Jonny Cut Corners

So I happened to take the front wheels off my Legacy yesterday (replacing driveshafts and ball joints) and I noticed that my nearside brake rotor was missing 3 of its 12 bolts.
They'd sheared off, as the shaft and nut were still in there.

Anyone experienced that before?
This car is my daily driver, never used on track. Mostly just medium-fast driving on A & B roads.

I'm not looking to vilify the supplier here, just trying to understand how normal/abnormal this might be?

stockcar

very abnormal.........would suspect that they are the 'wrong' bolt albeit brake bolts don't have to be massively strong or simply they have been over-tightened on installation and hence stretched??

you only require 14nM to be correct

Jonny Cut Corners

They're M6 high tensile 12.9 grade bolts, so I wouldn't say they're under specified. Obviously I can't speak for the torque they were originally tightened to.
But I've spoken to the manufacturer and he's suggested that the cause is most likely corrosion under the nut on the inside face. As the rust has expanded its increased tension on the bolts.
Entirely plausible and the inside face of the rotors is getting a bit scabby so it fits.

In fairness these brakes are 4 years and nearly 30k miles old, so I'll order up some replacements.

If anyone else out there has 2 piece brake discs and especially if they're looking a bit corroded then go check your bolts!
I wonder if you were to tap on the head of each bolt if you could hear if any were cracked?

stockcar

have never had a correctly installed rotor bolt simply fail either on road or track in far too many years to remember (must be circa 30+!!)

1509joe

iTrader: (2)

Agree with Stockcar have overtightened them before and sheared them myself