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Old 08-15-2016, 08:16 PM   #1
Mini-Skoolie
 
Join Date: Aug 2015
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Hypothetical Question about Lucas Girling Brakes

I have Lucas Girling brakes

So I have been thinking about if a wheel cylinder fails on me when I am driving and I absolutely need to stop.

My question is: If I was to be driving my bus (with a sudden brake system failure) could I put my bus in Nuetral and flip the parking brake?
^
Would that cause my rear brakes to lock up, or is there a safety that would not allow the parking brakes to activate while the bus is in motion?

Thanks in advance.
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Old 08-16-2016, 09:57 AM   #2
Bus Crazy
 
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If I'm not mistaken the big benefit of Lucas-Girling style brakes is that they will automatically brake if there is a line failure; similar to how air brakes work. I believe the pots on the rear brakes have springs that force the brakes on. The springs are only compressed when the engine is running and there is proper line pressure.

If a cylinder were leaking then the line pressure would drop and the parking brake would apply.
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Old 08-16-2016, 10:03 AM   #3
Bus Crazy
 
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But I might be wrong.. You'll definitely need to confirm it
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Old 08-16-2016, 11:32 AM   #4
Mini-Skoolie
 
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Quote:
Originally Posted by jazty View Post
-snip-

If a cylinder were leaking then the line pressure would drop and the parking brake would apply.
I had (and still have) a wheel cylinder that went bad and the last thing it did was stop. Unless something in/on my bus is not working right (which would not surprise me)....
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Old 08-16-2016, 04:35 PM   #5
Bus Crazy
 
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Quote:
Originally Posted by CStanley View Post
I had (and still have) a wheel cylinder that went bad and the last thing it did was stop. Unless something in/on my bus is not working right (which would not surprise me)....
Oh crud.. Well then.. I must be wrong!

I managed to find a diagram of a typical Lucas-Girling brake system, anyhow.



And it definitely looks like the parking brake is on a completely separate circuit. I was wrong.
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Old 08-17-2016, 01:23 PM   #6
Bus Nut
 
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You will notice that the brake system has two lines coming out
of the master cylinder which means that the system has dual
brakes. One side of the master cylinder powers the front brakes
and the other side powers the rear brakes. So if you have a brake
line or wheel cylinder that fails you still have brakes, granted not
full braking power but enough to slow the vehicle to a stop.
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