Guys

Just looking for opinions on what cylinders to run on the rears on the GTS's brakes.

I'm running AUII onwards front calipers on BA-BF rotors, with VT stepped bore master cylinder, HG booster and HK-WB rear drums.

Original HK disc/drum rear cylinders look to be 9/16".

Am I better off running HK 9/16" or one of the drum brake (or HQ) sizes: 13/16" or 7/8"?

It won't have a proportioning valve, apparently doesn't need it with the stepped bore booster.

Any suggestions also on what cylinder brand to buy that won't be stuffed in 2 years? This car has not been used since the front end was totally rebuilt about 4-5 years ago and all the tie rod and ball joint rubbers are shot, don't want the cylinder rubbers doing the same!

Edited by user Thursday, 14 February 2019 9:22:35 AM(UTC)  | Reason: Not specified

Thanks Terry

What did HJ have on the rear without the inline prop valve? I do have some old stock PBR 7/8” ones here from the 90’s that are not cheap rubbish.

Also not all VT had ABS? Or did they? Can't remember. Or did export ones have no ABS? I thought all VT master cyl were the same, the ABS ones used the extra port and the non-ABS had it blanked with a plug. I also thought they had an inbuilt proportioning valve in the VT master cylinder.

Edited by user Thursday, 14 February 2019 12:17:00 PM(UTC)  | Reason: Not specified

Cool. There is only one VT master cyl though for all applications? I'm pretty sure that is correct. I guess I have two options, find some quality 9/16" cylinders or try some 7/8" and possibly have to fit a HQ prop valve inline if I get too much rear braking. The VT master cyl definitely has no internal proportioning valve?

Will see if I have any 9/16” ones here. I think my Woodsman Green Monaro has some.
The brake place told me that VT cylinders have a prop valve internal but it doesn’t look that way to me.

I forgot these were arse about compared to a HK-HG, wasn't looking at the front. Brake place told me to use 7/8" due to the VT cylinder having an inbuilt prop valve, but I have grown to trust Dr Terry's experience. What I might try to do is use the 7/8" ones I have and see how it goes, but try and find some old 9/16" ones too and get them rebuilt ready to use if I have to.

Terry, the flare adapters, is it worth using them? I have to make up all new lines for the HK, and rather than use the distribution block down on the subframe I was intending to use the two front circuit outlets on the VT master cylinder, and also make up a new line for the rear that suits the VT rear circuit outlet. I cut pipe ends off a VT to get the nuts. So some of the car will have the old style flares, some will need those like what are on the VT cylinder. Not sure what Rodtech have on the hoses with the Ford calipers. Should I use all older Holden style flares and adapters or just have different flares on each ends of the lines? On the same matter, the VT lines look larger than the HK ones, so will the VT nuts work with HK size tube? If not I guess it means adapters! I think the VT cylinder has 12mm port for the rear circuit with ball flare and the front circuit has 2 x 10mm ports with same ball flare.

Edited by user Thursday, 14 February 2019 5:59:46 PM(UTC)  | Reason: Not specified

So many questions first thing in the morning !! Firstly the difference between P10046 & P10046G is that the G version is "built to a higher standard". It's more of a marketing idea where the G cylinders are actually plated a gold finish.

I think it was a PBR thing where there were so many cheap Asian-sourced cylinders on the market, all using the same part number, they needed differentiation. They are otherwise interchangeable.

AFAIK all the brake pipes used in VT-VZ etc. are still 3/16" even though the pipe nuts have metric threads. I have done plenty of conversions which have an SAE pipe nut at one end & a metric pipe nut at the other. Nothing wrong with that & in many cases it works out neater.

On the subject of so-called proportioning vales, they don't actually do any proportioning. The front/rear brake bias is controlled by the ratio of the cylinder sizes. This is why I prefer the 9/16" rears.

The proportioning valve is actually a limiting valve, where it allow unlimited braking up to a certain point & then limits the pressure to prevent rear lock-up.

Dr Terry

he cylinder mounting studs are horizontal so HK through to HZ?? cylinders will bolt on ok. To run this make sure you have the clearance 'dent' in the inner guard. Not all have it, mine doesn't. The one I run is a smaller factory booster. It's off a HK but not sure what model. I have to re-drill the mounting bracket to lift it slightly to clear guard. The cylinder mounting bolts are diagonal so commodore style cylinders bolt straight on.

Edited by user Wednesday, 5 January 2022 10:21:04 AM(UTC)  | Reason: Not specified