leperboy

Anyone got a good trick for separating a spacer and brake rotor? My 86.5 has the the stock spacers on the rear wheels and one seems pretty well stuck on the disc face.

I've got new discs, so I don't care about damaging the ones on there.

Thanks,
Matt

AO

I use a sharpened screwdriver. Usually a little tap is all it takes.

leperboy

You're the master, Andrew. That did the trick.

Thanks,
Matt

RyanPerrella

when you replace rotors and i suppose spacers as well, its not a bad idea to use anti-seize on the face of the hub to prevent the rotor from "freezing" onto the hub so that future removal is easy.

I had a real hell of a time on a BMW i owned, I had to break out a 10lb sledge hammer to break it free. That was only after dicking around with it for 4 hours with rust penetrant and other smaller hammers.

Garth S

Actually, antiseize may not be such a great idea : wheel studs act in tension to clamp the mating wheel/spacer/hub faces together ... it is the friction in these faces when clamped that keep the parts from rotating, for any rotation subjects the studs to a shear mode.
Not wishing to have any studs fail due to shear forces, I prefer to assembly with dry faces ..... even it that requires bringing out the BFH when it is time to knock things apart.

RyanPerrella

Garth,

I would love to hear others support your idea. Ive never heard of what your suggesting. The wheel properly torqued onto the hub will prevent any shearing of studs. If the wheel is properly secured then it DOSENT MOVE! Whats to shear? Nice idea but i dont think its realistic. What you suggest as a concern dosent seem like one at all to me.

Anyone else agree with this above theory?

RyanPerrella

Also,

Porsce wheels are hubcentric. They sit on a small lip on the hub, they never ride against the studs. The beveled nuts also prevent the wheel from moving even part of a degree in relation to the hub. If the wheels are properly torqued, you wont have any issue.

Your theory dosent make any sense to me

dr bob

Garth is exactly correct. There are more than a few warnings floating around about painting the hub faces, grease on them, anti-seize on them. All are pretty much a no-no if they modify the friction that's part of the clamping requirement. I can only speculate that the same requirements apply between the spacer and the rotor.

There are some pretty interesting things, like the zinc plated rotors, that are certainly OK. I'm not sure-sure, but one of the instant cold galvanize producte would likely be fine too. Look for one with a mil rating, like the CRC product. That's pretty much all zinc, with just enough "paint" to stick the zinc to the host metal. This stuff only goes on steel parts, never the aluminum BTW. Marine hardware stores carry the CRC, as will some better hardware and auto-parts places.

Shane

I got mine loose using a rubber mallet and a sharp blow on the side of the spacer!!

RyanPerrella

Garth and Bob,

While I had never heard that using anti seize was bad, actually i heard the opposite. After thinking about how the wheel is attached to the hub, and how the rotor is attached i can see some issue with not having enough friction on the face. While I mentioned that the wheel is hubcentric and the nuts are beveled to center the wheel. The rotor does not use the same system for mounting. The holes are typically slightly oversized and the hub slides through the center of the disc and it too is slightly oversized. Porsche does use 2 small screws but that is realy nothing. Often people never replace the screws cause they get stripped when removing them.

Ive honestly never heard of a failure where a brake rotor gets loose and shears off bolts, wether it had oil, anti seize or was dry. Not sure how big of an issue this is. It would then lead me to suggest that if friction is important, they i would suggest you remove all scale and surface rust from the hub whenever you have the rotor off. Scale will prevent full surface contact and you loose your friction coefficent.

I guess in the long run, removing rotors its not worth the peice of mind you get from mounting then dry, if you believe that. In all honesty, most rear rotors are only replaced once over the life of any car. The fronts you may go through 4 sets but all in all there are very few times when rotor removal ever done and is ever necessary. So the benefit of having an easy removal with the use of anti seize is then very limited.

leperboy

I don't want an argument, but I would like to know what is correct for my car. The WSM 46-11 says to "clean centering face for brake disc on wheel hub and apply a thin coat of Optimoly TA".

I did not apply the aluminum paste as recommended for the same reason that Garth and Dr. Bob state here, but is the WSM no longer the best approach?

Matt

AO

I have no idea what the radial forces are on a rotor while under braking, but as long as they are lower than the shear force needed to break the little screws that hold the rotor to the hub, the co-efficient of friction between the rotor and hub should not matter.

Gretch

I agree with it......... But I am just a nobody with a lot of shade tree and farm implement mechanic experience. You do not want those wheels to be able to move at all, period. For example, on hard braking, were the wheels/spacer combo move (twist around the center axis), even a little bit (streaching the studs as the did so), eventually you have a big problem.

Listen to the man. He knows what he is talking about. Clean the mating surfaces well and put them together the way they were designed to be assembled. Or don't.............. I remember a guy who thought it would be cool to use armourall on his tire treads..........You aren't that guy are you?

dr bob

I think the WSM recommendation applies to the centering surface only where the rotor slides over the centering ring. I've seen steel versions of those axles and hubs 'grow' inside the hole in the rotor from corrosion, to the point where they were one forever.

We are getting a little skewed from the original question, where the discussion is the surface between the rotor outer hub face and either the spacer or the center of the wheel. There's a difference between that and the rotor-to-hub interface.

ew928

I used to put Anti-Sneeze between the hubface and the wheel on my ex-Audi.
Galvanic action between AL alloy and steel would "weld" the 2 together nicely. Especially on the back wheels that got very little heat from braking action.
But that car had very little power but good brakes.

Before I learned how to swap on winter wheels, I used to take the Audi to a Tire shop.
Once this big 300ish lb mechanic came out all sweating and said it took him about 1/2 hour of pounding before that rear wheel would come loose.

So it wasn't safe to Anti-Sneeze the wheel/hub interface?
I don't do it on the 928 and the wheels haven't welded to the rotor. Yet. . . .

(One of the internet lores to loosen a stuck wheel was to loosen lugs and then drive car slowly and then jam hard on the brakes to free the wheel. Bet that shock against the lugs wasn't a good thing. Lucky thing was the Audi used lug bolts. Nice heavy duty steel ones. Cheep and easy to replace)