richwalker
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| posted on 17/9/06 at 07:03 PM |
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Brake bleeding with bias bar
Hi, I really hope this hasnt been posted before, looked but want to get it completly right!
Got a luego velocity with the gold pedal box and discs on the rear. Having trouble getting the rear brakes to work, pedal down and you can turn the
wheel by hand when the front brakes are completly locked. Tried bleeding it many many times. Today someone mentioned that there might be a different
technique for bleeding with a bias bar, is this so, if so what method is best?
Thanks
Rich
------------------------------------
Luego Velocity 1.8 Zetec
1998 Land Rover Disco 300tdi
04 BMW 320d Tourer
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Peteff
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| posted on 17/9/06 at 07:26 PM |
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It sounds more like you don't have enough effort going to the rear brakes if you don't have any more air in them. They are two separate
circuits front and rear, unless you have the rear calipers inverted and need to remove them to get the nipple to the top to release the air trapped in
them.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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piddy
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| posted on 17/9/06 at 07:27 PM |
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Hi.
I did mine with one of those one man bleed kits It's connected to a tyre valve to push the fluid through and the air out.
Sold at most car accessories stores.
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rusty nuts
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| posted on 17/9/06 at 08:16 PM |
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Gunsons Easibleed! If the system has been bled properly it sounds like you have the bias too much to the front.
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piddy
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| posted on 17/9/06 at 08:29 PM |
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Cheers Rusty thats the one.
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RazMan
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| posted on 17/9/06 at 09:20 PM |
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You could always disconnect one m/c from the pedal while bleeding the other - this will allow full movement for each brake circuit to eliminate air
easier. 
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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nitram38
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| posted on 18/9/06 at 07:38 AM |
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If you disconnect one of the master cylinders, you will not have enough leverage to force the other cylinder in.
Contrary to popular belief, if you lose one circuit, you will lose the other too.
In this respect, a single dual master is better because it will automatically close off the faulty circuit.
[Edited on 18/9/2006 by nitram38]
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RazMan
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| posted on 18/9/06 at 10:36 AM |
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Eh? I may have misunderstood your post but surely leverage is not an issue. If you disconnect one clevis pin it will allow full pressure to go to the
other (still connected) m/c. You can then bleed this one until happy and then do the other one. I can't see how you can lose both circuits
unless there is a leak in both front & rear systems at the same time. That is the whole point of having dual circuit brakes isn't it?
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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nitram38
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| posted on 18/9/06 at 10:50 AM |
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Have you tried it?
I have and I can assure you that all the balance bar does is 'take up the slack' until both pushrods are engaged. This means that they
lever against each other and not the pedal. It you disconnect one, you will run out of pedal travel before the cylinder is depressed enough.
Try it out.
The pedal is at the centre of a 'see saw' which is balanced by having resistance on each end. Remove one resistance and then you will have
to push the pedal in far enough that the edges of the centre tube lock against the threaded bar before it starts exerting force on the attached
cylinder.
The purpose of dual cylinders are for race car balance.
Dual master cylinders are for road safety use.
[Edited on 18/9/2006 by nitram38]
[Edited on 18/9/2006 by nitram38]
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RazMan
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| posted on 18/9/06 at 11:10 AM |
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Good point - I have only tried it without fluid and therefore no pressure. Maybe winding the balance bar one way hard against the stop might
compensate for the missing m/c during bleeding?
Just a thought.
Another good point about the dual m/c - I can now see that if one circuit blows then the other will be affected due to the leverage compensation.
[Edited on 18-9-06 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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nitram38
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| posted on 18/9/06 at 11:14 AM |
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Winding the bias over is not enough either!!!!!!!!!!
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roadboy
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| posted on 18/9/06 at 11:52 AM |
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Use the Gunson easibleed it's a great tool, turn the rear calipers around so the nipple is at the top & use a piece of wood between the pads
to stop the pistons moving, job done.
If there is still a problem it is likely to be master cyl seals, or badly adjusted pushrod.
HTH
Ian
Jude Performance Services
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NS Dev
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| posted on 18/9/06 at 01:56 PM |
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quote:
Originally posted by nitram38
Have you tried it?
I have and I can assure you that all the balance bar does is 'take up the slack' until both pushrods are engaged. This means that they
lever against each other and not the pedal. It you disconnect one, you will run out of pedal travel before the cylinder is depressed enough.
Try it out.
The pedal is at the centre of a 'see saw' which is balanced by having resistance on each end. Remove one resistance and then you will have
to push the pedal in far enough that the edges of the centre tube lock against the threaded bar before it starts exerting force on the attached
cylinder.
The purpose of dual cylinders are for race car balance.
Dual master cylinders are for road safety use.
[Edited on 18/9/2006 by nitram38]
[Edited on 18/9/2006 by nitram38]
actually this is not true!
You are right in principle but in reality we fit washers each side of the tube and just enough slack to let the bar pivot, but little enough that the
washers bind onto the tube and still give some braking on the good circuit if the other fails.
its crap engineering but its what is done on bias setups to give some safety.
the usual side clearance is around 5-6mm between the tube and the washer at one end with the bias bar fully pushed across (other washer against the
end of the tube)
PS liked your car when i saw it at Donny, nice work!!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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nitram38
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| posted on 18/9/06 at 02:04 PM |
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I have the washers either side and I have tried without one cylinder connected, but my pedal runs out of travel before enough pressure is exerted.
A block of wood on the missing side would work for the brake bleeding though.
I did n't have much time at donington as I had cooling issues on the motorway, so I didn't get about much and had to go home early. I
would have liked to have met more of the guys there.
Hopefully a redesign of my radiator duct will sort it out.
Regards Martin
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procomp
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| posted on 18/9/06 at 02:21 PM |
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Hi as ns dev says. If you have the washers in and it dosent work you should realy try and engineer it so it dose work espesialy as yours is a road
car.
There are some quite different bias kits available and not all of them are fit for the use of.
cheers matt
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richwalker
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| posted on 18/9/06 at 07:11 PM |
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wow, lots of replys, thanks for all of them, seems i need to be trying one of the easi bleed things, already tried swapping the master cylinders and
no differnce but never know could be two faulty ones but i doubt it. Tried adjusting the bias but doesnt really help.
------------------------------------
Luego Velocity 1.8 Zetec
1998 Land Rover Disco 300tdi
04 BMW 320d Tourer
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JB
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| posted on 18/9/06 at 07:28 PM |
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Bleeding Bias Bars
If your master cylinders are above your calipers then just open the bleed nipples and let gravity do the work.
Otherwise bleed the front and rear together.
Or wind the bias bar as far as it will go one way and just bleed that circuit.
John
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richwalker
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| posted on 18/9/06 at 07:44 PM |
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might be a daft question but how do you bleed the front and rear together?
------------------------------------
Luego Velocity 1.8 Zetec
1998 Land Rover Disco 300tdi
04 BMW 320d Tourer
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rusty nuts
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| posted on 18/9/06 at 08:01 PM |
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Have you adjusted the rear calipers?with pads in place you need approx 0.004" float or clearance between disc and pad. Adjust by turning the
caliper piston out to reduce clearance. Release handbrake adjustor before adjusting caliper readjust afterwards
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JB
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| posted on 19/9/06 at 04:11 PM |
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Bleeding Both Ends!!
quote:
Originally posted by richwalker
might be a daft question but how do you bleed the front and rear together?
You need 3 people. One at the front, one at the back and one on the pedal.
Push the pedal down and as it goes down, get the bleeders to open the nipples, then get them to shut it off before you get to the bottom.
John
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Stu16v
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| posted on 19/9/06 at 06:54 PM |
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quote:
Originally posted by nitram38
I have the washers either side and I have tried without one cylinder connected, but my pedal runs out of travel before enough pressure is exerted.
You have a fundamental design problem there then...
Back to the brake bleeding problem. If there is still a problem and you are sure that all of the air is out of the system, it may be that there is
*not enough* slack between the clevises and the brake pedal/washers...
Dont just build it.....make it!
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RazMan
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| posted on 19/9/06 at 10:12 PM |
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Coincidentally I had to do this very job today. A totally new system which needed filling & bleeding - Wilwood 4 pots on the front & Sierra
standards on the back with a bias bar.
I left the bias bar in the middle position and bled the fronts with no problem. I then removed the rears and turned them up the right way (bleed
nipple to the top) and bled them. The result was a little spongy so I repeated the excercise again, getting a little more air out of the rears this
time, and the pedal is now perfect.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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nitram38
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| posted on 20/9/06 at 05:10 AM |
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quote:
You have a fundamental design problem there then...
Must be on a lot of cars then, seeing as mine is a titan bias set up.
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procomp
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| posted on 20/9/06 at 07:47 AM |
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Hi i dont think it matters who's bias setup you are using as STU16V has said you have a fundamental desighn problem with that setup.
And i am in no way trying to insult you or your car but with that type of desighn of car being used on the road if you were ever to lose a brake cyl
you really are putting your life at risk.
Not to mention the fact that strictly speaking it shouldent have passed sva if your brakes work in that manner ie lose one cyl and end up without
being able to work the other one.
cheers matt
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nitram38
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| posted on 20/9/06 at 10:06 AM |
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How can I alter a standard setup?
Also how can sva check if the setup is roll pinned etc?
You haven't insulted my car or me.
I will try and get some photos.
[Edited on 20/9/2006 by nitram38]
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