TIL a lot of shops are over-tightening disc brake caliper bolts

I was helping a friend at his shop in Bend last week and saw three bikes come back with rotor rub after a 'quick' brake adjustment. The tech was just cranking the two mounting bolts down hard, like 15 Nm or more. The spec is usually 6-8 Nm, just enough to hold it while you align it and then a final snug. Over-tightening warps the adapter or the frame mount, making a perfect alignment impossible. He switched to a torque wrench and the problem stopped. Anyone else run into this, or have a different method for getting them set right?

3 comments

3 Comments

tessa1772mo ago

Yeah, the "cranking them down hard" thing. It's everywhere. People treat every bolt like it holds a bridge together. My garage door opener install manual said 30 inch pounds. The guy used a half inch impact gun. Stripped the hole clean. It's a lack of feel, or just not knowing that more torque can break things. A torque wrench feels like a cheat code once you start using it right.

kelly.felix2mo ago

It's the same mindset that makes people crank every knob and button until it breaks. They just don't get that more force isn't always the answer.

flores.tessa1mo ago

You saying "over-tightening warps the adapter or the frame mount" is exactly right, but nobody's talking about how the bolts' own tolerances play into it. Most guys don't realize caliper bolts are often torqued to yield on purpose by the factory, meaning they stretch a tiny bit when you tighten them right the first time. Once you crank them past spec, you're not just mushing the aluminum mount, you're permanently deforming the bolt threads too. Then when you remove and reinstall them later, the torque reading is all wrong because the bolt already stretched out. It leads to a false click on the torque wrench or the bolt loosening up over time because it's lost its spring. So you end up chasing the rub again in a month and blame the pads, not the hardware that was ruined from day one.