Alfa145
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| posted on 30/12/14 at 11:59 AM |
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Setting up Brake Balance Bar
I have a twin cylinder setup on my brakes and looking to change the cylinders for different sizes. Car is on the road and not needing to do the IVA
How do I reset up the balance bar? Do I need a rolling brake tester or can I just guess? Or something else?
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big-vee-twin
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| posted on 30/12/14 at 01:11 PM |
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Experimentation on the road.
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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rdodger
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| posted on 30/12/14 at 02:31 PM |
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Rally Design used to have some set up advice in their catalogue. Not sure if it's available online.
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Fred W B
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| posted on 30/12/14 at 03:24 PM |
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I've never tried it, but I've read you can get it somewhere close (as a starting point, before the road/track testing) in the garage on
stands by putting a little load on the brake pedal and trying to turn the wheels by hand. Adjust until you have them feel about the same, with a bit
more to the front.
Cheers
Fred W B
You can do it quickly. You can do it cheap. You can do it right. – Pick any two.
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Dopdog
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| posted on 30/12/14 at 05:46 PM |
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quote:
Originally posted by Fred W B
I've never tried it, but I've read you can get it somewhere close (as a starting point, before the road/track testing) in the garage on
stands by putting a little load on the brake pedal and trying to turn the wheels by hand. Adjust until you have them feel about the same, with a bit
more to the front.
Cheers
Fred W B
That is just what I was about to say.
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adithorp
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| posted on 30/12/14 at 07:43 PM |
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I did mine originally like this...
Car on axle stands, I placed a jack against the floor cross tube with a piece of 3x2 between that and the brake pedal. I then used the jack to
gradually increased the pedal pressure until I couldn't turn the front wheels by hand and then tried the rear wheels. I repeated and adjusted
the balance bar until the rears were just binding when the fronts were locked.
It passed SVA like that. I then gradually increased the bias to the rear until I scared myself and went back the other way a bit.
On the road (preferably somewhere closed/private) you can start off with plenty of front bias, do an emergency stop and see if the rears lock first.
Keep increasing/decreasing the rear. untill you get to the point where the rears do lock first and then back off a bit. Needs to be done on DRY roads.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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Angel Acevedo
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| posted on 30/12/14 at 07:54 PM |
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quote:
Originally posted by adithorp
I did mine originally like this...
Car on axle stands, I placed a jack against the floor cross tube with a piece of 3x2 between that and the brake pedal. I then used the jack to
gradually increased the pedal pressure until I couldn't turn the front wheels by hand and then tried the rear wheels. I repeated and adjusted
the balance bar until the rears were just binding when the fronts were locked.
It passed SVA like that. I then gradually increased the bias to the rear until I scared myself and went back the other way a bit.
On the road (preferably somewhere closed/private) you can start off with plenty of front bias, do an emergency stop and see if the rears lock first.
Keep increasing/decreasing the rear. untill you get to the point where the rears do lock first and then back off a bit. Needs to be done on DRY roads.
Wouldn´t Reaar brake Bias lead to ground loops??
I would think it is better to have the front to lock first?
This is a completetly uneducated comment as it´s been a long time since I read about the subject...
Beware of what you wish.. for it may come true....
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motivforz
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| posted on 30/12/14 at 08:08 PM |
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https://www.merlinmotorsport.co.uk/images/brakeclutchpartsl/Merlin%20Motorsport%20OBP.pdf
http://obpltd.wordpress.com/2010/03/30/60/
those 2 should see you right :-)
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rdodger
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| posted on 30/12/14 at 09:05 PM |
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quote:
Originally posted by Angel Acevedo
quote:
Originally posted by adithorp
I did mine originally like this...
Car on axle stands, I placed a jack against the floor cross tube with a piece of 3x2 between that and the brake pedal. I then used the jack to
gradually increased the pedal pressure until I couldn't turn the front wheels by hand and then tried the rear wheels. I repeated and adjusted
the balance bar until the rears were just binding when the fronts were locked.
It passed SVA like that. I then gradually increased the bias to the rear until I scared myself and went back the other way a bit.
On the road (preferably somewhere closed/private) you can start off with plenty of front bias, do an emergency stop and see if the rears lock first.
Keep increasing/decreasing the rear. untill you get to the point where the rears do lock first and then back off a bit. Needs to be done on DRY roads.
Wouldn´t Reaar brake Bias lead to ground loops??
I would think it is better to have the front to lock first?
This is a completetly uneducated comment as it´s been a long time since I read about the subject...
Did you read the post before you quoted it?
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threadbare wallet
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| posted on 31/12/14 at 08:28 AM |
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Very few things are "really" needed.
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adithorp
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| posted on 31/12/14 at 08:50 AM |
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quote:
Originally posted by threadbare wallet
To be fair, if the post had been in Spanish I doubt either of you would have understood it. 
The idea is to find the point where you have just too much rear bias and then move BACK slightly to the safe front bias.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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Alfa145
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| posted on 31/12/14 at 10:16 AM |
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Thanks for the replies all.
The links above just say how to get the bors bar level'ish but don't explain how you get more or less front/rear effort (unless I've
misread them)
Do I just make the rears bar shorter for less rear braking? or do I make the fronts bar longer? or a mix of both?
Don't fancy trying it out on a road initially but the slight pressure on the pedal using a jack seems like a good starting point.
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adithorp
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| posted on 31/12/14 at 12:58 PM |
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The bias is altered by turning the balance bar. This screws the bar into one and out of the other clevis and thus moves the pivot "ball"
(in the middle) sideways within the tube on the pedal, so applying more pressure to the front or rear master cylinder.
The bias isn't controlled/altered with the push rods lengths (common misunderstanding).
Imagine a plank across two sets of bathroom scales. Stand in the middle and you'll put equal pressure on each set of scales. Move towards on end
and you'll increase the weight on the closer scale and less on the other end.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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Alfa145
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| posted on 31/12/14 at 01:11 PM |
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<<Penny Drops>>
Now that's makes sense, cheers Adi
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rdodger
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| posted on 31/12/14 at 01:19 PM |
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It was my understanding that having the balance bar at an angle with the front master cylinder rod longer than the rear, with the balance bar set in
the middle, when you press the pedal then the pressure would be greater on the front MC. Moderate pedal pressure would straighten the bar and heavy
pressure cock it the other way. This is shown in the diagram in the link.
With it set that way then the front MC would always act first as in a dual cylinder.
I guess the differing length of the rods would depend on the MC sizes and piston sizes. Smaller front MC would require more travel than larger
rear.
Winding the bias across the bar would fine tune the balance.
That's my understanding. Not necessarily correct!
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motivforz
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| posted on 31/12/14 at 01:43 PM |
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In a simplified way, the bias bar will function regardless of it's angle, as it's to do with the point of application of the force, and
the lengths don't change.
In reality the compliance (travel per force - i.e. stiffness) of the 2 master cylinders will be different, and so you end up moving through the stroke
of the 2 differently. Normally the fronts are stiffer, and you end up moving through more on the rears. Hence you set it up with it a little longer on
the rears typically so that it moves level when the brakes are pressed reasonably hard.
The purpose of this is to avoid the bias bar necking out / bottoming out whilst accommodating the different travels. See figure 3 in the links I
posted. If you do this the forces all go to cock, you're putting your MCs into bending potentially, and likely to fail the bias bar unit.
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adithorp
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| posted on 31/12/14 at 02:43 PM |
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quote:
Originally posted by motivforz
In a simplified way, the bias bar will function regardless of it's angle, as it's to do with the point of application of the force, and
the lengths don't change.
In reality the compliance (travel per force - i.e. stiffness) of the 2 master cylinders will be different, and so you end up moving through the stroke
of the 2 differently. Normally the fronts are stiffer, and you end up moving through more on the rears. Hence you set it up with it a little longer on
the rears typically so that it moves level when the brakes are pressed reasonably hard.
The purpose of this is to avoid the bias bar necking out / bottoming out whilst accommodating the different travels. See figure 3 in the links I
posted. If you do this the forces all go to cock, you're putting your MCs into bending potentially, and likely to fail the bias bar unit.
Your middle paragraph is the wrong way around. Typically the front cylinder is a smaller bore (and/or the callipers are larger) (think how much more
pressure a stiletto heel creates compared to a flat shoe). As a result the piston moves further for the same pressure applied and creates more
pressure in the calliper pistons. The balance bar is set with the front push-rod longer (so balance bar angled) to give more range of motion before
the bar binds against the tube. The length of the push rods doesn't effect when the pressure is applied; Both pistons start to act/move at the
same time.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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Angel Acevedo
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| posted on 1/1/15 at 03:57 AM |
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quote:
Originally posted by rdodger
quote:
Originally posted by Angel Acevedo
quote:
Originally posted by adithorp
I did mine originally like this...
Car on axle stands, I placed a jack against the floor cross tube with a piece of 3x2 between that and the brake pedal. I then used the jack to
gradually increased the pedal pressure until I couldn't turn the front wheels by hand and then tried the rear wheels. I repeated and adjusted
the balance bar until the rears were just binding when the fronts were locked.
It passed SVA like that. I then gradually increased the bias to the rear until I scared myself and went back the other way a bit.
On the road (preferably somewhere closed/private) you can start off with plenty of front bias, do an emergency stop and see if the rears lock first.
Keep increasing/decreasing the rear. untill you get to the point where the rears do lock first and then back off a bit. Needs to be done on DRY roads.
Wouldn´t Reaar brake Bias lead to ground loops??
I would think it is better to have the front to lock first?
This is a completetly uneducated comment as it´s been a long time since I read about the subject...
Did you read the post before you quoted it?
I did but apparently I didn't understand it...
Happy New Year to you all...
Beware of what you wish.. for it may come true....
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