pbs
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| posted on 23/4/06 at 07:40 AM |
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Brake calipers
Try to work out the volume of my front brake callipers so I can check if my master cylinder will work with them.
The callipers are Mondeo 60mm.
I know that the callipers can move about 25mm when there are no pads fitted but I have estimated that they will only move about 1 to 1.5 mm per side
once I fit the pads. Is this correct?
Bruce
[Edited on 23/4/06 by pbs]
Build your own sports car for £250 my ar5e!!
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britishtrident
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| posted on 23/4/06 at 07:49 AM |
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Not worth working out -- if the calipers are set properly true to the disc the pads should move roughly 0.2mm. Many balance bar pedal boxes use
0.625" mastercylinders on the front circuit.
If you are using a tandem circuit master cylinder the problem is usuall finding a master cylinder with a small enough bore to ensure reasonable pedal
effort, ideally you want 0.75" (19mm) bore although Westfield use 0.7" (listed an Austin FX4D Taxi or Triumph Spitfre) but most builders
use the donor cylinder which is generally about 21 or 22 mm.
[Edited on 23/4/06 by britishtrident]
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pbs
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| posted on 23/4/06 at 08:40 AM |
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quote:
Originally posted by britishtrident
Not worth working out -- if the calipers are set properly true to the disc the pads should move roughly 0.2mm. Many balance bar pedal boxes use
0.625" mastercylinders on the front circuit.
Iam using a 0.625" front, 0.70" rear on my balance bar assembly, just wanted to check that the 0.625" was going to have enough
volume to move the Mondeo calliper before running out of travel.
With only 0.2mm of travel a 0.625" cylinder should do the job then.
Are there any maths experts that want to check my calculations?
Build your own sports car for £250 my ar5e!!
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JAG
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| posted on 23/4/06 at 09:56 AM |
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M/cyl' volume will be important if you ever encounter brake fade. Then more volume will allow you to keep pushing the pedal harder and harder -
that way you will still get some brake effort.
Obviously if the m/cyl' piston hits the bottom of the m/cyl' bore you'll have run out of brakes totally.
Only comfort is that brake fade is unlikely on such a small/lightweight car.
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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britishtrident
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| posted on 23/4/06 at 12:56 PM |
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quote:
Originally posted by JAG
M/cyl' volume will be important if you ever encounter brake fade. Then more volume will allow you to keep pushing the pedal harder and harder -
that way you will still get some brake effort.
Not really no --- a larger master cylinder bore might help if you boil the fluid and get "long pedal" but if the brake fluid is
"dry" boiling won't happen until long after the pad friction coefficient has fadded.
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JAG
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| posted on 24/4/06 at 08:26 AM |
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I'm afraid you're wrong. IF the pad/disc temperature gets high enough then the pad co-efficient of friction will drop. If you have enough
m/cyl' stroke left you can keep on pushing. Pressing the pad harder will get you more brake effect because although the co-efficient of friction
has dropped off it won't reach zero - hence more pressure gets you more decel'
If you size your m/cyl' too small then the m/cyl' piston(s) will hit the bottom of the m/cyl' bore at this point and you will truly
'run-out' of brake effort.
Make the m/cyl' bore and stroke big enough and you can keep on pushing through the faded pads until you either stop or boil the brake fluid.
I'm a Professional Engineer and brake system design and sizing is what I do for a living.
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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MikeRJ
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| posted on 24/4/06 at 12:24 PM |
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BUT...unless the fluid has boiled, there is air in it or some dodgy rubber hoses are balooning then pushing harder on the brake pedal should not
appreciably increase the amount of travel used.
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JAG
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| posted on 25/4/06 at 08:18 AM |
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Mike,
have you experienced pad 'fade'? In our system designs we aim for at least 50% extra m/cyl' travel to compensate for the increased
travel.
The pads themselves will become more compressible due to the heat and lots of other things begin to flex when you push hard enough to compensate for
the lost friction  
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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