Pedal Box/bleed Issue

[rex 1]

Hi all,

 

I'm currently scratching my head here. I've fitted the 406 Brembo calipers and Xantia V6 discs to a 205. I've fitted a Compbrake pedal-box, with the 0.625 m/c for the front and the 0.7 for the rear. There's also a hydraulic handbrake with a Tilton bias adjuster after the handbrake.

 

The problem I'm having is that the rear is bleeding up fine, whilst the front doesn't seem to have enough - if hardly any - pressure coming out when I'm opening the bleed valves. Also, the brakes will lock when pressue is applied to the pedal, but the wheels are not turning freely when the pressure is released from the pedal, in fact it's almost as if someone is still pressing slightly on the pedal...

 

I'm wondering if I've just been un-lucky and there's a problem with the new 0.625 master cylinder? Or maybe it's not enough pressure for the four pots?

 

Any advice will be appreciated as ever....

 

Rex

Edited March 28, 2009 by rex

[Tom Fenton 1,564]

IS the balance bar and master cylinder pushrods adjusted correctly? It sounds like possibly two problems, no 1 the balance bar is not pushing on the front m/c, no 2 the front m/c is not returning properly. Should be able to sort both with some adjustment.

[rex 1]

Wow Tom, that was quick!

 

I spent some time modifying the Compbrake box because I really didn't like the fact the axis could slide about in there so I added a stainless collar on each side. I've played about with the length of the front MC this morning, but after bleeding it all up again it's the same. There really isn't enough pressure coming out of the bleed nipples, more like a trickle compared to how the rear squirts out.

[Tom Fenton 1,564]

This link may help you

 

http://www.bgdevelopments.co.uk/balance.html

[rex 1]

Thanks for that Tom.

 

Well.....spent the day on it. I've finally got a decent squirt from the n/s right caliper, but still feeble on the left...WTF?

 

I've found that after pumping the pedal whilst bleeding, the front wheels are still blocked, but if I lift the brake pedal a tiny fraction - they release. I've never seen so much agg over brakes, in fact I wish I'd left it all standard

 

Any advice is welcome as I need the ramp free on Monday!!

 

Rex

[andychalmers 0]

to bleed the brakes properly on a pedal box (2 seperate master cylinders) you need either buy a vacuum bleeder or bleed the back at the same time as the front, otherwise you dont get the full pedal travel as your fighting against the other cylinder.

[welshpug 1,682]

thought I'd add, the bias valve should be before your HH, otherwise you might as go back to tugging on the cables!

[Cloverleaf 1]

You may already be doing it and it sounds obvious but are you adjusting the bias fully to the front when bleeding the front brakes?

 

If the brakes are dragging when the pedal is released, make sure the master cylinders are allowed to fully extend i.e. the brake light switch (or any other stop) isn't preventing the pedal from going back up far enough.

[Guest rs-tone]

As above, I always bleed a bias box by sending the bar to the backs to do the back set, then wind it over to the fronts to do the front set.

 

Then set the bias when all is bled up

[Rippthrough 98]

I'd take your stainless washers off, the axis is supposed to move!

 

The cylinders are going to move different amounts and you've stopped the bar compensating for that.

Edited June 22, 2009 by Rippthrough

[andychalmers 0]

this link will help you set up your pedal box

http://www.compbrake.co.uk/technical6.htm