curt_928

Hi everyone,

I'm about to replace the rotors on my 79'. Unfortunately 30 years have frozen those two phillips screws to the rotors. Impact wrench and many hits have not budged one bit.. So will have to drill them out.. Are they REALLY that needed?

Looks like wheel is main pressure holding rotor on.. If I drill will find a way to put a replacement screw on.. am just wondering how needed they really are..

As always, many thanks in advance!

Curt

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79 5sp silver/blk
02 boxster 5sp blk/blk

John Speake

I am told they help center that disc onto the hub. Once you drill the head off, the thredded part will be exposed and you should be able to get it out as it will not be under tension.

I sheared the head off one of mine trying to get it out, it was easy to get a replacement.

underdog928

Hey Curt:

I just went through this painful process in prep for SITM. I have new ones to replace the drilled-out, ruined ones. If they have any use it would be to ensure that the rotor is seated correctly on to hub so that it's flush before you put the brake caliper and brake pads back on. So my recommendation would be to install new ones. I'd also put some molylube on them so that they're easier to get out the next time.

I was able to use an impact hammer to get out 6 of them, but the two in the front left needed to be drilled out. But even after you drill them out, you haven't gotten to the "fun" part of the process, that is, actually getting your old rotors off the hub. The rotors are actually press fitted onto the hubs. There are two (8mm IIRC) threaded screw holes in each rotor at 180 degrees apart. You will need to lubricate the holes with WD-40 or liquid wrench to get the screws into these holes. Once the screws hit the hub, you will need to very VERY carefully screw them in max of one turn at a time alternating between each screw until you get the rotor to move out away from the hub. The rotor will not be free from the hub until it's about 3-4cm (1.5 inch) away from the hub. If you have long screws you should be ok. If you have short screws, like I did, you'll have to hammer the rotor the rest of the way off. If you want to reuse the old rotor (and I recommend not to), don't hammer it off, because you'll wreck it. Once you get the old rotor off, completely clean/wirebrush the part of the hub that goes into the rotor.

Hope that helps.

GlenL

The only purpose for these screws is to hold the rotor in place before putting on the wheel. Drill out the heads. If the shank doesn't come with vice-grips...forget it! Just put on the new rotors and whichever screws worked out. If it's "none" then just put it together without them.

mark kibort

as glen said.
However, once the brake calipers are on, you dont really have to worry about rotor seating position. the lug nuts do that. drill them out with just trying to get the head off, dont go too deep. bang off the old rotors with a mallet if they are stuck. as long as you drilled off the head of the screw, they will come off if they are frozen. Then, the remainng screw should come out with a twist of a vice grip if not, leave it there and use the other one as the securing screw . I think i have one active screw on one side with the same issue from the beginning of the holbert car.(i drilled it out and took out the threads so its just a hole now. because it is not important, i didnt re-thread it.)

curt_928

Everyone, thanks for the replies!

Sounds like what I had in mind.. will make sure to get long bolts to get the rotors off.... this is going to be fun. ;-)

All the best,

Curt

Formula94lt1

Just get an impact driver, like 10 bucks... "frozen" or not, that will do the trick and you will be able to reuse them...

StratfordShark

I've always been able to get these off 928s and other cars I've worked on by using an impact driver, but the key thing is to try the driver first while the heads are in good condition, and not after they've been chewed up after fruitless attempt to turn with screwdriver!

The retaining screws aren't important once wheel is bolted on, but I can imagine that without them it may be a little frustrating to get the wheel on as the rotor could slip round as you try to get it over the lugs, or the wheel could pull rotor away from hub if it catches on it. If you're stronger than me though it's straightforward to line up the wheel and push it on firmly first go!

If you're worried about leaving shaft stuck in after drilling out head then you could also try cutting fresh slot using dremel and then using impact driver (with blade bit) on this - whether this was practical would depend on how badly chewed up the existing philips slots are.

SharkSkin

IMHO the screws are for assembly(mostly) as has been mentioned, but one benefit to maintaining/replacing them is that without them, when you take a wheel off, if the rotor shifts around it is possible for some crud to flake off of the backside and drop between the hub and rotor. Then when you put the wheel back on it won't spin true.

I'd say put the rotors back on in the same orientation as they were in when they came off, after thoroughly cleaning the mating surfaces and replace/reinstall the screws with a dab of anti-seize.

Gary Knox

Whenever I've removed these on my car(s), I've replaced them with metric stainless steel screws - available at a local hardware store. With a bit of anti-sieze, never a removal problem again.

Gary Knox

mj1pate

very redundant here...so apologies.
The screw helps prevent torquing the lugnuts with the disc off-center. With care, the lugnets can be torqued with the disc centered (without the screws). Once the lugnuts are torqued, the screws would offer nothing that 90ft-lb lugnut torque doesn't offer already.

Tom in Austin

Interesting discussion, I buggered one of mine by drilling out with too large a bit (took the threads out along with the screw head).

Isn't centering the wheel handled by the hub? I'm at a loss to see what these screws do once the hub centers the disk and the lug nuts clamp the wheel down onto it ...

SharkSkin

Yes, they are hub-centered.

heinrich

works for me.

Imo000

Not needed, only there for ease of assembly!