Need suggestion on 4-wheel disk MANUAL MC - Team Camaro Tech
Brakes, Suspension & Steering Conversion questions, Steering & Handling

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post #1 of 32 (permalink) Old Nov 6th, 01, 08:08 AM Thread Starter
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Please don't yell at me too much, but I need some help from you experts on my '71 Chevelle SS with 4-wheel disk brakes.

A little history... the car has been upgraded to B-body spindles and 12" 1LE rotors up front, stiffer springs, and poly bushings. I just installed a new 12 bolt posi rear that I added a rear disk system off a 78 Caddy Fleetwood. I'm having a problem witht he rears not doing much braking or assisting and adjusting them has proven to be a BIG PITA! I am using an 80 Camaro Booster and Corvette 4-wheel disk MC that goes into the stock prop valve for the fronts, but the rear line bypasses the prop valve but has an adjustable in-line. It is fully open. The pedal is pretty hard, but does not travel very far. I have about 11" of vacuum, so I think the booster may not be helping much, thus the reason for looking for a manual master cylinder for a 4-wheel disk system. I have found several, but all seem to have either 1" or 1 1/16" bores, that might be too stiff for a big car?? It has a 454 motor and 400 tranny, so figure about 4,000 lbs without driver.

ALso, the Caddy calipers have the ebrake system in them that I think is the problem, anyone tried just using regular front calipers in the rear and have any problems?

Thanks a lot,
Bill C.


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Bill C.
Colorado Springs, CO

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post #2 of 32 (permalink) Old Nov 6th, 01, 10:42 AM
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A 1" bore is usual for manual front disc systems on an early Camaro and Vette.
With a booster use a 1 1/8" bore MC.
You are right, you are not getting much boost on your system.
With a complete Camaro disc setup the pedal pressure to stop is pretty high.
The Chevelle is heavier than a camaro, but your 12" rotor diameter is larger than the origonal Camaro which is 11".
If you use brake pads like the Performance friction pads, they have a higher coeficient of friction around .4 which will lower the pedal pressure required.
What is happening now, is you have the booster hooked up witch connects lower on the brake pedal than the manual brake pushrod. With poor vaccumn you can have higher pedal pressure than with a manual setup.
David


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post #3 of 32 (permalink) Old Nov 6th, 01, 03:23 PM
 
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Please don't try to run just front calipers on the car w/o some sort of mechanical e-brake. First, you might need an e-brake and second, you w/ prob. find that it is illegal to run w/o one at a safety or an I/M inspection. IMHO. pdq67

TSM in CO sells neat bolt on third-member (front of the pumpkin type) disc e-brake set-ups if you still want to go the front caliper install.



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post #4 of 32 (permalink) Old Nov 7th, 01, 07:01 AM Thread Starter
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Thanks for the info so far, a couple more questions...

David, do you think a 1" bore for a 4-wheel disk system would be very hard to push? I don't mind having a firm pedal that takes a little effort, but I don't want something where I have to pump some weights to be able to push! I found that the 73-77 Malibus with manual brakes used a 15/16" bore, so I'd like to find something like that. Unfortunately, they never came with 4-wheel disks. Are the Performance Friction pads a metalic pad, or that new-fangled ceramic stuff? Do they chew up rotors pretty fast?

pdq67, no, I don't really want to run without an E-brake, but since it doesn't work worth a crap now, it really wouldn't be any different. And being as it's an automatic car, I can never remember to use it anyway. I would like to check on the alternatives, does anyone have a number or URL for this TSM, I've never heard of them.

FYI, we don't have safetly inspections here, so I can get by with whatever I do, but would like to keep it very safe.

Also, since youguys are like the brian-childs of suspensions and brakes, have any of you have experience or checked into using the rear disk brake systems that have the smaller drum brake inside of it? I think the Explorers and some of the Jeep Grand Cherokees have this type of setup.

Thanks,
Bill C.


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post #5 of 32 (permalink) Old Nov 7th, 01, 08:39 AM
 
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Bc,
I will get you all info. on TSM when I get home tonight.

One thing that I am going to try BUT David doesn't think will work very well due to it not creating enough hydraulic pressure plus you have to do some modifying to to make work.


I read an old article about a four wheel manual disc Chevelle that the guy didn't think stopped very good so he installed a P/B 1.25" piston diameter master cylinder from a C-20 truck or Van.

The article said that the brakes worked a lot better due to the increase in fluid volume the big M/C had. The only trouble is that you need to rig up a pushrod holder to keep it from falling out of position if the M/C piston doesn't return properly. This is b/c the manual M/C has a deep hole that the pushrod fits into whereas the power M/C only has a shallow hole.

I have a big M/C but haven't got to where I'm ready to install it. I have figured out the pushrod containment thing, so that doesn't bother me. If it works fine, if not I will pitch it and get a smaller one off a manual f/w/d car!!

pdq67





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post #6 of 32 (permalink) Old Nov 7th, 01, 08:41 AM
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I've used the Performance Friction on my GMC truck and been very satisfied. The original pads were gone in 25K and wore out the discs too.The PF pads went 45K and the rotors were still fine, braking was noticeably improved and this was also pulling a horse trailer.

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post #7 of 32 (permalink) Old Nov 7th, 01, 09:02 AM
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BC, i have a lot of the same questions as you do. i am doing a 4 wheel disc swap on my nova-C4 12" stuff on the front, and something on the back that has the drum type parking brake setup. but i also want to use PBR calipers on the rear(they look cool). i think the 98 and newer camaros have the setup i need, but am not sure. my 94 9C1 caprice has a setup that might work, but the bolt pattern on the rotors is for the 5 on 5 wheels. i could re-drill the rotors for the smaller bolt pattern, but then it becomes a pain if i need a new rotor in the middle of nowhere on a sunday afternoon(it is my summer daily driver). maybe i can use camaro or vette rear rotors? anybody have any input?

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post #8 of 32 (permalink) Old Nov 7th, 01, 01:22 PM Thread Starter
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pdq,
it would seem to me that using a 1.25" bore MC that for for a PB system would make for an extremely hard-to-push pedal. Am I missing something there? I wouldn't think the pressure would be a problem if you could push the pedal hard enough. I've also heard of people snapping off their brake pedals because it was too hard to push. Don't think I want to try that until after you have proven it!!

Novaderrik, I agree that the PBR calipers would be cool, but you still have the same ebrake problem. Please let me know if you figure out a solution.

Thanks,
Bill C>
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post #9 of 32 (permalink) Old Nov 7th, 01, 02:56 PM
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BC,
The difference in cubic inches between the 15/16" and 1" bore is pretty small. A jump from 1" to 1 1/8" is pretty substantial and to 1 1/4 is BIG.
Only Trucks and vans have MC's that large a bore and usually have a big vaccumn booster.

If your current master cyl is 1 1/8" bore, AND has the deep hole required for a manual pushrod, you could try that on a manual system using the top hole in your brake pedal.
I'm assuming your brake pedal has the upper pushrod hole like the Camaro does.

The added weight of your car over a camaro will probably make your larger brakes act like stock brakes on a Camaro.
I kinda doubt you will be happy with manual brakes on your car. People I have heard from that like their manual brakes are pretty big guys with small block engines.
I'm in a quandry over this too, as I would like to dump my booster and put manual brakes on my Camaro.
A power brake system rarely needs over 50 lbs pedal pressure to lock the front wheels.
With a manual brake system, I think you will be in the 90 lb range, maybe a little higher, depending on car weight.

About the pads, I have a friend with a mid 70's vette with manual brakes, he bought a booster and MC to go Power brake on it.
He put new Perf Friction pads on it and his brake pedal effort declined enough that he sold his booster and is staying with manual discs. I think it is only a change from .3 to .4 coefficient of friction of the pads but that makes enough difference.
I don't know what the pads are, I think carbon Metallic, I don't think they are any harder on rotors than stock pads, probably easier on them.
The rear calipers may be too small a piston size. I don't know what they are offhand but I remember my old 85 Z/28 had fairly small pistons in the rear. If the rotor is small too, that's a double whammy. Look for a larger dia rear rotor that may swap with some mods to move the caliper mount out to compensate.
David

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post #10 of 32 (permalink) Old Nov 7th, 01, 03:36 PM
 
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TSM, 9635 Hwy 85 #1, Littleton, CO, 80125 (303)795-5259. This is from a 1987 Hot Rod mag. so might need to be checked! I got a cat. from them awhile back so they do exist. And they have alotta neat stuff for sale!

I know about the pedal pressure stuff b/c David and I have been discussing it at length. As I mentioned earlier, I will pitch it and get a four wheel non-power M/C off of something if it doesn't work to my expectations! And all testing will be done in a great big shopping center parking lot with nobody around, late at night so that I don't have to worry about crashing into something!!

I say this b/c I trust what David is saying, but I'm sooo hard-headed I have to try it myself!! Heck, I'm from MO, the Show-Me state!! He, He...pdq67




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post #11 of 32 (permalink) Old Nov 8th, 01, 03:27 PM Thread Starter
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Guys, thanks again for the replies.

David, I understand that the actual surface area covered by the change from 1" to 15/16" is pretty small, but it should help reduse pedal pressure by a certian amount. It would be nice to know that for every 1/16" change in bore diameter, the pressure was reduced/increased by X amount. Any ideas on figuring that out? My current MC is off a mid-8os Vette I think, and is the short pushrod kind. I know I can order a new MC for a 4-wheel disk Corvette with manual brakes, but they all show 1" piston bores. Do you think the larger rotors in front make pedal pressure any softer? I'm still out on that decision as to whether it makes pedal effort any less.

The manual brakes are for several reasons, lack of vacuum, lack of space, and better feel. FYI, I'm not that small, a little over 6' tall and slightly over 200 lbs, so a little effort isn't a problem.

I have also heard similiar claims about the BruteStop brake pads, how do you think the two compare? Aren't the Brutestop a carbon metallic pad?

The rear calipers do have the smaller piston, but the rotors are 11" rear TA rotors. Apparently, the 78 Fleetwoods are a pretty special deal, with the calipers being the same size dimentionally as the front GM calipers of the 70's and 80's, but with a smaller piston and that lame ebrake system. That is why the regular front calipers will bolt right up. Any other rear disk systems I have seen use the smaller calipers like you are refering to. The reason I like this system is that it has a much sturdier calipers mounting bracket then the other systems.


pdq, thanks for the info on TSM, I'll give them a call. Good luck with your experiment, let us know how it goes.

Sorry to hear your from Missory... HE HE!

Bill C.

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post #12 of 32 (permalink) Old Nov 9th, 01, 08:43 AM
 
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He, He, He!!!! pdq67



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post #13 of 32 (permalink) Old Nov 9th, 01, 09:01 AM Thread Starter
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Well, you beat me to the response...

Just wanted to let you know that the number you gave for TSM is no good! Must be that Missory thing!! hehehe...

I did however find a good number for them tho it wasn't easy! I found a reference to it off another web site, so here it is and I will be getting a catalog from them shortly: TSM, The Streetrod Manufacturing Co. Inc. of Castle Rock, CO. Voice: 303-688-6882.

Thanks,
Bill C.
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post #14 of 32 (permalink) Old Nov 9th, 01, 02:55 PM
 
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Thx, Bill.
Sorry, some of my cats. and a bunch of my mags. aren't with me at present so sometimes I'm off.

pdq67



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post #15 of 32 (permalink) Old Nov 25th, 01, 10:09 AM
 
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Bill,
What are you doing for rear e-brakes or have you thought anymore about them? I'm just curoius b/c I am going to have to buy new Seville calipers and use the ones I have from the boneyard for cores and to say the least they are "pricy".

Havr you got any info from TSM on the little u-joint mounted rear e-brake? I think it is fine but again, just more money.

I found the article on using the 1.25" truck master cylinder. It is in the January, 1978 issue of Hot Rod mag. on page 96, the very last page in the mag. pdq67



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