'Nuff said Chris
my back brakes are working, and I never get rear lock-up, so I'm going to assume the sleeping dog scenario that my LSV is indeed working. 
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Project 80: Codename Grey Ghost
- Thread starter Chris
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'Nuff said Chris
my back brakes are working, and I never get rear lock-up, so I'm going to assume the sleeping dog scenario that my LSV is indeed working. 
The LSV for those who are interested has three ports and a bleed. Fluid come in from the master cylinder and normally passes straight through and on to the rear brakes. However, inside there is a spring loaded plunger. As brake pedal pressure increases (due to soma asswipe pulling out in front of you) the pressure in the system reaches a point where it begins to depress the plunger. Fluid still goes to the back brakes, but essentially when the plunger drops it bleeds fluid off back to the front. It's just a relief valve in other words. But then there is the coathanger wire rod underneath to deal with. Contrary to popular belief this is not actually connected to the LSV. It pivots around the bracket, yes, but it's not connected to the plunger. What happens is, as the pressure builds up, the plunger drops, but also the car tips nose down. As it tips the long rod moves away from the LSV allowing the plunger to drop further allowing more fluid to go though the bypass. The rod does NOT pull the plunger down. So, adjusting the axle end thread to the top means that as you pitch forward, the plunger drop is restricted meaning more fluid pressure going to the back brakes. This doesn't necessarily mean you will lock up. You have to consider your tyres, brakes, suspension set up etc. Dropping the adjuster means that when you brake more fluid will bled off. If you have very soft suspension which dives readily, then this is more than likely where you will end up setting wise. If you have very stiff suspension then the back won't really lift that much and if you are heavy then you probably want to keep the back brakes working quite hard or all that effort will be on the front wheels.
I have found the best way to set the balance (for me) is to drive forward, brake hard note results. Reverse hard slam brakes on and note results. I am looking for really something pretty even in either direction. If you drive backwards and the brakes feel much better than going forwards, then I'd drop the arm a little to allow some bleed off. Remember the arm does NOT push the plunger up. It only limits how far it can drop. So in reverse, the rod acts in the opposite way and pushes up. If there is no free play in the rod when parked then clearly going in reverse means that max pressure is always going to go the back wheels. Ideally then I guess, there should always be a little movement in the rod both up and down when level. When you do a giant lift the rod does need looking at as you may not have enough adjustment for your set up. You can bend the rod quite easily if you need to so it has a bit more dip in it.
My plunger had not only siezed so it didn't bypass at all, but had blocked so fluid didn't pass through it either.
I have found the best way to set the balance (for me) is to drive forward, brake hard note results. Reverse hard slam brakes on and note results. I am looking for really something pretty even in either direction. If you drive backwards and the brakes feel much better than going forwards, then I'd drop the arm a little to allow some bleed off. Remember the arm does NOT push the plunger up. It only limits how far it can drop. So in reverse, the rod acts in the opposite way and pushes up. If there is no free play in the rod when parked then clearly going in reverse means that max pressure is always going to go the back wheels. Ideally then I guess, there should always be a little movement in the rod both up and down when level. When you do a giant lift the rod does need looking at as you may not have enough adjustment for your set up. You can bend the rod quite easily if you need to so it has a bit more dip in it.
My plunger had not only siezed so it didn't bypass at all, but had blocked so fluid didn't pass through it either.
Lorin
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You description Chris also explains the MOT test I was 'subjected' to for the LSV. I was told that to pass the test, the plunger had to be observed to move down when the brake pedal was pressed. After much messing about with the positioning of the rod, I can confirm that the plunger does indeed visibly move down (oh so slightly) when the brake pedal is pressed and thereby appease a particularly thorough MOT tester.
Good grief Lorin, really? So did they have to pull the rubber boot off then? I bet it doesn't move much. If you think about it, it only has to open to the cross sectional volume of a brake pipe doesn't it which is a couple of mm2 or so. What it doesn't do when it moves is close off the flow to the rear brakes as I thought it might. It just siphons off the excess. For two pins actually I'd replace mine with a rally style adjust with pre sets. Does it have to be motion adjustable? You could fit a brake bias valve easily, set it and forget it.
Towpack
Well-Known Member
So how would a malfunctioning LSV affect braking performance when measured on a brake dynamometer by the MOT man? Inability to lock the rear wheels or maybe lock them too easily? From what I've seen when I've had the LC MOT'd they just drive it onto the dyno, press the pedal until the wheels lock and note the readings. Not really sure if they even know it has a LSV.
Dumb question. I thought with ABS there was no LSV - correct??
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Knucklehead
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- May 28, 2013
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My '93 has both ABS and LSV.
Agree with earlier comment, I seriously doubt my local MOT centre would know what one is never mind if working correctly.
I thought when they did the brake tests they are looking for efficiency % wise compared to what they expect for cars of that age.
We have government run MOT centres over here, not appointed garages like in the mainland and they tend to catch most things.
I did also read one time about adjusting the LSV height when adding a suspension lift. I'm yet to do mine as the braking seems fine so far.
Dave.
Agree with earlier comment, I seriously doubt my local MOT centre would know what one is never mind if working correctly.
I thought when they did the brake tests they are looking for efficiency % wise compared to what they expect for cars of that age.
We have government run MOT centres over here, not appointed garages like in the mainland and they tend to catch most things.
I did also read one time about adjusting the LSV height when adding a suspension lift. I'm yet to do mine as the braking seems fine so far.
Dave.
Incorrect. They all have them Gary
TP I agree, but we've had this debate before. I use an MOT station locally and have been going there since I learned to drive. They don't road test with a decelerometer. I have asked them that and they just give me a hard stare. They put it on the rollers, press the brakes and watch the gauge one wheel at a time. They have failed cars of mine before on brake performance so they can clearly see what's going on. Yes centre transfer box yadda yadda but with the thing in neutral and the wheel being powered by a roller brake balance and brake effort look properly tested to me. So no it wouldn't show that an LSV was operating in terms of suspension dive but it would show if it was working passively I guess. But to have to strip it to show it's working is nuts. If the brakes work, they work in my book. I want my car to pass, properly and if this test isn't quite as it should be then I am still happy that it's valid enough for me.
TP I agree, but we've had this debate before. I use an MOT station locally and have been going there since I learned to drive. They don't road test with a decelerometer. I have asked them that and they just give me a hard stare. They put it on the rollers, press the brakes and watch the gauge one wheel at a time. They have failed cars of mine before on brake performance so they can clearly see what's going on. Yes centre transfer box yadda yadda but with the thing in neutral and the wheel being powered by a roller brake balance and brake effort look properly tested to me. So no it wouldn't show that an LSV was operating in terms of suspension dive but it would show if it was working passively I guess. But to have to strip it to show it's working is nuts. If the brakes work, they work in my book. I want my car to pass, properly and if this test isn't quite as it should be then I am still happy that it's valid enough for me.
Yes I know. Too lazy to fire up the pc to do it - will do anon, promise 
I'm on the same page as Chris, just want the brakes (and everything else) to be working as best they can, considering the truck is 20 years old this year.
The worry I have is rear wheel lock-up. Under heavy braking in the wet for example, cars are totally out of control if the backs lock up before the fronts.
Watch any of the thousands of "Russian Car Crash" vids on utoob and it's always a friggin old Lada spinning in the road with the back brakes locked
The worry I have is rear wheel lock-up. Under heavy braking in the wet for example, cars are totally out of control if the backs lock up before the fronts.
Watch any of the thousands of "Russian Car Crash" vids on utoob and it's always a friggin old Lada spinning in the road with the back brakes locked
Well winter isn't a bad time to set the LSV I guess. You can get the wheels to lock up without having to do any real speed. Find some snow, get someone to watch and see if the rears lock up. I have to say I am with Gary on the curious stakes. How does the LSV work with ABS. I mean why have one? If you back it right off does that just let the ABS do its thing?
Got some new pipes to fit this weekend, new bleed nipples and then I should be rolling for real. There is a nice gravel yard up at the unit and still plenty of snow. I should be able to get a good balance. I took the adjuster off and cleaned it right up so it's pretty much adjustable with fingers never mind spanners.
Got some new pipes to fit this weekend, new bleed nipples and then I should be rolling for real. There is a nice gravel yard up at the unit and still plenty of snow. I should be able to get a good balance. I took the adjuster off and cleaned it right up so it's pretty much adjustable with fingers never mind spanners.
OK so Tuesday I get an e-mail. Your delivery will be coming Wed. Be in or it's your loss. Luckily, I am able to be in Weds. I track the delivery on line and 15 before time this chap called Richard turns up with a bag and a set of Max Trax copies. Awesome. Where's the roof tent? No tent. So I contact D44. Ahh, no, sorry the tent needs a special carrier that will be with you Thursday. Great the day I am not in. OK then Friday. Excellent, I can sort that. So it gets to 15.00 on Friday and no sign of it. Contact D44. Well they have up to a 19.00 delivery time. You guessed it. 19.00 comes and goes. Nada. I get hold of D44 on Saturday who are very apologetic but can't get hold of the carrier.
So where the f*** is my effin tent then? I was going to fit it this weekend ready for the 4x4 show next weekend.
If it's one thing I can't stand, it's disappointment.
So replaced all the rear brake lines and bled them with my new toy. Brakes are great now. They lock the wheels on Tarmac seem balanced and good pedal pressure.
Job's stopped for now. Going to look at kitchens.
So where the f*** is my effin tent then? I was going to fit it this weekend ready for the 4x4 show next weekend.
If it's one thing I can't stand, it's disappointment.
So replaced all the rear brake lines and bled them with my new toy. Brakes are great now. They lock the wheels on Tarmac seem balanced and good pedal pressure.
Job's stopped for now. Going to look at kitchens.
Bugger, bugger and thrice b...... 
