Amazon brakes

[arcturus]

Hi,did the first Amazons have servo on the brakes as standard? Secondly, what would be the possibility of fitting a brake equalizer on a PV?

[classicswede]

a servo was optional upto 68 before it became standard.

If with the PV you mean fitting a pressure limiting valve for the rear then yes you will want to do that if converting to disks up front

[arcturus]

So the early Amazons had no servo and drum brakes all round. Do they still experience the unequal braking that the PVs tend to have? Almost impossible to get all four wheels to brake evenly and stay that way.

[Volvorama]

I think in chronological order it goes like this:
4 wheel drums. No servo.
Single circuit disc F, drum R - servo option on saloon, standard on estate
(1968 US market hybrid dual circuit with servo operating front discs only)
Dual circuit disc F drum R - servo integral with master cylinder
Front discs usually require a pressure limiting valve in the circuit to the rear brakes as otherwise the higher pressure required by the discs will lock up the rears too early.
Many disc brake cars have lost their servos and had them bypassed due to servo failure. Both of my estates are like this and although the brakes work they require a hefty shove. I'll be trying some EBC competition pads in an effort to reduce this. Yes, I know I should fit the new Lockheed servo I have in a box but servo 120s are such a pain to brake bleed.

[swedishandgerman]

Ah - the thing about balancing 4 drum brakes and keeping them balanced....

This is done to death over on the aircooled VW forums and the only way to do it is to keep adjusting them little and often. Adding a servo or a different master cylinder goes a little way to resolving the problem; brake fluid getting shoved down the pipes at a higher pressure. But if the shoes aren't adjusted right up to the inside of the drums equally, then they make no difference. I have no experience of 4 drum Volvos, but many years experience of aircooled VW which require adjustment once a year.

I'm not 100% on servos myself:

• Many horror stories of complete brake failure on Girling servos where they've failed and sucked all the brake fluid into the manifold or failed and locked on,
• Lockheed remote replacements available but:

• They can only be fitted much higher than the master cylinder and for RHD Amazons have at least 2m additional pipe resulting in almost impossible to bleed all the air out - you have to bleed the servo, then bleed each corner
• They give an "on/off" feel, particularly if you go too powerful. They give a small amount of non-assisted braking, then when the valve goes up and the power assistance comes on, you can feel.

I've been reading up on alternative master cylinders with bigger (7/8") actuating pistons compared to the 3/4" standard. I have no experience of fitting one of these, but I feel quite sure they are a very good alternative to a servo. Wilwood do one that is pretty much bolt in place AND comes with a high capacity fluid reservoir. As well, it's cheaper than a standard Amazon master cylinder and way cheaper than a servo.

By the way, be wary of the quality of these Powertune Lockheed replacement servos: I've sent 2 back. One was faulty from new and the other went sticky after a few months. The third one I now have seems OK, but I went from a 2.3:1 to a 1.9:1 which suits the car much better and makes it a lot less easy to accidentally lock the wheels up. Not good.

[tdz840]

Adam
Interesting
Can you post the info on the Willwood MC?
Cheers
Russ

Originally Posted by swedishandgerman

Ah - the thing about balancing 4 drum brakes and keeping them balanced....

This is done to death over on the aircooled VW forums and the only way to do it is to keep adjusting them little and often. Adding a servo or a different master cylinder goes a little way to resolving the problem; brake fluid getting shoved down the pipes at a higher pressure. But if the shoes aren't adjusted right up to the inside of the drums equally, then they make no difference. I have no experience of 4 drum Volvos, but many years experience of aircooled VW which require adjustment once a year.

I'm not 100% on servos myself:

• Many horror stories of complete brake failure on Girling servos where they've failed and sucked all the brake fluid into the manifold or failed and locked on,
• Lockheed remote replacements available but:

• They can only be fitted much higher than the master cylinder and for RHD Amazons have at least 2m additional pipe resulting in almost impossible to bleed all the air out - you have to bleed the servo, then bleed each corner
• They give an "on/off" feel, particularly if you go too powerful. They give a small amount of non-assisted braking, then when the valve goes up and the power assistance comes on, you can feel.

I've been reading up on alternative master cylinders with bigger (7/8") actuating pistons compared to the 3/4" standard. I have no experience of fitting one of these, but I feel quite sure they are a very good alternative to a servo. Wilwood do one that is pretty much bolt in place AND comes with a high capacity fluid reservoir. As well, it's cheaper than a standard Amazon master cylinder and way cheaper than a servo.

By the way, be wary of the quality of these Powertune Lockheed replacement servos: I've sent 2 back. One was faulty from new and the other went sticky after a few months. The third one I now have seems OK, but I went from a 2.3:1 to a 1.9:1 which suits the car much better and makes it a lot less easy to accidentally lock the wheels up. Not good.

[Volvorama]

My experience with servos almost identical. Scary Girling failures and on/off Lockheeds although I have found the more expensive genuine Lockheeds to be pretty reliable.
The original drums work very well if adjusted properly but they are fiddly and require frequent checking.