Ph1, cup abs delete - Rear brakes keep locking up

[Mash.]

Any suggestions before I throw the cup brakes lines in the bin on my ph1 and make my own lines with bias valve

Rear brakes keep locking up, when it's on stands and someone has there foot on the brake I can spin the rear wheels with not much effort at all (i.e. low braking effort) which is good meaning no lock up... ha ha

when it's on the road if I brake quite hard, but nothing compared to braking on track the rear wheels lock up leaving a good cloud of smoke behind me...

- the lever on the compensator valve is fully down (towards the ground - lowest braking effort) and I have also shortened it so the weight of the car moving the axle up does not hit the lever putting it upwards again (more braking effort)
- the car is fully striped and I've played around with the ride height to distribute a bit more weight over rear wheels.. still no joy.
-the lines are all correctly installed in the valve

I'm stuck ..

Thanks all

 

[bashracing]

@Mash.
take a picture of the compensator valve,
my guess is you have the in and out pipes the wrong way round.

 

[Mash.]

 

[bashracing]

that's right,
is the piston in the compensator that the the arm acts on moving in and out (not seized) when the footbrake is applied?

 

[Mash.]

Yeah all moving.

can you tell me what ports go where on the MC please?!

 

[bashracing]

Ii's a diagonal split system so, Right Front-Left Rear on the front master cylinder ports and Left Front-Right Rear on the Rear master cylinder ports,
or the other way around, it won't effect fluid pressure to the rear so don't worry about that,
Take it to an Mot test station and ask for a brake test,
you should see around 250kg-400kg (and locks) per wheel from the fronts, and 90kg-160kg (no locks) each from the rear wheels,
you may find your front brakes aren't working well enough causing the problem.
the last thing is tyres do you have wang ching ditch finders on the rear.
@Mash.

 

[Mash.]

Ii's a diagonal split system so, Right Front-Left Rear on the front master cylinder ports and Left Front-Right Rear on the Rear master cylinder ports,
or the other way around, it won't effect fluid pressure to the rear so don't worry about that,
Take it to an Mot test station and ask for a brake test,
you should see around 250kg-400kg (and locks) per wheel from the fronts, and 90kg-160kg (no locks) each from the rear wheels,
you may find your front brakes aren't working well enough causing the problem.
the last thing is tyres do you have wang ching ditch finders on the rear.
@Mash.

Right ok, yeah the lines are in the correct places, and its quite hard for them not to be, due to the different size ports - having an absolute mare with it.

just bought some 4 pots, so gonna put in some custom lines and bias valve along with the compensator valve, and hopefully that should be the end of the unstable breaking!

 

[Mash.]

and i do have ching chang NS2R's on the rear, which arnt that bad.

 

[bashracing]

Just annoying when you have gone to the effort of doing it properly and it still won't work,
The advantage of adding a bias valve for a track car is that you can give the rear more pressure in the wet as there's less weight transfer under braking, think of it as just upgrading early and it won't feel like such a chore

 

[Mash.]

Just annoying when you have gone to the effort of doing it properly and it still won't work,
The advantage of adding a bias valve for a track car is that you can give the rear more pressure in the wet as there's less weight transfer under braking, think of it as just upgrading early and it won't feel like such a chore

Yeah thats true!

Hey ho, just expenditure i didn't want to make onto of expenditure, hey ho.

thanks for your help anyway?

 

[Mash.]

So just to revive this, had the ph1 on MOT rollers to check the braking - the rears are putting out around 30kg of effort, so nowhere near the amount needed to essentially pass an MOT, but my rear brakes are still locking up while braking hard and the rear trying to overtake the front wheels...

What the f**k is going onnnnnn

 

[NorthloopCup]

What's the fronts pulling?

 

[Mash.]

What's the fronts pulling?

I can't actually remember, annoyingly - what are you thinking?

 

[NorthloopCup]

I can't actually remember, annoyingly - what are you thinking?

Well I'm thinking that if they're working exceptionally well, the rear is end is lifting up. So now your thinking, 'right so what's your point?', well what's this rod you've got connected to the lever on the compensator valve? The arm on the bottom of the compensator shouldn't be connected to anything whatsoever. On mine there's a spring that holds it in the up position. This allows the lever arm to move down under breaking effort, then return to the up position when the brakes are off.
Under load transfer during braking, the back end lifts up as the front end drops. This in turn pushes the lever up generating maximum (well as maximum as it gets on a cup!) effort to the rear brakes. End result - locking the rears.
Mine does it as well when your on it, but it's only very slight.

This would explain why it works fine in the rollers, but not when it's on the road in the real world.

Just my 2 pence worth.

 

[Mash.]

Well I'm thinking that if they're working exceptionally well, the rear is end is lifting up. So now your thinking, 'right so what's your point?', well what's this rod you've got connected to the lever on the compensator valve? The arm on the bottom of the compensator shouldn't be connected to anything whatsoever. On mine there's a spring that holds it in the up position. This allows the lever arm to move down under breaking effort, then return to the up position when the brakes are off.
Under load transfer during braking, the back end lifts up as the front end drops. This in turn pushes the lever up generating maximum (well as maximum as it gets on a cup!) effort to the rear brakes. End result - locking the rears.
Mine does it as well when your on it, but it's only very slight.

This would explain why it works fine in the rollers, but not when it's on the road in the real world.

Just my 2 pence worth.

Yeah nope not exceptionally well as they were cold ds3000s, so probs around 300-320...

I haven't got the rod mate, I asked a question ages ago whether I needed a rod, which you answered no too.

I used to have the spring but I removed it, to see if it would make an effect to what position the lever was at (so it stayed at the positon) rather than being controlled by the movement of the vehicle.

I've tried the lever closest towards the car (up)

and closest towards the ground (down) and pulling the lever down seemed to help a bit.

I've ordered some copper pipe and I've got a bias valve to go on, so I think I'm just gonna remove it completely... Although heard people (tony hunter) still needing the compensator with the bias valve, as the bias valve didn't reduce the effort enough.

 

[Jekyll]

Slighty off topic, but if your thinking of getting 4 pots you may want to consider a bigger master cylinder. I have 4 pots on mine and there was loads of pedal travel. Turns out the outlets are smaller on the ph1 master cylinder than on the ph2. (i had 4 pots on my old 182 and pedal travel was fine.

I run a 197/200 master cylinder now and feels fine. Just a heads up for you.

 

[Mash.]

Slighty off topic, but if your thinking of getting 4 pots you may want to consider a bigger master cylinder. I have 4 pots on mine and there was loads of pedal travel. Turns out the outlets are smaller on the ph1 master cylinder than on the ph2. (i had 4 pots on my old 182 and pedal travel was fine.

I run a 197/200 master cylinder now and feels fine. Just a heads up for you.

M ine isn't a ph1 master cylinder anymore, it's a 172 cup MC which has the 4 ports.

But yes i did wonder weather I maybe needing to go to a 197 MC, I will test that and rectify when/if it is a problem

 

[NorthloopCup]

Yeah nope not exceptionally well as they were cold ds3000s, so probs around 300-320...

I haven't got the rod mate, I asked a question ages ago whether I needed a rod, which you answered no too.

I used to have the spring but I removed it, to see if it would make an effect to what position the lever was at (so it stayed at the positon) rather than being controlled by the movement of the vehicle.

I've tried the lever closest towards the car (up)

and closest towards the ground (down) and pulling the lever down seemed to help a bit.

I've ordered some copper pipe and I've got a bias valve to go on, so I think I'm just gonna remove it completely... Although heard people (tony hunter) still needing the compensator with the bias valve, as the bias valve didn't reduce the effort enough.

It can only be the compensator that's the problem imo. There's no way it can be piped up wrong at the mc as the fronts are m12 and the rears are m10.

 

[Mash.]

It can only be the compensator that's the problem imo. There's no way it can be piped up wrong at the mc as the fronts are m12 and the rears are m10.

yep, that's what I'm thinking!

yep i thought I'd had fucked it up, but then yeah as you said you can't really go wrong as they sized to fit in the ports.

hey ho - brake lines through the car with a bias valve looks good too

 

[NorthloopCup]

yep, that's what I'm thinking!

yep i thought I'd had fucked it up, but then yeah as you said you can't really go wrong as they sized to fit in the ports.

hey ho - brake lines through the car with a bias valve looks good too

It'll lock up for fun mate with a normal bias valve as they don't reduce the pressure enough.

 

[Mash.]

It'll lock up for fun mate with a normal bias valve as they don't reduce the pressure enough.

ahh reet, i'll keep it in then! thanks again Mark

 

[Tony Hunter]

Yes i do run both, I did have one of those micky mouse bias valves with a lever, even in the off position it was too much.

Really need a dial one, so it can be screwed right down. If I could get away with it, I'd disconnect the rear completely.

 

[NorthloopCup]

Yes i do run both, I did have one of those micky mouse bias valves with a lever, even in the off position it was too much.

Really need a dial one, so it can be screwed right down. If I could get away with it, I'd disconnect the rear completely.

Easily done Tony! No one would suspect a thing. :wink:

 

[Tony Hunter]

The old track car didn't have any rear brakes, and that was mint. :wink:

 

[Mash.]

Yes i do run both, I did have one of those micky mouse bias valves with a lever, even in the off position it was too much.

Really need a dial one, so it can be screwed right down. If I could get away with it, I'd disconnect the rear completely.

Thanks for your input Tony, I will make sure I keep the compensator valve, yeah mines a screw dial one, so may make up two lines, one including and one bypassing.

yeeep, easily done... [emoji50]