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I say shoot for whatever is easiest first. The drum spring I believe is a lighter spring. It wont allow much force to the rears for disc. That white z car looks rad with those wheels.
I just ordered a pack of the 22lbs springs. Im converting to front ls1 brakes.Swapped from the stock 9bolt disk to the 94 lt1 rear pbr's and my rears barely do a thing.Even with my stock disk prop valve i think the 22lbs combined with my front ls1 brakes should bring the car upto snuff with the modern car crowd.Its super scary trying to stop at all with stock brakes no matter if it was disk/drum or disc all around..they never seemed adequate to me.
I also did the 19 lb spring after swapping out the drums for a set of PBR calipers and 13" Baer rotors. I am running NOS GM pads out back as well. Front brakes are Corvette C6 calipers with 14" Baer rotors. Stock GM pads. The car stops so good that I think I actually have too much brake for this car now. Brakes this good need to be used with ABS. I am extremely pleased with the performance.
I tested out my brakes now with 22lbs spring and it feels noticeably better. Mine leaked a few drops so yes you should bleed the system after install.It wasnt much mess at all but i know need to bleed it. My rears now show actual brake dust and in hard braking felt well balanced.I suggest the 22lbs spring.
Ok, I read thru the thread - did not find a solution for the 84 bird se iron prop valve. Is there a solution via the spring upgrade? Rear brakes (lines, rotor, etc all new - adjusted e-brake as much as possible) do not apply well. Thx byron
Glad this thread is still alive...and glad ThirdGen.org exists.
I just pulled out my 1985 IROC after 10 years garage stored. I too have braking concerns since I have owned it, purchased in 1988. I now have it road ready - after many repairs. WRT the brakes - I kept the original J65 disc brake setup (replaced back calipers and four rotors/pads around).
After reading this thread I am planning to do the 19# Grainger Spring (1NRC5) but have a question as many of you have the later model aluminum PPV. I did notice a picture from way back of the casted PPV which my vehicle has.
I want to hear from you experts that this PPV will also take the 1NRC5 spring.
Ok, I read thru the thread - did not find a solution for the 84 bird se iron prop valve. Is there a solution via the spring upgrade? Rear brakes (lines, rotor, etc all new - adjusted e-brake as much as possible) do not apply well. Thx byron
If they are four wheel disk brakes, I just replaced my rear calipers and learned a lot. You should not adjust the parking brake cable by tightening it. You have to loosen it so that the rear caliper arms come all the way out - this allows for the caliper piston to pop out a notch closer to the disc. This is how they self adjust. If you over tighten the parking brake cabling, then the parking brake arm on the caliper will never extend far enough to self adjust. Try taking the cable off the arm, pull it all the way back and see if the piston comes out. If not you may have bad caliper...
I had contributed to this thread some years ago when I did the spring change and reported that it didn't work for me. Fast forward to today when I have changed to a manual master cyl and a wilwood adj valve and I still can't get pressure to the back calipers. So I think the reason why the spring change didn't work for me back then maybe wasn't the springs fault. Still troubleshooting what's going on with the new setup.
OK, I will risk getting bashed. Does anyone wish to reason this out with me?
First, I have never seen the layout of the complete factory 4 wheel disc setup.
But converting from drums to discs presents a few questions and observations:
1) Drums use small wheel cylinders and discs use much larger calipers. What would you say the volume difference between the two is? At least 5 to 1 maybe?
Therefore, that section of the master cylinder (MC) needs to be able to push 5 times the volume of fluid, times 2 calipers, so 10X then.
2) Are the sizes of the metal brake lines running to the rears larger on disc cars compared to drums? Is there still only 1 line to a tee block on the axle on disc cars, or do disc cars have separate lines, or 1 larger diameter line? You follow how this alone could be a major restriction?
3) Do the MCs for rear disc cars have a larger chamber to feed the calipers? My 84 TA with original disc/drum setup has a MC with a much larger section that feeds the front discs, and a smaller chamber to feed the rear wheel cylinders. Is the MC different on 4 wheel disc cars?
Let's all figure this out together.
Last edited by NoEmissions84TA; Aug 13, 2017 at 06:50 PM.
OK, I will risk getting bashed. Does anyone wish to reason this out with me?
First, I have never seen the layout of the complete factory 4 wheel disc setup.
But converting from drums to discs presents a few questions and observations:
1) Drums use small wheel cylinders and discs use much larger calipers. What would you say the volume difference between the two is? At least 5 to 1 maybe?
Therefore, that section of the master cylinder (MC) needs to be able to push 5 times the volume of fluid, times 2 calipers, so 10X then.
2) Are the sizes of the metal brake lines running to the rears larger on disc cars compared to drums? Is there still only 1 line to a tee block on the axle on disc cars, or do disc cars have separate lines, or 1 larger diameter line? You follow how this alone could be a major restriction?
3) Do the MCs for rear disc cars have a larger chamber to feed the calipers? My 84 TA with original disc/drum setup has a MC with a much larger section that feeds the front discs, and a smaller chamber to feed the rear wheel cylinders. Is the MC different on 4 wheel disc cars?
Let's all figure this out together.
Lines are same drum or disk. Same t block set up. MC looks same but might have different piston size, not sure. Can easily check by part numbers.
And I also have 4 spare springs from grainger
OK, I will risk getting bashed. Does anyone wish to reason this out with me?
First, I have never seen the layout of the complete factory 4 wheel disc setup.
But converting from drums to discs presents a few questions and observations:
1) Drums use small wheel cylinders and discs use much larger calipers. What would you say the volume difference between the two is? At least 5 to 1 maybe?
Therefore, that section of the master cylinder (MC) needs to be able to push 5 times the volume of fluid, times 2 calipers, so 10X then.
A disc brake caliper requires less fluid to activate than drum brakes. The pads are already right up against the rotor compared to drums that need the shoes moved further to contact the drum.
2) Are the sizes of the metal brake lines running to the rears larger on disc cars compared to drums? Is there still only 1 line to a tee block on the axle on disc cars, or do disc cars have separate lines, or 1 larger diameter line? You follow how this alone could be a major restriction?
On our 3rd gens the brake line going from combo valve to the rear is the same with both rear drums and rear discs (~1/4"). There is evidence that going to a smaller line with rear discs is beneficial (3/16").
3) Do the MCs for rear disc cars have a larger chamber to feed the calipers? My 84 TA with original disc/drum setup has a MC with a much larger section that feeds the front discs, and a smaller chamber to feed the rear wheel cylinders. Is the MC different on 4 wheel disc cars?
Let's all figure this out together.
The actual M/C used varied through the years. But near the end of 3rd gen production the rear drum and rear disc M/C were the same.
The reason for the larger reservoir on disc brakes is due to pad wear. As the pads wear they move toward the rotor, this requires more back-fill in the caliper. Hence the larger reservoir to prevent loss of brakes. This is also why one shouldn't keep topping off a disc brake reservoir.
When it is time for new pads pushing the piston back will overflow the M/C.
Drum brakes adjust as the shoes wear. So no need for a large reservoir. Just need to remember to adjust them from time to time. This is done on cold brakes by backing up and pumping the brake pedal.
As for the premise of this thread, providing higher line pressure to the rear discs, has anyone actually tested this under all road conditions. Such as a wet roadway at say 50 MPH and heavy braking? I'm just not keen on the back of the car going first.
As for the premise of this thread, providing higher line pressure to the rear discs, has anyone actually tested this under all road conditions. Such as a wet roadway at say 50 MPH and heavy braking? I'm just not keen on the back of the car going first.
I have LS1 brakes on all 4 corners. with my stock 1988 IROC master and a 1NCF2 spring in the proportioning valve. I have BFG Comp 2's (not the all season ones) and have ran the car in at least a dozen SCCA TrackNight in America events at Gingerman raceway with one of them being in the rain. I use the cheap E-Bay Brakemotive drilled and slotted rotors and Ceramic pads and change them every season 3-4 track days and about 2-3k street miles). NEVER have had the back end lock up before the front. According to my data logs from the EBL P4 system I am pulling .75g's+ in braking with them holding up for en entire 20 minute session. (Note 2 years ago I did crack the outside face of the LF rotor after the 3rd track day. Last year I tried the Brakemotive rotors and Hawks HPS pads in front and Brakemotve ones in the rear. On one run the rears did start to lockup before the fronts going into turn 5 but it was the only time. I also like the cheap Brakemotive pads better they are predictable and consistent even when the front rotors start to glow red near the end of a run going into turns 11 and 1. They just only last 3 at most 4 track days but at about $130-140 for 4 rotors and pads it's considered a consumable item in my mind. I just keep an extra set in stock.
In summary even in the rain I am happy with it and would no hesitate to recommend the mod. The brakes on my car are unreal how good they are... As someone told me once "wait till you see God the start braking"
Snap oversteer on acceleration with really super sticky Pirelli Trofeo R tires.... That's a topic for another thread...
I have LS1 brakes on all 4 corners. with my stock 1988 IROC master and a 1NCF2 spring in the proportioning valve. I have BFG Comp 2's (not the all season ones) and have ran the car in at least a dozen SCCA TrackNight in America events at Gingerman raceway with one ...
OK, good data, but on a modified car. The brakes are well balanced with your setup. Has anyone with stock-ish brakes tried heavy braking in the rain with the larger spring? I just want you folks to be safe, nothing worse then swapping ends.
I'm in need of a INCF2 spring asap. I live just outside of Chicago (60142) and i'm willing to pay a little extra to get it overnighted or 2 day. Can anyone help me??
Guys can someone Help me out with a proportional Valve question.
My Car has 4 wheel disc brakes. Where is the proportional valve located, that’s if these Cars come with one or do we have to add one inline somewhere?
I hardly have any brakes after changing out rear calipers and my Uncle/Licensed mechanic is thinking either master cylinder or if the Car has the proportional valve??
All other brake components are near new.
Thanks!
Guys can someone Help me out with a proportional Valve question.
My Car has 4 wheel disc brakes. Where is the proportional valve located, that’s if these Cars come with one or do we have to add one inline somewhere?
I hardly have any brakes after changing out rear calipers and my Uncle/Licensed mechanic is thinking either master cylinder or if the Car has the proportional valve??
All other brake components are near new.
Thanks!
Yes, your car has an external prop valve. Follow lines coming out of master cylinder, they will both connect to a block just under/beside the master. This is the prop valve. Should be two lines coming out of it for the front brakes and one for the rears.
If, after swapping rear calipers you don't have good brakes, I would re-bleed the system. Most probable cause. Sometimes if the master gets low enough to draw in air you'll have a tough time getting first the master re-bled then the rears. I'd probably re-bleed the fronts as well.
If you have a 9 bolt with PBR calipers they can be tricky to get the Park brake adjuster sorted out correctly. I have purchased new calipers that were both "lefts" and the bleeder valve was in the wrong position to actually remove all the air when installed on the right side. Go back through the items you are sure were done correctly anyway. Sometimes it's just something easy that was overlooked.
Thanks for the response. He had full fluid, no air at both front and back calipers.
Both emergency brake cables are seized and of course no one has them in stock.
The Napa guys can not find a listing/part number for the proportional valve.
Any idea why this would be?
I have to go back to work for 2 weeks Wednesday so I won’t be going over the brakes again until like October 7-8th.
Yeah. And no need for an account. I called and they had them the next day. Paid card over the phone. Easy. Probably easier and faster than having someone ship it.
I gave this thread a read and it's a good thread, but I notice people are throwing around the wrong numbers for spring rates; and that can cause mass confusion when people are trying to fine tune things up/down.
Just to help clarify, these are the spring rates (lb/inch) by part number, as advertised on the Grainger website. All the parts have a (1.5 inch) free length, and between (0.48 - 0.6 inch) OD.
The 1NCF part numbers are high carbon steel music wire.
The 1NCR part numbers are 302 stainless steel.
It might be wise to use the 302 stainless since it has a higher usable temp limit. I think the general rule of thumb for music wire is max 250F. But I don't know how hot the spring gets.
I can also get them..but the shipping is almost $11.. or I can drive 35 miles one way to pick them up for less then $5.. just need the one..I have some sitting in will call ..if I make it there in 10 days..lol..
ill tell ya what..ill order a pack of ea..and keep them on hand and mail them out (sell them) to the guys that need/want them..will do $2.00 a spring + shipping don't think shipping will be over $3.00 1st class small padded envelope.. ill make the drive when dropping off parts to be chromed this week..anybody up for it?
Last edited by articwhiteZ; Feb 5, 2019 at 09:30 AM.
when I went to the platers to drop off parts. I orderd a set last week..I Picked up a bag of the springs..so now I also have a few 1NCR5's so I have a few also..
This is my proportioning valve on my 82 originally rear drum just purchased everything to convert to ls1 brakes on all four corners. Went to do the spring upgrade till I noticed my valve isn’t like anyone’s I’ve seen on this thread help!!!???
I know this is an OLD thread, but, it's still relevant. Hopefully. I am doing this to my car now. I have a 1985 Z28 with TPI. It originally came with front disc and rear drum brakes. I upgraded the rear to a Strange 12-bolt with Wilwood disc brakes. Here is what the original brake proportioning valve looks like...
It's the old looking cast iron type. The right side of the picture is what points towards the front of the vehicle, and a single tube goes to the rear brakes. The left side has two outlets that go to the front left and right brakes. The place where the spring upgrade goes is in the down pointing section on the right.
Here is the stock spring on the left and the new 1NCR5 spring on the right. It was noticeably stiffer but not drastically. The new one went in with no difficulty and no cross threading, but I put it together off the vehicle so that may have made it easier.
I cleaned it off and primed it and painted it.
Here it is finished.
And here it is installed with all the hoses hooked back up.
Unfortunately, I won't be able to test how well it works just yet. First of all, because I have no engine in it (in case you didn't notice). Also, I don't have my rear brakes hooked up yet. I still need to get everything from the T-block back. But the install was easy! I'll post again once I finish the lines and fill/bleed the brake system.
