Ruined rear brake calipers?

[Matastrophe]

Hi, hoping someone can help me after my latest blunder.

I got a really good deal on some brand new drilled and grooved discs for my 95 N/A. Fronts went on no problem at all as would be expected, the problems came when i tried to fit the new discs. In my ignorance of the MR2 parking brake mechanism i used a piston tool to push the piston back inside the caliper, only to find i didnt have enough clearance to fit over the new discs and pads. So i tried it again and applied....more force. I did manage to move the piston back to clear the pads, but now my handbrake no longer does anything. Having done some more reading and watched some videos on this, i feel pretty stupid. Is it likely i have wrecked the internal working of the calipers? i havent got quite as far as getting under the car and checking cables etc, but i feel these are unlikely to be the cause as the handbake was working previously.

Any thoughts much appreciated.

[jimi]

Pretty good chance you have damaged the mechanism, may be repairable but will mean totally dismantling the calipers.
There's a very good article on refurbishing the rear calipers on a MK1 in Know Your 2 https://mr2oc.co.uk/know-your-2/mk1/mk1 ... ipers.html
Although it's written for the MK1, MK2 calipers are the same construction/mechanism, just the sizes are different.

[Matastrophe]

I was afraid of that, can't believe i was stupid enough to do this.

Next question, anyone got any rear calipers to sell?

[jimi]

That question should not be asked here. It should be asked in the Classifieds https://mr2oc.co.uk/classifieds/place-advert.html

[BYRNEY1984]

The rear caliper have to be wound back in. Not pressed like the fronts. But you’ve now learned that lesson. Inside the caliper is a threaded rod that the piston sits on. When you pull the hand brake lever this in turn rotates a spindle on the caliper. This in turn causes the piston to rotate on the threaded rod. This engaging the brake. What will have happened is you have either stripped the threads on either piston or rod. Or both. You will need to either get replacement callipers or easier strip yours down and get a rebuild kit pistons and all. Its really easy to do and can be done in a few hours. Its a bit but hope it helps. Oh and you can get left hand thread pins too. Thats why the brake caliper rewind tool kit comes with both left and right. Many years ago I worked for brake engineering who were bought out by TRW and no Z1 or someone. So have seen all sorts of brake caliper design. Although I am crap at spelling the word

[jimi]

You can see the end of the rod in this picture from the article I linked to above I seem to remember that the rod engages in a nut that is attached to the piston and is removable, I remember reading a post from someone who bought new pistons and had to swop the nuts from the old pistons as the new ones came without nuts. I think it was on here, I'll see if I can find it.

[jimi]

Found the thread https://mr2oc.co.uk/forum/rear-caliper- ... 63135.html as a bonus it has a few pictures of the mechanism

[Matastrophe]

Thank you so much for all the info. I'll have a go at stripping the calipers down and hoping against hope that its the piston that has suffered rather than the made threaded portion!
Really appreciate the help and advice, wish i had done a bit more digging before diving in without thinking!

[mr2-man]

Brakes international and/or Paul at TCB should have rear calipers in stock if you fancied just getting refurbished ones (I know because I was needing rear calipers a few weeks back!)