Snapped rear brake rotor bolt - unsafe?

[Incubus]

So I pulled the rear wheel from my project bike to clean it up and mount the new tire. I noticed that one of the brake rotor bolts was sticking out, so I decided to pull it out since I was going to pull off the rotor to clean it up and make cleaning the wheel easier. Long story short, apparently the last person to work on this back wheel cross threaded that bolt or something, jammed it in as far as he/she could, them left it. When I tried to unscrew it, it snapped.

So how unsafe is a back brake rotor with five retaining bolts instead of six? Drilling out that snapped bolt is going to be a genuine PITA and I figure my chances of actually saving the thread to be about one in four or five at best. FWIW, I consider back brakes to be for emergency use only.

Patrick

[DGXSER]

I have no engineering data to go on here, but the old saying goes that if it takes 3.75 bolts to hold something in place, then americans will use 5, the germans will use 6, the british will use 3 (sorry to our british contingent for the slam there) and the japanese will use 3.75.

So my opinion would be that an emergency is the worst tiem to find your brake rotor spinning loose.

[thewiz]

Now that's funny ..

Dgsxr ... Not so funny Patrick.

I can't really see the problem drilling out that bolt though. If you first center punch it, drill a small pilot hole in the middle, then step up to a drill size just slightly less than the thread size, you can take a pick or tiny punch and collapse the theads of the bolt inward and pull the remaining metal out with a needle nose.

That should leave whatever thread that was there intact .. if it was or wasn't crossthreaded, just run a bottom tap down there and clean things up ... then you should be good to go

[bikerphil]

5 out of 6 would be OK in my book, JMHO.

[Ivan]

The only problem I see with running 5 instead of 6 would be rotor warping. With one bolt not being torqued down right, a nice long hard stop will heat the rotor and cause it to warp, potentially. However, it may never be a problem.

[fredintoon]

- - - - So how unsafe is a back brake rotor with five retaining bolts instead of six? Drilling out that snapped bolt is going to be a genuine PITA and I figure my chances of actually saving the thread to be about one in four or five at best. FWIW, I consider back brakes to be for emergency use only.
Patrick

Goddamit Patrick,
emergency use is when you really need the f**ker!
Bite the bullet and get it fixed. The life you save may be your own.

[skids]

I would probably live with it that way until I was good and ready for some down time (snow flying).