[gosi]

Hi, I am not that knowledgeable about brakes, so I was hoping someone could help me diagnose my issue.

I was doing a high speed stop when my brakes started shaking violently and there was a noticable sound as well and a bit of a burning smell. After that I took a picture of both my front rotors, shown below, which to me show signs of uneven heating. The back brakes look fine. I noticed some mild shaking with agressive braking before and also noticed some brake pad material build up on my left front rotor. Right now for normal usage the brakes work fine with no shaking even at high speeds.

I am on stock pads. I am looking to upgrade anyway, so my question is how much work do I need to do to restore my brakes? Do I need to replace my front rotors or could I refinish them? Is my issue due to poor OEM pads or could something else be the cause of this?

[overcoil]

was the noise a squeal or grind

1) inspect the tire pressure and lug nut tightness. Always chk the basic stuff first.

2) use your finger to feel if finger nail tip catches on grooves in the disc, if they do that a sign the disc are problematic - could be from brake pad.

3) then spot a light onto the pad friction material of the brake pad, look at a picture of a new pad to see the thickness of the backing plate and the actual brake pad friction material. I'm not sure what minimum pad material should be, however, it the friction material looks to be just a few millimeters thick then you probably just dealing with badly worn brake pads.

4) do you feel vibration in your steering wheel when braking in any of the scenarios ?

The odor kind of points to brake pads being overwhelmed. The shaking could be a warped rotor or even a front ball joint or damaged link. If you lift the front tire off the ground and grab the wheel at 12:00 and 6:00 and shake the wheel back and forth and if you have enough play to create a sharp knocking sound then ball joints may be shot.

Most important is that brakes should always be in prime condition and inspected.

[aerobod]

I would say that the brake rotors may have formed hard spots possibly spaced every cooling vent apart, likely due to uneven cooling after hard use. I'm assuming this based on the pitch of the heat treatment marks in the photos. If there are hard spots, rotor replacement is the only way forward, but the dilemma is that it would take a machining of the surface to see if that was the problem. From what I can see with the uneven heat marks, the surface of the rotors are not even from a friction perspective, leading to pulsing while braking.

Did you come to a complete stop with the car within 10 minutes of getting the rotors really hot? That or going through water with hot rotors would be the most likely scenario for uneven cooling.

[gosi]

Originally Posted by ScottSinger

was the noise a squeal or grind

1) inspect the tire pressure and lug nut tightness. Always chk the basic stuff first.

2) use your finger to feel if finger nail tip catches on grooves in the disc, if they do that a sign the disc are problematic - could be from brake pad.

3) then spot a light onto the pad friction material of the brake pad, look at a picture of a new pad to see the thickness of the backing plate and the actual brake pad friction material. I'm not sure what minimum pad material should be, however, it the friction material looks to be just a few millimeters thick then you probably just dealing with badly worn brake pads.

4) do you feel vibration in your steering wheel when braking in any of the scenarios ?

The odor kind of points to brake pads being overwhelmed. The shaking could be a warped rotor or even a front ball joint or damaged link. If you lift the front tire off the ground and grab the wheel at 12:00 and 6:00 and shake the wheel back and forth and if you have enough play to create a sharp knocking sound then ball joints may be shot.

Most important is that brakes should always be in prime condition and inspected.

Neither. A low pitched sound that got progresively louder together with increased shaking.

My tire pressure are good, lug nuts are tight as well.

As I was feeling the disc today I didn’t notice any grooves, but there is definitely a high spot on the disc at the point that is discolored. Pictures attached - this is after a day of driving after the event.

If my pads were below the minimum, I woulf get a warning. But there seems to be a good amount of material left.

Yes I noticed a very slight braking force variation at medium pedal pressure for a long time, but it was almost undetectable. After yesterday it’s clear to me something is wrong.

I check for suspension play today as I was looking at the brakes and all is good there.

[gosi]

Originally Posted by aerobod

I would say that the brake rotors may have formed hard spots possibly spaced every cooling vent apart, likely due to uneven cooling after hard use. I'm assuming this based on the pitch of the heat treatment marks in the photos. If there are hard spots, rotor replacement is the only way forward, but the dilemma is that it would take a machining of the surface to see if that was the problem. From what I can see with the uneven heat marks, the surface of the rotors are not even from a friction perspective, leading to pulsing while braking.

Did you come to a complete stop with the car within 10 minutes of getting the rotors really hot? That or going through water with hot rotors would be the most likely scenario for uneven cooling.

I always try to be easy on the brakes if they’re cold and if I do an emergency stop I put the car into neutral and use the hand brake instead. But clearly I am doing something wrong because I also ruined the brakes on my previous car

From the picture I posted above do you think it’s worth geting the rotors resurfaced? I can tell by using my finger that they are uneven. If I replace them, are there any better aftermarket alternatives (from a performance standpoint) or are OEM my best bet?

[overcoil]

Originally Posted by gosi

I always try to be easy on the brakes if they’re cold and if I do an emergency stop I put the car into neutral and use the hand brake instead. But clearly I am doing something wrong because I also ruined the brakes on my previous car

From the picture I posted above do you think it’s worth geting the rotors resurfaced? I can tell by using my finger that they are uneven. If I replace them, are there any better aftermarket alternatives (from a performance standpoint) or are OEM my best bet?

probably BEST getting NEW rotors and pads. I know nothing about aftermarket parts that would perform better, but other members are very knowledgeable.
You seem pretty knowledgable yourself.

your garage floor is very nice.

[aerobod]

Originally Posted by gosi

I always try to be easy on the brakes if they’re cold and if I do an emergency stop I put the car into neutral and use the hand brake instead. But clearly I am doing something wrong because I also ruined the brakes on my previous car

From the picture I posted above do you think it’s worth geting the rotors resurfaced? I can tell by using my finger that they are uneven. If I replace them, are there any better aftermarket alternatives (from a performance standpoint) or are OEM my best bet?

When they are resurfaced, the sound of the brake lathe should indicate if there are hardspots, as it won't be a clean "swooshing" sound that a sharp tool will produce as it cuts. If you have hardspots causing the unevenness (due to a change in crystal structure in the rotor with excessive heating), the only solution is new rotors.

For general road use the OEM brakes are fine, if you are tracking more than occasionally I would upgrade the whole brake system. Changing just the rotors to aftermarket won't have any significant effect on brake performance.

Also, from your pictures it looks like there is slight discolouration of the paint on the caliper due to heat. It is worth inspecting the piston seals and checking that the pistons still move freely (just a slight retraction under hand force should be enough to move them), as excess heat can damage the caliper.

[gosi]

Originally Posted by aerobod

When they are resurfaced, the sound of the brake lathe should indicate if there are hardspots, as it won't be a clean "swooshing" sound that a sharp tool will produce as it cuts. If you have hardspots causing the unevenness (due to a change in crystal structure in the rotor with excessive heating), the only solution is new rotors.

For general road use the OEM brakes are fine, if you are tracking more than occasionally I would upgrade the whole brake system. Changing just the rotors to aftermarket won't have any significant effect on brake performance.

Thanks to both of you for your information.

Do you have any idea what could have caused this? I’d prefer to avoid this happening again.

Edit: Where do you see discoloration? I think they are just dirty.

[aerobod]

Originally Posted by gosi

Thanks to both of you for your information.

Do you have any idea what could have caused this? I’d prefer to avoid this happening again.

Edit: Where do you see discoloration? I think they are just dirty.

You can see blue and straw coloured patches due to heating to at least 370C, that sort of colouration is a characteristic of reaching the tempering heat-treatment point of steel, which could lead to uneven hardness of the rotor.

I think it is likely due to exceeding the safe thermal capacity of the brakes, especially as you had a burning smell. A bigger brake system, efficient brake cooling ducts or change in braking technique would be the solutions. Better pads may make the rotor problem worse if you can't shed enough heat between stops.

Sometimes you just have to renew components between track events. My son's Corvette C5 Z06 requires new rotors about every 5 track days due to cracks forming in both stock and aftermarket rotors with OEM calipers and aftermarket pads. He could spend about $4,000 on a decent upgrade, but would rather just replace the rotors and pads at the moment. We did manage to increase the rotor change frequency from 2 days to 5 with better cooling, though.

[gosi]

The car was never tracked afaik, also I’m *relatively* gentle with my brakes, ie. I don’t abuse them, and what bothers me is that my rotors have a prominent ridge that must have formed slowly through regular use, not by just one hard stop. Apparently that’s where most of the heat build up is now and that’s causing the brakes to shake. But I think this latest event just highlighted an issue that was present before, I just didn’t task the brakes enough for it to become apparent. It annoys me because I don’t know if the issue will come back since I don’t understand the cause.

I’ll report back if I get any more information, if anyone will be interested.