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Volvo Amazon Brakes

Why is the dual circuit better? Isn't the pressure from the manifold the same regardless of how many lines are going to the wheels?

Safer=better
Volvo thought so too that's why they upgraded the late model Amazons to a dual, boosted, system. Plus boosted is so much nicer on a street car IMO.
 
Safer=better
Volvo thought so too that's why they upgraded the late model Amazons to a dual, boosted, system. Plus boosted is so much nicer on a street car IMO.

Also a booster where the failure mode isn't to eat all your brake fluid. Volvo's dual triangle braking system is a marvelous exercise in redundancy and safety for the late 60s.

Ahh, makes sense then. Read online that a larger bore will give less pedal travel, but require more force to stop. Anyone have any familiarity with the inline vacuum boosters? Found a model listed as a VH44 that people have used on MGs and Datsuns. Could I just run two of these for the front and rear, or junction my two MC outputs into a single input, and then split them after the booster to go into my proportioning valve? Looks like installing a booster behind the MC like in a modern car is a real PITA with the steering shaft where it is.

This is the sort of brake booster that was put on the Amazon and earlier 1800s from the factory. If I recall correctly it was made by Girling. The single circuit setups had all four wheels boosted with a proportioning valve in the rear and the weird dual circuit setup we got in '68 only boosted the front circuit. Over time many cars had this booster removed when it eventually failed. Also when it fails it can feed your brake fluid into the intake of the engine.

When it came time to look at the master cylinder on my 122S I just slapped a dual circuit master cylinder from a '68 on for peace of mind. I only had to fabricate two short brake lines. It feels about the same as a single circuit setup but you get something if one circuit fails. Although I have been very tempted to adapt a 140 style brake booster to fit similarly to the setup shown in Mike's pictures.

I have read about EBC green stuff pads working well to improve braking with a manual braking system on the Amazon. They are pricey though and I haven't had any problems with needing to stop quickly. The improved modulation is nice when driving mountain roads where I live.
 
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It's just a safety thing....

For the 1967 model year, the federal government mandated dual braking system via dual-reservoir master cylinder for vehicles. But, I do know a 1980 2-1/2 ton GMC trucks were using a slave cylinder that pumped into a hydro-vac unit. If slave cylinder failed, no brakes.

If one side of an older dual braking system failed, vehicle will have braking ability, but if extreme brake pressure is applied, vehicle may spin.

Somewhere in 1980s, GM was using diagonal-based brake line system, so if one side failed, then opposite front and rear shoes/discs would would working. Like left front and right rear.

When a brake system is maintained, single or dual reservoir master cylinder, I suspect there were few failures. With a single reservoir master cylinder (or slave cylinder), I suspect there was a warning sign of impeding failure in many failures, like a lower brake pedal position before brakes were applied. If a brake line busted, which was common many years ago, then a complete failure.

Brake Line History

A little history- Before WWII, many manufacturers used copper brake lines. Copper is both easy to form, and resists corrosion well. Unfortunately, copper is also prone to cracking. Shortly before the war, there was a transition to steel tubing for brake lines. Steel did not have the cracking problem of copper, but it did corrode. Steel brake lines would often fail after only a few years of use. The options to prolong the life of steel brake lines included many types of coatings to protect against corrosion.

Steel brake lines failing due to corrosion was not acceptable to safety obsessed Sweden. Both Saab and Volvo experimented with epoxy coatings, anodized steel and various other coatings to protect the brake lines. Volvo introduced a new type of brake line in 1976. This new brake line consisted of 89% Copper, 1% Iron, and 10% Nickel. This alloy proved to be durable with the corrosion resistance of copper and the crack resistance of steel.
 
Brake Line History

A little history- Before WWII, many manufacturers used copper brake lines. Copper is both easy to form, and resists corrosion well. Unfortunately, copper is also prone to cracking. Shortly before the war, there was a transition to steel tubing for brake lines. Steel did not have the cracking problem of copper, but it did corrode. Steel brake lines would often fail after only a few years of use. The options to prolong the life of steel brake lines included many types of coatings to protect against corrosion.

Steel brake lines failing due to corrosion was not acceptable to safety obsessed Sweden. Both Saab and Volvo experimented with epoxy coatings, anodized steel and various other coatings to protect the brake lines. Volvo introduced a new type of brake line in 1976. This new brake line consisted of 89% Copper, 1% Iron, and 10% Nickel. This alloy proved to be durable with the corrosion resistance of copper and the crack resistance of steel.

I assume this sort of brake line is similar to the cupro-nickel line you can buy pretty much anywhere now?
 
The brake lines on my'78 wagon still look like new except for road crud,but will clean up with a little scrubbing. I have used the new cu/nickle lines on some of the restoration/repair work that I have done and found that they get fuzzy green after a while on a DD but still last longer than the steel ones.
 
A friend of mine at work was bragging a bit on how his 10 year old Suburban had made it to 150K miles. Wow! OK....


Then a month or so later he was saying how he was driving it on the highway and the brake pedal went to the floor. Rusted out brake lines.
 
I assume this sort of brake line is similar to the cupro-nickel line you can buy pretty much anywhere now?

Yep. There's a marvelous pictorial of how/why, along with corrosion test results, at www.copper.org/applications/automotive/brake-tube/hydraulic_brake_tube.html. In the introduction, they mention "Volvo began the use of 90-10 copper-nickel ("Cunifer Alloy") tube in their 1976 model vehicles and have been using it since."

However... as with anything, I'd be careful about buying it "pretty much anywhere." Check out the pictures and dimensions at www.cunifer.com of their tubing compared to "the tubing made in Mexico, China and India that?s flooding the marketplace" which doesn't even meet SAE minimum specs. I'm generally in favor of saving a few bucks, but... on a brake system?
 
...the cupro-nickel line you can buy pretty much anywhere now?

Last time I bought brake line was via GM dealership for a 1987 Olds...sold in a roll. From parts manuals I've seen, Volvo sells it piece by piece....pre cut and shaped, I assume.
 
Safer=better
Volvo thought so too that's why they upgraded the late model Amazons to a dual, boosted, system. Plus boosted is so much nicer on a street car IMO.

They're fine on the PV, but it's a lighter car. 2150 lbs or thereabouts?
 
Volvo thought so too that's why they upgraded the late model Amazons to a dual, boosted, system.

Production 1956?1970


For the 1967 model year, the federal government mandated dual braking system via dual-reservoir master cylinder for vehicles.
 
They're fine on the PV, but it's a lighter car. 2150 lbs or thereabouts?
My old Chrysler weighed twice that. Dual circuit front/rear, 4 drums. Felt wonderful.

You are of course correct that more weight presents more challenge, but if the dimensions are engineered well, manual brakes can work very nicely... I'd love to see OP's project succeed. I've even considered modifying perfectly functional boosted systems to become manual -- just haven't gotten around to trying it.
 
I've even considered modifying perfectly functional boosted systems to become manual --

Smaller diameter MC-bore increases outgoing pressure for a given foot-input pressure...but more pedal travel is required since a smaller fluid volume is sent to wheels' cylinders/calipers.

Enough fluid volume is required to lock-up brakes. So, will max MC-volume be enough to lockup brakes. There might be a brake calculator out there, but I've not searched for one.
 
I don't know if anyone is still visiting this thread, but does anyone know any good sources to find brake boosters with the 2.25" master cylinder spacing? Im fine with welding up the "extender" that holds it off the firewall, but Ive been having trouble finding any boosters themselves that fit. I found an old P1800 booster on ebay that the owner says was in working condition when removed from the car. Does that have the 2.25" MC spacing? Thanks.
 
I don't know if anyone is still visiting this thread, but does anyone know any good sources to find brake boosters with the 2.25" master cylinder spacing? Im fine with welding up the "extender" that holds it off the firewall, but Ive been having trouble finding any boosters themselves that fit. I found an old P1800 booster on ebay that the owner says was in working condition when removed from the car. Does that have the 2.25" MC spacing? Thanks.

By spacing do you mean the spacing between the master cylinder bolt holes? If I recall correctly the 140, 1800, and 240 with a brake booster will have the same spacing. I may be wrong though. Ask the ebay seller to measure the distance for you.
 
Even if the spacing were the same between the 140/240 booster and the 1800/164 booster the master cylinder for the 1800/164 booster is somewhat unique. There is no vacuum seal around the pushrod like most boosters. The seal is made by an o-ring between the back of the master and the booster.

s-l800.jpg


s-l800.jpg
 
By spacing do you mean the spacing between the master cylinder bolt holes? If I recall correctly the 140, 1800, and 240 with a brake booster will have the same spacing. I may be wrong though. Ask the ebay seller to measure the distance for you.

Yes, between the MC bolt holes. Talked to an ebay seller about a 140 one, and I think he said the spacing was either 3.25" or 3.5". He also had another one that he showed as having 2.25" spacing, so I may order that one. I would prefer to find a new booster that fits though (or at least one that doesn't have a rubber diaphragm thats been around for 40+ years).
 
Even if the spacing were the same between the 140/240 booster and the 1800/164 booster the master cylinder for the 1800/164 booster is somewhat unique. There is no vacuum seal around the pushrod like most boosters. The seal is made by an o-ring between the back of the master and the booster.

I guess that's why they can be prone to sucking the fluid out of the system if the seals on the MC go bad? Not just leaking under pressure slowly, but actively being sucked out the back end of the MC even when not in use?
 
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