front brake upgrade: semi-huck to duo-servo

[ardiesse]

"Is it possible to upgrade FE-FC FB-EK front brakes to EJ-EH or HD" is a question which comes up fairly often. The accepted method is to change over to EJ-HD steering knuckles, supports, steering arms, backing plates and brakes as an assembly. But I got to wondering -

Is it possible to bolt EJ-HD front brakes directly onto FE-FC FB-EK steering knuckles without changing to EJ-HD steering knuckles and supports? There is no firm consensus. So I decided to find out, by doing.

Here is an HD kingpin front brake assembly happily bolted up to an FC steering knuckle. (Author's note: you can tell which forum I prepared this post for. And I'm fresh out of FB-EK steering knuckles a.t.m.)



From this angle it looks no different from the original HD steering knuckle and support. From the back side, though -



A couple of things of note -
The upper holes in the FC steering knuckle support are threaded, so I had to change to short 3/8" UNF bolts. This is also the case for FB-EK steering knuckles.
The steering knuckle forging has the number 3415/6, which identifies it as later FE and FC (7413415/6).

And here is a photo of an FE-EK steering arm (left and bottom) bolted up to an EJ-HD steering arm (right and top), showing that the bolt hole spacing is the same between both types of steering arm:



Conclusion: Yes, you can bolt EJ-HD front brakes onto (late) FE and FC FB-EK steering knuckles. You need to change the top two backing plate to steering knuckle attaching bolts to short 3/8" UNF bolts to suit the threaded holes in the FE-FC FB-EK steering knuckle. You also need to use the EJ-HD steering arms. And if you are using HD kingpin front brakes (probably rocking-horse-poo rare these days), you will need to use HD or HR wheels.

Rob

[Errol62]

Very interesting indeed. Dr Terry stated that the bolt pattern was different but apparently not.

I have it that the supports, left and right handed, have one part number for FB EK EJ EH and HD (kingpin). Whereas there are multiple numbers for FE FC, varying by both date, and plant.


FB ute fixer upper, EK van on rotisserie

[Blacky]

We were only talking about this yesterday at our club meeting, the main topic of discussion was is it actually worth going to the trouble of doing it ? What sort of improvement are we expecting ???

[ardiesse]

Blacky,

Your question goes to the heart of the matter.

All drum brakes self-energise to a certain extent on the leading shoe. I read somewhere that the self-energization is a very "steep" function of the lining's friction coefficient, in that small increase of friction coefficient will give a very large increase in self-energization.

Example: "Morning sickness" aka grabby brakes in early Holdens in humid weather. The humidity increases the coefficient of friction past a critical value, at which point the brakes lock on. After the linings have heated up a little, things return to normal.

FX-EK brakes are the semi-huck type, in which only the leading shoe has a degree of self-servo action. EJ-onwards brakes are the "duo-servo" type, in which the braking force of the leading shoe is transferred to the trailing shoe, adding greatly to the braking effort. Because the self-energization of duo-servo brakes is higher than that of semi-huck brakes, my hunch is that duo-servo brakes will be more prone to fade than semi-huck brakes -

Counterexample: my Humpy. It runs out of brakes surprisingly fast, and in city traffic too. When it's in a bad mood, I can't make the front brakes lock, no matter how hard I push on the brake pedal. Come to think of it, my FC's brakes do not fill me with confidence either (same 1-1/2" lining width).

You'd have to put both braking systems to the test. Get an EK and an EJ of similar weight and see which vehicle's brakes fade less. (I do remember road tests of the EH which were quite critical of the brakes . . .) Certainly the later wheel cylinders are much better sealed against moisture than the early ones, which is a plus for the later brakes. Pissy little 1/4" AF bleed nipples were a huge backward step though. There might be a noticeable improvement in braking performance if you went to the 2-1/4" wide HD front brakes.

But the most fade-resistant style of drum brakes is the twin-leading-shoe arrangement. I think the PA Vauxhalls had twin-leading brakes, in 9" diameter too. Here's an engineering challenge: to fit them to a Holden.

Rob

[Blacky]

I have been asking around over here for a set of HD king pin brakes, stubs and steering arms but they are unobtanuim ..... which is hardly surprising.

Guessing EH stuff would be considerably easier to source which is what led to the question regarding energy and cost expended versus benefit realised.

[Mick]

i've done it think from memory i just used whole EJ kingpins with everything, which considering you would need to get backing plates and all brake assemblies good chance the kingpins will be there also

[Blacky]

Got a lead on a set of brakes and stub axles on an EH wreck over here for a bottle of Wild Turkey - going to check them out Friday. Plan will be to unbolt the whole shebang from upper and lower wishbones and get all the bits in one go.

Watch this space.

[Blacky]

Part 1 complete - set of reasonably good condition brakes with uprights and steering arms sourced. Might be time to knock up a molasses tank



Sent from my iPhone using Tapatalk

[Blacky]

Stripped down, no real surprises- has lost a wheel on the passenger’s side at some stage in the last 60 years had a hell of a time getting this drum off - a bit of heat and a FBH got the job done





Will take the drums and the slave cylinders in for a birthday/replacement tomorrow


Sent from my iPhone using Tapatalk

[Blacky]

Cleaned up all the little bits


One of these is not like the other - minor drama just need a new bolt or 2



Sent from my iPhone using Tapatalk

[Blacky]

Took the drums and slave cylinders to Perth Brake parts today - drums are well oversize so in the bin they go , new ones ordered.

Slave cylinders they wanted $145 EACH to sleeve and kit them - and they couldn't supply replacements, said try Rare Spares or somewhere so I drove around the corner and bought new ones for $41 each at Veales.

Sandblasted the backing plates and steering arms and dropped them off at the powdercoaters - hopefully all the bits get done this week and the new parts turn up and I can fit them up this weekend

[Errol62]

Those wheel cylinders are readily available new and the quality is generally good. It is funny, I never thought of the HD kingpin suspension being rare, but the problem seems to be that you can not get the wider drums new. That makes this the most practical upgrade. I think it will be worth the effort.


FB ute fixer upper, EK van on rotisserie

[Blacky]

That was quick- only ordered them off Epay on Monday



Sent from my iPhone using Tapatalk

[Blacky]

Just waiting on the new brake shoes now ….



Sent from my iPhone using Tapatalk

[Blacky]

Went to assemble them today -I have 2 drivers side cylinders plus they are larger than the old ones so I will have to take the die grinder to my freshly powdercoated backing plates


Sent from my iPhone using Tapatalk