Caliper problem

[Mellow Matt]

My brakes are binding at the mo so I'm trying to sort them out, however, I can't swing the rear caliper up. I've undone the caliper lower mounting bolt but it won't swing up... I've retracted the pads using the alen bolt adjuster but they're still touching, so I thought that might cause a bit of resistance, but not much.

Any ideas as to what to do? I've got some plusgas, but don't want to spray it willy billy around the brakes!

I've pulled the slider pin out btw, so it's not obstructing it.

[MX-5 Lazza]

Have you got a lip on the outside edge of the disc that the pad is fouling on?

The calliper might be sticking a bit. If you've already retracted using the Allen key, try levering the calliper to force it back in a bit with something (don't force it too much though).

[Mellow Matt]

Thanks Lazza, I've got the caliper up I levered it a bit and jiggled it a bit harder than before (technical term, that).

I'm not sure what to do now though - the lower sliding pin was pretty greased up and corrosion free, and the whole caliper now swings up and now and in and out pretty easily - I'm guessing my brake binding problem is to do with the piston - it's pretty rusty:






The inside brake pad has a load more meat on it than the outside - is this indicative of anything?

The piston isn't completely seized, as the allen bolt adjuster does move it in and out, just not that much - any idea what I should be doing now?!

(I apologise if I'm covering the same areas as another thread, I know there are a lot of brake threads, and I have read through a lot of them!)

[piefacemate]

My rear brakes binding was caused by the pin that the caliper slides on, a new pin and plenty of copper grease cured it, but it looks like you've already eliminated that.

Reconditioned units aren't too expensive, especially if you do a swap for the old unit.

http://www.autolinkmx5.com/mx-5-mk1-18-192-c.asp

The rear brakes are complete crap at times.

Edited by piefacemate on Monday 11th April 12:43

[MX-5 Lazza]

piefacemate said:

Reconditioned units aren't too expensive, especially if you do a swap for the old unit.

[piefacemate]

Fixed ta!

[Richyvrlimited]

piefacemate said:

My rear brakes binding was caused by the pin that the caliper slides on, a new pin and plenty of copper grease cured it, but it looks like you've already eliminated that.

Ugh, copper grease is the worst thing you can use! It's an anti seize compound for threads, NOT a grease.

You want a moly grease for the slider pins, you can puck up a tub from Halfords for a tenner that'll probably last you your life and is useful for lts of stuff

Copper slip will gum up and re-stick the sliders in no time.

[Mellow Matt]

Thanks for the comments guys.

Does anyone have any advice for what I should do next? I'd like to try and fix them if possible (if only to learn how they should work!), but I'm not sure what to do?

Or is it pointless, and I just need to buy a caliper refurb kit (new piston/seals etc), or a whole new pair of calipers?

[Richyvrlimited]

Mellow Matt said:

Thanks for the comments guys.

Does anyone have any advice for what I should do next? I'd like to try and fix them if possible (if only to learn how they should work!), but I'm not sure what to do?

Or is it pointless, and I just need to buy a caliper refurb kit (new piston/seals etc), or a whole new pair of calipers?

The bit of the piston you can see in the picture is largely irellevant. It's the bit behind the rubber dust boot you should be concerned about, carefully pull it back and inspect the condition, it should be shiney, not corroded or pitted.

Unless you never change the brake fluid the piston is likely fine, but if it's not you can buy a new one (or easier just buy a new caliper). The poor mans method is to extract the piston and hit it with some fine emery paper to remove any raised spots, then replace, there's only 5 parts to the calliper, bleed nipple, the body, the dust seal, the piston and the piston seal, it's pretty simple, re-assembly is the reverse of disassembly (and a ballache )

90% of the time its the slider that's sticking, you remove the bottom bolt and the top pin is what the caliper slides on. If that's not extremely free, as in it takes barely any effort to pull it off the pin you need to de-grease the pin and the associated bit on the caliper, then add fresh grease - NOT COPPERSLIP.

[Mellow Matt]

Richyvrlimited said:

The bit of the piston you can see in the picture is largely irellevant. It's the bit behind the rubber dust boot you should be concerned about, carefully pull it back and inspect the condition, it should be shiney, not corroded or pitted.

Unless you never change the brake fluid the piston is likely fine, but if it's not you can buy a new one (or easier just buy a new caliper). The poor mans method is to extract the piston and hit it with some fine emery paper to remove any raised spots, then replace, there's only 5 parts to the calliper, bleed nipple, the body, the dust seal, the piston and the piston seal, it's pretty simple, re-assembly is the reverse of disassembly (and a ballache )

90% of the time its the slider that's sticking, you remove the bottom bolt and the top pin is what the caliper slides on. If that's not extremely free, as in it takes barely any effort to pull it off the pin you need to de-grease the pin and the associated bit on the caliper, then add fresh grease - NOT COPPERSLIP.

Thanks for that - I'll see if I can get a better look at the piston by pulling back the dust boot.

With regards to the slider, the whole caliper swings up pretty freely. It also moves inwards and outwards on the top pin pretty freely - it feels sprung though, so that if I let it go it will push itself outwards (i.e. towards me as I look at it), and I have to put some effort in to push it inwards. Is that what it's supposed to be like?

How would I pull the caliper off the top pin? There doesn't appear to be anything to undo - does it just slide off somehow?

Sorry for all the questions!

[MX-5 Lazza]

The pin goes into a blind hole. With a bit of grease in there it seals quite well so it's probably just a bit of vacuum sucking it back in when you try to pull it out. There shouldn't be anything physically holding it in.

[Mellow Matt]

MX-5 Lazza said:

The pin goes into a blind hole. With a bit of grease in there it seals quite well so it's probably just a bit of vacuum sucking it back in when you try to pull it out. There shouldn't be anything physically holding it in.

Ahh thanks, so that might be the crux of the problem!

So if I just pull it off the pin, re-grease and put it back it should stop this "springy" action, and hopefully sort the binding problem...?

Is there a method to getting the caliper off the top pin?

[MX-5 Lazza]

Mellow Matt said:

Ahh thanks, so that might be the crux of the problem!

So if I just pull it off the pin, re-grease and put it back it should stop this "springy" action, and hopefully sort the binding problem...?

Is there a method to getting the caliper off the top pin?

It should stay springy. Springy isn't a bad thing. Just gently pull the calliper off the pin giving it a bit of a wiggle on the way. There is nothing that should stop it coming off.
Clean off any old grease you find and put a thin layer of new grease on it and it should all be gravy

[Mellow Matt]

MX-5 Lazza said:

It should stay springy. Springy isn't a bad thing. Just gently pull the calliper off the pin giving it a bit of a wiggle on the way. There is nothing that should stop it coming off.
Clean off any old grease you find and put a thin layer of new grease on it and it should all be gravy

Ah, ok, so the this springiness might not be my problem. Balls.

I'll take it off and have a look at it and re-grease it anyway then.

[piefacemate]

Richyvrlimited said:

... NOT COPPERSLIP.

I'll sheepishly attempt to defend myself by saying my old man told me to use the stuff. Will do it properly next time.

[Richyvrlimited]

piefacemate said:

I'll sheepishly attempt to defend myself by saying my old man told me to use the stuff. Will do it properly next time.

Copperslip is brilliant stuff, I try to use it on every nut and bolt I fit if I remember, makes disassembly a breeze.

But it's not a grease

[skinny]

• carefully* press the brake pedal until the piston sticks out more - but don't let it pop out completely as it's a proper arse to get back in with the seal. pull back the rubber seal (making sure it's in good condition - if it's knackered then that's the cause of your rusty piston) and get some abrasive paper / wire brush / wire wool on there to clean the piston up. make sure not to leave any grit etc on there at all. then push the piston back in, grease up the sliders (as above, with moly or LM grease, not copper-slip)

[seismic22]

I fitted recon calipers a while back and still have issues with the rear brakes binding, i think thats why my mpg is so pants! I just cant seem to set them up properly, theyre either binding or if i back them off a little not working enough!

[skinny]

are you doing the adjustment properly?
back off the cabin end of the handbrake, adjust piston up using the screw until it locks the disc, then back it off 1/4 turn (or until it's free) then adjust handbrake so that it locks within 3 clicks but it's free when released.

[mozmajor]

I did exactly the same last weekend, the piston was rusty on top and basically the whole thing was full of crap and gunge. I cleaned it with loads of brake cleaning spray, peeled back the rubber seal covering the piston and sprayed in a ton of silicon lubricant. Went for a cautious drive on a road with no traffic and spent 10 mins continually applying the brakes and handbrake. It now works a treat with no rubbing. I've no idea if the silicon spray was a good idea, or how long it will stay working but my brakes are fine and it saved me buying a new caliper.