Daf
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| posted on 23/9/16 at 07:58 PM |
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brake balance bar setup
As some of you know I failed my IVA test recently and one of the items was front to rear brake blance, I wasn’t achieveing the 25% DGW on the rear
axle.
Originally I set the balance bar up by having an assistant press them and I made sure the fronts locked before the rears. Since the test I’ve made a
device from some threaded bar so that I can wind the brakes on without the use of an assistant and I’ve adjusted the balance bar so that the rears
lock much sooner now.
My question is; is there some crude way I can check I’m in the right ballpark? For example if I use my device to put the brakes on, and then use my
torque wrench (type that shows you how much not a clicky type) on the hubnut to see how much torque is required to turn the wheel.
If my understanding is correct: lets say it takes 100NM (60%) to move the front, the rear would need to be at least 41.6NM (25%). I know the torque
required to move the wheels has no relevance to the DGW but the percentage split should be proportional?
Any thoughts?
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rodgling
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| posted on 23/9/16 at 08:29 PM |
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Trial and error on your driveway? You don't need much space to get up to say, 15 mph and then nail the brakes.
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Daf
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| posted on 23/9/16 at 08:41 PM |
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quote:
Originally posted by rodgling
Trial and error on your driveway? You don't need much space to get up to say, 15 mph and then nail the brakes.
And look for what??? The front was locking up before the rear even before the first test.
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rodgling
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| posted on 23/9/16 at 09:34 PM |
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Adjust brake balance until they lock at the same time, then adjust slightly so the fronts (just) lock first?
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Daf
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| posted on 23/9/16 at 09:38 PM |
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quote:
Originally posted by rodgling
Adjust brake balance until they lock at the same time, then adjust slightly so the fronts (just) lock first?
I see, yep not a bad plan and a good way to pi55 the street off to 
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theprisioner
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| posted on 23/9/16 at 09:39 PM |
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I had the same conundrum on my Sylva J15 with it's balance bar. I jacked up one side (two wheels) and adjusted the pedal force till I could
(only just) not move the front wheel with all my strength applied with both hands on the tyre. I then adjusted the balance bar such that I could only
just move the rear wheel/tyre (with all my strength). Of course all this was done using a threaded vernier brake pedal contraption applying the brakes
for me.
Now I know this is not scientific but it got me through the dreaded IVA and many track days unscathed on the principle the back should never brake
before the front but you need that extra contribution from the rear esp going into the hairpin. I hope this helps.
http://sylvabuild.blogspot.com/
http://austin7special.blogspot.co.uk/
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big-vee-twin
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| posted on 24/9/16 at 08:42 AM |
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I put my car up on 4 axil stands, sat my missus in the car and asked her to gently press the brake pedal.
When the fronts were locked I made sure the rears just started rubbing.
I aslo balanced the handbrake side to side
Passed no problems.
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
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SteveWallace
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| posted on 24/9/16 at 10:34 AM |
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Depending on how your IVA tester interprets the rules and how friendly he is, you could also make final adjustments on the rolling road during the IVA
test if its not right when you get there. Just get it as near as you can before you go.
There has been a lot of discussion on here about what constitutes locking the bias bar. My test centre (Nottingham) was happy for me to use a pair of
nuts locked together on each end of the bias bar so that it needed spanners to unlock them and adjust the bar. In fact, they were actively against
the drill it and lock wire it method.
Check with your test centre first, but if they are happy with that approach then they may let you adjust it on the fly during the test whilst they go
for a cup of tea.
The other thing to watch out for is to not lock the bar too close to the bush through the brake pedal otherwise it will jam against the pedal and not
work properly.
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britishtrident
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| posted on 24/9/16 at 11:04 AM |
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As a rough guide you should still be easily able to lock the rears (ie. all 4 wheels) on gravel, but fronts should lock first on dry clean tarmac.
[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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Daf
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| posted on 24/9/16 at 01:43 PM |
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I did most of the above before I went first time, the mrs held the pedal whilst I made sure the fronts locked before the rears and slammed on in the
road to check in the real world- but it still failed!
I've put more to the back and they do lock up sooner, but I'm just looking for a more scientific way to see if I'm anywhere nearer
where I should be really.
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Daf
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| posted on 25/9/16 at 08:28 PM |
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So I've had a play today - with the fronts locked I can just about move the rears and when I stomp on the pedal the fronts lock first.
I've also been a little more scientific, I made a device to press the pedal and hold steady pressure:
Then I used this torque wrench to see how much torque was required to turn the wheels and comprised a table to work out what percentage the rear is
compared to the front:
I'll let you know in a month or two if I was successful 
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marc_cowley
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| posted on 26/9/16 at 03:45 PM |
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If you have a local mot station they may not mind you throwing it on they're rollers to check it out
C30 T5
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The Black Flash
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| posted on 3/10/16 at 07:49 PM |
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quote:
Originally posted by marc_cowley
If you have a local mot station they may not mind you throwing it on they're rollers to check it out
Yep, offer to pay them for an hour, they may even let you use it for free
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