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Old 04-14-2021, 02:23 AM   #1
blakemcelroy2000
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Default Volvo Amazon Brakes

Hey all. Just finished up rebuilding and bleeding the brakes on my Amazon. I have the single circuit front discs, and drums in the rear. I have rebuilt calipers up front, and new drum cylinders in the rear, as well as a dual output Wilwood master cylinder. Despite all this, the brakes still seem pretty weak. Im not accustomed to driving unassisted brakes, so Im unsure if they should feel so (for lack of a better word) terrible? Anyone have any experience with inline brake boosters? Since my master cylinder has a rear and front output, it looks like I could only make either the front or rear boosted. Seems like the steering shaft would have to be modified to fit a booster behind the master cylinder.
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Old 04-14-2021, 01:18 PM   #2
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Manual brakes were always harder to press down on.

Master cylinder's inner bore diameter, and wheel cylinders'/calipers' inner diameter determines foot pressure required.

If a vehicle had a single piston master cylinder, then front and rear wheel calipers/cylinders could have had different inner diameters, due to weight differences between front and rear axles.

So, if the dual piston MC has different sized bores for front and rear calipers/cylinders, then MC will most likely be exerting more hydraulic force on front wheels than on rear wheels

I don't know if they make a dual chamber MC with equal bore sizes.

Years ago, I installed a MC designed for a heavier vehicle onto a lighter vehicle...talk about touchy brakes.
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Old 04-14-2021, 01:22 PM   #3
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Yeah, what's the bore on your Wilwood MC?

I'm using 122 discs up front on my PV, with drums out back, with the stock PV master cylinder (I really, really should put a dual circuit MC on it).

The brakes take more pressure than normal, but nothing crazy. A *firm* press to get maximum braking (threshold).
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Old 04-14-2021, 01:24 PM   #4
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Can we get a bit more information? Like is the pedal low? Is the pedal firm but requires a bit of effort? When Volvo boosted this braking system. They used a remote Girling booster that mounts to the inner left fender. It was used on wagons and 123GT and was an option for other models. Then Volvo changed the booster to a Lockheed version and that is the only one available. I believe Volvo also installed a dual circuit master on the last couple years of production. You could try to get some more information on that setup.
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Old 04-14-2021, 01:46 PM   #5
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The Wilwood master is a 1inch bore from what I remember. The pedal isn't low and doesn't have a lot of creep. Just requires quite a lot of force to lock up the tires. I was able to make it leave tire marks on the pavement when slamming them. I have a Wilwood proportioning valve for the rear brakes, so Im able to relatively control their pressure. I have brand new pads and shoes all the way around, so maybe I just need to lay down some material on the old rotors and drums. The car hasn't been driven in over 5 years.
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Old 04-14-2021, 01:51 PM   #6
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Pad material makes a difference too.
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Old 04-14-2021, 02:04 PM   #7
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Stock MC bore size is 7/8". I think your master is too big.

Single circuit cars were boosted on all 4 wheels. Late '67-'68 dual circuit cars were only boosted on the front brakes. In '69 they used a 140 style booster/master but we didn't get those cars here.
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Old 04-14-2021, 02:06 PM   #8
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I was trying to google up the bore and not finding anything definitive. But yeah, larger MC bore than normal - less 'leverage' in the system, more force needed for a given amount of braking.
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Old 04-14-2021, 02:36 PM   #9
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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.
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Old 04-14-2021, 02:50 PM   #10
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It can be done. This is how the factory did it on the late cars. This one is plumbed for dual diagonal brakes.

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Old 04-14-2021, 10:47 PM   #11
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Quote:
Originally Posted by JohnMc View Post
I was trying to google up the bore
https://www.joesracing.com/master-cylinder-math/
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Old 04-14-2021, 10:55 PM   #12
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Quote:
Originally Posted by blakemcelroy2000 View Post
Could I ....

1" Bore...with 100 lbs of force, then 127.4 PSI of out going pressure to wheels

7/8" Bore...with 100 lbs of force, then 166.7 PSI " " " " " " to wheels.

https://www.joesracing.com/master-cylinder-math/
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Old 04-15-2021, 02:57 AM   #13
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Quote:
Originally Posted by blakemcelroy2000 View Post
I'm not accustomed to driving unassisted brakes, so Im unsure if they should feel so (for lack of a better word) terrible?
Manual brakes definitely can work. I've driven a lot of 1960s and 70s American vehicles so equipped, which I found exquisite. Wonderful feel, excellent modulation, not requiring a whole lot of pedal pressure. Have you ever had the pleasure of piloting a late 60s land yacht? (Floating down the highway on your living room sofa, it seats 6 in blissful comfort, 8 in a pinch, holds a half dozen suitcases and a surfboard inside the trunk... no kidding...)

Point is, if that thing can stop so well with 4 big drums and no power assist, then doing so is clearly not an insurmountable engineering challenge.

By comparison, I found power brakes feel mushy, take getting used to. But decades later, in today's world, no one is used to anything else.

Quote:
Originally Posted by blakemcelroy2000 View Post
The pedal isn't low and doesn't have a lot of creep. Just requires quite a lot of force to lock up the tires. I was able to make it leave tire marks on the pavement when slamming them.
Yes, it's possible to lock up all 4 wheels -- if you're in an "oh sh!t" panic mode it's actually pretty easy -- but you don't reach that limit anywhere near as soon as with power brakes, obviously. There's a lot more "room" to play with modulating the pedal. So, if lockup is how you're judging the efficacy of the system, it's going to fall short of your expectations. In my opinion, how it feels prior to lockup is vastly more important. A high, firm pedal as you describe, without creep, sounds positively delightful. You may have to tweak something so that a "normal" pedal pressure provides a "normal" stopping response, before you can judge how well you enjoy daily driving.
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Old 04-15-2021, 12:37 PM   #14
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Quote:
Originally Posted by Toybox View Post
Manual brakes definitely can work. I've driven a lot of 1960s and 70s American vehicles so equipped, which I found exquisite. Wonderful feel, excellent modulation, not requiring a whole lot of pedal pressure. Have you ever had the pleasure of piloting a late 60s land yacht? (Floating down the highway on your living room sofa, it seats 6 in blissful comfort, 8 in a pinch, holds a half dozen suitcases and a surfboard inside the trunk... no kidding...)

Point is, if that thing can stop so well with 4 big drums and no power assist, then doing so is clearly not an insurmountable engineering challenge.

By comparison, I found power brakes feel mushy, take getting used to. But decades later, in today's world, no one is used to anything else.


Yes, it's possible to lock up all 4 wheels -- if you're in an "oh sh!t" panic mode it's actually pretty easy -- but you don't reach that limit anywhere near as soon as with power brakes, obviously. There's a lot more "room" to play with modulating the pedal. So, if lockup is how you're judging the efficacy of the system, it's going to fall short of your expectations. In my opinion, how it feels prior to lockup is vastly more important. A high, firm pedal as you describe, without creep, sounds positively delightful. You may have to tweak something so that a "normal" pedal pressure provides a "normal" stopping response, before you can judge how well you enjoy daily driving.
I actually have had the pleasure of driving a '63 Plymouth Fury that I was detailing for a customer, and even though it had unassisted brakes, and had been fairly neglected mechanically, it still stopped somehow easier than my Amazon with brand new hardware. Which leads me to believe that something must be wrong with the brakes. Ive bled the system multiple times, so Im pretty sure all the air is gone, but I will try again and test all 4 corners are actually engaging.
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Old 04-15-2021, 12:56 PM   #15
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I've had the same issue on my single circuit system since I've owned my 122. I've just gotten used to them sucking.
http://forums.turbobricks.com/showthread.php?t=325555

I've decided to just overhaul the entire system and switch to boosted dual circuit. I also plan on doing all new hard and soft lines too. Not just because of the lack of pedal, but dual circuit is just safer in general.
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Old 04-15-2021, 01:04 PM   #16
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Quote:
Originally Posted by hiperfauto View Post
It can be done. This is how the factory did it on the late cars. This one is plumbed for dual diagonal brakes.

Here are some more pictures of the dual brake line set up on that same car if anyone is interested.




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Old 04-15-2021, 02:36 PM   #17
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Originally Posted by blakemcelroy2000 View Post
Which leads me to believe that something must be wrong with the brakes.
1" Bore...with 100 lbs of force, then 127.4 PSI of out going pressure to wheels

7/8" Bore...with 100 lbs of force, then 166.7 PSI " " " " " " to wheels.
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Old 04-15-2021, 03:15 PM   #18
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Quote:
Originally Posted by MikeJr. View Post
I've had the same issue on my single circuit system since I've owned my 122. I've just gotten used to them sucking.
http://forums.turbobricks.com/showthread.php?t=325555

I've decided to just overhaul the entire system and switch to boosted dual circuit. I also plan on doing all new hard and soft lines too. Not just because of the lack of pedal, but dual circuit is just safer in general.
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? I have the braided stainless IPD lines in all the flexible hose positions.
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Old 04-15-2021, 03:21 PM   #19
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It's just a safety thing. Any single failure anywhere in the system of a single circuit system and you have no brakes at all. Generally speaking, if one circuit fails in a dual circuit system, it's pretty unlikely that the other would fail at the same time, so you'd have 'half' the brakes.

In traditional dual circuit systems, that could mean the fronts (good) or the rears (not so great, very unstable to say the least). But Volvo went way above and beyond with their dual-diagonal system. Each circuit operates half of each front caliper, and one rear brake. So regardless of which circuit fails, you've got braking on both front wheels and one rear. Which works so well you probably wouldn't notice much of a problem if it weren't for the warning light.
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Old 04-15-2021, 03:27 PM   #20
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^ +1 to Volvo going far above and beyond.

I don't even know of any other car that has a brake failure light. Or would need one.
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Old 04-15-2021, 05:05 PM   #21
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Quote:
Originally Posted by blakemcelroy2000 View Post
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.
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Old 04-15-2021, 05:42 PM   #22
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Quote:
Originally Posted by MikeJr. View Post
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.

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Originally Posted by blakemcelroy2000 View Post
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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Old 04-16-2021, 11:35 AM   #23
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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.
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Old 04-16-2021, 11:39 AM   #24
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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?
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Old 04-16-2021, 12:02 PM   #25
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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.
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