- History -What’s Holdin’ Up Your Holden
- THINGS YOU MIGHT NOT HAVE KNOWN ABOUT HOLDEN BRAKES
- Have You Ever Seen One Of These?
- Bigger Brakes For Holdens
- HR Front Brake Upgrades In Ascending Order.
- HK/T/G Front Brake Upgrades
- HQ To WB Front Brake Upgrades
- Torana Brake Upgrades
- Master Cylinder And Boosters
- HQ To HZ Pedal Boxes
- Torana LC To UC
- Holden Gemini’s
- Front Brakes
- Rear Brakes
- Master Cylinders
- Balancing Front/Rear Brakes
- Commodore VB-VS
- Unterchangeability And Upgrades.
By Peter Koning of Hoppers Stoppers circa 2000
From the amount of enquiries we receive via the Internet, fax, phone and social media, it seems that Holdens from 1950s, to 70’s, and Torana’s, are as popular as ever with modifiers, particularly with the rising popularity of fitting injected V6 and V8 Commodore engines.
As pre 1976 ADR27 cars can be legally modified with no worries about EPA pollution control laws, the Australian love of hotting up an old Holden looks set to continue for a long time.
Us older guys were brought up playing on our EH’s and FC’s but as the next generation continues the tradition, it seems the tricks of swapping front suspension and brake parts needs to be passed on. The older amongst us will probably know most of the following but for the younger guy just starting on his first “early” the mysteries of the King Pin and Ball Joint front suspensions might use some explaining. So here’s some now.
History -What’s Holdin’ Up Your Holden #
From their release in late 1948 with the 48/215 (FX) up to 1964 with the EH, Holden’s used what was commonly called the King Pin front end.
This was a double A arm suspension, featuring pressed steel “unequal length” upper and lower control arms, pivoting off a removable pressed steel cross member which was bolted to the body at four rubber insulated mounting points and from FE onwards reinforced against torque by a nose section that bolted under the radiator support member.
The stub axle pivoted on a vertical pivot pin (the King Pin) and allowed for up/down movement on upper and lower steel bushes at each end of each control arm. Counting all the bushes and tie rods there are 28 greasing points on an early Holden front end, which needed to be lubed every 2000 miles! These king pin suspensions were tough as nails, but once worn rebushing the kingpins was not a cheap exercise.
By the late 50’s the Americans were replacing Kingpins with Ball Joints, and this caught up with Holden’s in 1965 with the HD model. The upper and lower outer pivots and kingpins were now combined into a lubricated spherical ball at each end of the stub axle. In Holden’s case the lower ball joint was pressed into the arm from underneath, and held there by the spring load, the upper joint was fitted from above and originally riveted in, but replacement upper ball joints bolt in, once the rivets are drilled out.
Midway through the HD run Holden introduced that wonderful invention, the DISC BRAKE ! As this had become popular on European cars in the early 60’s we might have wondered why it took longer to reach here. However Holden is an American owned company and the Yanks didn’t really see Discs until the late 60’s, relying on their favorite drums even longer than we did. Being a thin solid rotor we now look back at the HD/HR discs as a bit feeble but compared to drum front brakes it was a huge improvement. Actually Holden had Disc Brakes a bit before Falcons and Valiants, so being the first of the big three they didn’t do too bad.
It didn’t take long to realize that the HD/HR ball joint front end could be adapted to fit any FX to EH. You needed to relocate the engine mounts and weld on the correct nose extension, and then they would bolt in. Being an option not many HR’s got them, but disc brakes for early Holdens were easy once those highly desirable disc brake HR’s began reaching the wreckers.
With the bigger HK to HG range discs became more popular, even standard on V8 cars, but most 6 cylinder cars were still built with those basic old drums. HK’s had steel inner pivot bushes, then with HT/HG we got rubber bushes for a quieter ride and maybe a few dollars saved on the assembly line.
With the introduction of the HQ series Holden went to a half chassis style front end, the cross-member and front half rails being all one welded piece bolted under the base body shell. Steering went to the front of the cross-member and whilst still using unequal length control arms the bushes were bigger and softer, with design favoring ride over handling.
HQ’s got Holden’s first decent brakes; optional 11 inch ventilated front discs, with rear drums retained for a long time yet. The majority of HQ’s would have had front discs fitted.
With the HJ range front discs became standard, and that’s the way things basically stayed until rear discs became optional on HZ. (Standard on GTS)
The last of the big Holdens, the WB, had four wheel discs standard on the Statesman’s but drums on rear for utes and vans. My old PBR books show rear discs possible on Commercials but I don’t know if they were ever actually built. With their leaf springs I don’t believe those rear calipers would fit.
THINGS YOU MIGHT NOT HAVE KNOWN ABOUT HOLDEN BRAKES #
FX To WB #
At the risk of boring the older guys who probably know most of this already…
1/ FX and FJ had 15 inch wheels with a large stud pattern, the studs being out toward the edge of the drums. Rear axles have a taper hub/keyway drive which needs a special puller tool to remove the drum. Master cylinder is under the floor with a remote filling tin on the firewall optional.
2/ With FE ‘s Holden went to 13 inch wheels with the familiar 4.25 inch by 7/16 stud pattern and drums that could be removed leaving the rear axle flanges or front hubs in place. Master cylinder went up on the firewall with “swinging pedals”. Front and rear brakes were same width shoes.
Remote PBR VH24 power booster was optional, with a warning sticker on the rear window so that those with lesser cars would know not to travel too close!
3/ FB saw basically the same design of brakes as FE/FC but with wider shoes.
4/ EJ saw brakes changed to “Duo Servo” which means that the two shoes are joined by a floating adjuster, so that the front shoe gets pulled into the drum by rotation action, thrusts through the adjuster passing the load to the rear shoe, making the brakes more self energizing and equalizing wear.
5/ EH brakes are the same as EJ.
6/ HD/HR all got wider front brakes, with the same rear brakes as EH on Sedans and Wagons. However Utes and Vans came with wider rear brakes.
Same 1 inch master cylinder as FE onwards, with a remote VH44 booster to all four wheels optional.
Front discs were introduced with HD, mid model, and larger VH40 “hydro-vac” remote booster to all four wheels then standard with discs. Can someone tell me if discs came standard with X2 and 186S Engines?
As discs are not self energizing, rear wheel cylinders for cars with front discs are smaller (9/16 compared to 13/16) also requiring a different rear shoe as the smaller cylinder could not use a push rod. (The shoe has a different profile so the wheel cylinder piston can bear straight against it)
As it was possible to order a Ute or Van with front discs, there were therefore FOUR types of rear shoes and TWO types of rear wheel cylinder used on HD/HR Holdens. If converting your HR from front drums to discs, (and boosting all four brakes like Holden did) you should also fit the smaller bore rear wheel cylinders and matching shoes, or rear brake lockup will occur.
7/ HK went to 14 inch wheels, of the same early stud pattern, with bigger diameter front and rear drums, or bigger discs (but still solid) when fitted to the front.
Master cylinders went tandem split system for safety, and “Master-vac” booster between firewall and master cylinder for the first time. Drum brake cars could be optioned with a fairly big master-vac and disc equipped cars had positively huge boosters as standard. Brake fail switch now fitted.
As per HR, rear wheel cylinders were smaller bore and rear shoes were different when front discs were fitted.
V8 equipped HK/T/G had a thicker disc rotor than 6 cylinder cars, with a 1/8 spacer plate inserted in the middle of the caliper to allow the same basic caliper bodies to be used.
8/ On HQ front drums, size, shoes and wheel cylinders were identical to HK/HG, but now with 4.75 by 7/16 (Chevy) stud pattern.
Rear drum shoes and cylinders were same as the HK/HG four wheel drum brake type for all cases (using 7/8 wheel cylinders)
HQ had a brake fail switch on the top control arm inner bolt with a proportioning valve half way along the chassis.
HQ to WB disc brake stubs are functionally identical to HK/T/G but the tooling wore and was replaced over time so they do have differences in appearance.
HR disc stubs had the bearing center line 1 inch down, so fitting HQ stubs lowers your HR 1 inch, but the caliper mounting ears are further out and closer to the center of the car so you must use HK to WB calipers and matching rotors if fitting these stubs to a HR. As HR use 13 inch wheels this also means 14inch wheels and /or HQ stud pattern.
9/ With HJ the proportioning valve was combined with the switch, and fitted at the top control arm. Prop valves now have different settings for sedans, wagons, Statesman’s, and Commercials.
Half way through HJ series Holden changed to a different caliper type, with a long and short pad, and flat slide arrangement.
10/ Half way through HX another caliper change, this one had the slides on tubular sleeves, which were at the fixing bolts, probably the worst of the HQ to WB series.
11/ Half way through HZ, the Girlock “Collette” type caliper introduced, this has the alloy body and slide pins out at the edge of the caliper. This same basic principle is still used by PBR to this day.
With HZ, rear discs were offered, a different master cylinder with no rear residual valve and different proportioning valve then used. Reportedly a different pedal box ratio used for cars with four wheel discs, can any one shed some light on exactly how this was done?
12/ The new VB Commodore was released around the same time as the WB range. Most of the VB brake design and thread types were then carried over to other Holdens, (WB, Torana and Gemini.) For the WB metric brake fittings were introduced, the master cylinder went to plastic reservoir, angled bolts, and metric threads. Prop valve now in the master cylinder. Front calipers very similar to HZ but with the hose now shorter and to the rear of the control arms and on the side of the caliper, using a banjo bolt and 10mm threads. Hoses all have metric threads but the earlier 3/8 threads retained on rear wheel cylinders. WB rear calipers are not the same as HZ but very similar.
13/ Every Holden from mid way through FE to WB and every Torana used the same wheel bearings! (Commodore VB to VP too). Every Holden HD to WB including Torana used the same ball joints.
HQ to WB and A9X all had the same disc rotor. (DBA014)
HK to WB (and all Commodore) 7/8 wheel cylinders are the same.
Holden were always good at parts bin interchangeability when they could get away with it.
Torana LC To UC #
First lets forget about the four cylinder HB and TA Torana’s, these used the English Vauxhall Viva 4 stud front end and are very different underneath from 6 cylinder LC and LJ.
With the LC 6 cylinder cars Holden stretched the front structure and went to a much stronger cross member with 5 stud EH based drum brakes front and rear. When fitted, front disc brakes were similar to HR. 13 inch wheels used.
Torana and HR disc stubs look very similar to HR but there is a 1.5 degree difference in Kingpin Inclination (the angle between top and bottom ball joints measured from the vertical) This means that fitting HR or HQ stubs to a Torana causes the wheels to lean in an extra 1.5 degrees, and usually results in alignment problems. Whilst possible to fit a 1 inch lower HQ stub (to get the bigger vented brakes) also leads to steering geometry changes and some bumpsteer.
Just like HR and HK, LC/LJ had smaller bore rear wheel cylinders and different rear shoes when fitted with front discs. For XU1 the discs were made thicker with a 1/8 caliper spacer, smaller but just like V8 HK.
LH/LX was a whole new car; same body and brakes were used on 4, 6 and 8 cylinder cars. A few poverty pack LH cars had drum fronts (same as LJ) but most cars had discs. Front discs used same stub axle as LC/LJ but with new single piston caliper and thicker solid rotor. Still 13 inch wheels with 4.25 stud pattern.
Midway through LX a different caliper like early HX used.
L34/A9X cars use HQ style vented brakes and 14 inch HQ GTS wheels. Holden made a special HQ style stub axle incorporating Torana KPI, and a special steering arm to compensate for the 1inch lowering. Caliper type followed HJ or HX usage and Holden had to grind metal to get them to fit over the steering arm. If you try to fit them to the rear they hit the top control arm and the bump in the crossmember on full lock, causing the pads to be pushed back and no brakes next application. Rear brakes were larger HQ drums. Some later A9X reportedly had HZ rear discs, but I’ve never seen one and they don’t show in the PBR books.
All Torana’s LC to early UC used similar 1 inch master cylinders with the metal lid. Quite a few different boosters fitted, V8 were double diaphragm and not all interchange.
Early UC Torana’s had same brakes as late LX. . By this time Holden discovered that LH/LX front brake hoses rubbed on tyres on full lock so UC front hoses were longer and relocated higher on the inner mudguard.
Concurrent with introduction of Commodore VB, later UC’s got a new angled bolt booster, a plastic reservoir 15/16 master cylinder with combined prop valve (identical master to VB) and Commodore style calipers on the same solid rotors.
Fittings and hoses went metric and rear wheel cylinders and shoes went identical to Commodore with a different (now unavailable) drum. Was this drum the same as 4 cylinder Commodore, which did use Torana stud pattern?
Have You Ever Seen One Of These? #
A small number of UC Torana’s were made with a disc brake rear.
This looked like a smaller HZ Salisbury disc rear with unique rotors and calipers, they took 13 inch wheels in the early stud pattern.
I’ve only ever seen one, and couldn’t say how many were made.
Interestingly, the PBR book shows two different part numbers for UC rear calipers, so its possible that they had an imperial thread and a metric thread version like HZ/WB. Try getting an aftermarket disc rotor for this one!
OK that’s a quick outline of what occurred over the years before WB and Torana’s were replaced by the new Aussie Icon, the Commodore, and but that’s another story. Now, how can I make my Old Holden’s brakes better?
Bigger Brakes For Holdens #
OK here comes the Hoppers Stoppers Plug!
Why did you think I was doing all this anyway?
Lets start at the earlier types, the 48/215 (FX) to EH.
Its not really that practical to fit discs to the kingpin stub although it can be done with brackets and Torana or HR discs. The better way is the time honored HR ball joint front end conversion, as you can then do the following, obviously then from FX to HR, or cars like street rods using HR front ends.
HR Front Brake Upgrades In Ascending Order. #
1/ HR opposed piston cast iron calipers and thin solid discs, as standard on HR front end. (But that’s only an upgrade over drums)
2/ Torana LC/LJ cast iron opposed piston or LH/LX/UC floating piston calipers in their cast or alloy types with Torana rotors will bolt on to HR stubs. Not much of an improvement but you can still have 13 inch wheels.
3/ HK/T/G Stubs fit HR fronts, giving a bit bigger solid rotor but you will need 14 inch wheels, at least still in FE to HR pattern. Not much better than HR or Torana discs.
4/ HQ stubs (being same as HK/T/G) fit HR front ends, use HR steering arms, then you can fit HQ to WB calipers but watch for clearance re top control arms and having to grind a bit off the caliper brackets to fit over the steering arms. This gives you 11 inch ventilated rotors but usually in HQ pattern unless you are prepared to pay for blank rotors and then have them studded in early pattern. Note that HR and HK/T/G use 2.5 wheel centers where HQ use 2.75, so if getting HQ blanks drilled it might be necessary to have the nose of the rotor machined down. These ‘Blanks’ are NLA but we do have a solution to keep you small Holden stud pattern with vented rotors to suit both HR/Torana Stubs or HK-WB Stubs. It will still use the HQ-WB Caliper but will give you the option of 13”-14” wheels with vented brakes and standard track on the early cars.
5/ On a standard HR disc stub we can fit our steel hub with normal Holden Taper roller bearings and using a simple banana shaped bracket, bolt on 290mm diameter by 28 thick rotors and twin piston PBR calipers. These are based on Ford AU2/3 XR8 stuff with the rotors ex DBA and bought blank so we can do any stud pattern at all.
(Don’t worry you Holden Fanatics; these bits are PBR and DBA, not made by Ford at all.)
Minimum 15 inch wheels needed, and watch for Simmonds wheels which will touch at the ring of rim nuts, requiring an 8mm wheel spacer.
6/ A 330 by 28 twin piston version of the above is available, minimum 17 inch wheels.
8/ If you have HQ stubs on your HR front end we use a BA style 300 by 28 rotor, this is OK with 15 inch wheels except for Commodore or AU offsets where 16 inch are needed. Same problem occurs with Simmonds hitting calipers, and also sometimes Weld Wheels, needing 8mm spacers. Basically the wheel hub must not dish in past the hub face before it attaches to the rim.
9/ A 330 HQ upgrade is available too.
HK/T/G Front Brake Upgrades #
1/ HQ/WB calipers and rotors bolt right on but watch for caliper to top control arm interference. Same as above, this means either going HQ pattern or getting blank rotors studded and/or nose diameter turned down.
2/ A 300mm by 28 BA/AU3 combo (as above in 8)
3/ A 330mm Upgrade (as in 9)
HQ To WB Front Brake Upgrades #
1/ 300mm by 28 BA/AU3 kit as per 8.
2/ 330 by 28 kit as per 9.
Torana Brake Upgrades #
1/ For LC and LJ, fit LH to UC rotors and calipers. A bit of an improvement and can still use 13 inch wheels.
2/ Find a genuine A9X at the wreckers and fit the stubs and steering arms. (yeh right!) This will need 14 in wheels in HQ pattern.
3/ Fit HQ to WB stubs and rotors, grind the calipers and the top control arms, end up with HQ pattern and suffer alignment and bumpsteer issues.
Fit the calipers to the rear and they hit the lump in the crossmember on LH/UC.
4/ Keep you standard disc stub, mount to the rear, and bolt on our 290mm by 28 kit with no cutting or hitting of anything. Minimum 15 inch wheels needed, same problems needing 8mm spacer for Simmonds. (You Torana guys seem to love those Simmonds wheels too!)
5/ Go 17 inch wheel for a 330 version, and this will still need control arm and lump in crossmember surgery.
Master Cylinder And Boosters #
1/ FX To FJ #
There are a lot of ways to do this because the original was under the floor.
One way or another you are going to go to a swinging pedal and that means adapting a pedal box. Any 1 inch bore master cylinder and booster will be fine with all the above, whether a HQ tandem master and remote VH40 or a master-vac combo is up to you. The latter will work better.
2/ FE To EK #
The standard 1 inch single master should be dumped for safety reasons but the clutch master is right next to the brake master. That’s OK if going Auto trans, but fitting a tandem master with combined master vac will require relocating the clutch master across if going hydraulic manual clutch.
A smaller Gemini booster (push rod lengthened) with an XB master will free up a bit of room. HQ or XB 1 inch master with remote VH40 is OK too but you will need larger rear wheel cylinders if not boosted. If going 4 wheel discs and remote boosters then two of the bloody things will be required.
Your Friendly Engineer will also ask for a brake fail switch/light, and this must be piped so the pressure is the same both sides, i.e. before any remote boosters. Of course all tandem master cylinders require a split system pipe up but that’s the price you pay for progress.
3/ EJ And EH #
Same story as above but the bonnet hinges don’t allow any decent size master vac on manual cars. Even auto’s will need a pedal box with brake push rod moved across.
4/ HD And HR #
Basically see above for FE to EK, not much different here.
5/ HK To HG #
At last, an easy one.
Use the original standard booster and tandem master with any HQ/WB brakes or any of our big brake upgrades, the smaller booster is fine but the bigger V8 one has a stack of power assist. If fitting rear discs, take the residual valve out of the rear brakes, it’s under the brass seat at the outlet fitting, use a self tapper to get the seat out.
6/ HQ To HZ #
Basically the same story as HK, standard master cylinder and booster are fine but on HQ replace the proportioning valve with an adjustable one if fitting rear discs, or maybe no valve at all is worth a try first. (The front must lock before the rear)
On HJ to HZ using the tin top master, remove the prop valve if fitting 4 wheel discs; fit a HQ one with no valve so that the brake fail switch will be still be there.
Use an adjustable prop valve if needed, or a HZ unit for 4 wheel discs will work if you can find one.
7 / WB #
Don’t forget that WB had the plastic reservoir master with angled bolts and inbuilt prop valve. If yours is a Statesman with 4 wheel discs, then bolt on the front upgrade and go, the rest is right. If you have a Ute, Van or Tonner, and you want to run rear discs then fit the Statesman disc type master with its correct prop valve etc.
HQ To HZ Pedal Boxes #
One way around the disc verses drum pedal box question is to go to a 1.125 bore master cylinder. And where will I get one of these, you ask?
Well it happens that 68 to 82 Corvette master cylinders are a bolt on, same fittings and all, and they don’t have to cost any more than a new HQ to HZ one. How’s that?
Torana LC To UC #
All Torana’s came with firewall mounted Master Vacs boosters and tandem master cylinders, and as a rule when the big cars got a change in design the Torana’s followed. If you have been taking notice of the above in the Holden HK to WB section, the same things apply. In fact Torana’s used the same master cylinder as the equivalent big cars year to year.
Therefore generally, standard master cylinders are fine with big brakes, and remove residual valves and propvalves when going to rear discs.
The XU1 and V8 cars had the bigger double diaphragm boosters but they are not essential. Lastly if fitting big brakes to one of the last UC’s that had that metric 15/16 VB master, replace it with a 1 inch VB unit. (P10330 bolts on)
Why always use 1inch masters? Well that’s to keep the twin piston calipers compatible. All LH to early UC Torana’s and HQ to WB use 64mm caliper pistons. Twin 43mm pistons have a nearly identical hydraulic area, matching the big calipers with existing rear discs or drums and existing master cylinders.
Holden Gemini’s #
One of the more popular small cars amongst the modified car fraternity is the rear wheel drive Gemini. They lend themselves well to big 4 cylinder, turbo, rotary and V6 conversions. However those 250mm solid discs do leave a bit to be desired and most Engineers require a brake upgrade to match the increased power.
There are various brake improvements available, such as Piazza vented rotors, and adaptations to fit early Commodore rotors. Some need thin shrink sleeves under the wheel bearings, and this creates difficulties for the home mechanic as well as the known risk of the bearings not seating squarely or spinning on the spindle. Where ever possible Hoppers Stoppers fit original bearings in the bores of steel conversion hubs, and design the outer diameters to carry the upgrade rotor, making the brake upgrade a bolt on proposition.
Front Brakes #
Hoppers Stoppers upgrades for Gemini’s utilize VT/VZ 296 diameter by 28mm thick vented rotors and twin piston calipers, with original Gemini wheel bearings, seals and grease caps. The holes on the VT caliper cradle bracket need a 0.5mm elongation, and then bolt right on with no brackets required.
The special part is then really the hub, and our ability to source blank rotors to drill them in 4 stud or other special patterns. 5 stud brakes in Commodore pattern use standard VT rotors. On full lock the caliper will just touch the lower control arm, to stop this we suggest you weld a 6mm block against the lower control arm where the steering arm touches, this slightly reduces the turning circle. 15 inch or bigger wheels are needed for this conversion.
One small think to watch is a small increase in wheel offset, as the hub face is now 10mm further out per side. Some find this helps with issues with wheels touching the shock absorbers, but if clearance is tight between tyres and mudguards the change might be of concern. If you haven’t bought new wheels then factor this into your plans. As a rule we find 15 X 6 standard Commodore offset wheels with 195/60-15 tyres clear nicely.
Rear Brakes #
A lot of Gemini owners do not realize that their standard rear drum brakes are in fact 4 stud versions of the Torana and Commodore rears used at that time.
The shoes, wheel cylinders and all spring and clips are identical, and Holden interchangeability being what it is, early Gemini’s used the same basic parts as Torana’s (incl V8) up to when the Commodores were released and then Gemini and Torana got the Commodore rear drum design, as used up to VL.
The differentials are all in the same family, and use the same wheel bearings, it is therefore easy to have a VL axle shortened and resplined, and thus convert to 5-stud rear.
Better still the Commodore rear disc brake assembly fits the Gemini axle housing ends, the only other difference being the wheel bearings sets are different between drum and disc rears, so you can have a Commodore axle shortened, fit disc brakes bearings, bolt on the full handbrake housing, and slip on Commodore rear discs and calipers. A bit of a fiddle to make the Gemini handbrake cable connect and its all done.
To do a 4-stud disc rear you can simply change the wheel bearings on the original axle to the disc type and bolt on the rest. This of course needs us to drill from blanks some 4-stud rear discs.
All this assumes you will not have issues with diff center strength, as the Gemini’s use a 23 spline axle. Anything stronger means a full diff upgrade such as a 28 spline Commodore conversion.
Master Cylinders #
Any big brake kit needs a bigger bore master cylinder; we recommend a 1-inch tandem master be used with VT brakes. How to go about this depends on whether you engine conversion requires relocation of the booster.
Gemini’s came in three basic types; the early TX cars used remote fill reservoirs and a four-bolt mounting between master and booster. If you can keep the booster then we have a 1-inch remote fill master that is a straight bolt on.
Later TC to TE cars had a horizontal two-bolt arrangement. Again if you can keep the booster we find an XB Falcon master fits, but you need to extend the output pushrod length to correctly preload the master and repipe to 3/8 ball flare fittings, or use 3/8 to 10mm adapters.
The TF and TG series used an angle bolt master cylinder with a plastic reservoir, and to date we have not found a 1-inch replacement for this unit.
You therefore have to fit an early booster to have a firewall fitted unit on this series.
V6 Commodore conversions VN to VP seem to need total removal of the booster, but it seems that VS and later Ecotech engines are narrower and clear. If you have to go to a remote VH40 booster we have a neat 1-inch bore tandem master, which suits this engine type. If going to four wheel discs you will need two remote VH40’s. Don’t forget that you should retain your brake fail warning light and that the original proportioning valve is the wrong pressure for rear discs. A HZ four-wheel disc unit will be right (now obsolete new) or an adjustable unit needed.
Some cars made in the 70’s worked acceptably with no boosters at all, albeit with higher pedal efforts. In fact rare poverty pack Gemini’s were sold without boosters. I remember one car coming in for a service, after a test drive was about to ring the customer to tell her that her booster had failed only to find it never had one! Bigger calipers and rotors of course stop better, so as long as you use soft high friction pads acceptable brakes can still be had with no booster. Not the thing to let your slightly built girlfriend drive.
We hope all the above is a help in getting your Modified Gemini safely on the road.
Balancing Front/Rear Brakes #
REAR DRUMS #
With so many variables and mixing and matching, it might be necessary to fine tune front/rear balance. Holden made their basic rear wheel cylinders in a variety of bore sizes, from 9/16 to 1 inch. 7/8 inch is the standard HQ to WB size and ¾ inch most often used on Torana’s LH to UC.
Fit smaller bores for less rear brakes and bigger bores for more rear brakes.
This might be more likely if fitting larger rear drums, 9 inch diffs etc.
In the end you MUST have a design that locks the front brakes just before the rear. This is to ensure the car doesn’t spin around if the rears lock first. Don’t use an adjustable prop valve to attempt to fine tune incorrectly balanced rear brakes; you want them to do the correct share of the work at low pressures as well as on hard braking. The real point of a rear prop valve is to basically make sure that the rear brakes never lock, even with a full panic effort, so that the car will never spin.
REAR DISCS #
It’s not possible to fiddle with rear caliper bores, so you have to fit rear calipers which were originally a match to the hydraulic area of the front’s in question. As the weight distribution of the car and tyre sizes etc are probably different from the donor car a bit of educated guess work is needed. If small adjustments are needed then harder or softer brake pads are a way to adjust brake balance.
As a general rule we find rear brakes do a smaller percentage of the work, and do not make much heat even when the fronts are working hard. We even have one customer’s racecar that can brake so hard the rear tyres come several centimeters off the road at full effort.
Therefore we don’t usually fit hard “metal king” type rear pads for street use.
Commodore VB-VS #
I will take the liberty of adding to this as Commodores are becoming old enough to be seen a colectable and desireable if they were not already!
VB-VK: These models ran the same brakes all they way through comprising of 256mm solid (4cyl) or 270mm vented rotors up front with single piston calipers and drums (same as HQ) on the back or 279mm solid rotors with single piston calipers and internal drum style handbrake inside the rotor ‘hat’. Later model V8 cars (310 pack, HDT inc) got larger 290mm vented front with a finned single piston calipers. Alloy Master Cylinders 13/16” bore with built “brake fail switch” and plastic reservoirs were the order of the day. Single Diaphragm Booster on 6 cylinder cars, Double Diaphragm Boosters and larger 1” bore master on V8s.
VL-VP: Thankfully the 4 cylinder was dropped, so 6 cylinder brakes remained at 270mm and V8 (inc Turbo and HSV) 290mm rotors up front. By VN the Commodore had become 4 wheel disc only, still using the same rear brakes from the first VB Model. Apparently the there were some VN’s with drum rear brakes but I have never seen one. Even the ground breaking HSV Walkinshaw Group A’s used the same brakes as the standard V8 and Turbo cars. It wasn’t until HSV re-ignited the GTS name plate that we saw some more exotic brake hardware in the form of 330x28mm front rotors with C4 Corvette calipers. Some Statesman’s began to see 280mm Ventilated rear rotors also. VP also saw the introduction of basic ABS systems on up-spec Models. Same Master and Booster specs from previous cars.
VR-VS: Saw the move away from Tapered Roller bearing hubs in favour of ball bearing units and dropping the small front rotor. Every vehicle this side a a HSV badge running the 290mm front rotor and 279mm solid rear. HSV continued with the C4 Corvette rotor and Vented 280mm rear brakes on their “top of the range” GTS, Senator and Grange. Plastic brake booster also made a short appearance of VS series 2/3 but these were prone to cracking and were gone with the next Model. ABS becoming more common across the range.
VT-VZ: A return to a full size sedan meant Twin Piston Calipers up front with larger rotors and larger rear rotors to compensate for the extra weight of the larger body. Handbrake grew in diameter althought stayed the same internal drum type. Return to Double Diaphragm Steel Booster across the range with an Alloy/plastic res. Fast Fill Master to compensate for the retraction of the pistons in the new front caliper. With the push for more economy from our vehicles the brakes were designed to retract the piston to stop any ‘Drag’ on the rotor maximising efficency, back in the days of the HQ this was achieved by a small degree of wheel bearing play to “knock” the pads back. The Fast Fill function of the Master Cylinder was added to speed up pad contact to the rotor and reduce pedal travel. HSV and VZ Models started to add more and more brake options inc C5 Corvette Calipers on 320x32mm rotors (VZ SSV) and 330x32mm rotor for Clubsport etc. Harrop and AP Racing were also part of the HSV catalogue with 343mm and 355mm rotors. ABS got smarter and combined with the traction control to gather more info. 315mm vented rear rotors were available on some HSV models larger again with the last AP Racing equiped VZ models.
VE-VF: A new generation car built on an international platform to continue the legacy of the larger rear drive sedan. Front brakes grew in thickness from 28 to 30mm, 298mm diameter for the V6, 321mm for the V8. Rear brakes became vented across the range, 302x22mm for V6 and 324x22mm for V8. Same internal Handbrake design as VT. Redline Models offered with Brembo Calipers front and rear, 355x32mm rotor on the front, same V8 rotor on the rear. HSV again offering huge 6 piston AP Racing and Harrop brakes up to 365mm in diameter. Vehicle Stability Control offered in various guises acorss the range using more and more sensors to allow the ECU greater information and control in emergency situations.
Unterchangeability And Upgrades. #
Long story short Holden made this very easy across the Commodore range right up to and including the VZ. Basically you could choose any front brake package from the later model cars and fit it to the early models with the use of and adaptor hub (Hoppers Stoppers can Supply) to allow your tapered roller bearing front strut to take a “Top Hat” style rotor from any of the VT-VZ series cars. Remember some of these HSV models will use brackets to mount the caliper, you should obtain these with the calipers. VR-VS is a little trickier as the spiggot of their hub is slightly smaller than the VT-VZ cars meaning the rotors are a loose fit. Spiggot spacers are available to rectify this and centralise the rotor properly. Calipers bolt on the same. Modified brake hoses will be required due to differences in mounting position and flare types used.
Rear brakes up to VS are pretty much as good as your going to get.. if you can find some rear calipers to go with the vented rear rotor, more power too you, they are very rare these days. If you VB-VL has drum brakes and you want discs, no probs just go a grab yourself a set from the wrecker and dismantle the drum assembly and bolt the Disc assembly. (We would recommend some component reconditioning in the process.) Avoid any rear kit that is using a welded in ring inside the cast rotor the resize the handbrake… this is just plain dangerous. There are 330mm kits on the market though that use a custom made rotor specifically for this set-up, these are great and offer a massive step up in looks and function.
For the earlier car up to VS, flexible firewalls were a bit of and issue and meaning you may not get the pedal feel you want with your new upgraded brakes. We recommend fitting a stronger brace from the Master Cylinder to the strut tower to firm everthing up. Failing that Conversion Kits to fit VT Master and Booster to earlier commodores are available and will help this issue..
As you will have gathered from above, anything that fits a VZ will bolt straight to a VT or anything inbetween.
VE and VF have the same part interchangeability so you can bolt so,e Redline Brembos to youe SV6 no problem at all. Even Chevrolet Camaro brake packages can be made to work with a bit of attention paid to bolt sizes.
There you go, a lot of our hard earned knowledge for free.
I think we have covered most of the important things about Holden Brakes and how to upgrade them, and if this helps me re having to answer those same questions over and over on the phone and “net” it will all be worth while!
DRIVE SAFELY – FROM THE GUYS AT HOPPERS STOPPERS
Edited by Duncan Benn 2017