1.8 Na Front Brake Caliper Problem? - Problems - MX5Nutz Forum

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1.8 Na Front Brake Caliper Problem?


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#1 Popeye110

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Posted 16 May 2020 - 08:55 AM

Hi - I have been working on my '97 Harvard. I've replaced the discs and pads and sent the original calipers off for a full refurb and paint.

The discs are 20mm and I have fitted greenstuff pads.

 

37ECio.jpg

 

The problem is that the caliper will not now fit over the discs and pads - nowhere near! The rear ones were tight, as you would expect, but I reckon I'm somewhere around 8-10mm off getting the fonts in.
The piston is fully retracted;

C1Fd4e.jpg

My recollection is that the original pistons went back further? My worry is that the wrong pistons have been fitted, here is the length below. Can someone confirm my thinking or measure a piston if you have one kicking about, or have I missed something else - please help, this is driving me nutz!!

WM16te.jpg

rasWjs.jpg


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#2 Dickie

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Posted 16 May 2020 - 10:32 AM

Hi,

I have not got a piston to measure but the ones you have fitted are too long. they should fit flush with the caliper with the it retracted.

Have a look at the Mx5parts website picture of a mk1 piston.

You might have to take the paint off the mounting surface where the caliper bolts to the hub assembly as well, even with the correct pistons.

Its a bit snug with all new parts.


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#3 Martin Y

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Posted 16 May 2020 - 10:45 AM

I agree with Dickie; the piston should be able to retract until it doesn't protrude from the seal. 

I might have an old one in the garage - will check.


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#4 carl s

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Posted 16 May 2020 - 01:05 PM

Yep, I just changed the front pads and I compressed them back to being flush with the caliper body, Silly question but in the third pic you have the end with the sealing O ring facing outwards is that right? surely it should go in the other way.


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mk1 1991 Eunos with RS NB drivetrain: https://www.mx5nutz....howtopic=322586

ex - mk3 2006 2.0 sport

ex - mk2 1999 1.8is JRSC


#5 Martin Y

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Posted 16 May 2020 - 01:42 PM

…  Silly question but in the third pic you have the end with the sealing O ring facing outwards is that right? surely it should go in the other way.

 

Not sure what you mean.  Which pic shows that?  The groove on the outside of the piston is to locate the dust cover seal and should be toward the outside end and so the open end of the piston faces out.  The brake fluid seal o-ring is in the groove inside the caliper of course.

 

Anyway, I checked the garage but sadly it looks like I took my old front brake parts to recycling.  Sorry.  I suppose it's possible they're the right pistons but there's something obstructing their going right into the caliper.


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#6 Martin Y

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Posted 16 May 2020 - 01:55 PM

Handy photo on Autolink website shows how a refurb caliper ought to look with the piston fully retracted:

 

https://www.autolink...new-11267-p.asp

 

Yours definitely isn't going in nearly far enough.


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#7 carl s

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Posted 16 May 2020 - 04:06 PM

Ah that's the groove the dust cover seal goes into, I forgot the brake fluid seal was in the caliper itself

 

There's a few on eBay that show the sizing, this one is for front brakes for an early NB but it should be the same I think when you look on the NA/NB compatibility charts on Miata.net

 

s-l1600.jpg


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mk1 1991 Eunos with RS NB drivetrain: https://www.mx5nutz....howtopic=322586

ex - mk3 2006 2.0 sport

ex - mk2 1999 1.8is JRSC


#8 Martin Y

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Posted 16 May 2020 - 05:48 PM

Interesting.  Good find.

 

That shows a piston 46mm long and Popeye measured 47mm.  But the problem is a lot more than 1mm.  Closer to 8-9mm.

 

Looks like the length of the piston is not the issue, rather it's that for some reason it can't be pushed right down into the caliper.


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#9 carl s

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Posted 16 May 2020 - 06:04 PM

Interesting.  Good find.

 

That shows a piston 46mm long and Popeye measured 47mm.  But the problem is a lot more than 1mm.  Closer to 8-9mm.

 

Looks like the length of the piston is not the issue, rather it's that for some reason it can't be pushed right down into the caliper.

 

Bleed nipple screwed in too far? or is that a daft idea


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mk1 1991 Eunos with RS NB drivetrain: https://www.mx5nutz....howtopic=322586

ex - mk3 2006 2.0 sport

ex - mk2 1999 1.8is JRSC


#10 Popeye110

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Posted 16 May 2020 - 06:17 PM

Thanks for all the answers - its definitely fully home, although I will re-check again for my own sanity... I think if it was the bleed nipple fouling it would be much more obvious, I hope.

That 46mm one I am guessing is the same as I have.

Still mystified - I've changed discs and pads a few times but never a caliper and never sent one away for refurb by someone else.

The difference between the Autolink pic and mine looks about the 8-9mm I am needing.

I'm going to ring MX5 parts on Monday and get them to measure one for me. 


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#11 dadbif

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Posted 17 May 2020 - 12:15 AM

Are both callipers the same?
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#12 Popeye110

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Posted 17 May 2020 - 08:19 PM

Hi - yes both the same and just been and double checked they are 100% fully back against the barrel of the caliper


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#13 Popeye110

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Posted 21 May 2020 - 08:51 PM

And they say size doesn't matter!!
Got some pistons from MX5 Parts today and bingo. Not as much in it as I though, maybe just 2-3mm, difficult to measure in situ when trying too fit. But this went straight on. Lesson learned...

 

GyKL4j.jpg

 

MgiuLk.jpg


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#14 dadbif

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Posted 21 May 2020 - 09:19 PM

Looks good
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#15 carl s

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Posted 21 May 2020 - 09:37 PM

Good to see it's resolved !


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mk1 1991 Eunos with RS NB drivetrain: https://www.mx5nutz....howtopic=322586

ex - mk3 2006 2.0 sport

ex - mk2 1999 1.8is JRSC





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