Author Topic: Removing brake caliper from aging rotor  (Read 678 times)

bender

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Removing brake caliper from aging rotor
« on: July 27, 2017, 09:38:07 AM »
I'm having some trouble removing a brake caliper.  Removed both caliper mounting bolts, and the caliper/housing now move somewhat freely on the rotor.  Unfortunately there's a rusty 'lip' that's formed on the rotor (the pads have worn away rotor material and are seated into the rotor a bit) and I can't get the caliper off the rotor easily.  The pads are bumping into this lip and won't come off.  I tried gently hitting it with a hammer and it's not working.

It would be great if I could get the piston to retract while still mounted, but that's not likely.  I only have access to one slide pin while the caliper is mounted, and the hex bolt had a dust cover that allowed the head to rust out so it can't be turned with a hex driver.  So I can't take the slide pin out easily.  I was hoping to get better access once I take the caliper off the rotor.

Goal is to replace the brake pads, possibly the rotors if it needed, but they are still thick enough despite the rusted lip.  Everything looks safe and functions well, there's probably about 10-20k left in the pads.  I'm just trying to get in there and do some maintenance (lube pins and new pads).  Any tips on how to get the caliper off?  Do I need to be more aggressive with the hammer?  I don't want to break things...


Clean Shaven

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Re: Removing brake caliper from aging rotor
« Reply #1 on: July 27, 2017, 10:14:54 AM »
Hit the caliper harder with a hammer.  Use a dead blow hammer if you're worried about harming the caliper -- personally, I'd just use a 2 or 3# hand sledge.  Calipers are tough. 

WranglerBowman

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Re: Removing brake caliper from aging rotor
« Reply #2 on: July 27, 2017, 10:49:18 AM »
Be more aggressive with the hammer or unbolt the caliper and use a pry bar or press to put pressure on the loose caliper's piston to push the piston back into the caliper a little.  You could probably also hammer a screw driver or wedge between the brake pad and brake disc to try and get the caliper piston to depress a little.
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trammatic

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Re: Removing brake caliper from aging rotor
« Reply #3 on: July 27, 2017, 01:19:37 PM »
Why replace the pads if there's 10-20k left in them?

To get those off, I usually just pry with a large screwdriver.  You'll likely crack the pad getting it out this way, but if your goal is a new one anyway, it doesn't matter.

bender

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Re: Removing brake caliper from aging rotor
« Reply #4 on: July 27, 2017, 01:29:16 PM »
Why replace the pads if there's 10-20k left in them?

To get those off, I usually just pry with a large screwdriver.  You'll likely crack the pad getting it out this way, but if your goal is a new one anyway, it doesn't matter.

Pads have 80k on them now (I'm easy on the brakes).  I at least wanted to lube the slide pins, but figured I might as well put in new pads while I'm in there.  Thanks for the tip with the screwdriver - I may try that too.

trammatic

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Re: Removing brake caliper from aging rotor
« Reply #5 on: July 27, 2017, 01:41:37 PM »
Why replace the pads if there's 10-20k left in them?

To get those off, I usually just pry with a large screwdriver.  You'll likely crack the pad getting it out this way, but if your goal is a new one anyway, it doesn't matter.

Pads have 80k on them now (I'm easy on the brakes).  I at least wanted to lube the slide pins, but figured I might as well put in new pads while I'm in there.  Thanks for the tip with the screwdriver - I may try that too.
Yup, just put the screwdriver down the middle of the caliper and pry against the middle of the rotor. 
Image courtesy of: http://builttodrive.com/wp-content/uploads/2007GMCEnvoyFrontWheelBearings/07GMCEnvoyFrontWheelBearings00012.jpg

bender

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Re: Removing brake caliper from aging rotor
« Reply #6 on: July 27, 2017, 01:45:58 PM »
Great picture - that should make it easy thanks!

Clean Shaven

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Re: Removing brake caliper from aging rotor
« Reply #7 on: July 27, 2017, 01:55:57 PM »
[car geek]

Photo of screwdriver prying against GM caliper bracket is not the way you want to pry if you just want to remove the caliper, on that type of a disc brake.  On some GM (and some Nissan, and I assume others), the bracket remains affixed to the axle housing, and the caliper detaches separately, and then you can remove/replace the pads.  You don't have to remove that bracket unless you want to remove the rotor.

[/car geek]

BlueMR2

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Re: Removing brake caliper from aging rotor
« Reply #8 on: July 29, 2017, 10:03:19 AM »
If you think you may be doing this often enough to buy tools, instead of a large screwdriver, there are actual small screwdriver sized pry tools.  They have the advantage of a bend for prying as well as a tip more suitable.  Less likely to do damage with those, and they're not expensive.

I usually pry (very carefully) a little to push the pistons back a little (if they're the kind that actually do push back in, some are screw in...) and then use a rubber mallet to beat the caliper past the lip.  Note that there's a spec for replacing rotors based on thickness.  A rotor with any wear to speak of will obviously have a lip, but the if the lip is really bad, you're probably past the rotor service limits anyways.  Easily checked with a micrometer, but they're a bit pricy to buy and aren't commonly available for borrow/rent.

Syonyk

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Re: Removing brake caliper from aging rotor
« Reply #9 on: July 29, 2017, 08:59:29 PM »
Is it a single piston caliper (pads exposed on one side, as shown in the image)?

A large C clamp will compress the piston back and get you the clearance you need - it goes between the back of the piston housing (on the back side) and one of the visible openings for the pad on the near side.  Put the frame around the back and put the screw side on the front.  Then compress the piston back gently.

This works on most calipers.  I've run across a few where it won't due to how the parking brake adjustment mechanism works, but it's worth a try.

If you've got pistons on both sides, just use a good sized screwdriver.

Reusing pads with 10-20k miles left on them when you're replacing the rotors is just sort of silly.  IMO.  Put new pads on - the old pads are mated to the likely grooved rotor surface, so won't mate properly to the new rotors, and you'll have very poor braking until they wear flat again - and, oops, there went a lot of those 15k miles.  Get new pads.
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HipGnosis

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Re: Removing brake caliper from aging rotor
« Reply #10 on: July 31, 2017, 08:29:04 PM »
Is this just one caliper you can't get off?
If you can get the one on the other side off, it may give you some insight on how to approach the 'stuck' one.

One shade-tree way of compressing a caliper piston is:  put the 'head' of a big screw driver between a pad and the rotor.  Then put a big vice-grips on the shaft of the screwdriver and use that to turn the screwdriver.

But...  Some rear brake calipers NEED to have the piston turned for it to be compressed.   Google your model to find out if that applies to you.

HipGnosis

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Re: Removing brake caliper from aging rotor
« Reply #11 on: August 05, 2017, 10:51:12 AM »
Well..?

Did you get it off?

bender

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Re: Removing brake caliper from aging rotor
« Reply #12 on: August 05, 2017, 06:46:19 PM »
Thanks for all the advice!  I haven't had a chance to give it a try again.