Difficulty compressing the rear brake piston (while rotating). Why?

[DaveTinNY]

Let me ask this after reading all of the great information: Is there any potential problem if the rear pistons were NOT pushed in all the way? (aside from not the obvious problem of having enough room to install the pads and then mount the whole caliper assembly in place around the rotor)...

What if I *thought* I had them pushed in all the way, yet the pistons were just binded as described above? I was able to remove and replace my pads and remount the calipers; I just hope a problem doesn't come up because the pistons weren't initially pushed in all the way.

Side note: The brakes have been fine aside from an initial problem of the left side inboard pad (with the clips on it) popping off the piston head groove. When it popped off I'd hear a clicking sound because the pad was skipping across the slotted rotor. Drove me nuts but I seemed to have resolved it.

[cristo]

You just need to push them in far enough to have enough room to
install the new pads.

[ofioliti]

... and with new pads, you pretty much have to push the piston all the way back otherwise there isn't much wiggle room to get the assembly back on.

[Hawkeye]

I provided the following on another thread this morning re: rotating/compressing the rear wheel piston(s). I just installed a set of CT 1521 Bobcats and, on the rear wheels, used a DISC BRAKE PISTON TOOL, mfg. by KD Tools of Lancaster, PA. to rotate/compress the rear pistons. I've had the tool for many years and have used it on both domestic and import vehicles. My recollection is that it was not expensive and makes this part of the job very easy. It works with a 3/8" drive rachet. You will need to use an extension but that is all. Go to KD Tools website and you can see what the tool looks like. Search under their "catalogue".

[scarletswalk]

[QUOTE=ofioliti;2725074]Well, I finally got to finish this 'project.'

It was the rear right piston that was giving me problems, so I decided to start on the left rears. I used the Harbor Freight tool. I rotated an PUSHED while rotating (with muscle power; not the screwing in action of the HF tool). After about 15 minutes of this (with breaks to find a more comfortable position to get more leverage!) this darn thing finally started to move in. Once it began moving in, it was actually not too difficult to push and twist. I switched over to needle nosed pliers (just for fun) and got it pushed in all the way! Whew! Got the new pads and rotors on and took a break.

Then I returned for the right rear piston. Worked on it for an hour with HF tool. I turned the heck out of it but it would not move back at all! I figured I just did not have the strength to push the darn thing in. So, I decided to try one more method described by Dr. Obnxs in one of his MC2 articles: Compress with a C-clamp and rotate with channel lock pliers. It worked like a charm!

I tightened up the clamp and even without rotating the piston, it moved back slightly. After I could not tighten it anymore, I took the pliers and gently grasped the end of the piston (careful not to catch the rubber) and rotated 1/4 turn. Then, tightening the c-lamp pushed back the piston some more. After about 4 turns with the pliers (1 full turn of the piston) I was able to push the piston all the way back in the with c-clamp alone. As it tightened the rotating disc at the end began to rotate as well and rotated the piston with it until the piston was completely retracted.

So, my experience was:

1. The rotating and pushing are indeed "independent."
2. Once you cannot push in, you need to rotate.
3. Rotating alone will not retract the piston (I tried for an hour!). (Markjenn, I am guessing that when you rotate, you may be also pushing in slightly on a less resisting piston.)
4. Even if the piston is ready to be pushed back (i.e. the 'sleeve nut' has been rotated back enough--see picture in post above), it may require some force especially at the beginning. That's where the c-clamp helped me.
5. I did this without dealing with the hand brake cable; no cracking open the bleeder valve; I did crack open the brake fluid reservoir and checked the level as the piston(s) compressed (had to remove a bit of fluid to prevent overflowing).

This little entry right here saved my ass today. Thank you so much. My dad and I tried changing the rear brakes and had a helluva time. Thank you.

[ofioliti]

Cool! Glad it helped.

Great MINI by the way!

[poushag]

only after I discarded the "plate" (part #1 as stamped) and hung the caliper using the bottom hex bolt (only) so that the caliper is rotated back on that bolt but part of the caliper is still braced against the rotor. This way I was able to use the thrust bolt to push and twist (clockwise) and the piston went back in smoothly (although it does take significant pressure). The disc adapter I used was stamped "M" and fit perfectly into the piston. My pads were pretty worn so I think the hardest part was just getting the piston started back into the threads. Every time I tried with the plate attached the thing would just bind up. Once I got rid of the plate it went pretty easy. BTW, it doesn't matter which thrust bolt is used after that. Either one can be turned clockwise while leaning into it with full body weight.

[jrwmini]

Thanks for all the helpful information. I spent a full day looking for the kit to compress the piston. FYI: The ones that Pep Boys and Advanced Auto parts have for loaners do not have the correct disc adapter. Borrowed a friend's Ampro disk brake kit and came across the same issue: The adapter plates are not the right size but are so close it is frustrating.

I called the dealership and they said the tool was over $400...Not a viable option if you're trying to save some $$.

Sounds the the HF tool kit works well... Will pick up today and hopefully finish the brakes tonight. Did not know about this whole twist and turn bit until I popped the caliper off and tried to compress it. Needless to say it is NOT going back on without compressing the piston.

Let's hope this works! She's sitting on jack stands in the garage at the moment.

[ofioliti]

Originally Posted by jrwmini

Thanks for all the helpful information. ...

Sounds the the HF tool kit works well... Will pick up today and hopefully finish the brakes tonight. Did not know about this whole twist and turn bit until I popped the caliper off and tried to compress it. Needless to say it is NOT going back on without compressing the piston.

Let's hope this works! She's sitting on jack stands in the garage at the moment.

If the HF tool does not work for you (it did not work for me) then try the C-clamp and pliers method as described in the earlier posts. Good luck!

[Capt_bj]

last time I looked

and I'm a post'er about the HF kit

it appeared that HF had CHANGED the kit . . . . so take all the comments about it with a grain of salt..... and/or come back here and tell us what's up.

[jrwmini]

You are indeed correct. The tool differs from the one pictured in the walkthrough. It is in a blue case and produced by "pittsburgh professionals". I bought the 18 piece kit for about $40. It worked like a charm. The adapter plate marked M was a perfect fit and it went pretty smooth.
It did bind up a few times one my first caliper, but overall was pretty easy. I was surprised, but I only needed to use the backing plate to get it started. Once I had it going in, the tool began to bind and was difficult to turn. I just backed off the plate a little and used hand force to push while turning. Holding the back of the caliper to brace it helped to stabilize it. Worked just fine for me! Good buy for $40 for sure.

[fanta]

I was having problems getting the rear piston to push in until I saw this thread. I could not get the brake caliper tool to push in the piston and gave up and saw the mention of using needle nose pliers. Worked like a charm on the driver side. The passenger side was a different story. I just didn't have the pressure needed to push in the piston with the pliers. Back to the brake caliper tool and no matter how hard I tried, I was just fighting myself as it appeared the tool was getting bound. It would get to a point and just not move anymore. After loosening the tool a bit, I did notice that the tool would turn, but the disc that actually fits onto the piston wasn't. After some inspection, I noticed the pin that held it in place was missing. Luckily the first screw I found on the workbench fit perfectly. A little grinding with the dremel and I was good to go. After that, the caliper tool worked perfectly and the piston went right in. Just a thought that you may want to look to see if the pin is still in place before trying to use the tool.

[kukaepe]

I just completed replacement of the rear pads and rotors on my '07 MCS. I have read all of the posts here concerning the HF tool and the binding being a function of the threads of the tool being different from the threads within the caliper and that made perfect sense to me. I decided to try the following HF caliper tool:

http://www.harborfreight.com/four-wh...ool-95713.html

I lined up the side of the "cube" with the pins that fit the caliper piston the best, inserted a 3/8" extension and using a short ratchet, simply rotated the piston clockwise slowly while applying a bit of inward pressure. The piston retracted into the caliper very easily...piece of cake. I did lubricate the boot between the caliper and the piston with silicone spray as suggested and did not experience "bunching" of the boot until the piston was all the way retracted....just reversed the ratchet and straightened the boot out. Perhaps to much is being made of the amount of pushing force required while rotating the piston....maybe that's why needle nosed pliers work. I hope this adds something to the "body of knowledge" on the rear pad replacement topic. By the way this alternate tool is quite cost effective at $6.99.

[MisterClean]

I took advantage of the 15% holiday discount by MINI MANIA and bought the red ebc pads set for my front/rear brakes. So later this year I will have the pleasure of working on the brakes for the first time.

I didn't purchase it...mostly because I didn't think about it at the time. However did anyone try the MINI MANIA brake caliper tool for the R56? Wonder if that would work better than the harbor freight tool?

Also, how difficult is it to gain access to the brake sensors if you replace those? Do you have to remove the wheel well liner to get to the connector?

[fanta]

Originally Posted by MisterClean

Also, how difficult is it to gain access to the brake sensors if you replace those? Do you have to remove the wheel well liner to get to the connector?

You do not have to remove the fender liners, but you will have to remove some screws to help bend/move the liner out of the way and snake your hand though to get to the connectors. The front is much easier than the rear.

[kukaepe]

I was able to replace the brake sensor without removing anything, there was enough room in my '07 MCS to get to the connector (actually 2 of them in the same location...also the ABS sensor in same place).