8 replies to this topic

[LHoon]

Hey guys, I’m trying to fix up my brake performance to pass Engineering. Currently I get the rears locking up first, so I need to fix that. From what I have read online already, I need to change wheel cylinders in the rear drums (unless I install an adjustable proportioning valve).

Equipment Currently Fitted:
Car is LC Torana with a Holden 355 (std VN heads) and 9 inch diff.
Brake System:
- LJ (Disc) Master Cylinder
- LJ (Disc) Distribution block (I guess it doesn’t have a proportioning valve?)
- Small diameter no-brand (Chinese) Chrome Booster, single diaphragm
- Fronts: HQ disc with HZ PBR Alloy Calliper
- Rear HQ Drum (I assume with standard HQ wheel cylinders)

I have just purchased all new HQ drum and shoes to freshen up the rears.
The guy who sold me the drums and shoes just suggested I use a 13/16” wheel cylinder which is a direct replacement.
But the posts on here suggest I purchase 9/16” cylinders P5573 as the rear brakes need a very small bore. So I bought the 9/16” cylinders instead. Now I see that those cylinder have a flat button-style piston. The HQ ones have a little pushrod.

I also spotted that one forum member buys a Nissan cylinder JB2558 just to steal the pistons and swap those over. So I have those on order too. This all seems like a lot of stuffing around just to get “standard” HQ brakes to work. Am I doing the right thing, is this the right approach? What does everyone else do?

[76lxhatch]

Why not just install a proportioning valve?

[yel327]

I think the 9/16" cylinders are for HK-HG with front discs. They use different brake shoes. Confirm with Dr Terry but I think you can fit the HK-HG shoes for front disc, rear drum on HQ-WB backing plates with the 9/16" cylinders.

[dron]

Hi

   You can run the HK T G rear shoes and 9/16 cylinders with the HQ backing plate and drum; I have done the same thing when playing with the brake balance on my uc with a UPC front disk setup. The only difference in the drum is the stud paten and the internal parts interchange. The 9/16 cylinders do not use a push rod and the shoe is their foe different to allow this to work. In my case this left the rear brakes not doing enough work so I went up 1 size and back to a push rod type shoe and cylinder.  Lots of cylinder sizes to try 5/8 is where I ended up. The HQ brake and HZ caliper will change the overall ballance to mine so I would guess somewhere arround 5/8  to 3/4 would be where you end up on cylinder size. Cheaper to play arround with wheel cylinders than the rest so pick a smaller one that uses a push rod and test it's performance.

Edited by dron, 12 March 2023 - 05:22 PM.

[yel327]

That’s what I thought, glad my memory is still intact. Only the backing plates and the drum stud pattern differs. Plus that shoe difference with the oddball cylinders.

[dattoman]

If you used N1338 shoes instead of N1337 shoes you wouldn't need to swap the pistons in the wheel cyls

Just use the STD 9/16 ones P5573

[LHoon]

Thanks for the information

[claysummers]

Hi
You can run the HK T G rear shoes and 9/16 cylinders with the HQ backing plate and drum; I have done the same thing when playing with the brake balance on my uc with a UPC front disk setup. The only difference in the drum is the stud paten and the internal parts interchange. The 9/16 cylinders do not use a push rod and the shoe is their foe different to allow this to work. In my case this left the rear brakes not doing enough work so I went up 1 size and back to a push rod type shoe and cylinder. Lots of cylinder sizes to try 5/8 is where I ended up. The HQ brake and HZ caliper will change the overall ballance to mine so I would guess somewhere arround 5/8 to 3/4 would be where you end up on cylinder size. Cheaper to play arround with wheel cylinders than the rest so pick a smaller one that uses a push rod and test it's performance.

Dron is on the money with the 5/8” cylinders I reckon. Means no need to change shoes.


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[LHoon]

OK great. Anyone know the part number for the 5/8” cylinders?