Hope this finds everyone well during this holiday season.

I am in the beginning phase of a brake upgrade for the 1966 1800S and wanted to ask fellow bricksters if anyone has found a good direct bolt in dual circuit master cylinder? I know that Girling did produce dual units (#64068680 & #74066070) with the same bolt pattern as the single circuit units used on the older Volvo's, but as of yet I have never seen one installed. Which leads to the question why not???

I would like to upgrade to a dual circuit system but really don't want to drill holes in the firewall. I have the stainless steel tubing, and am planning to run the front brakes off one circuit and the rear off the other. The idea is to look as stock as possible. Any suggestions would be appreciated.

Happy holidays to all....

Oliver
1966 1800S

I have used a dual master cylinder on my 1968 122S, split circuits to front and rear, used booster for front wheels only. Feels a bit safer than one circuit only. The master cylinder is from another 122S. These units are still available new from www.scandcar.nl.

Attached is a picture of the unit from my web site www.volvoadventures.com/amazon.html

Regards

Jim
VolvoAdventures.com
New Zealand

Jim that looks really well done. Did you use the dual line front calipers or retain the single line units? Do you happen to remember the part number or do you think scandcar will know what I am talking about?

Thanks for the input.

Happy a happy new year down under.
Oliver
66 1800S

Hi Oliver, I have just uploaded a dual brake schematic image, its actually from a volvo manual so that shows that it was done on a standard version, I think on 1967/8 USA and Canadian models, mine came of a wrecked South African model, they were also assembled there. I cannot remember the part number, but it is called a Dual Barke Master Cylinder, just email Sjef Spijker of Scandcar in the Netherlands www.scandcar.nl my photo of the unit and you cannot go wrong.

I have updated my Amazon restoration project pages, there are two pages and a pop up updates page: http://volvoadventures.com/amazon.html


Regards

Jim Hekker, New Zealand
volvoadventures.com

Jim,

Thanks for the info and diagram. Hard to go wrong with this information. Thanks again.

Oliver

Hi, I have a 68 120 and the original MC has been replaced with a dual circuit from a Nissan, I don't know the model though. I'm pretty sure the dual that came with the 68 fits on the earlier models, but it's cold out and unless no own else has the info you need I won't be going out to check.
Also, installing the twin line system has other complications. YOu should really get twin line calipers for the front. I have seen conversions where guys split the system front back, this is hardly any better than the one line system as hydraulic failure in the front would leave you with only rear brakes, and from experience I can tell you that rear only is no better than the e-brake and barely slows you down.
Anyway good luck with that, Patrick.

Thanks Patrick,

I have heard of Nissan and or Toyota parts that are suppose to fit, but yours is the only one I have confirmation of. (I can wait for the snow to melt if yours is the only conversion out there.)

The dual circuit four piston calipers are something that I have thought about. I think that they are a direct bolt in from the single line two piston calipers. Thanks for the suggestion.

BTW how much better do you think your brakeing is with the dual circuit unit? Other than peace of mind?

Thanks

Oliver

pretty easily, but you have to modify the mounting flanges just a bit.
THe neat thing is that you can get all different diameter Nissan parts. The 280Z, 310, roadster, etc used the vertical bolts, and the holes are just 1/4" too far apart.
Noone else, in the UNIVERSE, used vertical bolts... at least, in the scrapyards I frequent...
The Volvo MC (on MY car, others may differ) was 7/8", and I found a 15/16" on a 280, a 13/16" on the 310, and my roadster has a 3/4" diameter. So if you feel comfortable messing around with hydraulic ratios, you can adjust the "pedal travel versus pressure" ratio.
Of course,
if you're not comfortable with this, the online parts vendors WILL sell you a '68- only MC, for $200+, that LOOKS for all the world like a horizontal pattern cylinder with an aluminum adaptor...
(www.importpartsspec.com)
HTH,
Toby

There's no reason that the dual lines should stop the car any faster, as the single produces plenty of pressure. It just feels weird pushing on the pedal so hard. My old '65 single line 120 could lock up the front no problem at 60 mph. If I was going to do anything I would add a booster so that the pedal pressure could be reduced. As far as safety is concerned all the 120 and 140 are mossing a "LOW BRAKE FLUID!" warning light. Like I said the dual system can still cause your front to fail so a warning system would be best. When I had my single line system I maintained peace of mind by repacing all the flex lines and any suspect hard lines and checked the level at every fuel up, but I'm a little paranoid as I once drove a VW bus down a mountain dirt road at insane speeds after the brakes failed. FYI the old 65 VW bus flies very nicely with neither the front or the rear higher than the other.

Patrick,

I also had a bad experience in a VW micro bus, but at least my experience was on the autobahn in Germany. We did not lose brakes, but the throttle cable broke and the engine went to full open. Not nearly as bad as your situation, just a bit of bad engineering.

Oliver
66 1800S

I've got a 67.5 122 with a dual circuit brake
system. I've also driven a 67 with the single
circuit brake system. They're both identical.
My 122's booster no longer works and isn't
connected. Both require much more brake force
to make the car slow down than modern cars,
but both are able to lock up new 195/60/15
tires on dry pavement so they must be okay...
chris