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Sheared off brake bracket screw...what did I do wrong?
Hi -
I have a 2010 base Boxster that I track; recently decided to have a dedicated set of track rotors and pads. Was swapping out the track brakes for my street ones (first time I have worked on the rotors so not experienced at this).
I had removed the screw that holds the bracket for the brake line so that I could swing the caliper out of the way and not risk pinching the lines or hurting anything. When reattaching the screw, I sheared off the head. I have attached a picture. I tried to be careful and insert with a small socket wrench as I had used my cordless impact driver on another one and sheared it off too (ugh...the downsides of being a repair newbie).
The net is that the rotor in the picture I couldn't remove, I think that the parking brake was snagging on the bottom of the rotor so I essentially have given up and will take to my trusted Indy to fix. But for my own learning, what did I do wrong so I prevent this issue in the future.
(brake calipers are horribly dirty...previous owner of the car painted them yellow and the brake dust seems to have baked into the paint)
I'm guessing you removed those bolts using the impact driver? That weakened them enough that when they saw even normal torque on them the heads came off. What to do? With brakes - an impact driver should only be used to LOOSEN high torque bolts - like the wheel lugs and the caliper mounting bolts (which are one-time-use according to Porsche - replaced every time they're removed.) Never use the impact driver to tighten. Tightening should be done with a proper size torque wrench for the fastener being tightened,
Also, that fastener looks like steel screwed into aluminum which can cause corrosion and make it impossible to remove. If you use a small amount of aluminum Neverseize when you install those types of screws, that will prevent lots of fastener problems.
Ouch! I know being track-side this advise may not wash, but I give a good soaking to older undercarriage (chassis and brake) bolts with Kroil or another good brand of penetrating oil. I usually let it soak overnight then go to it the next day. Also anti-seize is good but can affect some torque values depending on the size/depth of thread engagement. As for impact tools I rarely use them first, usually as the "last resort" so to speak. Good on you for getting into it though! Each thing you do will increase your knowledge of your car and no matter what may break it always be fixed (so far at least for me!).
I will order that kit too for my upcoming brake job.
Alternatively, if you have a local Fastenal store you can buy your own stainless steel stud "kit" and save a few bucks. Here's what you need with part numbers. I did this conversion 4+ years ago.
Fastenal part #:
Brake line bracket bolt replacement (8 needed for my GT4):
M6 x 1.0 x 25mm SS stud (MX2550025A40000)
SS washers (1140355)
SS nylock nuts (1L2550000A40000)