iiyama
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| posted on 25/1/09 at 10:12 AM |
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Balance bars.....again!
Ran the car for the first time yesterday for a bit of a shake down before SVA, (Tuesday week). Since I'm a little green on the workings of
balance bars I was quite pleased to see that I can lock the fronts before the rears. However the brake peddle seems a little soft. Is this due to more
bleeding required? Or can I dial some of this out by increasing the amount of thread showing on the MC pushrods? At the moment the clevis' are
screwed quite a long way onto these rods so more peddle movement is required at the start of the brake peddle push......if you see what I mean!!!
Shown a piccy below to help with my pooor discription!
Ive also read somewhere that you can leave a small amount of adjustment to fine tune at SVA. I wont have a chance to run the car again before next
Tuesday, so if I make adjustments I want to try and keep the balance as it is currently. how is this done?
All help much appreciated!
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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BenB
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| posted on 25/1/09 at 10:16 AM |
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Balance bars control just the fore / aft balance, if you've got a soft pedal it's something else (unless you've got slack or play in
the balance bar set-up).
I'd suggest re-bleeding the system. It took me a good two or three bleeds (using an easi-bleed) before the pedal firmed up.
It's also worth looking at the location of your brake light switch. If you've put the terminals pointing upwards you can get bubbles
forming under the switching, therefore causing sponginess.
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BenB
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| posted on 25/1/09 at 10:20 AM |
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Looking at your system the highest point if the big loop directly above the MC. I bet that's full of lovely bubbles!!!!! You can try the old
trick of using something heavy to keep the brake pedal down for 12 hours. The pressure in the system will force some of the bubbles to dissolve into
the brake fluid. Then bleed the system. Otherwise just use something like Easibleed to quickly bleed the system and you'll "drag"
any bubbles of the sides of the brake tubing....
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ReMan
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| posted on 25/1/09 at 10:22 AM |
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If the pedals soft it may need more bleeding.
If there's too much travle it may need more adjustment. And possibly more bleeding.
For SVA theoretically the balance bar needs to be permanatly locked/pinned to prevent movement/adjustment.
The reson they are sometimes left unlocked is to ensure the balance satisfys SVA and then locked at the test, but this is the testers discretion I
believe and could in theory be a fail
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iiyama
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| posted on 25/1/09 at 10:29 AM |
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Brake light switch has terminals down for exactly the reason you specify! 
The loops above the MC's would fill with fluid wouldnt they? The fluid is being pumped away from these, not toward them, or am I wearing me
blonde wig again?? LOL
Ill get some more fluid ordered up and do some more bleeding, already done it twice! 
If I use a clean resevoir, can I use the bled fluid again??
Edited to add that I would like to reduce the peddle travel as well!
[Edited on 25/1/09 by iiyama]
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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BenB
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| posted on 25/1/09 at 10:39 AM |
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If they can be adjusted then they need to be locked / pinned.
I got round the problem by covering the pedal box with a permanent cover IE then no-one could adjust them so they could be tested as they were. Of
course even permanent covers fall off eventually post SVA.....
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BenB
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| posted on 25/1/09 at 10:43 AM |
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quote:
Originally posted by iiyama
If I use a clean resevoir, can I use the bled fluid again??
[Edited on 25/1/09 by iiyama]
I wouldn't personally especially not for the fluid you are going to leave in the system. I suppose if you're going to bleed it 5 times you
could re-use the same old stuff 4 times to get the bubbles out and then do the final bleed with new stuff..... Just make sure you let it (the bled
fluid) sit for a while for all the bubbles to come out of suspension first otherwise you'll just end up adding the air back into the braking
system!!!
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britishtrident
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| posted on 25/1/09 at 11:30 AM |
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Which circuit is giving the excess travel ? you should be able to tell by watching the balance bar when pressed.
Also what calipers are you using --- particularly if you are using bling alloy calipers they have to present the pads 100% square to the disk surface
or you will gey a "springey" rather than spongey pedal.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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iiyama
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| posted on 25/1/09 at 11:33 AM |
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Got Hi-spec calipers all round. 4 pot on the front and handbrakes on the rear. Standard Sierra disc on the rear, Hi-Spec grooved discs on the front.
Pads are Mintex 1144. Was wondering if this may be a bedding in issue? Everything is brand new!
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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BenB
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| posted on 25/1/09 at 11:58 AM |
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Normally braking efficiency improves during bedding in but not necessarily brake feel. Thats my experience anyway....
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Mal
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| posted on 25/1/09 at 12:36 PM |
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Have been bleeding front and rear circuits at the same time?
If you just bleed one circuit the closed circuit will restrict pedal movement.
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Echidna
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| posted on 25/1/09 at 12:39 PM |
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Have you engineered your braking system properly? What size of MCs do you use and what's your brake pedal ratio?
Is your pedal soft, while the pedal travel is quite large?
[Edited on 25/1/09 by Echidna]
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britishtrident
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| posted on 25/1/09 at 01:32 PM |
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quote:
Originally posted by iiyama
Got Hi-spec calipers all round. 4 pot on the front and handbrakes on the rear. Standard Sierra disc on the rear, Hi-Spec grooved discs on the front.
Pads are Mintex 1144. Was wondering if this may be a bedding in issue? Everything is brand new!
I am willing to bet the front calipers aren't true to the disc, everytime you press the pedal the caliper bracket has to bend very slightly,
bedding-in might help a bit it won't completely go away.
Assuming you don't have a dial gauge and have braided flexy hoses which can't be clamped the only test is to get someone to pound the
brakes on and off while you feel with your hand for relative movement between the caliper and disc --- even the slightest perceptible movement
indicates a problem.
If you feel movement you will then have to probe the gap between the pad and disc to figure out what adjustment is required. You may find you have
to shim the caliper mounting at one end or file or bend the mounting brackets a very tiny amount.
Easier cure is just bolt on a pair of standard Sierra floating callipers -- less bling and more unsprung weight.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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prawnabie
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| posted on 25/1/09 at 01:44 PM |
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May be way off here, but don't the master cylinders have to be gravity fed with fluid? It looks like the pipe from the resevoir to the m/cyl is
lower than the m/cyl itself?
Shaun
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iiyama
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| posted on 25/1/09 at 01:59 PM |
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Resevoir is higher then then the MC's, but the supply pipes drop underneath to keep things neat. They are difinatly under +ve pressure though,
even though it might not be much due to restrictions in hieght.
Take the point about the discs running true to the calipers but dont believe this to be the problem. If it is, it means the Dax fabricated upright
and/or the caliper mounting have not been manufactured properly. Actually after all the problems I had with Hi-Spec this may be a porblem!
Ive ordered up some more fluid and give them a good bleedin next week, wont have time to do it before then.
WHile Im on the brake subject, anyone know what the OD of the threaded bar is? Need to get some tube to slide over it. Think its 9/16 thread. Or is it
7/16?
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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nitram38
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| posted on 25/1/09 at 04:04 PM |
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Are the master cylinder pushrods returning fully so that they are not under pressure with your foot off?
Also, what size of cylinder are you using and on which circuit?
Could you be using two of the same size or have the wrong size on each circuit?
Just some things to check!
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iiyama
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| posted on 25/1/09 at 04:23 PM |
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got .625" on both circuits. Front discs are Cosworth size, (forget the diameter now), and running 4 pot calipers. Rears are standard sierra
rears with 2 pots. Figured there would be a large difference here anyway so fitted two MC's of the same size.
Playing around yesterday saw the fronts lock first, although I couldnt get the rears to lock. That could be due to not having bled them enough and/or
everything being new. Or it could be that I havent gt a clue what Im talking about...........!!!!!!!!!!
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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goaty
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| posted on 25/1/09 at 05:48 PM |
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quote:
Originally posted by nitram38
Could you be using two of the same size or have the wrong size on each circuit?
Just some things to check!
Is it wrong to have two of the same size??
i was thinking of putting two .70 on mine....sorry to butt in there
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nitram38
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| posted on 25/1/09 at 06:19 PM |
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I have a different set up on my car (rover calipers on F1-2).
I used 0.7 and 0.625.
Remember that front calipers usually hold more volume of fluid than the rears.
Someone will advise which circuit they should be in.
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