Tremo

Bleed rears only?

TORN

iTrader: (17)

Ok need some input. I am installing LS1 front brakes and PBR rears with 315 rear tires. Car had disc from factory. Would you install the 1NCR5 or 1NCF2 spring?

Drew

iTrader: (58)

Could call up Miss Cleo's 1-900 psychic super friends hotline and probably get as accurate an answer as asking here. No offense but most people doing this mod are using voodoo and hearsay to guess and comfort themselves that it's the solution to a problem. At best folks are going by trial and error.

TORN

iTrader: (17)

Just read QwkTrip post and info he posted about this subject. Drew I understand your post now.

https://www.thirdgen.org/forums/ltx-...ml#post6282726

Drew

iTrader: (58)

A person only has to go back and look at the origin of the thread. Someone made a valid observation, and developed a plan and acted upon it, he was happy with the results in his scenario. Years later people are just ***** nilly throwing different springs in there with little understanding or concern about what they're trying to accomplish or the consequences involved. It's not doing the research, and deciding that this mod might have a positive effect, it's "well i read on TGO I need this spring cause I modded my brakes". It used to be (before this thread) 'oh I need an adjustable Wilwood valve because that's what someone said on TGO' or 'I don't need a different valve with my completely modified brakes, because so and so on TGO said the drum valve worked fine for him with no mods'.

Changing the spring apparently does change the bias to a limited variable, changing the spring and plunger has another limited effect. As far as which is right for any application under the sun, there's no telling that even if someone has the same make/model car and same brakes, if their solution will work for someone else because the ideal brake balance and weight distribution of two nearly identical (on paper) cars might be vastly different in person. No one is really looking into the science of what quantifying what issue they're encountering, or the desired effect, or the real world result of the mod, folks are just buying whatever spring, and communicating it's attributes based on completely different specs from other people reporting on their spring, and reporting back with placebo effects and random nonsense. It's all very very far removed from being a clear cut equation of (Xbrakes + Ycar = Zspring). I don't have the answer to the problem, or the question, but I know this thread sure isn't doing anyone any favors unless they're already smart enough to take the suggestion that it's a spring/plunger issue as a general direction to look, and have the ability to work it out on their own.

QwkTrip

iTrader: (22)

This thread is more comprehensive. https://www.thirdgen.org/forums/brak...ng-torque.html

I would take baby steps and walk up the scale. 1NCF2 is the King Kong spring and too risky for your first experiment. 1NCF1 and 1NCF5 are the next steps above stock.

Better to have too little rear brake than too much. Too much rear brake is how people lose control of their cars. And by definition it will only happen when you need the brakes the most (slamming down on them hard), so pretty much a guarantee that you'll crash your car, or at best crap your pants.

Or you can just get an adjustable prop valve and stop messing around. That's what I did. (And you know I put a lot of thought into how to keep the stock valve!) The adjustable valve is far more practical and gives you a wider range of adjustment than anything you can do with the factory parts.

Drew

iTrader: (58)

This is what drives me a bit crazy about this topic and the cavalier nature of how some people are approaching the problem.

GM initially dialed in a greater bias to the rear with the PBR rears and 1LE brakes. They dialed it back after a couple years to the brake balance used on the 89-92 PBR cars. Reportedly GM's engineers reduced the rear effectiveness to correct issues and make the brakes safer for all drivers. You can take that as meaning a good driver isn't going to have as much trouble, and well obviously everyone here is a professional racer with skills to put the Stig to shame... Or you can assume it's CYA liability reduction, to keep GM from being held responsible for idiots wrecking their cars. Or you can view it as "Oops, we goofed, back up a bit". Any way you look at it, folks around here should be a bit more cautious about just chucking in any spring some doofus on here recommends.

IROCZman15

iTrader: (25)

same here. I got the $50 in-line Wilwood valve and have been fine tuning it over the last month. works great. need to take the car out on a rainy day and crank the valve way up )in) to find the point where the rear is overwhelmed and spins out.. then I can dial it back down (out) from there and really find the spot for proper aggressive braking (for autoX etc)

racerx520

iTrader: (1)

planning on doing a rear disk conversion...i've read through this and havent been able to find out if this works for drums currently on the car. I understand that drums and disk share all the same exact parts until the end of the brake line, but was curious if this would work in my application. If i adjust the star wheel it seems just ok, but these drums have never really had any braking power at all (was once out in snow with it stopped at a red light and rear tires were still spinning). thanks guys.

Drew

iTrader: (58)

I swear it's like I'm talking and no one can hear me.

No, this is not a universal fix for "I want more rear braking." It's not for drums (AT ALL!) By 1982 GM knew drum brakes. You're not going to outsmart all the engineers when it comes to drum brakes.

racerx520

iTrader: (1)

Ok, i'll wait until I do the rear disk conversion and i'll see how that does before looking into modding other parts. thanks for your help drew. (and yes I know I probably wont outsmart engineers on drum brakes, however I dont think they quite knew drum brakes by even 1987....since these have been rebuilt and never worked right. I have had the car for 14 years and rebuilt the brakes twice with OEM parts and they still do not grab hardly at all; thus why i'm converting to disk brakes)

Drew

iTrader: (58)

The stock drums have never really been a problem as long as everything is just right. The rear brakes just don't necessarily do a lot of the braking. They especially don't do much unless car has some forward momentum going. The shoes expanding into the drum is only so effective, what they really do best is biting and cocking into the drum. The animation in the video below illustrates what I mean better than I can explain. It's a topic for another thread, but you can't necessarily go by say... jacking the back up, setting on jackstands and trying to stop the tires from turning in Drive at idle. They should stop the wheels, but it wouldn't necessarily be unusual if they didn't.

HellHound

iTrader: (1)

dude. You can get those in eBay for rear disk. Those came on a few different gm cars. You just have to look around. They are out there new. I don't recommend playing with those they can leak and do weird things.

I wouldn't. Drew has valid points. I dropped the spring in mine and it was a touch more. And I mean not even a lot. But Just what I wanted. The drums in mine were crappy too. However the spring in mine was all rusty and corroded, so just as well. The talking about stainless springs was after I bought mine I think, otherwise I would have got those.

HellHound

iTrader: (1)

1971-77 Disc 4WD Brake Prop Proportioning Brass Combo Valve Correct Wire Lead https://rover.ebay.com/rover/0/0/0?m...2F190785682858
there you go. I was using these before. Not from this vendor I don't think but I dont remember. that is a five port. And Double check first before you order it. And do NOT use pipe tape. It WILL leak.

Out-Cast

iTrader: (1)

Would you have a part number for this and where inline within the system did you install the Adjustable valve? I just ordered the 1NCR5 springs today and will have them Monday. Installed 2 new rear calipers so far, doing E Brake cables and master cylinder tomorrow. If none of this gives me sufficient rear brakes then I will install the Adj P-Valve.
Thanks.

QwkTrip

iTrader: (22)

I have the Wilwood with single inlet and outlet. https://www.wilwood.com/MasterCylind...CylinderValves
You have the choice of getting 1/8" NPT thread, metric bubble with M10-1.0 thread, or SAE double flare with 3/8-24 thread. It really looks like the Summit Racing brand is the Wilwood at a fraction of the cost.

Tilton makes a nice unit with 1/8" NPT thread. https://tiltonracing.com/product-category/brake/valves/

Stay away from SSBC brand. I've had 2 and they were both useless devices. Not broken, just useless.

I'd stay away from the Wilwood 5-port model. I had 2 of those and finally took it off my car. It's cast aluminum and the body cracks around the threaded insert. The Wilwood 2-port models are billet aluminum that is less troublesome.

I don't think it matters much which thread type you get because you're going to have adapters any which way you cut it. Just choose your poison and buy quality parts and flaring tool. Personally I have best luck with metric bubble fittings.

You probably noticed I've had a lot of prop valves on my car. The aftermarket stuff can be a real pain in the butt sometimes. Stick with the OE stuff if you can because it's trouble free.

Out-Cast

iTrader: (1)

Thanks for the info!
I seen one of them Willwood valves in an automotive shop
I was I today looking for the springs. My Buddy said that the drag racers use them a lot.

So so where did you plum it inline at and where did you mount it?
Thanks

QwkTrip

iTrader: (22)

I mounted to the stock bracket in every instance. I cut the original prop valve off, pounded the bracket flat with a big hammer, drilled some mounting holes, and rattle can painted over the whole mess.

My current iteration is shown in post #1177. You can see a picture in post #1206.
https://www.thirdgen.org/forums/ltx-...ml#post6293639

Out-Cast

iTrader: (1)

That's pretty slick. On that link in post 1206 what;s the line from the master cylinder running into, is that just like a junction box and and they split to front and rear and then a line to each wheel?

QwkTrip

iTrader: (22)

The prop valve is on the rear brake line. The front brake line drops down to a tee that's just out of sight and then both front lines peel off to their respective side. Beware that you're going to be making some brake lines to do these things.

IROCZman15

iTrader: (25)

I'm a not an expert in this, but I am glad that I did the adjustable wilwood in-line prop-valve. I drove my car into work this morning and at 6am on a saturday, the roads are mostly free and clear of traffic. I almost cracked a smile a few times as I was getting more and more rambunctious on the road and leaning heavily into the braking. I think I have found "the sweet spot" for my particular car/setup with the front/rear brakes now. maybe some minor adjustments of the **** will be in-order next weekend for the autoX event.. but the brakes are all working properly and as a team.

I have the billet in-line wilwood valve. I decided to put it under the rear drivers seat area under the car, near where the old stock style fuel filter would belong. Many people mount it in the engine bay near the master.. and that works great. I kinda wanted mine out of sight, but still reachable/adjustable. I simply cut the new-ish stainless rear brake line and plumbed it in . I built a bracket/mount out of some aluminum channel I had laying around and painted it black. I can reach the valve from the drivers side without needing to jack up the car at all too. no messing with springs or guessing spring rate and plunger combinations. just adjust he **** and find the happy spot.

92RSv6

I know this post is old, but wanted to add to it to help others be safe. Just changing this spring without understanding what is going on is dangerous to say the least. It is also the least effective way to resolve the problem. Since there are so many variables going on with each person's setup there is no one size fits all solutions.

Here are some things to keep in mind.
#1 1989 to 1992 used the same master cylinder for stock disk/drum & disk/disk setups. The bore size of the front circuit is roughly 1.25" that steps down to about 1" (24mm) more on this later. The rear circuit bore is just under 1" 0.9***. Some earlier years were in the range of 0.7*** for the rear circuit.

The reason for the stepped bore in the front circuit is, in the master cylinder's front circuit there is a quick take up valve. This results in a dynamic pedal feel that is most notable when braking in a tame manner. It feels some what mushy for a moment then firms up once the initial caliper travel is taken up.

#2 the fact that the same MC is used for disk/drum and 4 wheel disk setups means that the 2 lbs residual valve for the drum breaks is in the combo valve not the MC. After converting to rear disks this can be an issue. As the rear calipers will be under a small amount of preload. This can cause a slight brake drag situation that will glaze your rear pads and/or rotors. Reducing the effectiveness of your new rear disk breaks. This is a big reason changing your combo valve is important.

#3 disk breaks require more volume of fluid to be moved vs drum breaks. The smaller rear circuit bore becomes an issue when upgrading to 4 wheel disk. A larger bore will move the greater volume needed, but at a lower Psi, causing greater pedal effort. The same is true in reverse. Small bore equals higher Psi with less volume of fluid.

The benefit of the 3rd & 4th gen brake system is the stock 9" dual diaphragm booster. This should be sufficient in offsetting the increased pedal effort of a larger bore MC. Worst case, you need to source a little bigger booster. Maybe 1 or 2 inch bigger dual diaphragm booster. InLine Tube would be a good place to contact. If they don't have one, they will help direct you in the right direction if you are pleasant to deal with.

I believe the 4th gen 1995 to 1998 master cylinder had a front & rear circuit bore of 1.25" with no quick take up valve system, rear residual valve, or any speed/abs valving. I will
l see if I can find my link to a good table that gives all the MC dimensions. This MC requires using the booster as well to accommodate the bolt size differences of the MC, and booster to MC push rod length. It would be best to use the the disk/disk combo valve from a 3rd gen 1989 to 1992. This will avoid introducing a residual valve to a disk/disk system, and maintain the proper proportioning of the rear circuit & the correct metering of the front circuit.

The 1.25" front & rear MC bore should provide plenty of fluid volume for the 4 wheel disk upgrade without screwing up the brake bias. Maintaining safety on wet & dry road panic stops.

#4 Just changing the spring will only change the proportioning curve in a hap hazard & unsafe manner. It will not correct anything in a predictable fashion. It's far better to understand how the system is supposed to work so you can better choose your componets, and know what each change will do.

The thread by Qwktrip that someone linked to in a previous post is well done, and gives the formulas needed if you are in doubt about the amount of force your breaks will produce after a given change. There are several books about brake system design that are accessible, and understandable by most people who are mechanically inclined

It's important to understand at the very least the basics to keep your self, and just as equally important, everyone else on the road near you safe.

With just some research I was able to convert my front drums on my 1968 F100 to disks breaks. While at the same time improving the effectiveness of the entire system, and upgrading to a modern MC with modern amenities. It's not massively expensive either. With the exception of an aftermarket 2 lbs residual valve ($10), everything was stock production parts. Of course it's 100% possible to apply the knowledge to performance aftermarket parts as well.

Safety does not need to be expensive or overly complicated. It does however require effort.

raptere

Agreed, there is some questionable info here... I'll say I have been using the 1NCR5 and it gives me too much rear braking with my factory rear PBR discs, and front C6 Brembo discs. During a recent track racing event I was told by another racer I was totally locking up my rears on heavy straight line braking before turning in... These 30.82 lb/in springs were too much for me, I just ordered the 9657K352 from McMaster which are supposed to be 28.4 lb/in. Hopefully that is closer to the sweet spot, where I get a nice brake balance. 78_SG4 a number of posts above came to a similar conclusion. 78_LG4's post

I doubt by the way that the master cylinder sees 250 deg f... most plastics will soften before that temp... my reservoir has never felt soft to me... ( Moulding / Melting points of plastics )

My research...