pbs
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| posted on 25/4/06 at 03:12 PM |
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Master cylinders and pedal ratio
Having a real problem trying to get the recommended minimum pedal ratio of 5/1 with my twin master cylinder and balance bar setup.
Because of the limited space in my foot well I run out of travel on the pedal before the master cylinder is fully compressed. The master cylinder has
a travel of 40mm but the most that I can get it to close by is 35mm, but is typically 25 to 30 mm with an acceptable pedal length.
Would this be acceptable or do I run the risk of running out of pedal travel before the brakes have applied fully?
Has anyone else built a pedal box with twin master cylinders?
Build your own sports car for £250 my ar5e!!
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nitram38
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| posted on 25/4/06 at 03:57 PM |
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Is that with or without fluid?
My brakes are the same setup as yours (not a 7 replica) probably only compress 15-20mm with fluid.
[Edited on 25/4/2006 by nitram38]
[Edited on 25/4/2006 by nitram38]
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pbs
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| posted on 25/4/06 at 04:03 PM |
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quote:
Originally posted by nitram38
Is that with or without fluid?
My brakes are the same setup as yours (not a 7 replica) probably only compress 15-20mm with fluid.
[Edited on 25/4/2006 by nitram38]
[Edited on 25/4/2006 by nitram38]
That is the travel without fluid. What front calipers are you using?
Build your own sports car for £250 my ar5e!!
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nitram38
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| posted on 25/4/06 at 06:50 PM |
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I am using rover 214 single disc and single piston calipers. My rears are off the same car.
Your brakes will probably not require full travel of the master cylinder to operate, but the only way to find out is to finish the brakes and juice em
up!
[Edited on 25/4/2006 by nitram38]
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JAG
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| posted on 25/4/06 at 08:04 PM |
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Seems like common sense to me to make sure that your pedal can fully stroke the m/cyl'
You really wouldn't want anything limiting the stroke in an emergency would you 
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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nitram38
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| posted on 25/4/06 at 08:42 PM |
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quote:
Originally posted by JAG
Seems like common sense to me to make sure that your pedal can fully stroke the m/cyl'
You really wouldn't want anything limiting the stroke in an emergency would you
When was the last time your pedal hit the floor?
By then, you have n't got any brakes anyway !
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pbs
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| posted on 25/4/06 at 09:14 PM |
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quote:
Originally posted by nitram38
quote:
Originally posted by JAG
Seems like common sense to me to make sure that your pedal can fully stroke the m/cyl'
You really wouldn't want anything limiting the stroke in an emergency would you
That’s what I was thinking, but everything is a compromise. I would need a total pedal length of 300mm to move my cylinders 40mm with a stroke of
180mm.
When was the last time your pedal hit the floor?
By then, you have n't got any brakes anyway !
Good point, I think it case of balancing pedal ratio and cylinder travel. Providing you have enough cylinder travel to work the brakes effectively.
Build your own sports car for £250 my ar5e!!
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nitram38
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| posted on 26/4/06 at 07:49 AM |
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Your pedal moving 180mm for full stroke seems a bit long. Why not move your cylinders closer to the fulcrum on the pedal or move the fulcrum closer to
the cylinders?
This will produce a short pedal stroke.
But all this may change to a shorter stoke once your fluid is in, anyway.
[Edited on 26/4/2006 by nitram38]
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britishtrident
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| posted on 26/4/06 at 03:10 PM |
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No master cylinder on a production car is designed move its full stroke length if it did you stroke it fully in earnest would likely damage the
internal springs.
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Mix
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| posted on 26/4/06 at 03:21 PM |
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Agreed,
I have designed mine with a view to the fact that I expect the master cylinder travel under normal braking to be in the region od 15mm but I have
allowed for the full (40mm in my case) to be available, (in the case of a hose that developes a leak for instance).
Mick
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MikeRJ
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| posted on 26/4/06 at 03:43 PM |
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quote:
Originally posted by nitram38
Your pedal moving 180mm for full stroke seems a bit long. Why not move your cylinders closer to the fulcrum on the pedal or move the fulcrum closer to
the cylinders?
This will produce a short pedal stroke.
Move the pedal fulcrum closer to the master cylinder pivot point will increase pedal travel...
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nitram38
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| posted on 26/4/06 at 04:06 PM |
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quote:
Originally posted by MikeRJ
quote:
Originally posted by nitram38
Your pedal moving 180mm for full stroke seems a bit long. Why not move your cylinders closer to the fulcrum on the pedal or move the fulcrum closer to
the cylinders?
This will produce a short pedal stroke.
Move the pedal fulcrum closer to the master cylinder pivot point will increase pedal travel...
Reverse it !
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pbs
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| posted on 26/4/06 at 04:43 PM |
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Spoke to tech support at AP brakes. The cylinders are made larger then need be so they can be used on clutches as well as brakes.
As long as I provide enough pedal travel to operate the brakes there isnt a problem in not using the full dry cylinder travel.
Just a case balancing pedal ratio (min 5/1)cylinder travel and pedal travel in the foot well.
[Edited on 26/4/06 by pbs]
[Edited on 26/4/06 by pbs]
Build your own sports car for £250 my ar5e!!
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