Proportioning brake valve

[Pasquale]

Hi I'm a new member with a GTV-6. Currently having the rear brakes repaired and require a proportioning valve to suit 1985 GTV-6. I understand these are not rebuildable and have to be replaced. Can anyone tell me where I can buy one in Aust.

Cheers

Pasquale

[MD]

Pasquale,

If you suspect that the valve is faulty and not fuctioning the alternative to replacing it is to simply do away with it and install a rear adjustable proprtioning valve substitute. This will give you a limited ability to adjust the rear brake bias based on the size and nature of your rear tyres, the type of barke pad material you are using and payload.

While you are at the workshops, make the enquiry about such a device and they may install one while the other work is being done. Best time to do it.

[Pasquale]

Thanks guys, apparently International Auto have them in the USA but they are currently out of stock untill 15 Oct, so I'll try Monza motors for 2nd hand option. 

Pat

[dehne]

 i have a secondhand 1 if u need

[MD]

Pasquale,

Regrettably unless the valve is removed from a car that was running recently or the braking system has not been pulled apart, there is a very good chance that the valve will have internal corrosion from having fluid in it and absorbing moisture from the air once it was removed and put on the shelf.

My recommendation is either fit a new one original type, a new adjustable type or simply by-pass it altogether and leave it out.

My brakes on my GTV6 actually work better without it.

[116gtv]

be careful with after market adjustable valves, some of them dont have a full range of adjustment, leaving you with not enough or too much bias to the rear..

[Bob Morey]

Hi Martin, I'm about to upgrade my front brakes & will probably need an adjustable brake proportioning valve.  Do have details of one that has adequate adjustment.  Conversely which ones are no good.

Thanks

[MD]

I think this topic is heading for a discussion.

My experience with the transaxle cars is that the difference in pad size (front > rear) alone provides sufficient front bias to prevent rear lock ups. Matter of fact, there is insufficient braking at the rear even if you completely remove the proportioning valve. This was not the case with 105's I have had in the past. I believe this is due to the weight differences at the rear between these cars. I have driven many thousands of kilometers in transaxles and I cannot recollect EVER having a rear wheel lock up with or without the valve in place.

I am talking about street cars only as racing applications vary too much to make a simple conclusion.

I would be interested in other peoples experiences in the same context.

[david sammartino]

yes, i agree with you md, and have had similar results, except for when i have used vastly varied pad compounds front to rear. ie a much better pad at the rear and a 10 dollar set of cheapies at the front, but even then, was only slight, and when driving spirited on private roads 
another concern could be an insurance scenario, and if some strange reason the brake system had to be looked at, like if someone was killed or something in an accident.

[Bob Morey]

Thanks guys, I've had similar advice from other sources.  I am fitting V6 vented discs & Commodore calipers on the front & the car will only be used on the road.  I was a bit nervous about removing the proportioning valve & locking the rears.  If I'm going to slide off the road with the brakes locked up I'd like to do it frontwards

[MD]

Bob,

I am no authority in this stuff. It is the realm of hydraulic engineers to calculate the total fluid and pressure balances for modified brakes but just going by things that I have tried in the past, there may be master cylinder issues that evolve and just about certain that the rear brakes will be under performing compared to the fronts and you will have too much front braking and insufficient rear braking.

Best of luck with it anyhow..

[Pasquale]

Hello MD and others,

It seems that there are a host of options that could work its just a matter of deciding which option best suits the specific need. In my case, I've had the rear brake calipers fully reconditioned and new pads fitted. The proportioning valve in my GTV6 is still working but is just starting to show signs of some leakage, but not much.  I want to maintain originalilty so will be fitting a new replacement as it becomes availble from International Auto in mid October or thereabouts.

Cheers

Pasquale

[carjunky]

Highwood Alfa in the UK, I bought one for my 1983GTV6, the 85 model is a little more expensive but they have them and Chris is fantastic to deal with, the best i have ever bought from.

[Pasquale]

Thanks, I'll check them out.

Pasquale

[njh1964]

My apologies for partially hijacking this thread, but does anyone know if fitting an aftermarket adjustable proportioning valve (eg Wilwood, Tilton, etc) is road legal in Victoria?