Brake proprtioning or equalising

[wires]

I have a 1990 (or so) Dax Cobra, and the front brakes lock up really easily under heavy braking.

I am almost certain that the front and rear brake circuits are connected the wrong way round on the master cylinder that is attached to the servo. My system has a single line connected to the union nearest to the servo, and this goes to the rear brakes. The front brakes are connected to the two unions at the front of the servo. Nearly all of the Haynes manuals (for MGB, Rover, and Jaguar) show the rear brake line conected to the front union and the front brake lines to the rear, with a brake pressure warning switch underneath the spare outlet.

Does anyone know the answer ?

I also do not know from which car the servo comes. Any suggestions welcome.

Pictures attached.

Cheers,

Wires

[TINKA]

Hi Wires, not sure what setup your brake master comes off but the set up you have is exactly the same as mine. If you were to swap it around and the effects were also swapped over you would find your rear wheels locking up and possibly overtaking you ,as you might then go into a very dangerous spin.

[mylesdw]

Unless the cylinder changes bore half way down, swapping the pipes will make no difference anyway. Front brake locking is a well known feature for the Ram (don't know about the Dax) and the fix is to place an adjustable limit valve in the front circuit.

Looks just like the Morris Marina/Ital setup that is on the Ram but I can't be sure from the photos.

[Miket]

Wires

It looks like Sierra, if it is the pipes are connected the correct way, single to the rear.

It is not Marina, as they only have 2 pipes and the one nearest the servo on this setup does go to front brakes.

Picture enclosed off Marina.

[wires]

Thanks for your help chaps. Seems like I will need a limit valve.

Cheers,

Wires

[kurrmet]

Wires

I have a 1993 Dax which uses a E Type jaguar remote servo and have had no problem in brake locking up. I will try to put a picture on a thread tonight.

If you do go down the route of a brake bias valve i would suggest a tilton one as these last i have found and my race car where some of the other tend to fail. I purchased mine from Demon Tweeks but any good motorsports dealers will be able to help.

[wires]

Thanks Kurrmet. But where can you get an E-type servo, and how much would it cost ? Anyway glad to hear that your Dax does not lock up.

Cheers,

Wires

[kdavies3]

If you do fit a limiting valve I'd go for and adjustable one so that you can fine tune it.
Don't over do it though 'cos the last thing you need is the rear locking up and overtaking the front.
I've made adjustable ones from Mini rear brake compensators in the past, it's been a long time though.

[wires]

Thanks, Kev. Do you ever get any rest ? You are always helping us out !

I had read about, and downloaded info' from the 'net on, adapting Mini rear compensators. I also know that Summit Motors in the States do a Willwood adjustable compensator for $39.99.

However I am getting a bit concerned about locking up at the rear rather than the front - it's just that mine locks up at the front SO easily. Overall though I reckon that I'll live with it. I have twin brake lines at the front, one to either side, so the though of fitting and correctly adjusting, and keeping correctly adjusted two (apparently not very reliable) proportioning valves is no longer very appealing. I am now starting to think about the possibilities of adapting an ABS system instead !

Cheers,

Wires

[mark_biddle]

I am building a De-Dion with upgraded brakes at the moment. I am using Brembo calipers and big discs. I was down at Dax the weekend and talking to the guys there about it, and they have put big discs on their demonstrator. They were having problems with the fronts locking and have come up with a new master cylinder arrangement and apparently will be selling it soon.
Not sure if they are doing same for XJ6 based Dax. Might be worth a call to find out.
They tried using a bias adjuster but could not get enough to the rears, hence their design.