I read the thread found at: [ http://brickboard.com/RWD/index.htm?id=904877 ]. I have a good idea of how to actually install the disc assemblies, but I still have a few questions regarding the parts. I have not yet been able to find any used 120 or 1800 front disc brake parts, though I continue to keep an eye out for them. I have discovered that I can purchase new and/or rebuilt parts, but the price is less than enticing.

My main question is in regard to what difference the year/design makes. What exactly would I be looking for? I know that there are the Circuit 1 (single piston) and Circuit 2 (two piston) set-ups available. Is there any advantage to one or the other? I have also read that 1965 and earlier calipers from 120s are different, and less desirable? And 120s with the B16 engine did not have suitable front discs for a conversion? Could somebody clarify exactly what I should be looking for, and perhaps give me some direction of where to look?

Thanks

I put disc brakes on the front of my 64 544 a couple of months back. I found a donor P1800 in a salvage yard in Kansas. Got the entire assemblies for both wheels for $100. I did move the shocks to the front of the A-arms (easy job), and there is a little interference when the wheels are turned to the lock. At first I adjusted the turn stops to eliminate contact, but that reduced the turning radius quite a bit, so I went back to the original setting--and don't bang the stops when I turn. I got the units off a 1967 1800, and the only real difficulty was getting them cleaned up and servicable after 30 years of non use. The bearings and spindles are the same, but the plate the calipers bolt to had to be re-drilled to fit the 544 spindle. I also had to move the brake hose brackets on the back of the backing plate to the front, and manufacture new hard lines so the original 544 hoses would work. I made no modifications to the master cylinder, or the original lines on the 544. Everything seems to work fine and the brakes are MUCH better. Also, the calipers are 3 piston and I ordered pads from the local auto store. Hope this helps.

Thanks for the info. This sounds like the common method, and I am guessing that it is probably common because it ultimately ends up being the simplest/easiest/best method. Now I just need to get my hands on some 122 or 1800 disc brake assemblies.

Early front calipers (that most rebuilders DO NOT accept as cores) can be identified by a short, external, hard brake line connecting inboard-to-outboard sides.
Thru '64 I think.

AFAIK the B16 powered 122's had drum brakes up front, same as the PV. The -65 cars had 3 piston calipers up front for whatever reason - 1 big piston on one side and two small on the other. I think pads are slightly easier to find for the later (65-) 4 piston calipers.

I don't think you will be able to buy the caliper mounts and (possibly) the dust shield new, although you could get new calipers, rotors and wheel bearings. You'll probably need to find a donor car for the mount and shield. I don't know if the early and late caliper mounts are the same - I'd check part numbers on www.gcp.se but it seems to be down right now.
--
I'm JohnMc, and I approved this message.

Thanks for all of the information.

Is the dust shield the same as the "brake backing plate" sold by swedishtreasures.com?

Also, I just had the "bright idea" of possibly fabricating a mounting plate that would position the caliper in such a manner as to not interfere with the shock assembly. This way, I would not have to relocate the shock position and I would also not be dependent on finding a donor car. Has anything like this been tried before? It doesn't seem like it would be very complicated, but of course these things never do until you are neck deep into them.

I'm not sure what they are calling a 'brake backing plate' - although it does bring to my mind the back plate of a drum brake.

You are somewhat limited in where you can place the caliper. It needs to be more or less vertical so the bubbles will rise to a bleeder valve. And there are suspension pivots and steering arms. You could swap them left to right if you put them in front of the disc instead of behind. But I think you will interfere with the steering mechanism or the sway bar there. Maybe in the 11 o'clock position (looking at the left front wheel)? I seem to recall trying some different positions with mine while I had everything apart and coming to the realization that the behind-the wheel 3 o'clock position was the best (that's what the factory rally cars used AFAIK). If you have a caliper mount you will need to redrill it anyhow to fit the 544 spindle - it wouldn't be any more work to use a different positioning. Well - not much more - I reused one hole and had to redrill 3 of them.

I cut and rewelded my lower shock mounts at a slight angle to retain the full turning capability. I'd say that about 1/2 of my time was spent fighting with stuck rusty shock mounts.
--
I'm JohnMc, and I approved this message.

Thanks for the further advice. I've been taking some closer looks at photos taken of my front suspension/steering (the car itself is in TX at the moment but I am in WV) and I think that the 11:00 front position may work, but the sway bar end links may be in the way at full lock. It seems that my best bet may be to just find the parts and mock them up in different positions to see what would work and what would not.

I briefly entertained the thought of using rotors and calipers from some other 5x4.5" lug vehicle such as 50s-70s Fords (since they seem to be readily available and reasonably inexpensive) but the amount of uncertainty regarding fitment in a wide number of respects seems like just too much trouble. Perhaps I will reconsider this option this summer if I haven't found a set of the Volvo parts, don't need to use the car as a daily driver, and have some time to dig around local junkyards.

If you have any photos of your disc brake setup available, I would appreciate seeing them. You could e-mail them to me at jnshk@aol.com or ajaneshe@mix.wvu.edu. Also, did you receive my email regarding your wheels?

Thanks!

Yes. I don't have that many pictures of my car. I could borrow the wife's digi and take a few I suppose. When you actually have everything apart is is much simpler than it sounds.

The *very big* advantage to using Volvo rotors and calipers and caliper mounts is that everything fits and lines up perfectly. The wheel bearings on the rotor fit perfectly on the PV's spindle. The caliper mount fits onto the PV spindle just right (excpet for the 3 holes that must be drilled) and holds the caliper at the right position. No fabrication at all, just about a straight bolt-on.

Here's all the pics I have on the 'net at the moment:





Those pics were taken not long after I put a new set of springs on the front (one original one broke into 3 pieces one day). I waited for them to settle down for about 6 months before finally just cutting them down about 3/4 of a coil and getting rid of the nose-high stance. When these pics were taken the tires were 205/65/15 Yokohamas on the 15X6 wheels. The tires filled the fenders to perfection front and rear - at least to my eye. Not protruding from the fenders in the slightest, but more of less flush. I had the very slightes amount of rub with the outside lip on the rear fenders which I cured by rolling the lip in with a thick round wooden dowel. No external bending at all - just closing in that inner 1/4 inch of lip. It is a bit hard to tell how much clearance is on the inside at the back - but there isn't much. No rubbing, but I don't think you can squeeze any more tire back there to the inside - at least without tubbing it. On the front the main limitation is the upper/outer suspension pivot - which sticks up slightly past a 15 inch rim. Any more than perhaps 3.5 inches backspacing and it will rub - I tried on a 3 3/4 backspaced wheel one time (the common backspacing for most 15X6 4.5X5 patterned wheels) and it touched. You could go *around* those hard points in the front with a bigger rim, but extending the tire inward would make it hit the sway bar sooner, and dramatically reduce the turning circle. So IMO 205 width tires are about the limit if you want to keep the tires within the stock fenders. Any more width has to be added to the outside, and anymore than that will poke out of the fenders.
--
I'm JohnMc, and I approved this message.

no message

I re-drilled only one hole in the caliper mounts, and I think I reversed left and right from original (not sure about this) but the calipers mounted at about 2:30 looking from the outside. I'll look tonight for pictures. of course I also had to drill one new hole in the backing plate. I also had to trim off the raised metal area on the backing plate around the spindle to eliminate some interference with the seal housing on the inside of the rotor.

AFAIK, no B16 cars had disks.

Jensen-built 1800s had unique calipers -- don't know the details, sorry.

'63 - '68 122 sedans and all 1800s had the same calipers with three pistons. 122 wagons got disk front brakes later, but they are the same brakes once they did. These all work with a single circuit system, but can be used in a dual circuit system with a front / rear split, although not a triangular split.

'68 - onwards are different and should be used with a dual circuit only.