Yup I was going to try that but ran out of steam . The calipers are supposed to be emergency type according to the listing.Quote:
Originally Posted by Matthyj
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Yup I was going to try that but ran out of steam . The calipers are supposed to be emergency type according to the listing.Quote:
Originally Posted by Matthyj
NAVY, I've got that Wilwood kit in mine, the "parking" or "emergency" brake is basically worthless! It won't hold the car on a hill and even if it's "on / engaged".. you can drive right over it without knowing it. I've done it a couple times so now I don't bother setting it. :mad:Quote:
Originally Posted by Matthyj
I even added short pieces of metal to increase the leverage and it isn't much better.:(
More testing today. The e-brake arm on the caliper is only moving 1/4 to 3/8 when brake is set.
I removed the brake pad from piston side and moved the E-arm 3/8 to 7/16" dozens of times and no piston advancement, moved out but right back in when arm was released .
Moved the arm a full stroke 1 -1.5" and piston did advance. Whats this mean ? I wish I knew . Still can't understand the lack of stopping power when stepping on the brakes, only .015" gap between pad and rotor when brakes are off/at rest.
Does one side of the Master cyl.affect the other, I've been trying to work just one side of the cyl. so the front doesn't give me false high hard pedal. mumm ?
Yes it does-thats why oem setups have that combo valve thingie-dingie-------and your pad probably isn't setting on the piston at the .015 -------piston is retracted into the housing
You might want to look at rear brake package Ford Motorsports sells for rear disc around $300 complete just like what is on Explorer rears------
As I said earlier, I have the Explorer brake setup on my 46. Brakes work fine and the parking/emergency brake will hold the car in gear (NSRA Safety 23 test).
What master cly. are you using the Explorer one ? ThanksQuote:
Originally Posted by Hotrod46
Navy, a little confusing here, you said no piston advancement but then it moved out and back in? Just trying to figure out if its "#2 - The sprag will seize on the inside of the piston and will never work again" or what. I still say swap a front & rear caliper which would check your master cylinder as well as valving, about 15-20 minutes should tell something then. Just really curious at this point.Quote:
Originally Posted by Navy7797
Just curious, have you talked to the manufacturer?
I'm running the Corvette style 1" bore with a booster. A very common street rod part.Quote:
Originally Posted by Navy7797
I thought that might be confusing. When the e-brake is applied it pushes the piston out but retracts without adjusting the brake when released. The sprag seems to only work with a full throw of the e-arm on the caliper, that can only happen when the caliper is off the rotor or a pad is removed.Quote:
Originally Posted by Matthyj
I'm running a Corvette MC with 1 1/8" bore. 8" dual diaphragm booster. So I guess I have that part right.Quote:
Originally Posted by Hotrod46
No I haven't, I have no idea who made them they came in a kit from Speedway. Haven't talked to Speedway either just short on time during the day.Quote:
Originally Posted by 36 sedan
navy------don't you have a quick change rear end in that car??? Those brakes are for c clip type axles only and your q change isn't that type rear- the clip axles can move in or out a little so calipers can squeese disc evenly-with your set up they can't do that
That's a new one on me. I've never heard that there are calipers that require the rotor to "float" between the pads in order to work right. Can you explain and give examples?Quote:
Originally Posted by jerry clayton
Roger--those type calipers were designed for rear ends that happened to have "C Clip " axle retainers. Those axles could move in and out a slight amount. Brake calipers are critical to mounting and rotor thickness. It amounts to a stacking of the tolerances. If a floating caliper(only hydraulicly pushes from one side to squeese the rotor) isn't mounted on an rear end that has the correct axle flange to housing deminsion, designed spec thickness of rotor and/or pads, it will not function as designed. Add in an function like a parking brake that mechanically is applied vs the hydraulic function and is adjusted with a sprag ratcheting device that might not be installed correctly---like reversed sides of vehicle, upside down, backwards, etc-----
Remember that back in the 60s when self adjusting brakes came out that they were adjusted when brakes were applied while backing up. That line of engineering was applied to the early rear disk brake vehicles ( not necessarily the reverse thingie but the application of the parking brake EVERY time you parked was an element of the design/thinking.
I think Navy should replace the calipers to single purpose ones like most things use and add an electric hydraulic park valve to meet regulations. I'd suggest a disc on the pinion yoke but I think he has a quick change rear and the bottom shaft would not have enough ground clearance. A transmission output shaft brake would work best.
Oh and examples are the front wheel drive GM cars are what I think these calipers were designed for and then they got added to other rear wheel drive models for a while .Probably others also but I don't have time to cross referance all the part numbers
Navy, I don't disagree that you're not going to end up changing calipers, but I don't see it being tied to the fact that your axles are not c-clip. I believe that disc brake calipers are by design self-centering on the rotor, whether they are fixed (opposing piston) or sliding (one piston). You've got a lot of folks scratching their heads on this one, and I'd try Matt's caliper swap idea, just for grins.
Navy, I'm not convinced that you don't have a problem with the sprag assembly. Reading the instructions that Matt provided one thing that jumped out at me was their caution to never buy re-manufactured calipers, because the #1 failure of them is that the piston/sprag assembly was not used and froze up, rendering the caliper assembly/piston pretty much useless. Second is that you've said that when you pull the e-brake lever on the caliper the piston moves out, but the returns to the original position. Third is that you've said that your brake package came from Speedway, not from Master Power Brakes directly, and I'm wondering if Speedway may source their calipers from a re-builder rather than supplying brand new hardware.
It seems to me that the key to your problem is the sprag assembly in the rear caliper pistons. When you unhook the e-brake cable and pull the lever full travel it should ratchet out the sprag assembly and lock in a new position, ready for the next advance with the lever until it squeezes the rotor before grabbing the next tooth. To start I'd swap the front calipers to the back like Matt suggested, which should confirm MC operation. Assuming the MC checks out and the rear brakes work with the single purpose front calipers we would know that the problem is internal to the rear caliper. At that point I'd be confirming the operation of the sprag clutch assembly, or maybe buying a pair of new calipers from Master Power Brakes, but first I'd call MPB to see if they have any ideas. They seem to be pretty well versed in these "unique" GM rear calipers.
The other option is to buy a pair of single purpose calipers for the rear, and do something else for your e-brake function like someone else suggested earlier. Best luck chasing the gremlin, and thanks for your continued posting even when it's so frustrating.
I'll echo Mr.Spears, the sprag (I believe) should prevent the piston from returning to it's original position, when it does - you've lost any adjustment of "play".
a note for easy switching of front/rear calipers------just switch the lines at the master, you don't need to move the calipers-then see if the fronts react correctly!! saves a lot of time and effort.
Sprags-----if calipers are on wrong side of car????????
And----If during the assembly/rebuilding of the sprag cored calipers------if the sprag was installed backwards it won't work-----same deal if rollers are loaded with rust/crud
Oh the HORROR of it ! Well testing went on today with a change to a 1" bore Master Cyl. from the 1.125 cyl. that helped but did not stop the wheels. I attempted to swap calipers front to rear but there just wasn't enough fittings in the shop to make that happen. One thing did happen today was that the pads are staying right against the rotor after the e-brake is released, before they moved off .015 to .020". don't know what changed there. I bought a pressure gauge tonight on the way home and will see what kind of pressure is at the back end tomorrow .
I talked to Speedway Tech guy about the brakes and he had no idea if the calipers were new or rebuilt. He also had no idea of what the trouble was. He did tell I should have 900 to 1000 PSI at the caliper.
My axles don't move in or out at all. the bearing is pressed on to the axle and then retained via a plate and 4 3/8" bolts into the axle housing. Winters use's Ford Big Bearing style housing ends on this rear.
My calipers float on the pin/bolts with the bushings and the rubber o-rings. There's no issue with the calipers centering on the rotor.
http://i990.photobucket.com/albums/a...psh5h9h45g.jpg
Thanks for all the inputs, we'll figure this out soon er or later.
Navy-maybe you missed it in my post-you don't need to move the front calipers to the rear to see if they work proving that your rears are the culpred---just change the lines at the master or combo valve and then see if the fronts still work-that will prove/disprove wether its calipers or master issue. However, since neither rear works now, its probably something thats common to both that is wrong and if when you hook the fronts up you'll prove it.
I agree with Jerry simple & easy, swapping questionable parts with known good eliminates one or the other, just swap them at the mc will work well. If those calipers don't collapse when hooked to the known good side of the mc you have 1 of 2 things that I can see.
1. Siezed brake piston
2. Too big a bore on the rear caliper, you can't move enough fluid to collapse the rear without the fronts collapsing fully. This could be easily confirmed by c-clamping the piston into the caliper and taking some calipers and measuring the inside bore or the outside of the piston of each and confirming fronts and rears are the same.
If either one is the case like mentioned by others you could always swap out the calipers with the same front calipers using them on the rear (no ebrake but your state inspection might require it, my state doesn't might have to use a pinion mount type e-brake) or replace the front calipers with bigger bore calipers that match the diameter of piston of your rear calipers, the gm metrics are available in many different bore sizes to "tune" a system from Speedway.
If the piston is siezed get new calipers.
We are staying tuned here, we are all curious!
I have already switched lines on the MC and that had no effect on the rears I never did try the fronts to see what they do with the lines switched, I can only turn them by hand and it doesn't take much to stop them. With todays MC change I doubt its the master cyl. I will run pressure test tomorrow on both ends and see what's what. I hope. Thanks again for your help.Quote:
Originally Posted by jerry clayton
The pistons are not seized I know that for sure. The caliper bore size now that another question all together. Looking at the fronts and rear calipers it would seem to me that the fronts hold more fluid because of the E-Brake stuff that's in the rear caliper . Physically they look very close other then the e-brake.Quote:
Originally Posted by Matthyj
Thanks for your help I hope after testing tomorrow I'll have an answer.
OK----one other thing-I have always said about brake issues-but it was generally about braking from speed but I do see how it could be possible in this case-------when you have a braking problem-look for the cure at the other end of the car-----Maybe the choice of either the front and or rear calipers is the wrong size ratio of area/volume. It could be that the fronts are too small and your master cylinder is being stopped at that point before the rears do proper contact-OR, the rears are too big and you don't have enough volume for them?? or both??? Since they went to the dual brake anti fail system back in 1967?(I think) the volumes and pressure are strickly regulated to get a certain reaction from your brakes for if one end of your vehicle fails, the other end will stop you BUT there will be severe symthons from pedal pressure and travel.
As this gets more and more complex I would resort to a very basic method of chasing down where the faults lie-I would procure a simple master for a single brake port (maybe clutch master?) and with a pressure guage to verify pressure would then check ONE caliper at a time to prove each separate part/ component and then go deeper as I put the complete system together.I'd remove all the valves, combo, residual, delay, porportional, etc and only work with pedal, manual master,etc, etc
If you don't have it worked out by the time that plane is ready to fly , I'll come down ??????????????Selma Texas?? I remember Selma, Ala 1965
Suggest you go back and re-read the instruction sheet that Matt posted regarding the symptom if you don't get the sprag unit properly adjusted. Seems to me that's a perfect description of your problem, but I may be missing something in what you said. Also, your rear calipers are designated L & R. Is it possible for them to be reversed and still hook to the cables and function? The sprag units are threaded LH/RH to "unscrew" tighter with application of the e-brake lever, as I understand.
Sounds right.Quote:
Originally Posted by jerry clayton
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Quote:
Originally Posted by rspears
I can't disagree with Jerry's approach of proving each component one by one, using a single port master, etc, and I expect it could be done on the bench with a hand full of pre-formed brake lines and simulated rotors, but it seems that you ought to be able to slay the beast on the car. One other thing, it's my impression that you've got to work both rear calipers together unless you take one out and plug that line. I believe that even one rear caliper with the sprag unit down in the bore will "rob" volume from the system and keep you from generating full line pressure.Quote:
Originally Posted by jerry clayton
Good hunting, Navy!
In post 34 you state that with the front brakes connected that the pedal push rod only moves about 3/4 inch but without the fronts hooked that it moves 1 1/4 inches-that says "the brake caliper volume requirements aren't compatable with the system--front calipers should take more volume than rears in a properly sized system---Your combo valve I haven't seen one like it????
I believe that this situation would be caused by the rear sprags not coming out of their "pockets", increasing the volume capacity of the rear calipers. The more we talk about these "e-brake rear calipers" the less I like them.Quote:
Originally Posted by jerry clayton
Not trying to re-post what has already been posted, just trying to simplify a step by separating it;
Attachment 65154
Roger, I would almost agree with you but I put the kit on from MPB and it could not have been any easier, I have zero issues, now keep in mind 80% of braking is done by the front and my rears could be siezed tighter than a drum and I might not know it yet!:whacked:
As for Navy, I still say either incorrect volume (too big) on rears or sprag is siezed.
1.) Volume issue, you could not probably physically see the size difference, heck a Wilwood is twice the physical size of a GM and holds way less volume even with 4 pistons so, you could take one of the front calipers off swap it with the one of the rear still, don't hook up of e brake and hit the peddle if this is the case, on the front brakes the smaller volume caliper would collapse and the other larger on the front would not, problem either solved or eliminated about 15 minutes on a bare frame as the caliper mounts are the same for these. if they both stop the rotors while pressure is applied when you are swapping them back simply crank the e-brake arm and see if they are ractheting.
I know this to Navy is about 6 guys barking commands from their easy chairs but this can be figured out and eliminated pretty easy, if both collapse at the same time when you have a rear and a front caliper on the front and then find they are ratcheting I would then start eliminating valves etc. But swapping calipers is free (no fittings to buy) and would also confirm or check the valves to some extent since both calipers could be compared on one end of the vehicle with the same valving.
OK the results are from pressure testing
Without engine running at the MC 100-150 psi
With engine running At the MC 600 psi
lines to front 600 psi each side
line to rear 600 psi
With a 3 foot cheater bar on the brake pedal I reached 900 psi at rear with lots of pushing on the bar which was way over and beyond anything anyone could do with foot power on the pedal.
I did a search and found that 900 + psi seems to be the norm.
IS IT POSSIBLE THAT THE DARN POWER BOOSTER IS BAD ? Its new but ?
In post 34 you show a 33* angle in the brake pedal arm---and stated later that you had 3/4 inch travel in master rod-----thats not a very good mech leverage ratio-looks like maybe a 3 inch arm and a 7-1 would get it out to 21 inches? 5-1 maybe 15? you can raise the pressure by a better leverage/geometry and even a smaller diameter bore master. maybe down to 7/8? there are graphs out there that show the volumes/pressure differances-------
Keep in mind there is a difference in pressure & volume, If you unhooked the caliper and put a gauge on the front and back and got the same pressure (you did) that means that you still could have a volume issue or stuck piston, as of now you know that the fronts collapse at 600 psi and the rears don't, I still believe the easiest and no cost option would be to swap calipers on one side, those fronts could collapse at 600 psi as could the rears but the volume could be to much of a difference to ever get full pressure on the rear, it would also check your plumbing (valves, etc) if the rear don't collapse on the front rotor and the front does on the rear you now simply have a stuck piston or volume issue, and all else is kosher.
It doesn't mean your booster is bad either. A person can exert alot of force in a panic stop when his back is against the seat and he's using his legs, keep in mind that 99% of the time you don't exert full force on a brake pedal because you don't normally panic stop (normally), pedal leverage as Jerry said is mechanical advantage, as well as a smaller diameter master cylinder normally the pedal ratio is different for power brakes than non power.
stick a fork in me i'm done.
Ok I'm back on the job, it looks like I'll be doing some remodeling of brake pedal mounts and ratio. Had to walk away for a bit. Building aircraft is so much easier than getting a bunch of mismatched brake parts to work.
What I hate is that I'm going to have to cut the bracket on my frame and it's all painted etc. :(
Thanks for the help guys, I'll keep you posted.
Before you cut your pedal, did you check the power booster to master cylinder rod adjustment?
Imagine if it was powder coated! :eek: At least the paint can be blended / patched / insert your term here...Quote:
Originally Posted by Navy7797
OK perhaps some slack can be taken up?, right now the rod is screwed onto the threaded rod coming out of the booster and that pushes in 1/4 " before it hits solid but I believe thats correct, its acts just like the other boosters I've looked at.Quote:
Originally Posted by 36 sedan
