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I'm changing the rear brake discs and pads on my Ford Focus C-MAX. I've done one side which was fairly easy, but on the other side I can't get the disc off. There is nothing holding it on as far as I can see but it won't budge. I can't pull it too hard because I don't want the car to fall off the jack, and I'm reluctant to hit it too hard with a hammer in case I damage the wheel bearing.

Does any body have any ideas about how I can get it off?

UPDATE

I've been hammering and bashing and levering, but the damn thing still won't budge. Thanks for all the tips, but are there any more ideas?

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up vote 19 down vote accepted

Cars falling off jackstands are no fun.

If you're careful you can heat up the rotor with a torch prior to whacking it with a heavy mallet. If you're not careful, you run the risk of warping the rotor (which is ok if you're getting a new one). Don't try this near fuel lines or the gas tank.

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Thanks! I tried your suggestion of heating the middle of the disc with a blow torch... and then after a slight tap with a hammer it fell off!! This is a much less violent method, and if anyone else has this problem then I strongly recommend trying this. Excellent tip - I just wish I could vote for this more than once!! – BG100 Mar 9 '11 at 18:09
    
Good tip. A heat gun may work for anyone that doesn't have a torch handy. – S_Niles Mar 9 '11 at 23:42
    
What about WD40? – Juann Strauss Nov 11 '14 at 8:53
    
WD40 is primarily a water displacement chemical. There are other things (Kroil, PB B'laster) that work better for freeing rusty bits from one another. – MrDoom Oct 23 '15 at 5:22
    
Worth mentioning that if you use a lubricant on a stuck brake disc you want to make sure that if you are re-using it you clean it thoroughly before re-fitting it, and then clean it some more so you wont contaminate the braking surface of the disc or pads. – Mauro Jan 15 at 10:42

Assuming there is not a screw holding it on (your experience with the other side tells you this), just give it a solid smack with a hammer. When I worked for Mercedes, it was not uncommon to need a 2-lb sledge to knock the disc loose. We would use two hands and swing really hard sometimes.. never heard of a messed up bearing from that.

Of course, this assumes you aren't reusing the disc.

If you aren't pressed for time, you can try spraying some penetrating oil around the hub and let it sit for awhile. It's questionable whether this will really penetrate far enough to help.

When you are putting on the new disc, use some anti-seize around the hub to help prevent the same issue in the future.

Edit for your update: Don't be shy. Smack the heck out of the rotor from the front and the back (if you can, sometimes the back is covered by a shield). Hitting it on the front face may seem counterintuitive, but it may jar it the right way to get it loose. Also, carefully aim for the outside edges of the disc. This applies more leverage compared to the center hub, which is where it's seized.

Use a real hammer.. a 2 -5 lb mini-sledge. A regular claw hammer isn't going to cut it. Swing that sucker with both arms like you are batting in baseball.

Double-check for a screw in the center area around the hub. Some manufacturers use a screw to hold the rotor in place while they build the car. The other side may have been missing this screw for some reason.

Safety Note: Wear safety glasses! You should be doing this anyways, but in particular, when you hammer at the edges of a rotor, bits of metal will come flying off.

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Thanks for the tips... I would have tried a bigger hammer if I had one, in the end heating it with a blow torch did the trick. – BG100 Mar 9 '11 at 18:10
    
+1 for suggesting penetrating oil. WD-40 is not as good for this as PB Blaster and other proper "penetrating" lubricants. – William Cline Apr 1 '11 at 19:40

In my experience when removing the old type of brake hubs you would need to hit quite hard without that hurting the bearings.

You might try spraying the disc with WD-40 and let that soak in for a bit and then knocking it again with a hammer. You would wan't to spray mostly around the bolts that fasten the wheel since there is most likely some corosion there that is making the disc stuck.

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1  
Keep tapping the rotor around the edges in a circular motion and the rotor will start to rock back and forth. – dave thieben Mar 7 '11 at 22:10
    
+1 for the WD-40 idea! – Tom Macdonald Mar 7 '11 at 22:10

I don't know about your model but most discs I've encountered have a couple of threaded holes in the hub part. They are often clogged with general road crud, so you may need to scrub the disc hub down to find them. If yours have such holes get a couple of bolts to match and screw them in, as evenly as practical. This will push the disc off the axle.

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Try a smaller hammer. What I mean is that a smaller hammer won't damage things like bearings, but it might get the disk to vibrate and shake loose. Otherwise a small masonry chisel inserted into the right crack and tapped quite gently could move the disk in the right direction.

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I have used a sledgehammer many times with great success. If you don't have a sledge, sitting on the ground and kicking the rotor (with heavy boots) works just as well. BUT I use 4 jackstands and the jack to support the car if I need to use this technique, because it's obviously dangerous. Loosely install one lug nut prior to trying either of these options to keep the rotor from flying off. I never had any issues with wheel bearings afterwards.

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Try this method. Looks like it would work for most cars and trucks. https://www.youtube.com/watch?v=pMuHKDI00rw

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I discovered a method purely by accident not long ago. It only works on a driven wheel and you need to be very careful when using this method.

Jack the car up and support if firmly on axle stands. If the car has a locking or limited slip differential you'll need all driven wheels off the ground.

Remove the road wheel from the brake disc you wish to remove and remove or drill our any retaining screws. Start the engine, engage the gears and get the wheels spinning. Now apply the foot brake sharply. This technique very rapidly overcomes any issues of corrosion of the brake disc to the hub. I've personally done it and it works but is certainly not a prescribed method you'll find in any workshop manual.

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This is exactly how I wound up owning the cheapest angle grinder I could find, except it was a Mondeo.

In my case, the inside of the disc had rusted enough that it was wrapping around the back of the hub, I could belt it with a mallet to the point that the whole car was shaking but it wouldn't budge.

I made 2 radial cuts in the disc on opposite sides, working from the outside right down to the hub. You don't need to cut through the mating face or even all the way through the rest of the disc as the heat stress will crack it along the cut when you're close to the hub. Once the cuts/cracks reach to the mating face of the disc (where the bolts go through) it'll open up slightly and you'll be able to hammer it off the hub. Be careful not to hit the wheel studs with the angle grinder... like I did.

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Also, be mindful of what's behind the disc where you're cutting through it and what you're firing sparks at. – squigbobble Jan 15 at 11:58

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