's normal because the ABS or whatever it is called is activated.

 

[TalonTsi90]

ABS or whatever it is called is activated.

Not possible unless its really wet or icy out. The OP needs good rotors and pads. Centric and Powerstop z23 pads are what i run on my 3.

 

[bdc101]

Hard to see it being anything other than warped rotors. You sure they were brand new (replaced) and the shop didnt just resurface?

 

[Cdn17Sport6MT]

Really rare to have warped rotors; rather, it is differentially-deposited brake material due to improperly bedded-in brakes. Bedding-in new brakes is not practised by many people. They are usually properly bedded-in on racecars, not so much street cars.

 

[TalonTsi90]

Really rare to have warped rotors;

No, its not rare. People dont know how to drive. They wait till the last second to stop at a light and dont get any heat into the rotors and pads, then stand on them to stop quickly heating them and then holding the pads against them to keep the car moving. This will certainly warp the rotor. Since car pads are made differently, its rare that they glaze like they could a couple decades ago.

Bedding them helps, but a pre-stop contact before the actual braking can help heat the whole rotor more so that holding at the stop light doesnt create a smaller hot area. Even with the proper bedding i do/did on my current ones, i still try to keep my foot off the pedal at stop lights when i can. Of course this means i have to be vigilant to make sure someone doesnt rear end me if they dont see the brake lights. Also, getting that lttle bit of a pre-heat helps you stop faster if you can get into that habit, it does take a while.

 

[GerryB]

That's great advice on proper brake bedding, however a statistically zero percentage of drivers will know anything about it. As mass market passenger cars, it can't be expected that anyone will do this. So, Archer makes a good point. That doesn't in any way dismiss the presence of substandard parts being part of the problem and yes, rotor warping does happen. But pad residue after firm stops is more likely the issue unless the OP is really testing the limits of friction.

Sent from my SM-G960U using Tapatalk

 

[Archerfish]

So, Archer makes a good point. That doesn't in any way dismiss the presence of substandard parts being part of the problem and yes, rotor warping does happen. But pad residue after firm stops is more likely the issue unless the OP is really testing the limits of friction.

Sent from my SM-G960U using Tapatalk

I was running about 60 kph or below and I was downhill when I tried braking hard. I felt that shuddering and I did this on the same private road several times with the same result. I can also feel this if let's say I'm running at 100 kph and I need to brake suddenly.

I dismissed the idea of a warped rotor because he said he replaced it and I assumed that it's good.

As explained, it could be possible that all of you are correct that something is wrong with the rotors and pads. Now, is there a way to confirm that you have a warped rotor by simply looking at it?

 

[tango]

I was running about 60 kph or below and I was downhill when I tried braking hard. I felt that shuddering and I did this on the same private road several times with the same result. I can also feel this if let's say I'm running at 100 kph and I need to brake suddenly.

I dismissed the idea of a warped rotor because he said he replaced it and I assumed that it's good.

As explained, it could be possible that all of you are correct that something is wrong with the rotors and pads. Now, is there a way to confirm that you have a warped rotor by simply looking at it?

If it's very bad you might be able to see some differences in the way light hits the shiny surface. But, the best way to do it would be to use a dial indicator. These are not super expensive, costing around $50 or so. That's above the "sweet spot for buying nice-to-have stuff" so I have no plans at this time to get one. But this is the professional way to do it.

I recently experienced pulsing while braking, and subsequently replaced all the rotors and all the pads. Problem solved. There is the possibility that defective parts were used, especially if we are talking about budget items. I replaced the stock rotors with Bendix in the front and Wagner in the rear. Bendix pads front and rear. The only reason I didn't go with Bendix rear rotors was because I couldn't get them at the time when I purchased. But I'm satisfied with the setup as it is. No biggie.

 

[Archerfish]

But, the best way to do it would be to use a dial indicator. These are not super expensive

And it is possible to use that without removing the rotor? You'll have to excuse my ignorance with cars. 😀

 

[tickerguy]

Yep.

In my ~40ish years of driving and wrenching on my cars, as well as that of many others, I have only ONCE seen an actual rotor that was out-of-true but wasn't wildly obvious (e.g. gouged due to the rivets when the pads were worn beyond limit, etc.) But I have seen SEVERAL times people complain about "warped rotors" and in about 30 seconds (after taking how much time is required to jack up the vehicle and remove the wheel) proved to them that the rotor was NOT warped.

It is differential deposition of pad material which results from improper (or no) bedding. Over a few hundred to a couple of thousand miles of ordinary driving in most cases the pads will bed properly, but if you get them hot and then stop with the pads on the disc JUST ONCE during that period, and didn't bed them first, you start the destructive cycle that leads to judder.

If you have actual warped rotors you can feel the feedback from it in the pedal. If that feedback is not there the rotor isn't warped. Unfortunately once it happens, unless you catch it VERY early, it produces crystalline changes in the rotor disc and there's nothing you can do to unscrew that condition -- thus the rotor(s) involved have to be replaced or it will come back. Even turning them doesn't help.

 

[Archerfish]

Even turning them doesn't help.

I'll have to ask why. I mean, isn't it that you are removing the "excess" material? And in doing so, you balance it.

EDIT: I think I get it now. Since you removed the "excess" material, it is no longer balanced in terms of mass. One side can be lighter or heavier. I still want to hear your explanation, please.

 

[TalonTsi90]

When i say warped, i mean, out of true and it takes a few passes to turn them back. As in, they wobbled on the lathe.

 

[bdc101]

When i say warped, i mean, out of true and it takes a few passes to turn them back. As in, they wobbled on the lathe.

In my younger wrenching years I tried this, and turning them most definitely did not get the rotors true again.

 

[tango]

And it is possible to use that without removing the rotor? You'll have to excuse my ignorance with cars. 😀

The proper way would be to remove them, but the dial indicator will usually have a magnetic base that can be fitted in a convenient location. You can rotate the rotors on the car by hand and wherever there is an out-of-true situation, the dial indicator will pick it up. But...if that out-of-true condition is in the bearing (ie a wobble) it could very well show up as a wobble in the rotor as well, even though in this case the rotor might be fine. But that can be checked as well, to eliminate that possibility.

No need to worry about not knowing, my brother. We're here to learn. If I have said something above that is incorrect then I would have learnt something too.

 

[Cdn17Sport6MT]

The claim being made is that somehow, due to the cooling - locally, and not uniformly around the periphery of the rotor (due to getting the brakes hot then stopping and not moving, with brakes continuing to be applied) the metallurgy has been changed... so much so that turning them on the lathe results in either the cutting of the bit being non-uniform (i.e. the rotor remaining thicker [once machined] where the material is harder [this is a bit unlikely, though]) or the rotor being harder locally and then subsequent rotor wear is less at the harder areas and accordingly the brake action pulses. Doesn't happen immediately though.

Essentially the cast iron rotor(s) are being heat treated. Actually, the grey cast iron, being quenched... the faster-cooled areas of the rotor being converted to martensite (I think). Actually, it may be that the area under the brakepads might be cooling slower than the rest of the periphery of the rotor... or if it's wet, rainy, it may be that the area under the pads is being cooled much slower than the rest of the rotor periphery...

Martensite is hard... but to be honest I don't know if it is steel that is heated to a certain temp then quenched converts to martensite... or if grey cast iron does this. (My engineering metallurgy course was ~ 45 years ago, hehe).

SO, in these circumstances, the only solution is rotor replacement.

Interesting side note... The first car I drove, learned to drive on, had for a good while after too... a '70 Oldsmobile Cutlass, had 9" dia frt brakes, drum brakes. Absolutely inadequate for the car... (which had a Rocket 350 4 bbl, 310 gross HP...). BUT... that car had absolutely smooth brakes, no pulsing... fade, yes, but no pulsing, no vibration.

 

[tickerguy]

I'll have to ask why. I mean, isn't it that you are removing the "excess" material? And in doing so, you balance it.

EDIT: I think I get it now. Since you removed the "excess" material, it is no longer balanced in terms of mass. One side can be lighter or heavier. I still want to hear your explanation, please.

The problem is that there is no "excess" material (e.g. "high" areas.) The judder is caused by different coefficients of friction (deposition of pad material) and if you don't catch it quickly (if you DO just wire-wheel the rotor and re-bed the pads -- it'll be ok) is that you wind up heat-treating the rotor unevenly. If you chuck such a rotor in a lathe to turn it you'll find it isn't out-of-true.

Once that happens you can remove a bit of material but the heat-treating problem (and thus the different coefficients) remains as its well into the metal and the problem comes right back.

If you actually have a warped rotor (or one that's not sitting flush on the hub due to debris or corrosion you didn't remove when you replaced it) you can feel it in the pedal. Judder doesn't reflect back into the pedal at all.

 

[Racoon293]

Could sticking caliper guide pins cause the OP’s issue? Or the rubber bushing that’s on the pin being worn out or damaged?

 

[tickerguy]

Yep @Racoon293 it will.

 

[astateofmike]

I have this same problem with my 2016 6 Touring and I am using EBC Redstuff pads and their rotors. Red Pads were great on my 2014 6mt, but with the AT I have now, I have the problems even more so. My theory is I don't down shift....so rely on the brakes.

I change the fronts myself (leave the rear and Ebrake to the shop) and take the time to bed them in. My issues started when I had to go to SoCal for a weekend and well, traffic is just an issue and with more than a few close encounters and super hot stops, I got the judder.

My question is, does anyone think changing from the 1 pot Mazda OEM caliper to and aftermarket 4 pot caliper would help? I have been on the fence as I am just a commuter driver and spirited weekend play, but have questioned if a 4 pot caliper would apply more even pressure on both sides of the caliper and help with this issue.

Ironically, my wife's 2015 CX5 GT AWD/AT (and driver input may be the difference) has never had this problem even when I have driven it 2 or 3k miles in a few days...