And, what happens when I take it all out? Like the spring, and it's two retainers... If I empty it like that, will it act as nothing and not reduce the bias? I guess we're having trouble finding fittings that do the inverse thing to replace the whole valve and brake line in one SS line.

Also, got my carbs back from Rhys after having the choke cable connecter thing fixed on them. Look great! I'll try and start the 142 up in the next couple of days hopefully. Also was informed that I had been plugging some little fittings on the carbs that I'm supposed to have left open to the air... w00ps!

So after the brakes are done, the 140 will be up and running again, although without registration, and with a still leaking gas tank... I wonder how much gas is still in it. I'm wondering if I should just toss a fuel cell in there, get the current tank repaired, or convert to the one out of the '72 145(and have it cleaned and coated inside). The car will be strictly a weekend only/track car, and I'm in no rush whatsoever to get it up and going again, meaning, probably even summer 2007, as I'm currently trying to "build up" my Daily Driver.

Thanks!

How can I adjust the stock ones? Tell me everything you know about them... How to adjust, how much to adjust, blah blah, what it's doing exactly, (increasing the pressure on the spring I assume, or the opposite). I haven't taken then apart all the way yet(haven't taken the BIG screw off, or the whatever thing on the other side that's hidden underneath a bunch of gunk)...

This wouldn't be a really big deal if there were only one valve, but remember you have a pair of them, and if you end up with a significant mismatch between the two, the right and left rear brakes are going to behave differently. Not good.

So... I'd be reluctant to mess with the valves at all unless I had test equipment to read inlet and outlet pressures. The manuals are even more adamant on the subject; in addition to the requirement for test equipment, there is a very unambiguous statement that says adjustment of the valve "...may only be carried out after reconditioning".

Finally, there is some fair amount of detail on how the valve works and what the pressures should be, but AFAIK there isn't one word addressing how much adjustment equals how much theoretical increase or decrease.

Gary L.
--
1971 142E ITB racer, 1973 1800ES, 2002 S60 T5

Very true... Argh. I guess I may just end up buying some new lines back there and calling it good for a while until I'm ready to spend money on that car again and get some SS lines made to eliminate the things. But right now, I'd rather have it running so I have a car to drive while I take my 240 out of commission for a little bit while I do a tranny swap(auto-m47) and later when I toss the turbo stuff on, if it takes me more than a day anyway. I'll need to make an exhaust methinks, so that'll take some time/designing.

What part of the valve adjusts it? I want to take them apart as much as possible and clean them up before I put them back together and in the car. I still haven't looked in a manual yet, I'll see what I can find in there.

The easiest thing to do is to try the wagon valves since you have them.

Yeah. I cleaned up the valve that I took off the 140 today, and I was blowing compressed air through it along with some carb/brake cleaner. Is that ok? I took off the cylinder end, and cleaned up the spring and the retainers, and the little piston that pops out and pushes on the spring. Can I take the big bolt thing off to clean inside there(other than just spraying the cleaner in there and then blowing through it)?

I'll probably just get some new rear brake lines(they're cheap), and clean up the current 142 ones, just so I can move the car around, and then when I get a house, I'll drive the 145 over there and then I'll start swapping parts between the two. They're both at different locations now, so, yeah.

Thanks for the words guys.

Please don't call them bias valves. They aren't.

Get a pair from a wagon & try them. My '72 Greenbook says 142 & 144 are set to 484psi, 145 is set to 711psi. A '73 Greenbook that is on the WWW says the same thing.

Ooooh, yes, about the wagon, good idea. I have a 72 POS that's just hanging out, I guess I can nab it's limiting valves(is that what I should call them? lol) I think I'm going to nab the tank out of the wagon as well, and have it cleaned and coated while it's out. I still have to get some SS lines made up though then, but only to replace just the stock lines, which are hopefully easier to duplicate.

Back to the beginning.
The valves are adjustable.

John
V-Performance.com

Can you explain the procedure, and your findings with experimenting with them? Assuming you have done so? Thanks.

It's so good to see I'm not the only pedant, now if people will stop talking about 1 series cars and vacuum leaks.....

Regards


Pete

But I don't know anything about PV's. :)

If you take out the valves, the rear brakes will have the same pressure as the fronts. Not a good idea if you want to keep the rears from locking up. Current pressure is about 10-15% of the fronts.
Good news on the carbs. Bad news on the leaky tank. Aren't there any tanks in the pick yards you can experiment with?

Klaus
--
(V♂LV♂s 1975 164, 1995 854T, 1998 V70R)

They are not bias or proportioning valves.

They are pressure limiting valves, kind of like a very crude form of ABS. They are intended to stop the rear wheels locking up but the pressures they are set for a for 1970's tyres, so getting rid of them lets the rear do some more braking & your car will stop in a shorter distance.

Are these functionally the same as what I've been calling 'proportioning valves' on 240s for all these years? Or are the ones installed on (& rusting off) 240s an actual proportioning valve?
--
Chris, Dartmouth NS Canada 70 M-B 280SE, 83 245DL, 84 244 turbo, 90 780 turbo, 92 VW Golf, 90 740 Rex/Regina

Yes, they are the same.

The proportion of braking is set by the diameter of the caliper pistons, discs, tyres, etc.

Wouldn't better tires create more frontward weight shift and require even less braking fom the rear brakes?
--
I'm JohnMc, and I approved this message.

Good question, I don't think it would make much difference. The 140's torque rod layout tends to try & pull the rear end down in either direction. When I ditched them back in the late '80's I did so because I wanted the rear to lock up when braking for a tight corner & pushing the clutch in. (Dirt track Hillclimb) The front brakes still locked up first & the rears didn't. Pad wear has never been any different & when thrashed down a mountain until the front discs are bright right, the rear discs still only have a dull glow.

I have to agree with John on the tires... all other being equal, better traction (modern tires vs tires made 40 years ago) during braking means more weight transfer to the front wheels. It cannot be avoided, as better traction results in greater deceleration and a greater force acting upon the CoG, which is clearly above ground. This rotates more weight to the front wheels and that means less weight on the rear wheels, regardless of suspension design features.

Having said that, the question is still... Did a typical 60's or 70's Volvo sedan have enough overall front brake bias (with the proportioning valves intact), that it would actually go to an overall "neutral" brake bias, and therefore stop quicker, with the proportioning valves removed? Or would removing the valves slip us (pun intended) from front, through neutral, to overall rear bias? Too much overall rear bias drives vehicle instability under hard braking.

In Paul's examples (on dirt, with low traction coefficients), you may in fact be better off without the valves, especially if you WANT instability under braking. But my opinion is that with modern rubber on normal paved surfaces, I might want to keep the valves intact to avoid getting into an unstable situation under panic braking conditions. Because even if Volvo was ultra-conservative with their overall (front) brake bias, you are definitely going to move towards a more rearward overall brake bias with the newer stickier rubber.

At the really sticky end of the traction spectrum, I can state unequivocally that my 142E race car on race rubber is truly a handful if driven with no pressure proportioning on the rear brakes. I do not have the stock brake valves on the rear system; they have been legally removed and replaced with a Tilton Engineering driver-adjustable rear brake proportioning valve. I can go from no rear brake pressure reduction whatsoever to considerable rear pressure reduction while underway, so it is not at all difficult to experiment with varying levels of pressure proportioning. But again, like Paul's dirt track examples, this is not a typical 142. Although the disks, calipers, and master cylinder are bone stock, the pads are not... I run a very agressive racing pad on the front, but just a high performance street pad on the rear.

Bottom line, IMO... If I were to remove or disable the rear proportioning valves on an old Volvo, I think I would want to do some serious abandoned-road evaluation of what to expect when you REALLY need to get stopped in a hurry.

Gary L.
--
1971 142E ITB racer, 1973 1800ES, 2002 S60 T5

Gary, the Volvo valves aren't propotioning or bias valves. You might have a little trouble in your ITB car because you probably take all the excess weight out of the rear of your car.

Paul - I didn't use the term "bias valve" anywhere in my post. I did call the devices in question "proportioning valves". What exactly, do you call them? I realize that Volvo typically referred to them as simply "brake valves", but I don't think that is the norm in the industry. Seems like the majority of the auto manufacturers refer to this type of pressure reducing device as a "proportioning valve".

WRT my race car, I have not made any attempt to reduce the weight on the rear wheels. In fact, quite the opposite is true. The only things missing from the trunk area are the rubber matting and the stock fuel tank. These were replaced by a 22 gallon fuel cell assembly that is significantly heavier than the original tank. And yes, the spare tire is still back there as well, despite the fact that I could legally remove it. I have a minimum vehicle weight of 2640 pounds (with driver) per IT rules. The spare tire and large fuel cell help me meet that minimum, while keeping weight on the corner of the car that is the most lightly loaded... the right rear. In any case, compared to a bone stock 142, I have a *higher* percentage of weight on the rear wheels. With just enough fuel in the cell (about 8 gallons) to meet the 2640 minimum, the weight distribution is 50.4% front, 49.6% rear.

Gary L.
--
1971 142E ITB racer, 1973 1800ES, 2002 S60 T5

Paul - I didn't use the term "bias valve" anywhere in my post.

Execept for the title of your post. :)

I describe them as pressure limiting. Up to there set pressure they have no effect at all, when they get to the pressure they are set to they limit to that pressure. I find it very strange that you get too much rear braking/lock ups, do you get any wheelspin coming out of 2nd gear corners?

"Up to there set pressure they have no effect at all, when they get to the pressure they are set to they limit to that pressure. "

Actually, the typical valve (Volvo 140's included) does not limit to a fixed pressure... they limit pressure increases. After the tripping pressure is reached, the rear brakes will still see higher pressures as output pressure from the master cylinder is increased. But the pressure rise to the rear brakes will be less than that to the fronts.

"I find it very strange that you get too much rear braking/lock ups, do you get any wheelspin coming out of 2nd gear corners?"

Nope... but keep in mind the car has a Tru-Trac limited slip diff. Unless I run over the FIA curbing and get a wheel completely airborne, no real problem with 2nd gear wheelspin.

BTW, I also trail-brake the entry to most turns, so I cannot afford any tendency towards rear wheel lockup whatsoever.
--
1971 142E ITB racer, 1973 1800ES, 2002 S60 T5

Actually, the typical valve (Volvo 140's included) does not limit to a fixed pressure... they limit pressure increases. After the tripping pressure is reached, the rear brakes will still see higher pressures as output pressure from the master cylinder is increased. But the pressure rise to the rear brakes will be less than that to the fronts.

The Tilton one works like that, but does the Volvo one? If the Volvo valve works the same way why would you buy a Tilton?

I always use the shorter rear end rods & arms in my cars, but I don't think it puts that much extra weight on the rears. Are you using all poly bushes in the rear?

"The Tilton one works like that, but does the Volvo one?"

Yes... as stated in the first line of the quoted post above. :)

"If the Volvo valve works the same way why would you buy a Tilton?"

It's the adjustability factor... if you want to change the behaviour (trip point, etc) of the Volvo valve, you must stop the car, jack it up, adjust the valve, lower the car, get back in, and take off. This tends to play Hell with lap times. :)

The Tilton is adjustable by the driver, while underway, to 7 distinct positions. These range from significant pressure reduction (position 1), to what amounts to no pressure reduction at all (position 7). For example, P1 starts limiting press increase on a 1:3 ratio at about 150 psi, P4 starts limiting press increase on a 1:3 ratio at about 650 psi, and P7 starts limiting press increase on a 1:2 ratio at 1000 psi. For reference, based on numbers from a 140 shop manual, the Volvo valve nominally kicks in at 427 psi, then limits pressure increases on an approximate 1:3 ratio. This is essentially the equivalent of the Tilton position 3 (not quite midrange on that valve).

"I always use the shorter rear end rods & arms in my cars, but I don't think it puts that much extra weight on the rears. Are you using all poly bushes in the rear?"

I have stock style bushings in both ends of what Volvo calls the "support arms", or lower trailing arms. All other pivot points in the rear suspension (support stays, panhard rod, anti-roll bar, and shocks) are heim joints. This is simply what the rules allow, as a maximum. I could also use poly bushings in those locations where I have heim joints, but in this case, it costs very little extra to go first class.

--
1971 142E ITB racer, 1973 1800ES, 2002 S60 T5

Looks like you are 99% right, it works as you say, but it never gets near 3:1.
The sedan valves are in:out 427:427, 711:555(Averaged) & 1422:774(Averaged)
The wagon valves are in:out 640:640, 924:774(Averaged) & 1422:931(Averaged)

What settings do you use with the Tilton valve?

"Looks like you are 99% right, it works as you say, but it never gets near 3:1."

Make that 100%, or at least 99.9%. :)

I was talking about the ratio of pressure increase... the rise in output pressure compared to the rise in input pressure. If you use the numbers above for the sedan, the overall rise in output pressure is 347 psi (774 minus 427), while input pressure goes up 995 psi (1422 minus 427). 347:995 is very close to 1:3.

"What settings do you use with the Tilton valve?"

On dry pavement with decent rubber, I am typically in position 3 or 4 on the Tilton. P3 shifts from 1:1 to 1:3 at 500 psi, P4 kicks in at 650 psi. If you haven't looked it up already, here's the link for the Tilton valve:

http://www.tiltonracing.com/content.php?page=listb

Click on "Brake proportioning valves", then "Lever type".

Gary L.
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1971 142E ITB racer, 1973 1800ES, 2002 S60 T5

I was talking about the ratio of pressure increase... the rise in output pressure compared to the rise in input pressure. If you use the numbers above for the sedan, the overall rise in output pressure is 347 psi (774 minus 427), while input pressure goes up 995 psi (1422 minus 427). 347:995 is very close to 1:3.


Now you're just showing off! :)

What sort of speeds are you doing when it wants to swap ends when you have too much rear brake?

Do you run the short or long wheelbase?

"What sort of speeds are you doing when it wants to swap ends when you have too much rear brake?"

I would say the tendency is there at any speed, but the "pucker factor" is greatest on the higher speed corners; let's say those with 70-80 mph or higher turn-in speeds.

"Do you run the short or long wheelbase?"

If you're talking 102.4" vs. 103.1", my car is a '71 with the longer wheelbase. FWIW, I cannot legally swap suspension parts between year models. Not that I would know what to swap... exactly what was the difference between the short and long wheelbase cars? Were there different support arms and support stays in the rear?

Gary L.
--
1971 142E ITB racer, 1973 1800ES, 2002 S60 T5

Do you run a rear bar?

exactly what was the difference between the short and long wheelbase cars? Were there different support arms and support stays in the rear?

Yes. Shorter torque rods & the lower arms had the diff mounting holes further forward. I use the shorter stuff in my cars, I like the handling better + the wheels fit the wheel arches better. It's more helpful to the 164.

I recently tried to fit the long arms to my '70 chassis (I actually think the longer fills out the wheel well better...go figure) and found that the upper spring mount was too far forward and caused the spring to bow. Maybe fitting the short arms to a later body works ok.

The bow in the spring was hitting the upper mount of the panhard rod.
Strange, I didn't expect that the upper mount location would have moved as well.
Had to settle for the short arms. Makes the 195-75x15 tires run close to the body on the front lower section of the wheel well which was another reason I wanted to use the longer arms.


--
'60 544, '68 220S, '70 145S, '72 144E, '86 745T

"Do you run a rear bar?"

Yes... and if I remember correctly, you don't like them. We'll just have to agree to disagree on that. :)

FWIW though, the rear bar is .875" tubular fully adjustable (rotating blade) used in conjunction with a 3-position adjustable 1.375" tubular front bar. Unlike the brake proportioning valve, IAW IT rules the bars cannot be tweaked by the driver while underway. :(
--
1971 142E ITB racer, 1973 1800ES, 2002 S60 T5

Yes... and if I remember correctly, you don't like them. We'll just have to agree to disagree on that. :)

There's your reason that you can't run much rear brake. I know it feels better to have some rear bar, but it always ends up being slower. The problem with putting sway bars on live axles is that they lift the inside tyre, this gives the outside tyre positive camber at the all the worst times & around you go.

"I know it feels better to have some rear bar, but it always ends up being slower."

I think you're attempting to transform a conditional premise into absolute fact... always dangerous! :)

There may be rear swaybar-equipped cars that lift the inside tire, but it does not have to be that way. It's all a matter of balance... in this case, the relatively large front bar offsets this tendency nicely. As currently set up, the car picks up the inside front wheel first.

Now, about being "slower"... This car has been raced at a total of 6 or 7 different road courses by myself and the previous owner. It is the current ITB lap record holder at 3 of those tracks.

I've said it before. You'll take my rear swaybar away by prying it from my cold, dead fingers. :)

Gary L.
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1971 142E ITB racer, 1973 1800ES, 2002 S60 T5

It is the current ITB lap record holder at 3 of those tracks.

Yes, I remember reading about that, I remember reading that you were disappointed in the lack of opposition.

the car picks up the inside front wheel first.

It will always lift the inside front wheel first, excluding doing something silly to it, but that doesn't mean that the weight isn't coming off the inside rear.

You'll take my rear swaybar away by prying it from my cold, dead fingers. :)

You still should consider trying a few meetings without the bar to see if you can solve your rear brake problem.

"You still should consider trying a few meetings without the bar to see if you can solve your rear brake problem."

I do not have a rear brake problem. I do not have a corner entry problem. I can make both of those statements with no reservation, because I have a proportioning valve. :)
--
1971 142E ITB racer, 1973 1800ES, 2002 S60 T5

I think we definitely need to agree to disagree on this one. :)

He used it as the title of his post because that's what the title of every other post is... So those were my words. And, he says "I do not have the stock brake valves on the rear system; they have been legally removed and replaced with a Tilton Engineering driver-adjustable rear brake proportioning valve. I can go from no rear brake pressure reduction whatsoever to considerable rear pressure reduction while underway, so it is not at all difficult to experiment with varying levels of pressure proportioning. So that would explain why he can get too much rear braking/lock-up, but only on purpose.

He used it as the title of his post because that's what the title of every other post is

I know that, that's why I put a smiley on the end of it.