antwan
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| posted on 15/7/11 at 06:56 PM |
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Brake balance bar - please HELP!
Someone please HELP!!
I had the car at the IVA test centre a week ago and it failed on (amongst other minor trim bits) underperforming brakes. Now presumably these need
bedding in before the balance bar is fiddled with as they are all new - bit tricky when boys in blue dont allow you to without a registration
number.... grumble grumble grumble
Anyway when I was at the test I had a number of attempts at adjusting the brakes whilst the car was on the rollers. I have a remote knob to adjust the
bias but no matter how much I moved it the reading were coming out pretty much the same every time (no smut intended in that last sentence).
Any idea what sort of position it should be in and why it made no difference?
BTW car is an MNR Vortx.
Thanks all.
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loggyboy
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| posted on 15/7/11 at 07:04 PM |
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Bias wont make brakes work better, should only allow you to tweak the levels at each end. The bias will not be causing the problem. Try bleeding,
check calipers are mounted correctly (and the right side, some wont bleed properly if mounted on opposite sides). Maybe take the car on a trackday to
bed them in?
[Edited on 15/7/11 by loggyboy]
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BenB
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| posted on 15/7/11 at 07:24 PM |
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Are they new discs? If so have you cleaned them? They usually have an anti-rust finish on them which doesn't help the braking efficiency- guess
how I know 
I just drove to SVA via the route with the highest number of speed bumps and made sure I was going nice and fast 6 foot before them. Did the job
nicely (that and bleeding the brakes properly!).
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Dangle_kt
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| posted on 15/7/11 at 09:01 PM |
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gunson easy bleed is what you need - works a TREAT and really is easy.
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macc man
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| posted on 15/7/11 at 09:08 PM |
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Did you check that the master cylinder piston sizes are correct. The front one should be smaller than the rear to give more braking effort to the
front brakes. An easy mistake if not marked up correctly.As said the rear cylinder may have the bleed nipple at the bottom and will not bleed without
removal and turning upwards off the car to bleed it. Check the handbrake auto adjuster is set correctly. Search on here for similar threads and more
detail.
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bassett
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| posted on 16/7/11 at 11:49 AM |
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Whats your setup?with our provided mnr setup we did some minor testing up and down our road and locked the bar in a central position. As above rebleed
the brakes and make sure you bleed the sensor in the front split. is anything leaking slightly? The centre sensor on ours needed the thread wrapped
with some ptfe.
My MNR Blog Updated Jan 2010 - Track Day Prep Begins!
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antwan
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| posted on 17/7/11 at 08:08 AM |
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Thanks guys.
Brakes have been bled and re bled a number of times.
MNR provided the master cylinders which are different sizes to suit the front and rear circuits.
I think the problem are the new discs and pads. Rears have original discs but new pads, front are new discs and pads. The car was weighed at the IVA
test and is around 570kg total. I think i just cant get them bed in enough to get steady consistant readings. You can actually see the inner part of
the disc is being used more than the top as its a little more shiny.
I took the car out yesterday to a local MOT garage to check over (20 miles away  ) and nearly made myself sick from using the brakes. I think they
are finally improving but until they have fully bedded in, I dont think I can be confident that these readings will remain the same when I get to the
IVA centre.
I think I need to book it back into another local MOT garage!
Ant
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antwan
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| posted on 17/7/11 at 08:10 AM |
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One last thing. On the threaded portion of the balance bar, should the pivot point be more towards the rear master cylinder therefore providing more
lever arm to the front...
Or am i being a spanner??
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bassett
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| posted on 17/7/11 at 09:25 AM |
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Yep ours has the short portion on the rear cyclinder and long on the front. is yours the other way then?
My MNR Blog Updated Jan 2010 - Track Day Prep Begins!
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antwan
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| posted on 17/7/11 at 12:34 PM |
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It is now!!!
Mr IVA said i had to remove the balance adjuster however i can still adjust by hand and I can adjust to full extents now quite easily. The bias knob
didnt seem to be doing the job. I just need to find a rolling road who can set this bias before retest day.
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Toltec
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| posted on 17/7/11 at 02:43 PM |
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quote:
Originally posted by antwan
One last thing. On the threaded portion of the balance bar, should the pivot point be more towards the rear master cylinder therefore providing more
lever arm to the front...
Or am i being a spanner??
The master cylinder nearest to the pivot point will get more force than the other master cylinder.
Think of it as a seesaw, the fat kid needs to sit closer to the pivot to balance out.
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GeorgeM
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| posted on 18/7/11 at 11:53 AM |
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Hi,
is the pedal firm when you press it ?
If not, you may need to remove the rear callipers when you bleed them.
The bleed nipples need to be the uppermost part of the calliper during
bleeding, otherwise air will remain in them. Make sure you put something
between the pistons to take the place of the disc while doing this.
Other place air gets trapped is under the brake switch sensor, loosen a bit
until fluid appears then retighten.
For the test, just make sure that the front brakes lock up before the back.
You can play with the bias after
Good luck
PS if you have already done the above, please ignore.........
My conscience is clear - I drive a GREEN car
MNR Racing
essexkitcarclub.com
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antwan
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| posted on 18/7/11 at 07:22 PM |
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Hi Guys,
Yes the brake pedal is very tough to press. I am almost positive they just need bedding in. After the 40 miles (to the garage!) the other day, you can
see the disc surfaces are changing and the overall stopping force is definitely improving. I have now put the balance bar all the way to the front
cylinder then turned back by about 5 turns.
Using the rule of approximation.. cant be far off ey! Another £90 and away we go!
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first350
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| posted on 18/7/11 at 07:37 PM |
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I may have experienced the same issue...
-when I first drove my car (old pads/rotors) I couldn't even lock up the front tires (Bias was set to close to 100% front for initial testing).
I think the pads were glazed over, and rotors were rusted from sitting around for ~9 months.
-after a few more drives around the neighborhood and dragging the brakes (to get them nice and warm & scrub off all the rust), I was able to lock
up the front tires w/ a good amount of pedal pressure.
-After swapping to new pads (Carbotech XP8) and properly bedding them in, it was much easier to lock up the brakes.
If you've got 20 miles to your garage, you should have more than enough time to bed them in.
G'luck!
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Wheels244
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| posted on 6/8/11 at 01:21 PM |
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Bit of slow to response from me on this one.
It sounds like we've got similar set up.
My tester tested the brakes at both extremeties of adjustment of the remote adjuster and it passed in both positions - I was originally going to pin
it in the 'pass' position and had drill the front face of the remote adjuster to accept a small roll pin in readiness - the tester said
there was no need to pin it due to passing the test and put in the central position.
All my discs and pads were brand new and had never been driven - the tester gave it some time on the rollers to assist in getting them warmed up which
definately helped and it passed no problems - good testers at Beverly, very fair.
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MikeRJ
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| posted on 6/8/11 at 01:41 PM |
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quote:
Originally posted by antwan
It is now!!!
Mr IVA said i had to remove the balance adjuster however i can still adjust by hand and I can adjust to full extents now quite easily. The bias knob
didnt seem to be doing the job. I just need to find a rolling road who can set this bias before retest day.
That's a new one; I was pretty sure any any kind of adjustable brake bias was expressly forbidden in the IVA rules, and the only way the testers
would accept an adjustable bias bar is if it is welded to prevent any possible adjustment?
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