Ugh. Everyone wants the whole cake.

I have the late '67 "Wagner" dual circuit system (front/rear split with a remote booster for the fronts). Currently, the booster is non-functional and I will be removing the booster bits soon (to be replaced by a single piece of hard-line).

This is a very common late 60's early 70's type split used on probably every single 1970-MY car in existance (except the safety geeks at Volvo and a few others I'll no doubt hear about, now).

The added safety is substantial. Sure, the front brakes do 60-90% of the work and only having rear brakes will likely lead to a rear lock-up situation in a panic stop BUT... part of the swap is to install a "shuttle" switch from any of the myriad cars that used the system so you know when pressure has been lost to one of the circuits and IMMEDIATELY find a safe place to pull over to assess the situation and then limp it off to be repaired. The shuttle switch lights a "brake failure" light on your dash to warn you.

The swap is not difficult. Source a late '67 only MC (dual circuit with proper flange to mount to your current holes), The aforementioned shuttle switch (large block of brass or iron with a switch and four female ports for the hard-lines) and some new hard-lines. If you are clever, any dual circuit MC with the proper approximate stroke length and cylinder bore will work. You will just have to be clever with the mounting flange.
The lengths of the hard-lines will be dictated by where you put the shuttle switch and the exact MC you end up with. If you want boosted brakes, using the later MC with the integral booster works OK but will require some new holes for the mounting flange (and the fun of holding a nut while you start a bolt on either side of the firewall). The remote system can also be used but you will need a donor car (good luck) for the bits. Remote systems were pretty common in the '67-'69 era due to interim "fixes" by various cash-strapped manufacturers.

You already have a proportioning valve under the rear seat if your car has front disc brakes, otherwise you will need to source front discs, calipers and the adaptor braket, as well as the proportioner from some junker.

This conversion WILL NOT have any effect on pedal pressure, stopping distance, or any other aspect of braking other than being able to use the hydraulic brakes in the event of a failure rather than the "parking" brake. Of course, if you install a booster you will have a definite effect on pedal pressure!


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Mike!

Try this link:

http://volvoadventures.com/amazon3.html

I looking into this on my early 1967 122, I was comparing diagrams in the dealer parts catalog from 1971. You'll need a number of parts not the least of which is a new master cylinder. You'll also need the dual circuit junctions for the front and rear sections, a second (or entirely new) set of brake lines, and new calipers. The single circuit system uses one-line caliper. while dual circuit has dual line calipers. I think this is why they are dual triangular systems (each system controls 3 wheels). If you go for a 122/1800 rear axle switch you have won half the battle.

In looking at a lot of engine pictures, I think the master cylinder mounting bolts will have to be moved (need to be horizontal not vertical to work with any of the dual-system master cylinders.

I couldn't tell you what kind of trouble this would be, but I gleaned this much just from comparing the dealer diagrams. It may involve a lot more that just a new master cylinder, lines, junctions, and calipers. It's a worthy upgrade if you ask me, but it may not be feasible if you don't have many old volvos available where you are.

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You mean Volvo makes cars that are *NOT* Wagons?!?

Hi. I make it on my rojo due local regulations (single brake circuit is forbiden by law on my country).

Need to use the right size of master cylinder (internal piston diameter).
Also, the rear drum circuit need a valve pressure limiter (or it will be lock with hard braking).

By now I'm using a brazilian Varga brand master cylinder (with a adapter) plus a non-regulable valve limiter, both available on my city (sure best and more economical or optimal parts will be available to you, on that, I suggest to follow Shayne lead).

Braking is now more easy and powerfull (but, it could be only my feeling due I've a servobrake attached to my front calipers).

Btw, Amazons uses originally a single circuit. Due US regulation, on 1967 or 1868 it change to a dual circuit (front / rear) and in the next year they redesign the system with a in-line serve (non remote as the previous servos) with dual circuit (two front calipers plus one rear drum on every circuit).

The latter is the way used on modern cars, due it I believe the change to dual circuit without updating with dual front calipers produce only a marginal advantage (but, of course, it help me to pass the annual tecnical control).

You can see a photo of my klutz on:
http://www.brickboard.com/GALLERY/images/3954.jpg

Happy volving,

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Joaquin (yogui the bear) / Rojo 121 / Lima, Peru

I think it's a good upgrade.
If one loses the rear brakes, front brakes should still stop the car, right? I've never put it to the test:o)
Better than single circuit, I would think.
I've never had a leaky caliper, but I've had my share of leaky (rear) wheel cylinders.
I've done the conversion to both my 122's (and my new beater had it done by a previous owner), gimme a call.
800-444-6473
Shayne.

If you just split front/rear, you really don't add much safety. If you are
going to do it, go all the way with both fronts, 1 rear/both fronts, the
other rear. For real safety you gotta have front brakes on both systems.
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George Downs Bartlesville, Heart of the USA!