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Removing servo . Good or Bad

haasad

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I'm thinking of removing the servo fitted to my bn4 it has later front discs fitted and I'm assuming the correct servo size master cylinder .
I'm happy with the higher pedal effort this step will give and am looking to improve feel and reduce pedal travel a little to give a nice solid platform for heel and toe down shifts. I use the car for some low key hill climbing and a bit of fastish roadwork.

Any advice or experience with this ?

Andy
 

Keoke

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A "servo-sized master cylinder" without a servo requires near super-human strength to stop the car__this is really not recommended!

If you have a tree about four feet (4') from your house, imagine yourself sitting on the ground against the tree, and pushing against the house' foundation with your braking foot. If you can move the house__even a little bit__then you will probably be okay without the servo; maybe...
 

John Turney

Yoda
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I have 4W disc brakes and no servo. If you have the right size master cylinder, it works fine. IIRC, a 3/4" MC works fine.
 

BoyRacer

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If you are not using a servo, and you have front disc brakes, you should be using a 5/8" master cylinder. Anything larger will only make you have to push harder on the brake pedal. Nothing else. Only... you.... having to exert more force with your leg and foot in order to stop your car. I am constantly amazed by posts I see on this list where some people think more pedal pressure required to stop the car is a good thing!
 

RAC68

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Hi Andy,

First, If you are going to remove your servo, compensate with an re-sized MC as previously stated. Randy described it appropriately, although a little additional peddle pressure can be acceptable, the extent of this increase will affect driving safety, operational comfort, and your ultimate pleasure in your Healey.

Over the years, I have been privileged to have driven a number of Healeys and can testify that every braking system had its own unique feel. Before finding and replacing a broken air valve in my servo for a complete rebuild, I purchased and installed a Lockheed replacement. Over a year of driving with the Lockheed, I found this replacement provided "ME" with less driving comfort with less braking assist and happily returned to the original Girling (after completing the rebuild).

Although you are receiving very good advice and properly sizing the MC is critical to good braking, you will not be able to evaluate and determine how these changes would affect your driving comfort until you install each and experience then within the context of your braking system. However, this would be less then practical and could be quite expensive. So, if I were going to remove my servo, I would go with Rich Mayor's suggestion as I expect the 5/8" MC would provide sufficient hydraulic leverage at the expense of an acceptable increase in peddle travel. However, as with the Lockheed servo replacement, it will take installation and experience with the replacement to determine if driving comfort is acceptable.

Good luck,
Ray (64BJ8P1)
 

British_Recovery

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Is there a formula to determine master cylinder size based on the volume of fluid that is needed in the calipers and wheel cylinders? It would seem that too small a master cylinder might not provide enough fluid when really needed. With the larger pistons in the BJ8 calipers, is that something to consider?
Bob
 
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haasad

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Thanks all, I think that listening to this advice and talking to others I will convert the car to a dual circuit bias adjustable non servo system. That's exactly what I did on my 911 and the brakes were amazing. It'l take a bit longer and be a project for next year , I need a pedal box to convert to start with !!!

Andy
 

steveg

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Thanks all, I think that listening to this advice and talking to others I will convert the car to a dual circuit bias adjustable non servo system. That's exactly what I did on my 911 and the brakes were amazing. It'l take a bit longer and be a project for next year , I need a pedal box to convert to start with !!!

Andy

Andy,
Following the lead of some Healey racers in the '90s, I converted to a Fiat 124/131 dual 3/4" MC, using a separate proportioning valve on the rear circuit. Not sure if the dual MC balance-beam setup offers any actual advantages over my setup. I know mine's simpler.
See:
https://www.pbase.com/stevegerow/dualmcproject

I'm using ceramic pads and have absolutely no problem with excess pedal pressure.

I wouldn't add the booster in until you've tried the non-boosted setup.
 
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haasad

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Steve that looks very interesting and as you say simpler to engineer and fully reversible. Do you happen to have the detailed identification of the fiat cylinder?
Andy
 

steveg

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