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Old 04-11-2015, 08:36 PM   #1
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front brake piston bigger that pads!

a real head scratcher here boys, and I'd love to hear ANY thoughts AT ALL regarding this puzzle!


anyone else notice this? can this be right? will try to insert pics along the way:


so pic 91... just put new pads in caliper. look in the window please... from left to right you see: the piston, the empty-void-shadow inside of the piston, new pad, new rotor. it's not obvious from this angle - but the piston is way bigger than the pad it will be pushing on.


maybe it's easier to see with this next one - pic 93. this is the other side's old pad I just pulled. see what I mean? the old and new pads are just too narrow! right?


here's that pad's piston - pic 95.


so WTF? I notice when you go to buy a rotor, they want to know US or Canadian model (US is larger diameter - about a full inch). but when you go to get pads there is no such distinction... both models will get you the same pad! been to 3 different national chains... none of them can answer this question: "why the larger rotor if the pads are all the same? plus the narrow pads you just handed me won't even cover the diameter of my US caliper's piston?!".


the funny thing is: these "narrow" pads fit perfectly into the channels of the US(?) caliper - meaning they fit snug, and they will travel inwards as the pads wear...


but something is surely not right here, right? look at all the unswept (unused and wasted) area on the new rotors I installed: pic 85




and the old ones I pulled: pic 97





so anyway, would love to hear any thoughts at all you guys care to offer about this matter - it's really got me pissed. and I just can't believe I'm the only one!




thanks!
-Mike
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front brake piston bigger that pads!-phone-091.jpg   front brake piston bigger that pads!-phone-093.jpg   front brake piston bigger that pads!-phone-095.jpg   front brake piston bigger that pads!-phone-085.jpg   front brake piston bigger that pads!-phone-097.jpg  

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Old 04-12-2015, 04:07 PM   #2
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I have replaced numerous rotors and pads over the years, not necessarily all together, but eventually. Lots of aftermarket parts available for Z31s now, which is good. If they really fit right, they take over where Mother Nissan drops a part or is out of stock. Getting ones that fit isn't hard because parts stores give warranties and money back. No problem - but it can take time to return for warranty and then try another part.

I think at some point someone working on your Z substituted aftermarket parts that weren't right for your Z brakes. Your best solution is to get the FSM and the parts fiche at XenonZ31 Reference , look up the actual Nissan part numbers for rotors and pads, see if the parts are available through a Nissan dealer ($$$ - but take your VIN with you) price them, and then buy there - or just compare prices elsewhere.

Then check aftermarket stores and use the original Nissan parts numbers when asking. (I doubt that Nissan used different rotors in Canada - but who knows.) The store will guarantee that their available parts will fit the Nissan spec. If they fit, your problem is solved - unless somebody also modified the shoe to make the wrong parts work with it. In that case, you have more work to do. But try to take your brakes back to OEM spec for performance, etc.

I recently returned a set of aftermarket pads for bad fit. Exchanged them for another set, fit perfect. Looked just like Mother Nissan's OEM pads too - but half the price. All I want is no-squeal from my pads anyway!

Last edited by zxguy1986; 04-12-2015 at 04:10 PM.
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Old 04-12-2015, 04:56 PM   #3
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Quote:
Originally Posted by zxguy1986 View Post
I doubt that Nissan used different rotors in Canada - but who knows.
ZBUM knows, ZBUM's New Z31 Homepage

I used Wagner ThermoQuiet Ceramic pads on my last service. Part # PD266A on the fron, PD272 on the rear. Perfect fit. I bet any parts house can cross refeence those numbers.
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Old 04-12-2015, 11:35 PM   #4
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thanks Ken

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ZBUM knows, ZBUM's New Z31 Homepage

I used Wagner ThermoQuiet Ceramic pads on my last service. Part # PD266A on the fron, PD272 on the rear. Perfect fit. I bet any parts house can cross refeence those numbers.

thank you Ken!


my new pads (pictured) are from AutoZone. they are packaged as Duralast Max (part# DGC266M). now, with your info, I'm thinking my car's calipers are not stock... ? weird... ?


thanks again!
-Mike
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Old 04-12-2015, 11:47 PM   #5
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thanks ZXGUY

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Originally Posted by zxguy1986 View Post
I have replaced numerous rotors and pads over the years, not necessarily all together, but eventually. Lots of aftermarket parts available for Z31s now, which is good. If they really fit right, they take over where Mother Nissan drops a part or is out of stock. Getting ones that fit isn't hard because parts stores give warranties and money back. No problem - but it can take time to return for warranty and then try another part.

I think at some point someone working on your Z substituted aftermarket parts that weren't right for your Z brakes. Your best solution is to get the FSM and the parts fiche at XenonZ31 Reference , look up the actual Nissan part numbers for rotors and pads, see if the parts are available through a Nissan dealer ($$$ - but take your VIN with you) price them, and then buy there - or just compare prices elsewhere.

Then check aftermarket stores and use the original Nissan parts numbers when asking. (I doubt that Nissan used different rotors in Canada - but who knows.) The store will guarantee that their available parts will fit the Nissan spec. If they fit, your problem is solved - unless somebody also modified the shoe to make the wrong parts work with it. In that case, you have more work to do. But try to take your brakes back to OEM spec for performance, etc.

I recently returned a set of aftermarket pads for bad fit. Exchanged them for another set, fit perfect. Looked just like Mother Nissan's OEM pads too - but half the price. All I want is no-squeal from my pads anyway!


sure appreciate your detailed response GUY, and I'm working on getting those "real" part numbers, so thank you very much!
but just one more thing: what is "the shoe" - do you mean the caliper?


thanks again!
-Mike
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Old 04-13-2015, 12:19 AM   #6
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Yeah, I meant the caliper. That big thing that hangs down by its hoses when you set it free. Lots of stuff to screw with there...
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Old 04-13-2015, 01:20 PM   #7
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real part #s from fiche

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Yeah, I meant the caliper. That big thing that hangs down by its hoses when you set it free. Lots of stuff to screw with there...

looking at fiche slide 4-B14 sec# 440A-1, as my Z31 was built at the Hiratsuka plant in November of 1984. that's on the plaque in the door jamb. plus the following code from the plaque under the hood tells me it's a US model: KHLGZ31XUGY


anyway, speaking of calipers: the genuine Nissan part # is 41001-03P90. I go to Autozone website, enter # and it cross-references to caliper pictured below (pic 4). look familiar? yep... it's identical to what's on my car. strike one.


pad kit: genuine Nissan part # is 41060-11P29. I go to Autozone website, enter # and it cross-references to pads pictured below (pic 3). they are the 266 series. yep... same stuff I just put on the car. strike two.


rotor: genuine Nissan part # is 40206-03P00. I go to O'Reilly website, enter # and it cross-references to rotor pictured below (pic 9842rgs). sure enough, it's the same rotors they sold me. strike three.


so these stores have handed me the correct parts and my existing caliper matches what Autozone says is stock. so I'm back to square one - why is this piston too big? and why me... :-) have I missed something... ?


once again - I appreciate your help guys, and welcome any thoughts at all about this puzzle!
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Last edited by 300aZphX; 04-13-2015 at 01:28 PM. Reason: spelling
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Old 04-13-2015, 08:49 PM   #8
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I'm gonna stick with my first guess. However it happened, you have a mongrel brake set up. Plus, I see the folks offering you a 'caliper' aren't giving you the whole assembly, just a 'shoe' to hold the assembly. That would not solve your problem. And, your photo of that brake pad back shows the piston crushing it - or something. I have never seen anything like that. Wrong piston for the pad?

Would be cool if your buddy had an '84 and you could compare assemblies. If not, looks like you need to dump that piston+assembly and go with OEM - which means checking the guys here (WTB/FS forums) or recyclers. I doubt that Nissan would have them new - but check it out anyway. Bring your life savings account with you, just in case. $$$ Then check this site in the WTB/FS forums. Guys here have brake parts to sell.

For recycled, I would check out Car-Part.com--Used Auto Parts Market and sort results by distance from my zip. Drive there to check the parts out if possible. They will sell you the whole caliper assembly, at least, not just the 'shoe' you found.

Otherwise, are you up for grinding the pistons down? You could use your buddy's '84 caliper as the standard. Get out your micrometer

Last edited by zxguy1986; 04-14-2015 at 03:55 AM.
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Old 04-14-2015, 07:33 PM   #9
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A novel thought...

Perhaps Nissan designed the brakes this way. Page BR-19 of the '86 FSM indicates OEM pads are 43 mm wide. The cylinder piston bore of the caliper is 60.6 mm. So yes, the piston is 17.6 mm (~7/10th of an inch) wider than the pad.
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Old 04-15-2015, 09:55 AM   #10
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solution? I think so!

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Originally Posted by ken99 View Post
Perhaps Nissan designed the brakes this way. Page BR-19 of the '86 FSM indicates OEM pads are 43 mm wide. The cylinder piston bore of the caliper is 60.6 mm. So yes, the piston is 17.6 mm (~7/10th of an inch) wider than the pad.

WOW Ken, thanks a million for pointing this out to me! my '85 FSM says the exact same thing. I'm calling this "case closed". reasons for this:


1 - the brakes sound, feel, and perform great.
2 - all the hard facts (FSM, fiche database, 3 different national chains) say these are the proper parts.


really, the arguments the other way are all SUBJECTIVE: the arrangement doesn't look right, it doesn't make sense, and others have never seen this, etc...


a novel thought indeed! thanks again Ken, appreciate your time. should have found that info myself. funny how a guy can convince himself of something and then just head off in the wrong direction without looking back. think I learned something :-)


best regards,
Mike
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