Brake Disc Retaining Nut Broke

[angrys3owner]

Hi All,

I was changing the brake pads and discs on my car yesterday and the screw holding the disc to the hub broke off in the hole, tried drilling a hole in the centre of the screw that was left then bashed an old allen key into the hole to let me turn it out, guess what, that broke off it the hole too.

Any ideas where to go from here, bought a new drill bit or ten today and nothing will drill out the screw anymore, I don't really want to buy a new Hub, so how does everyone else suggest sorting? Was thinking of drilling a new hole somewhere else on the Hub and threading that? any other suggestions as to drill bits or other ways of clearing out the hole? I'm sure if it take it to most garages they just say new hub sir.

Cheers,

Ben.

[grahambell]

Only DIY option I can think of is to use the end of a small cylindrical grindstone and slowly grind into the broken stud. Did it once with a snapped bolt with a broken stud extractor in it.

Apart from that it's off to the pros for spark erosion, though it's not likely to be cheap.

Either way, expect to have to re-thread the hole, possibly with an insert.

Might be less hassle trying to get used hub.

[steve_D]

Are we talking about the single countersink screw?

If so, and the configuration is how I suspect, then the wheel studs (or bolts) also go through the disk and into the hub thereby trapping the disk between the wheel and hub. In which case don't worry about the screw just make sure that when you replace the wheel the disc is sitting correctly on its register.

Steve

[angrys3owner]

yep steve that's the one, it's just to hold the disc in place whilst your putting the wheel back on as far as I can tell. but I don't really like the idea of leaving it like is for ever... Think I'll try and drill a new hole and thread the new hole at another point on the hub.

[lukeb]

Have you got access to a welder, and if so is there enough of the screw protruding to weld a bit of scrap steel to?

I find this often works. It's a two pronged attack, you have a welded connection to the offending screw which is mostly better than mole grips, stud extractors etc. You're also introducing a great deal of heat into the broken screw which has a similar effect to heating it with an oxy-acetylene torch.

[GreenV8S]

Drilling and tapping a new hole seems harmless but personally I wouldn't bother.

[angrys3owner]

thanks for the advice guys, looks like I'll leave it as it is as welding isn't an option because it snapped off in the hole with nothing sticking out.

Then when the weather is less upsetting I'll make a new hole and thread as it makes it a lot easier putting the caliper and wheel back on.

[DoctorD]

I did this on my M3 CSL a few months ago because I used too much torque when tightening the bolt up. They're deliverately made using quite soft metal. I retrieved the bolt by drilling a small hole into the centre of the head and then hammering a torx screw bit into this hole. Then using either a wrench or the socket set I just turned it anti-clockwise to remove. It wasn't difficult once I'd got a good hold of it and I was surprised to find that no matter how tightly I had torqued the bolt, it still took only a little effort to turn.

I personally wouldn't just leave it (particularly since it only takes 10 mins to remove using the right tools). Picture this, it's 8 months on and you drop your car off at the local tyre-fitters for a change of tyres. The kwik-fit boys use a rubber mallet to loosen the wheel from the hub and in doing so your disc moves a little off the hub face. Perhaps it's not as tightly on as you thought (but of course you cannot tell any more can you?). They re-affix the wheel, torquing it as normal but perhaps in reality there's a little movement because the disc wasn't seated flat when the wheel bolts were tightened.

Since it's probably possible to fix this broken retaining bolt wouldn't it be better to do so than take the risk?

[GreenV8S]

DoctorD said:

They re-affix the wheel, torquing it as normal but perhaps in reality there's a little movement because the disc wasn't seated flat when the wheel bolts were tightened.

The screw only holds the disc loosely in place; it is securely located by the wheel and will be clamped up tight by the wheel nuts. The screw stops the disc from rattling about when you take the wheel off, which is hardly a big deal when all's said and done. If you can refit the screw easily then it does no harm to refit it, but in my mind it's not something that is worth putting a lot of effort into.

[angrys3owner]

I have to say even on the other side of the wheel it doesn't hold the disc flat against the hub, but I agree I will do something about it, however it is not going to come out, I drilled a hole in the screw to start with then I as well hammered an old torx bit into the hole, went to undo the screw (had been soaked in WD40 for a long time) and the torx snapped in the hole too. you can even see it twisted before braking. Not amused!

I think I only have two choices, one is new hub - which seems a waste of money as it'll be a fortune in labour the other is drill a new hole further around the hub using the old disc as a guide as to when the hole should be, unless anyone has any bright ideas?

[davejw]

I did a track day at Bedford on Saturday and have to replace my discs cos they're trashed. The disc retaining screw was seized so I just drilled it out. It does nothing other than save old ladies loads of panic if the disc moves without a wheel to sandwich it in place. In my opinion, it's better to leave it out so that the new one you fit won't seize and do the same.....

Cheers,

Dave.

[spnracing]

I'm with the 'leave it alone' point of view.

A Mk1 Golf also has these screws and co-incidentally I just bought some cos mine were missing. However I only did this because lining up the wheel with holes in the wheel spacers, disks AND hub is a bit of a pain and I do this regularly because I go through a set of pads every other race meeting and swap wheels around lots too.

Other than making the wheel easier to fit these screws have no function whatsoever.

[iaint]

Same happened on my rx-7, had to drill them out. No problems after well over a year, lots of miles and track and v-max action...

[angrys3owner]

As I appritiated everyones comments I thought I should post up what I did...

I've drilled a new hole almost opposite the original in the hub and threaded the hole - hey presto I can now use the shiney new screw I bought (audi now use torx bolts so I'm hoping it won't happen again).

If anyone's interested whilst I've been looking around for other bits some tuning companies now sell a bar with a thread only at one end that you can use for holding the disc and wheel in line whilst you put the wheel bolts back in. can't seem to find the link now though. DOH!

[rumpelstiltskin]

You don't need to worry about it at all,the wheel bolts will hold it all together.If i have to take these broken head screws out i drill right in the middle of the screw with a very smal drill bit,then a bigger one,then a bigger one until you are a fraction off the diameter of the original hole,now poke about with a small pointed object(thick sewing needle etc) and try and lever out the very thin spiral of the original screw that is left,it should come out in a spiral,or bit by bit!