Using a small grinder or disc cutter.
What ten years does to a brake disc!
Occasionally a brake disc gets so rusted in place that it will not come free using normal methods.
A ten year old Honda CRV came into the household this week that was riding on it’s original brake discs, yup, ten years old! They were incredibly rusty and corroded.
I tried the usual methods to try and dislodge them based on 25 years of doing this kind of stuff.
- Gentle (and not so gentle) tapping around the brake disc edge with a soft face hammer.
- Soaking the rusted parts with a penetrative oil and more tapping.
- Using the caliper bolts in the ‘push out’ screw holes, which just cracked the disc and ruined the bolts (only available from the Honda main dealer).
- Using a pair of bolts in the caliper mounting holes to try and force the disc outwards (whilst hitting rotor). So much tension built up in the mounting that I feared it would break.
OK then, what to try next. Big hammer? Nope, that could ruin the wheel bearings by dimpling the ball bearing races inside. Judicious application of heat with a torch? Nope, a brake disc is big and would need a LOT of heat to work which might scorch the grease in the wheel bearing and anyway it’s way too risky.
But then I had an ‘aha’ moment. Remember how easy the disc cracked when I tried to use the caliper bolts to screw the disc out? If the discs are so brittle why not try cutting part way through the outer edge of the disc and then splitting it the rest of the way.
OK, I know that sounds extreme, but was actually not too bad once I’d accepted that this was the only sensible option. The tool: a 4″ mini grinder fitted with a very thin cutting disk.
Of course suitable eye and hand protection is a must with this kind of job and you’d be a fool to attempt it without them.
Wear something to protect your hands and eyes for this job.
Find a space on the disc where there is already a hole, either a wheel stud hole or other fixing hole.This makes it easier to split the disk once you have cut part way through it.
Rotate the disc so the hole you’re cutting towards is in a place free of obstructions. Usually at the top is good just to the side of the disk shield etc.
Slowly cut through the disc from the outer edge towards the wheel bearing in the centre. Cut down and into the hub part of the disc slightly. Stop and lift away the cutting disk every few seconds once you hit the hub, looking for a dark spot which indicates that you have cut through the disk/hub to the backside. Don’t cut further or you risk cutting into the wheel hub itself.
Work slowly through the disc towards the centre.
You will not be able to cut all the way through the disc/hub without damaging the wheel hub but that’s OK. The metal is very brittle and can be ‘cracked’ the remainder of the way using a chisel or even a big old screwdriver. Simply tap the chisel or screwdriver into the slot you just cut until the disc cracks through, from the end of your cut, through the hole and into the centre.
Gently tap the chisel into the cut until it cracks through the remaining metal.
Usually this is enough to break the rusty bond and expand the disc enough to wiggle it off. You might need to drive the chisel in further to open it up more.
Wiggle back and forth to remove the rusty brake disc
In extreme cases you might even need to do another cut directly opposite to completely cut the disc in half.
The rust that was preventing this brake disk from coming off.
I hope that helps! I won’t deny that this is an extreme way of removing a brake disc, but if it won’t come off by using all the usual methods this method will always work with minimum fuss and no damage to the wheel hub or bearings.
Let me know how you get on!
Stay well
By Ian Anderson
Comments 13
Great info. In fact, I “invented” this very same method on my own just a few days ago, not having the good sense to first do a web search. I did, however, use a reciprocating saw as well as the mini-grinder to make the cut. With good quality bi-metal blades, the cast iron cuts easily and, because you can cut straight across (rather than at the radius of the 4″ wheel), you can cut the rotor right down to the hub. Beyond that, sawing probably poses less risk of injury than grinding.
Author
Nice one Don, great minds think alike! One tool I don’t have, but one I suspect, should it join the stable would lead to another ‘how did I manage without this tool’ moment (the first, many years ago the purchasing of a Fein Multisaw…).
You’re right about the narrow radius of the mini grinder, hence the gentle tap with the chisel to crack the tiny last little bit. I still like the method, I always hated using a big hammer on anything with a bearing.
Glad you got the blooming things off, amazing how rusty they get huh!?
Thanks for the kind comment and for stopping by,
Have a great weekend!
Ian
Just wish I’d read this before I pulled out the bearing using method number 4…
Author
Ouch! Hope you managed to get it sorted out. Must be something in the design on these motors. Been working on cars my whole life but never seen rotors as rusted as these…. Cheers for the comment.
The chisel the guy used to spread the cut in the disc is old and has a mushroomed head.
never use a chisel in this condition, grind off the mushroom head, you will note the
mushroom has several splits around it. grind these off until there is a nice smooth
circumference to the end of the chisel you hit with the hammer. If you leave these split
bits on they will fly like bullets when struck with a hammer, they will penetrate your skin
of takes your eye out if you are not wearing googles
Author
Thanks Peter, you have a keen eye! I have to agree with you, I should dress the end of this particular chisel and your observation is perfectly valid. But also I have to note that the said chisel was manufactured in the 1950’s and in all my 32 years on the tools I think I’ve only had a piece break off once and that just fell harmlessly to the side. I recon the steel was better tempered in those days (softer and more malleable maybe?), I doubt the more common cheaply made Chinese chisels would fare so well (I suspect the tempering may be the same throughout….) so, yes. Keep your chisel ends tidy folks!
Thanks again Peter, well spotted!
Best regards
Ian
what is the size of the bolt at the center
Author
What do you mean, the hub bolt? You don’t need to remove that to take off the brake disk.
Thanks
Ian
Wished I saw your tip before trying all the others. It worked like a charm. Well done and thanks for sharing!
hammered for hours seen your video and it was off in ten minutes great video
never though to do that
Author
Did exactly the same Vince. Got to the point where I was desperate, so I thought; desperate measures! It was the ‘new’ thin blades for the mini grinder that made me think of this method.
Marvelous that it got you out of a jam too, magic!
Thanks for the comment!
Cheers
Ian
great tutorial…..instead of pounding with a big hammer, used your idea to cut off the rotor — worked great. thanks!
Author
It’s much easier since they brought out those really thin blades isn’t it Fred? The old thick ones used to remove so much material and make so many sparks!
Thanks for dropping in!
Cheers