Fitting FC 4 pot calipers and discs to FB and early rotary

Technical info not specifically 1st gen RX7 related.
TOOL
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Fitting FC 4 pot calipers and discs to FB and early rotary

Post by TOOL » Mon Feb 02, 2015 2:37 pm

Ok, seeing as there's some interest in this, I figured I'd do another tech thread.

I have personally fitted FC 4 pot front calipers and discs to one of mr RX2s. It's pretty straight forward. This is what I have done. There's other ways to do it too, but this is what I have done and would make suggestions based on my experience.

You could also fit the entire FC front subframe, brakes struts etc, and then you would have the 5 bolt hubs too. You could then get som custom axles made for the rear. Dom had some axles made and they were about £300 the pair, which seems kind of cheap imo. You could also get whatever spline you want this way, then if you needed a 24 spline diff, you could get them made as 26 spline and save about £100-150 and get a S3 unit instead of the earlier 24 spline S2 unit.
Things to think about.
Hopefully that makes sense.

The guys in Oz also fit Skyline rakes as well iirc.

I went for the 4 pot FC front calipers and matching FC discs though. It keeps it all Mazda and it is completely reversible, something I always have to consider with a rare car.

What you will need to do what I did:
A pair of FC or FD calipers (duh) - FC and FD are the same thing
A pair of FC discs
A bracket to mount the calipers to your strut/stub axle

Brake hose adaptors to convert metric coarse thread (M10x1.5mm) to metric fine thread (M10x1.25mm) - only for S1 and earlier cars (yes we have discussed this a few times)
A larger brake master cylinder to drive the bigger calipers - optional, but I've done this too so will share it
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TOOL
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Re: Fitting FC 4 pot calipers and discs to FB and early rota

Post by TOOL » Mon Feb 02, 2015 2:50 pm

On with the show.........

I stripped the brakes, hubs and backing plates off the struts leaving them bare.

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I then fitted up the custom bracket:

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Note, the bracket fits snugly over the stub axle, so it is the centre hole over the stub axle that locates it. There is a slight difference between RX2 and RX3 mounting holes, so the holes can be slotted to fit either, with the bracket remaining centred at all times.

Here's the trick with the hubs, you need to machine the outer edge of the hubs to reduce the overall diameter. You only need 3-4mm off. By doing this, you can mount an FC disc over the top of the RX2 hub.

Here's the hub (note standard RX2 hub has the disc mounted onto the back of it, and uses bolts, not studs):

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TOOL
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Re: Fitting FC 4 pot calipers and discs to FB and early rota

Post by TOOL » Mon Feb 02, 2015 3:00 pm

To mount the disc on the hub, you need to re drill the stud holes. Because the disc sits snugly over the hub, the hub locates the dics. The studs effectively stop the dics from spinning around the hub, exactly the same as other modern cars.
No pic though.

Before you mount the caliper, fit your brake hose adaptors:

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Here they are fitted behind 15 inch wheels, but some 14 inch wheels will also clear the caliper:

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Painted gunmetal grey they are almost invisible.
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TOOL
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Re: Fitting FC 4 pot calipers and discs to FB and early rota

Post by TOOL » Mon Feb 02, 2015 4:16 pm

Here's the stock RX2 disc (which fits behind 13" wheels) compared to the FC disc:

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Not such a big deal, you say? Here's another shot:

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Re: Fitting FC 4 pot calipers and discs to FB and early rota

Post by TOOL » Mon Feb 02, 2015 4:28 pm

The issue you will have is getting hold of the mounting bracket.

RESpeed used to do them but we all know the company imploded when Billy left. You can still find them though.

I do have one spare set of brackets here somewhere.

Failing that, you can make your own or get someone to make you some. Here's a template:

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It's for an RX2, so just check the stub axle size and bolt hole positions. This gives you the major dimensions though. Then just space it in or out based on your chosen disc.
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Re: Fitting FC 4 pot calipers and discs to FB and early rota

Post by TOOL » Mon Feb 02, 2015 5:26 pm

The brake master cylinder upgrade uses a Nissan Patrol master cylinder. It's a RHD unit as standard, but I modified it for LHD by swapping the nipples over, otherwise they foul on the strut tower in my car.

It's a 1" bore unit, bigger than the 13/16 or 7/8 units found in early rotaries.

Here it is:

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It bolts striaght onto the early RX brake booster. You just need to open up the hole for the spacer, shown here:

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Or use a late RX4 unit, which is bigger.

Here you can see the nipples foul the strut tower, on LHD only:

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Here it is installed:

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Re: Fitting FC 4 pot calipers and discs to FB and early rota

Post by TOOL » Mon Feb 02, 2015 5:28 pm

Note that with having an FC disc over the top of the hub, the offset has been reduced from +25 to +15, so the front wheel sit out a bit further. No big deal, as you can get spacers for the back or have a staggered wheel set up.
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Re: Fitting FC 4 pot calipers and discs to FB and early rota

Post by TOOL » Mon Feb 02, 2015 5:45 pm

And this place makes all kinds of awesome shizzle:

http://msfracingcomponents.com.au/mazda ... omponents/

Check out the steel hubs.

Andy Robinson Racing near Reading can do the rear axles for you.
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myatt1972
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Re: Fitting FC 4 pot calipers and discs to FB and early rota

Post by myatt1972 » Mon Feb 02, 2015 9:35 pm

Cheers Tool 0-0
Keith...

apexheid

Re: Fitting FC 4 pot calipers and discs to FB and early rota

Post by apexheid » Tue Feb 03, 2015 1:04 am

Same here.. cheers

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