1976 Mazda 929 brake upgrade - Our Shed

By: James Secher - Words & Photos

Date: 25.10.2021

James has upgraded the stoppers in prep for a rotary rocket transplant

As mentioned in the last episode, I bought myself an old Mazda 929 project car and have committed to the arduous task of taking it from a mild-mannered piston motor bowls club car to a raucous rotary powered RX-4 tribute cruiser.

There have been a couple of significant events happen in my little 929’s life of late. Much to my wife’s delight the Mazda has moved from the carport on the side of the house to inside the garage, out the elements and away from neighbours judging eyes. 

Seriously large drilled discs and callipers should do the trick

The brake upgrade is the first cab off the rank in the laundry list of improvements needed. Its original brake callipers began to seize on the last lap around town and in my opinion were not worth rebuilding as there are plenty of disc brake upgrade kits available for reasonable money. 

Realistically ,brakes are not something you want to skimp out on when they’re pretty much the only safety aid in the car other than the seat belts.

The project has arrived home

After shopping around I found a few good options, however some kit suppliers wanted to know a few measurements and specifications, which didn’t instil me with a lot of confidence with their knowledge of this particular vehicle. I just wanted an off the shelf kit that would fit. 

In the end I opted for a Castlemaine Rod Shop Wilwood front disc upgrade.  The company has been around since the 1970s supplying diffs, brakes, suspension and chassis upgrades and, according to their website, are the biggest Wilwood dealer in Australia, so a well-established and knowledgeable bunch.

The ‘Mercedes’ face as it’s known

The price of the kit was sharp at $1450 and, although there is not a great deal of info on their website about the kit, it seemed relatively straight forward. The infor was along the lines of, here’s the kit, for your stud pattern, four-pot calipers, 320mm rotors and you will need a minimum 15-inch wheel diameter after installation. Enough said!

The kit I ordered was for an RX-4, which in my opinion should mean it would fit my Mazda. My belief is that there are only minor differences between the 929 and RX-4. It’s a common conversion to build a 929/RX-4 tribute, mock-up, or whatever you’d like to call, so for all intents and purposes most RX-4 specific kits should fit my 929.  I’m sure as with all cross-model conversions I will come up against some fitment issues, but I’m forever the optimist and don’t mind some problem solving on the fly.  If in doubt get a bigger hammer.

All the tools to do the job

When the box arrived, I was more excited opening it than a birthday present, which isn’t hard nowadays. Once you’re over 40 with kids, you’re at the bottom of the list when it comes to birthday presents, other than the obligatory "world’s best dad" mugs and socks. It was pointed out by a mate that I was a little bit too excited by the amount free stickers in the box considering there was a large diameter disc brake kit with forged billet calipers and all the fruit in the box too, but who doesn’t like car part stickers?

The Rod Shop kit comes with everything you need for a relatively straight forward process: calipers, rotors, custom hub adaptors and caliper mounting brackets, pads plus all the bolts and shims you need. The rotors and Wilwood calipers are huge in comparison to the original single piston set up and wouldn’t look out of place on a car with a much sportier pedigree, the differences are chalk and cheese. Everything in the kit slides and clicks together with purpose and the Rod Shop etched logos on the callipers are a nice touch.

Fit and fiddle

It has been a long time between swinging spanners on my own cars, so I engaged the help of good mate Shane, who happens to be a mechanic and fabricator.  He fitted the left side while I watched on taking mental notes, then I cracked on with the other side, occasionally checking in that I’d fitted everything in the right order. There were plenty of shims provided in the kit, which was handy as I required two shims to centre the calipers over the rotors.

Fitting a set of discs and calipers is a relatively straightforward affair, but my confidence with working on old cars is only just coming back, so reaching out to a more competent fellow enthusiast for an extra pair of hands helped prevent any accidental damage to new or old parts. Plus, it’s nice to have someone sign off on your handiwork before you take to the roads for a good shake-down. 

Coming together nicely

I often use ‘working on the Mazda’ with a mate as a good excuse to catch up, a couple-of-hour job will generally turn into an all-day affair, reminiscing about cars we’ve had, plans for the current projects, speculation on pricing. Go and grab a coffee or some parts or tools that you hadn’t planned on needing, then get cracking with the rest of whatever needs fixing or fitting. Add in the kids ducking their heads into the garage to ask questions and offer unsolicited advice, it’s a slow process but one I thoroughly enjoy and not a bad way to spend a Sunday.

Spot the new parts on the family-friendly Mazda

One thing I didn’t factor in was the incompatible standard brake lines, it should not have come as a surprise when the factory lines did not match up to the Willwood calipers… who’d have thought?!  Upon closer inspection the original lines were well and truly ready for replacement, they had more cracks than a plumber’s convention.  A quick phone call to the Rod Shop had a trick looking set of stainless steel flexilines to match my kit in the post two days later. The factory lines come as a two-piece set up and the flexilines are only made to replace the second half that connect to the calipers, so I just had my local Pirtek shop make up a set of lines to run from the hard-line connection at the top of the wheel arch to the flexilines.  The connection between the two lines then sits in the bracket on the back side of the strut.

New brake lines of course

With the new lines fitted some new fluid and a bleed of the system, the Mazda has some yet-to-be-tested new stopping power, although I have a sneaking suspicion the master cylinder might have an issue, or it may just be the change in volume of fluid needed by the larger calipers. We’ll see how it goes on a road test.

The process went like this. Remove original callipers, hubs, rotor and backing plate from the strut.

Remove hub from the and clean the mounting surfaces, paying attention to nick or burrs.  

Fitting new wheel bearings and seals is recommended. In this instance the bearing had been recently replaced.

Fit rotor to hub adaptors and use Loctite and tighten to 25ft lb in sequence.

Fit calliper brackets to the strut.

Fit the rotor and hub assembly to the strut.

Fit the pads to the callipers and fit the callipers to the brackets. Use shims to centre the calliper over the rotors if required. In this instance 2 x shims per calliper were required.

Fitted up and rarin’ to stop

The new kit requires a minimum 15-inch wheel for clearance, so the next item on the agenda to get it back on the road is a new set of rims. With only the factory 13s on hand, the old girl will be on the jack stands till I source an alternative.  

As the mediaeval saying goes, wheels maketh the car, so this decision should not be made lightly. I’m sure my wife is thankful the cars is now in the garage while it sits on jack stands with no wheels on, out of sight from the neighbourhood busy bodies.

Next, wheels to hide this

From Unique Cars #458, Oct 2021

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