Frozen screws on front brake rotors

74goldtarga · 08-10-2007, 05:12 PM

Like all things on my car the screws that hold my front rotors to the hubs do not move and I have stripped the screw heads in my attempt to remove them. (I think the screws might be made of cheddar) What do I do now? All advice welcome as I have no idea. Tapping the screws out of the hubs doesn't sound like something I would be good at, I would probably end up having to buy new hubs, spindles, bearings, A-arms, struts, and ball joints (assuming I could get those parts off of the car successfully). Thanks in advance.

Techno Duck · Techno Duck's Garage

Depending how damaged the head of the screws are, you can use a impact driver to get them off. I have removed some really messed up screws before with one and never had one it couldnt remove.

If the heads are really toast, you can drill them out.

http://www.sears.com/sr/javasr/product.do?cat=Mechanics+Tools&pid=00947641000&vertical=TOOL&subcat=Automotive+Specialty+Tools&BV_UseBVCookie=Yes

toolboy62 · 08-10-2007, 05:40 PM

Just drill 'em out and replace 'em. If they are phillips head they will tend to center your drill bit so all you have to do is keep the drill straight. Use a small-ish drill to start, then drill the head off. you may then remove the rotor. then select a drill bit 1-2 sizes smaller than the normal tap drill size for the thread of the screw. Assuming that you don't just wind the rest of the screw out the back of the hub while drilling, you should then be able to do it with the tap. Use anti-seize on the new screw.

It does take a little bit of a special touch, but it's not all that difficult. If you're near DC stop by my house and I'll do it for you. I have done this quite a bit due to my habit of restoring rusty old cars. Just did this on the seat mounts for a guy's '63 Studebaker the other weekend, and those were snapped off bolt stubs so I had a little work to get 'em straight.

nate

nynor · 08-10-2007, 05:43 PM

i use a manual impact driver to remove these, the kind that you smack with a ball peen hammer while twisting. works like a charm.

HondaDustR · 08-10-2007, 05:54 PM

Yeah, drill the heads off, pull the rotor, and clamp some vise grips on the stub to screw it out.

74goldtarga · 08-10-2007, 06:30 PM

Thanks a lot guys for the good advice, I'm encouraged.

Tidybuoy · 08-17-2007, 09:52 AM

After you do get those screws out, replace them with BMW allen head screws. The fit perfectly and the allen head is musch less likely to strip...

Vern

74goldtarga · 05:52 PM

Thanks guys, I bought a impact driver - the kind suggested that you whack with a hammer, $10 at a local tool store. Worked like a charm, can't express how thankful I am for the advice given here. I bought some metric stainless screws at the hardware store, the allen head screws were there as well and I thought about getting those but since the technique with the impact wrench worked so well I plan on using it in the future. BTW - by the time I got going with the impact driver the screw head had a round hole in it - didn't seem to matter though - verifies what duck said about messed up screws - I concur. Thanks also for the suggestions for techniques I didn't use, I have no doubt those concepts may help me in other areas in the future.

idontknow · 08-18-2007, 06:23 PM

I'd be careful about the quality of the stainless screws. I replaced a few suspension bolts and nuts with stainless a few years ago. After a few autoxs I felt the rear suspension was not gripping right and eventually would clunk while turning. Jacked up the rear end and noticed the nuts holding the sway bar bracket on the right side were missing. The nylon lock ring was still there and on the left side the nuts had split almost through. The hardware was brittle, weakly magnetic, and failure prone under stress.

Just my $.02 on using stainless hardware in critical areas.

deekay911 · deekay911's Garage

These screws aren't in a critical placement. They don't do anything useful a far as I can see. Can you imagine those 2 screws holding your front suspension together? All they do is keep the rotor from falling off (it wouldn't anyway!) while the wheel is off. When the wheel is on the lug nuts are doing all the work. Replace them with anything you like, even leave them out, doesn't make much difference.

74goldtarga · 08-18-2007, 06:32 PM

thanks Idontknow,

It was the best available in the correct size at the corner hardware store.

idontknow · 08:42 PM

Quote:

Originally Posted by deekay911

those 2 screws holding your front suspension together

It's the 5 screws that bolt the rotor to the back of the hub, those 5 screws transfer all the braking force from the rotors through the hub to the wheels.

The 2 screws that hold the rear rotor in place are fine to leave off, the wheel studs transfer the braking force on them.

DarylJ · 08-19-2007, 06:16 AM

Quote:

Originally Posted by idontknow

It's the 5 screws that bolt the rotor to the back of the hub, those 5 screws transfer all the braking force from the rotors through the hub to the wheels.

Can you explain that one? The wheel studs go through the front rotors as well. NOBODY would build a car that had a few screws holding the braking system rotating force together (and yes, I know by making that statement I'm opening myself up for pictures of weird cold-war era eastern european cars, but I'm willing to bet nobody will find any).

deekay911 · deekay911's Garage

i think there is some confusion here. The 5 wheel studs, that the lug nuts attach to, are the things that hold everything together at the front - the rotor to the hub and the wheel to the hub. These are more than screws, they are IIRC a splined interference fit into the hub itself. The 2 screws I believe 74 goldtarga is referring to, which in my opinion do practically nothing, are the the 2 small, short screws that locate the rotor to the hub whilst the wheel is off. These regularly round off and can be safely drilled out and left off.

Dark Skies · 08-19-2007, 05:24 PM

Quote:

Originally Posted by idontknow

I'd be careful about the quality of the stainless screws. I replaced a few suspension bolts and nuts with stainless a few years ago. After a few autoxs I felt the rear suspension was not gripping right and eventually would clunk while turning. Jacked up the rear end and noticed the nuts holding the sway bar bracket on the right side were missing. The nylon lock ring was still there and on the left side the nuts had split almost through. The hardware was brittle, weakly magnetic, and failure prone under stress.

Just my $.02 on using stainless hardware in critical areas.

You should NEVER use stainless steel on stressed areas - it work hardens and is prone to letting go.

toolboy62 · 08-19-2007, 05:42 PM

Quote:

Originally Posted by Dark Skies

You should NEVER use stainless steel on stressed areas - it work hardens and is prone to letting go.

most stainless hardware commonly available is somewhere between grade 2 (cheap hardware store crap) and Grade 5 or 8.8 (minimum acceptable in automotive applications.) I'll use stainless for engine dress up or hanging exhaust systems but never for anything under any serious amount of stress. Stock suspension bolts are probably 8.8, 10.9 or possibly even 12.9 depending on application so definitely you do not want to downgrade to stainless. Just use anti-seize paste on the threads if you anticipate corrosion being an issue.

nate

toolboy62 · 08-19-2007, 05:47 PM

Quote:

Originally Posted by deekay911

i think there is some confusion here. The 5 wheel studs, that the lug nuts attach to, are the things that hold everything together at the front - the rotor to the hub and the wheel to the hub. These are more than screws, they are IIRC a splined interference fit into the hub itself. The 2 screws I believe 74 goldtarga is referring to, which in my opinion do practically nothing, are the the 2 small, short screws that locate the rotor to the hub whilst the wheel is off. These regularly round off and can be safely drilled out and left off.

True.

to elaborate, the lug studs don't actually hold the rotor in position on the hub rotationally, the friction between the rotor and hub due to the lugs being tightened down actually does. in other words the lugs aren't loaded in shear to any substantial amount during acceleration or braking, only in tension. the real transfer of torque is from hub to rotor through friction, and then again from rotor to wheel through friction.

The screws... I'm not sure why they're there. They make sense on a VW or BMW where the lugs are actually bolts. But on a Porsche they aren't necessary to help you put the wheel on (and anyone who's had a VW with a busted off stub of a screw left permanently in their hub can tell you, when you don't have that screw indexing the rotor to the hub, changing a tire is a royal PITA.) Maybe the hub and rotor were balanced/trued as an assembly at the factory, and they're there to help you index the rotors if they're removed for whatever reason?

nate