james g
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| posted on 20/4/18 at 09:21 AM |
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Brake residual pressure valve
Morning All
Has anyone needed to fit one of these?
http://www.mcgillmotorsport.com/brake-residual-pressure-valve-2psi-for-disc-brakes-675/
After bleeding the brakes on my MNR, the pedal is nice and firm and the pedal travel is short, but after a short spell of ordinary driving the pedal
travels further before I can feel the same firm resistance. A second pump on the brake pedal and the travel reduces back to where is was immediately
after bleeding.
So it feels like brakes fluid is draining from the calipers, either that or the seals on the master cylinders are failing, but I am not sure which.
I am running a dual master cylinder circuit, with the master cylinders slightly below the front calipers (Willwood). Rear calipers are Sierra. The
reservoirs sit higher than the calipers
Thanks
James
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40inches
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| posted on 20/4/18 at 10:23 AM |
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I fitted a 10psi one to the rear (shoes), made a hell of a difference.
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james g
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| posted on 20/4/18 at 11:24 AM |
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Thanks for the reply
I'll figure out which circuit it is and get a 2psi one fitted
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JAG
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| posted on 20/4/18 at 01:59 PM |
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These things are a waste of money
They may reduce pedal travel but they increase brake drag - not a major issue but why spend extra money to increase fuel consumption, shorten pad and
disc life and burn extra fuel!
OP - sounds like your car needs bleeding properly 
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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907
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| posted on 20/4/18 at 02:16 PM |
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I have one fitted to my clutch.
I have a concentric slave unit that's higher than the master cylinder so it's fitted to prevent drain back.
When I bought it I had to have a pair, and now I know its normal use I realise why.
Paul G
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40inches
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| posted on 20/4/18 at 02:38 PM |
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quote:
Originally posted by JAG
These things are a waste of money
They may reduce pedal travel but they increase brake drag - not a major issue but why spend extra money to increase fuel consumption, shorten pad and
disc life and burn extra fuel!
OP - sounds like your car needs bleeding properly
Nope! Worth every penny. If the master cylinder is lower than the calipers 
Before fitting the valve
 
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james g
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| posted on 20/4/18 at 03:03 PM |
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Thanks guys
So before I shell out on parts, I have bled the brakes using both an Eezibleed and the pedal pumping method and there is no air coming from the
calipers. When the pedal is firm it is properly firm so this does not feel like an air issue.
Only thing I could do extra here is make 100% sure that both front and back master cylinder pistons are at their maximum inside the cylinder when the
brake pedal is fully depressed using the pedal pump method.
A quick google suggests other possibilities
Warped discs- probably not as the brakes have not got that hot since the car has been built.
Worn bearings/loose hub nuts. - again probably not as the car has just passed its MOT and the chap was super keen on looking for play in front and
rear suspension.
Anything else I should be looking for?
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