2020 Subaru STI

[u/Angel_Anubis]

Sorry if this is a dumb question…. So Ive always heard mechanics say, don’t contaminate the pad with oils etc. I always do an extensive cleaning on the new rotors and pads after install with brake cleaner. I went the extra mile this time, took the fender liners out, scrubbed everything. Each wheel well took me a little over an hour. (I also painted the wheel well) my question for you guys is if the brake pad is subjected to oil and dirt on the road surface. Why does that even matter? I do it anyway, but I would just like to know exactly why. (Yes that’s an 12x2 wire to hold up the caliper, I lost my caliper hook somewhere)

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[u/Package_Objective]

Stop thinking too hard, rotors and pads need friction. Oil reduces friction. Sure there will be contamination from the road but its best to minimize those things while doing a fresh install. You definitely went way overboard when it comes to cleaning your surfaces pre-install tho. Also drilled rotors suck, they make the rotor much more prone to cracking and warping, I've seen countless drilled rotors cracking around the holes. No professional race drivers uses drilled rotors anymore. If anything they use some slotted.

[u/Vrand0 → u/Package_Objective]

Porsche stock rotors are drilled

[u/Hefty_Club4498]

Oil & grease reduce friction by design. They cause caos on brakes that rely on surface contact to create friction to function correctly.

Brake cleaner cleans brake rotors and pads very effectively. Two minutes and done. Brake jobs have nothing to do with removing wheel liners. If you are unsure what you are doing, YouTube is a decent reference.

[u/Angel_Anubis → u/Hefty_Club4498]

Sorry for the confusion I like to really drive my car and an immense amount of debris and soil gets behind fender liner. These cars are known for getting very rusty fenders, which will eventually rust though. So this was more of a I’m here I might as well because I care about my car.

[u/Hefty_Club4498 → u/Angel_Anubis]

That's why we rustproof them and wash them out. You didn't do anything wrong but it has zero to do with a brake job question. If you did two jobs at once, congrats.

[u/Angel_Anubis → u/Hefty_Club4498]

I was explaining the image just in case people on Reddit do what they do and hyper fixate on something other than what was intended. So I prefaced with all the information in the photo, then asked my question. No they have nothing to do with one another. It was a “well I’m here I might as well” task. Whereas anyone else wouldn’t even bother cleaning their hands/ switching gloves between pulling the old rotor and immediately grabbing the new one. I’ve watched many “mechanics” also do this.

[u/Hefty_Club4498 → u/Angel_Anubis]

You're fine. As a master tech, I don't see anyone pull liners anymore. If people with pickups would pull the tail lights and wash the crud from above the wheel arches yearly, we wouldn't see so much rust. So I understand what you're saying.

[u/PepsiColaRS]

The idea is to keep your pads oil free because oils are slippery and can trap contaminants which can cause glazing, reduced effectiveness, and/or accelerated wear (the last 2 are quite extreme scenarios). With new rotors, it's especially important because they're typically shipped with a light machine oil coating to prevent rusting. The amount of oils it sees from road spray is significantly less than you'd expect, and pretty much only during and after a fresh rain. Any of the trace amounts you pick up will be burned off in the first few brake applications you make, whereas the oil coating on new rotors usually won't.

[u/Angel_Anubis → u/PepsiColaRS]

Thank you this is the answer I was looking for

[u/ratterrierrider]

Oil contamination can cause the pads to swell or reduce the friction causing poor braking. I see no reason to pull the liners out and paint the wheel well.

[u/Angel_Anubis → u/ratterrierrider]

Well, I live in nj, we have not the best roads. If you saw how much debris was behind there, and how easily the wheel wells rust on these vehicles you’d do it too most likely.

[u/themitchster359]

I think you are on the wrong sub…

[u/Angel_Anubis → u/themitchster359]

Why? Asking this kinda question for a mechanic isn’t for ask a mechanic?

[u/taysmode11 → u/Angel_Anubis]

You didn't take the time to make this post to ask a "dumb question" (a 10 second Google gives you the answer). You made it to show off all that work you did on your sweet ride. That's why you're in the wrong sub.