NB8B front caliper rebuild help

ianoz · Postby **ianoz** » Mon Feb 12, 2018 6:30 pm

I have rebuilt calipers several times, but I'm having grief with the fronts on an NB8B - hopefully some kind person has solved this before

One of the slider pins is plain, and the other has a rubber tube on part. For the life of me I can't get the slider with a rubber section to slide back into the caliper bracket. The rubber section keeps jamming and sliding up the pin. Have tried both the old and the new sliders. I'm using Bendix disc brake lube for assembly (blue ceramic hitemp)

silver are new (BiggRed) and gold are what was in it - I assume original but no maintenance history so could be anything.

front brake slider pins.JPG

I assume this rubber section is for anti-rattle? Car is track-only so not worried about rattles etc, but not sure if this also has a role in reducing pad knockoff?

I have enough parts to just install two plain sliders instead of one plain/one rubber. Would that have any negative effects (track use, no road use)? I'm thinking that might actually be better and give less resistance to sliding considering how tight the rubber section fits.

(serves me right for not just getting original Mazda parts from the start...)

Luke · Postby **Luke** » Mon Feb 12, 2018 7:21 pm

I have had this happen more than once.
I have had it tight with the same symptom of the rubber pushing up.
It can be caused by a build up of brake dust that had corroded and hardened in the hole if the rubber boots were not sealing properly.
I cleaned it out by using a pencil wrapped in very fine sandpaper on a drill at very low speed and lots of brake clean.

The other problem I find is the rubber loses its elasticity and expands overtime. This would explain your old pins not going in.
So the rubber than pushes over the pin easily making it impossible to install.
I am not sure if this is due to track generated heat or the Bendix Blue goo.
I literally change the pin with the rubber every time I change pads because of this.

That aftermarket pin just looks wrong like you probably see yourself.
The bottom looks way to big to me just looking at the pic. Plus the rubber should be longer.
To me they would have stretched that rubber on. That would have ruined the integrity of the rubber.
The factory pin has a brass fitting on the end which would have been fitted after the rubber was put on. ie no stretching to fit the rubber.

I have toyed with the idea of just putting plain ones only before as well.
I also assume the rubber is there for anti-rattle and pad knock off so have not tried it.
I have heard of race cars using just the plain ones but cannot confirm who has done this.

I have had a rubber completely break away more than once.
The first time when i had no spare I did a quick fix. I wrapped black electrical tape several times around the pin instead. I did not feel any brake difference when i did this. The pin did slide a lot better than it did with the rubber though.
I would guess just running 2 metal only pins would be much the same feel.

So just another thought, can you slide the metal pin into both holes?
I have had that little brass clip come off the rubber pin on the NC. It was stuck in the hole which was a nightmare to get out and stopped the pin going in all the way. NC has same slide pins as a NB8B. Never happened on my NB though.
Make sure both your original rubber pins have those attached still.

Magpie · Postby **Magpie** » Mon Feb 12, 2018 7:23 pm

I assume that you have the pins in the correct holes? From memory the one with the lower boot is the lower one.

ianoz · Postby **ianoz** » Mon Feb 12, 2018 9:23 pm

Magpie wrote:I assume that you have the pins in the correct holes? From memory the one with the lower boot is the lower one.

I think so Magpie

- lower bracket hole is the one I'm using. Did try the other just in case but no go there either.. I took photo's while disassembling and it's going back the way it was.

Luke wrote:That aftermarket pin just looks wrong like you probably see yourself.
The bottom looks way to big to me just looking at the pic. Plus the rubber should be longer.

Thanks Luke. I went and measured the new vs old, and they're the same every way within under 0.1mm - except - that the old one is stepped down from 9.8mm shaft to 9.0mm for the end, while the aftermarket is 9.7mm for both shaft and end. The rubber being shorter i thought might be deliberate to remove some of the 'stick' due to the rubber - the pin can slide in it without loosing the anti-rattle snugness.

Had a close look at the old pins and the rubber has a small brass ring below it, so they look like Mazda originals. Both have the rings still.

The bores are clean and shiny, but tried your trick with some 2000 wet&dry. With some careful work I can get one of the old pins to fit, but still not the new ones. I think the new rubbers are just too big for the bore, and have a thought that with the grease they might be air-tight and compressing the air in the bore below them.. Could hone out the bores but that all seems like hiding an issue.

Very tempted to just run two plain sliders - haven't been able to find any references to anyone doing that so far though. Dr Google isn't succeding :lol:

but other calipers don't have the rubber sleeve on the pin.

Failing that I think it's turf the aftermarket and order Mazda..

Tony · Postby **Tony** » Tue Feb 13, 2018 9:36 am

ianoz wrote: Very tempted to just run two plain sliders - haven't been able to find any references to anyone doing that so far though.

Ditch the rubber ones and just run two plain pins. I've been doing that for years with excellent results; both on and off the track. Don't over think it.

93_Clubman · Postby **93_Clubman** » Tue Feb 13, 2018 10:16 am

FWIW, after research for another road car with Girlock/Girling front calipers, I've gone to two solids per side.

Magpie · Postby **Magpie** » Tue Feb 13, 2018 10:25 am

FWIW I ran for a period with no lower rubber boot as well.

ianoz · Postby **ianoz** » Tue Feb 13, 2018 12:54 pm

Thanks all for your help. Pretty clear it's OK to run with two plain sliders so that's the path.

Now I just need to learn to stay off the middle pedal more :lol:

GR124 · Postby **GR124** » Tue Feb 13, 2018 1:02 pm

Hey guys I don't want to side track this informative thread, BUT, Where do you normally get ya rebuild kits for all four corners NB8A?

Magpie · Postby **Magpie** » Tue Feb 13, 2018 2:42 pm

Just found this photo, these had been in the car for about 18 months

ianoz · Postby **ianoz** » Tue Feb 13, 2018 9:11 pm

Magpie wrote:these had been in the car for about 18 months

18 months - the one on the left looks like new ;)

What grease are you using? Originally I was just going to use moly disulphide, but while hunting this topic found the SpecMiata guys using Permatex ceramic - couldn't find that but the Bendix spec's the same temp performance. Probably overkill for me - but Repco stock it.

interesting that the rubber boots are different to the ones on mine.

GR124 wrote:Where do you normally get ya rebuild kits for all four corners NB8A?

BiggRed on ebay are about the cheapest I've found (UK based), but next time I'll just go original parts.
Haven't priced 8A parts, but NB8B front seal kit (2 calipers) was about $30 from UK aftermarket vs around $80 for original via Amayama
Rear seal kit $42 vs $140 (ouch).
(all plus shipping).
Slider pins... well this is the first time I've had a problem, but it's the first time I've done 8B brakes.

In the scheme of everything else it's not much...

Magpie · Postby **Magpie** » Wed Feb 14, 2018 5:23 am

My bad, the middle and right one were in the car. Yes, the left one is new.... :mrgreen:

I use bendix grease. After every few track days I wipe off the old grease and replace with new.

I ordered my parts from the UK MX5 Parts website.

GR124 · Postby **GR124** » Wed Feb 14, 2018 9:44 am

GR124 wrote:Where do you normally get ya rebuild kits for all four corners NB8A?

BiggRed on ebay are about the cheapest I've found (UK based), but next time I'll just go original parts.
Haven't priced 8A parts, but NB8B front seal kit (2 calipers) was about $30 from UK aftermarket vs around $80 for original via Amayama
Rear seal kit $42 vs $140 (ouch).
(all plus shipping).
Slider pins... well this is the first time I've had a problem, but it's the first time I've done 8B brakes.

In the scheme of everything else it's not much...[/quote]

Cheers Ian

RS2000 · Postby **RS2000** » Wed Feb 14, 2018 10:01 am

GR124 wrote:Where do you normally get ya rebuild kits for all four corners NB8A?

I see you're in Newcastle. Last year I bought front & rear NB8A kits from First Choice Automotive Parts (was called First Choice Clutch & Brake) in Cardiff - they supply the local auto industry.
Front $50 (for 2 calipers) & Rear $98 (for 2 calipers)

GR124 · Postby **GR124** » Wed Feb 14, 2018 3:18 pm

RS2000 wrote:
GR124 wrote:Where do you normally get ya rebuild kits for all four corners NB8A?

I see you're in Newcastle. Last year I bought front & rear NB8A kits from First Choice Automotive Parts (was called First Choice Clutch & Brake) in Cardiff - they supply the local auto industry.
Front $50 (for 2 calipers) & Rear $98 (for 2 calipers)

Sorted then, i'll go see them, Thanks RS2000 very helpful