Stupid question about iron remover and brakes

**koj11** · 07-13-2022, 05:39 PM

So I had never used an iron remover before, but as I had gone much longer between details than normal, I added this step to my routine yesterday evening. I used Gyeon iron, and it seemed to provide great results. Wheels and all brake components were hit with the product as well, let it dwell for a few minutes, and hosed it off. This morning as I drove to work, I'm hearing a thumping noise from the rear when braking. There is no vibration in the car or the steering wheel. I feel a bit stupid asking this, but there's no way that the product could have somehow damaged something right? Usually thumping from brakes would make me think warped rotors. I just had brand new brakes put on in April, but it just seems like such a coincidence for there to be no issue at all until after I applied this product for the first time ever...

**dgage** · 07-13-2022, 05:56 PM

I don’t think it is possible for the product to have that effect, if anything it might cause surface pitting or similar surface issues but nothing structural. The only thought I have is had you driven much prior to washing the car? You have to be careful because metal quenching is done with oil andor water. If you hit hot brakes/wheels with a blast of cold water, that could potentially cause warping.

The only other thought I have is the iron remover got through some seals on the brakes or other component and it isn’t working as smoothly. But I’ve not read about any of that happening on any of the detailing sites I frequent.

**koj11** · 07-13-2022, 06:04 PM

The car had not been driven that whole day, and although it was a hot day over 90, it was evening and I was in the shade.

**Bruno Soares** · 07-13-2022, 06:39 PM

I don’t think it can cause it but I’m pretty sure the instructions on Iron-X say to not spray on the rotor directly. A little overspray is fine but don’t put it on the rotor on purpose.

**koj11** · 07-13-2022, 06:44 PM

Originally Posted by Bruno Soares

I don’t think it can cause it but I’m pretty sure the instructions on Iron-X say to not spray on the rotor directly. A little overspray is fine but don’t put it on the rotor on purpose.

I wasn't sure beforehand, so I tried to look up some information before I used it. Gyeon's page for iron literally has two pictures of rotors absolutely coated with the stuff.

**koj11** · 07-13-2022, 06:44 PM

I mean logically it doesn't make sense to me that it could cause it somehow, but the coincidence is huge. It's just so strange..

**JTS** · 07-14-2022, 01:53 PM

A stupid question is better than a dumb mistake.

**oneheadlite** · 07-14-2022, 02:20 PM

It's probably not rotor warpage, but brake pad transfer. If you look at your rotors, you'll likely find a couple shadow marks the same shape as your brake pads.

It's not uncommon for this to happen when cars sit in a wet/humid environment (at my work we called it Covid Rotor, from all the people that stopped driving when they could work from home), I'm guessing something about the iron remover caused a reaction and now you're stuck with the after effect.

In the future, I'd drive the car after using an iron remover on your wheels to minimize the chance of it happening.

As far as a fix for your current situation - a lot of times just the act of braking will "shave down" that pad transfer and it might go away on it's own, but if it's deep into the rotor they'll need to be replaced. The thumping you're hearing is the friction difference between the pad transfer spot and the rest of the rotor. You could try taking the car out and doing several firm braking applications from highway speed (slow from 70-40 in a safe space) with cooling time in between each application. Then drive at highway speed for a bit to let your brakes uniformly cool back down. Make sure not to sit stationary with your foot on the brake if your brakes are hot (recipe for pad transfer - happens all the time at track days. People come in from their session, park in the paddock with their foot on the brake while they talk to their instructor, and now the hot pads are bonding to the hot rotors).

**koj11** · 07-14-2022, 02:33 PM

This makes sense, but could this reaction still happen when cold and parked without the emergency brake on? My assumption was there is no actual contact between the pads and the rotor until/unless the brake is applied.

For an update today, on my morning drive to work, the noise is still there, but it's greatly diminished from yesterday. I have an appointment tomorrow morning to get the brakes looked at to make sure nonetheless.

**oneheadlite** · 07-14-2022, 02:42 PM

Originally Posted by koj11

This makes sense, but could this reaction still happen when cold and parked without the emergency brake on? My assumption was there is no actual contact between the pads and the rotor until/unless the brake is applied.

For an update today, on my morning drive to work, the noise is still there, but it's greatly diminished from yesterday. I have an appointment tomorrow morning to get the brakes looked at to make sure nonetheless.

Yes, even in your situation. Even though they're cold, yours is a result of the chemical reaction. And the pads are in contact with the rotors, even if only just.

If they're getting better, I'd try scrubbing them in like mentioned above and see if that takes care of it.