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I was swapping my brakes today, and did not wear gloves. My fingers were blackened and probably had some grease/oil mixed in on them.

At one point, I grabbed my disc brake's rotor accidentally. I left several full fingers' prints on the rotor.

I cleaned the rotors with brake cleaner afterwards. However, if I had not, would the finger prints have caused any problems?


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  • 2008 Toyota RAV4
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    All grease/oil should be removed before the last bolt is tightened. This is precisely one of the primary uses of the CRC Brakleen product. Oil and/or grease can become embedded in the brake pad thus diminishing its effectiveness longterm. – user16128 Feb 9 at 7:10
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    Hit the brakes a few times and see if the prints are still there. (Hint: they won't be.) – 3Dave Feb 9 at 20:38
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I've never considered fingerprints to be a massive problem in a "I drive a family wagon to the shops" context but if this is on your Porsche just before tomorrow's track day you might feel differently. That many rotors come with a film of oil to prevent corrosion is slightly more significant, and that should be thoroughly cleaned off.

Safety purists will likely advocate that all grease and contamination should be removed but in real life terms driving through a puddle contaminated with oil/ diesel is likely to splash your brakes with an equivalent amount of oily contaminants - the volume of grease deposited by fingers will be low because you can't work with fingers laden with large gobs of grease; most of it will be on the rag. In addition to this, the temperature that well-used brakes run at will tend to reduce oily contaminants over time, but don't be tempted to go out and deliberately cook new brakes just to try and remove a minor amount of oil as overheating new pads will do more long term damage

Only you can judge whether you feel your braking system is now deficient. It's normal for new brake pads and rotors to feel less grippy than the old ones, because the friction surfaces haven't had time to wear and bed together to form a large contact area, but after a few hundred miles they will have

Tip for future changes, if you didn't do it this time; open the bleed nipple on the brake calliper before you push the piston in, and drain the fluid as you retract the piston; doing this routinely reduces the amount of time brake fluid stays in the system, helping with the regular change needed. Fluid in the callipers is the most likely to be contaminated and is best expelled rather than pushed back into the rest of the system

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  • Thank you for the answer, and the tip on opening the bleed nipple! – Intrastellar Explorer Feb 9 at 22:11
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You should clean the rotors with brake cleaner.

If it was just normal skin oils you wouldn't have a problem, but your hands were contaminated with all manner of lubricants which are designed to stay put and not break down in the presence of heat and moisture. These could definitely degrade your braking performance, so clean the rotor thoroughly.

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