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.


------------------
Bill C.
Colorado Springs, CO

68 Camaro... someday!
71 Chevelle SS
70 Nova

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


------------------
Check my web page for First Gen Camaro suspension info:
David's Motorsports page (http://ourworld.compuserve.com/homepages/David_Pozzi/)
First Gen Suspension Page (http://ourworld.compuserve.com/homepages/David_Pozzi/first_gen_suspension.htm)
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer

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.

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.

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

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.

------------------
Rick Dorion
69 RS Conv,355,M20,4.10's and I don't worry about stone chips.

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?

------------------
1971 Nova(looks like 69 camaro from underneath!)
355sb, vortec heads, HOT cam,T-10 tranny, 3.70 gears 16" IROC wheels

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>

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

------------------
Check my web page for First Gen Camaro suspension info:
David's Motorsports page (http://ourworld.compuserve.com/homepages/David_Pozzi/)
First Gen Suspension Page (http://ourworld.compuserve.com/homepages/David_Pozzi/first_gen_suspension.htm)
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer

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

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.

He, He, He!!!! pdq67

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.

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

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

I have no problems with the 1 in corvette master and 4 wheel disc with pedal pressure.
I use the 11.75 corvette fronts single caliper and the 11 in rear ta disc set up.

BC,
If you can give me the following I'll run it for you.

car weight.
tire height
Brake pedal ratio for manual brakes.
1.Measure from pivot to center of pedal pad.
2.Measure from pivot to upper (manual) hole.
divide 1. by 2. to arrive at pedal ratio.

front rotor OD (actual measure)
front caliper piston dia.
Rear rotor OD (actual)
rear caliper piston dia.

I can only do one end at a time for now.
David


------------------
Check my web page for First Gen Camaro suspension info:
David's Motorsports page (http://ourworld.compuserve.com/homepages/David_Pozzi/)
First Gen Suspension Page (http://ourworld.compuserve.com/homepages/David_Pozzi/first_gen_suspension.htm)
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer

[This message has been edited by davidpozzi (edited 11-25-2001).]

pdq,
I did get the catalog from TSM, but it doesn't show any applications for GM 10 or 12 bolts. I'm going to call them in the next day or so, but it looks like most applications are for rears that have a bolt-in center-section and from the front. The brackets to hold the caliper look like they bolt to the housing using several of the third member bolts, and the rotor bolts to a bracket bolted on the yolk. Not sure if this will work for our cars.
I may go tomorrow and try to get a new set of calipers from the junk yard, I think I saw another 78 Fleetwood last week. Only thing is, it's damn cold and snowing here! I would like to see the article on the truck caliper if you could scan it in or fax it?

If you want, I can send you the part numbers for the new ebrake cables I bought to make it work with the rear calipers, although the Camaro will probably be different from my Chevelle.

legrand198,
I am leaning towards that MC, do you have a part number?

David,
My best guesses are:
Car weight: about 3,900 lbs
tires:255/60x15 front, 275/60x15 rear
stock brake pedal whatever that is, can't measure right now.
Front rotor:11.75 in
front caliper dia: 2 15/16 in
rear rotor: 11 in
rear piston: 2 15/16 in

Do the best you can if you have to guess, any help is greatly appreciated.

Thanks,
Bill C.

Picked it up at the local auto parts store - $30.00 - 1967 corvette manual 4 wheel disc master cylinder fit right in, just needed to lengthen the brake rod about a 1/2 inch for the increased throw of the master. I am running it without any combination valves as that was how they ran them on the corvette. I may put in an adjustable one next spring when we get back out to the track.

BC, you leave that "derned" snow over west of MO!! LOL.

I just got back to a guy tonight that I have asked if he wants to make for sale to us guy's caliper brackets that fit our 10 and 12 bolt rearends in both, the rear 1980 Seville and the front 1969 Camaro calipers as well as my front pdq67 bracket.

I am working with two guys on making these b/c I know it is tooo much of a pain to hand carve brackets out of 1/4", 5/16" or even 3/8" thick, flat plate steel unless you have access to a machine shop!!

Heck, if I had it to do over again and know what I know now, I would have bought all four of the suckers, AND, I think I will!

Heck, I just figured out how to lay the caliper bolt patterns out accurately/correctly, so you can see how hard it was for me to make the two front ones that I did.

Guy's, I hope to be able to tell you where we can buy custom caliper brackets for several CBB combinations shortly! Front and rear. And at a fair price each, too.

pdq67

legrand,
thanks for the year and all, I'll ask my shop to get that one in for me. Does that have a 1" bore? I'm pretty sure all the Corvette ones were for manual brakes. When you say increased throw of the master cylinder, do you mean that it moves farther in and out than a power MC? I would think it might move slightly more, but it sounds like you noticed a significant difference? Was the pedal hitting the floor? Is that why you made the push rod longer? Is that MC a long or short pushrod and did it come with a pushrod?

pdq67,
If I could find a way to send you the snow, I would!! I chickened out of going to the junk yard yesterday, it was dang cold, snowing and the wind was blowing, so the high was like 20 degrees or something close. Too cold for me to be banging around under cars!

So are you looking to make brackets that go on the rears for both the 80 Seville and front calipers? And then your 'special' brackets for the CBB front 12" or 13" truck calipers? I ask because if you make a rear bracket to fit the front Camaro calipers, then the 78 Fleetwood rear calipers will fit that bracket also. This is a bigger caliper than the 80 Seville, but still has the same type of ebrake system.

Has anyone ever figured out what the best thickness for the brackets is? I see you mentioned 1/4", 5/16" and even 3/8", but the stock rear brackets are not even 1/4" thick! I have some 1/4" plate steel I was going to try, and it seems like it would be way strong enough.

The custom caliper brackets sound great, let me know the options you have.

Bill "freezin' my arse off" C.

Here is the brake pedal effort difference using three different MC sizes.
this considers the front brakes only as they do most of the work.
Chevelle brake data, pedal force to lock a front wheel, assumes .9 tire traction coefficient which is a very sticky street tire.
89 lbs - 1" bore -ptr - .53
112 lbs - 1.125"bore ptr- .42
139 lbs - 1.250" bore ptr-.34
ptr is pedal travel to move one side of ONE caliper .010"
Below is a screen from my computer calculations.
I have no idea if these are correct as my "model" has not been tested and proven.
Things like fpr, bias, fop, are names of variables used in the calculations and are described after the number.
If a variable PRECEDES a number, it is a calculation result.
If a variable comes AFTER a number, is is an entry number, not calculated.

The formulas were taken from brake system books. I have been adding to it in the form of adding weight transfer effects on front end traction to arrive at a more accurate model of braking performance.
I can vary any of the variables and the model can back calculate to whatever I need to know.
For instance, if you tell me you want 50 lbs pedal press, max, I can back figure what bore you would need. the problem is the travel would go beyond what is available.
I haven't talked a lot about this setup as I don't have it completed and tested out yet.
It scrambles my brain!!!

--------BRAKE SYSTEM ANALYSIS---------
VEHICLE: Chevelle manual disc brakes
fpr 89.261899 lb foot pressure on pedal (lb) (100-125 l
6.25 l to 1 brake pedal linkage ratio (to 1)
1 bias percent bias bar setting percent (decimal)
fop 557.88687 lb force on master cyl piston (lb)
1 mdia " master cyl dia
2.9375 cdia " caliper piston dia
a .78539816 master cyl piston area (in sq)
p 710.32362 psi brake line pressure (psi)
1 n qty number of pistons per caliper
(double piston # for floating caliper)
ac 6.7771271 " caliper piston area (in sq)
calarea 6.7771271 " caliper total piston area (in sq)
fc 4813.9535 lb clamping force of brake pads (lb)
5.375 r " effective brake rotor radius
.4 c dec lining coefficient (typicaly .30 to .4
t 10350 in lb braking torque in inch lbs
12.5 rt " tire rolling radius (inches)
cvol .06777127 caliper vol displaced for .010" moveme
mct .08628906 " master cyl travel " for .010 movement.
ptr .53930664 " pedal travel for .010" pad travel (1 c
828 f1 lb braking force per wheel at tire patch

--TIRE TRACTION DUE TO LOAD TRANSFER--
dtwt 828 lb wheel skid wt/max braking G-one wheel.
tirlmt 735.45117 lb wheel skid wt/one wheel 0 G-static
.9 tcf lb tire coefficent/friction (usual 1.4)
tirwt 817.16797 lb weight on ONE tire, (static)

NOTE --- THESE CALCULATIONS ARE WRONG!
THEY ARE CORRECTED ON THE NEXT PAGE.
SORRY, DAVID

------------------
Check my web page for First Gen Camaro suspension info:
David's Motorsports page (http://ourworld.compuserve.com/homepages/David_Pozzi/)
First Gen Suspension Page (http://ourworld.compuserve.com/homepages/David_Pozzi/first_gen_suspension.htm)
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer



[This message has been edited by davidpozzi (edited 11-27-2001).]

BC,

Yes,I will keep all informed as to hopefully making our one-off caliper brackets for CBB conversions, front and rear for purchase.

My homemade front caliper bracket using my stuff will only allow a 5/16" thick steel plate.

The bent stock 1969 caliper bracket is only about 3/16" thick, but bent to allow some cold work strength increase.

Somebody mentioned using 3/8" plate with the (I think) C4 Vette stuff, so it fits.

And finally the bracket that I bought from A-A Mfg that I used as a pattern for the guide bolts and thoat area was 1/4" thick.

I hear we might catch some weather tonight and I am certainly not looking forward to it b/c we are always fairly damp in central MO which to me adds to the "bone chill" if you know what I mean. Later. pdq67

David, WOW! that is a pretty cool program, thanks for running the numbers. I can bet it would be some pretty serious calcs! One question comes to mind, do you know what the actual pedal travel distance is? I know that the smaller the bore, the less pedal pressure is required but the further the piston must travel. Obviously, the 1" bore was used quite a bit, but I was contemplating using the 15/16" bore of a 73 Malibu, but would I run out of pedal travel? Also, the specs I read on adjusting the rear calipers shows a 'relaxed' distance of .030 between the pad and rotor. This would mean that the piston must take up that .030" when depressed right? So is it correct to assume you would multiply the distance to travel .010" by 3 or 3.5 to find the actual pedal travel distance? Seems pretty excessive to have over 1.5" of ptr to move one side of one caliper .035"?? Does that make sense? I ask because with my 4wheel disks and the power Corvette MC, I get a pretty hard pedal that does not travle much, but I cannot lock the wheels on dry pavement?? Seems like with 4 wheel disks (12" fronts and 11" rears) that I should be able to plant all four wheels pretty easily. I'm thinking that since I only have 11" of vacuum, that is my problem? Does the factory use a bigger piston than 1.25" on factory 4 wheel cars?

I'm thinking the 4 wheel disk manual Corvette MC is the way I should go.

Sorry for so many more qusetions, but this stuff gets real interesting quickly!

pdq67,
please keep me posted, I'm looking at possibly doing some CBB stuff to my nova this winter. And speaking of, I hope this cold air gets to you soon, the high today was about 20degrees F, and tomorrow the high is only about 10 dgrees F.!!

Hopefully back to 50's by Friday, I hate this crap!

Bill C.

the brake rod throw for the drum master is about a 1/2 inch shorter that the 4 wheel disc master. I basically would get 100% rear brakes and maybe 25% fronts. lengthened the brake rod using the adjustmnet and problem fixed.

Some late model calipers like most rear discs, are low drag type calipers. They have more retraction of the caliper piston for less drag. I haven't been able to find a clearance for them.
I need to measure actual caliper piston movement to get a real number for the front caliper. I suspect it's .010 to .020" total as the pads ride right on the rotor usually.

The other travel factors are bending of brake linkages, swelling of hoses, flex of the caliper. At near lock up pressures these can have an effect on travel.
The larger rotors are keeping your pedal pressures and line pressures lower.
I've seen 1200 psi before at lockup.

With the power brakes the pedal ratio is much lower and the pedal travel (3.846" vs 6.25") much lower for a given pad movement. Also the master cyl bore is larger so that too reduces pedal travel.
You can see the pedal ratio is almost double for manual without the piston dia difference.

The manual brake setup is critical as to master cyl dia and travel. You will use up a bunch of travel to operate and effort will be about double that of power brakes.

Here's an idea.
You might try using a manual brake 1" MC to make up for your lack of vaccum. Pedal travel would be less than a manual brake, and pedal effort less.

An even better selection for power brakes is a third gen Camaro aluminum master cyl. It is 1" bore quick take up.
OR- I can probably dig up an application for a 15/16" bore aluminum MC that is the quick take up type and will still have low pedal travel compared to a 1" master cyl. It won't be useable for manual brakes because of the shallow hole in the rear piston, the pushrod for manual brakes would fall out of it.
You have to make sure you have the correct pushrod for the master cyl depth.

I'll try to run the 1" and 1 1/8" bores for power brake. I don't have the model set up for power boost factors, so can't model that.
David

------------------
Check my web page for First Gen Camaro suspension info:
David's Motorsports page (http://ourworld.compuserve.com/homepages/David_Pozzi/)
First Gen Suspension Page (http://ourworld.compuserve.com/homepages/David_Pozzi/first_gen_suspension.htm)
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer

Will do.

I will know by tomorrow morning, Brrrr!!! pdq67

legrand, I have several manual pushrods to play with so hopefully one will be close. Any idea of what length you ended up with?

David,
It sounds like the manual MC with 1" bore is the way to go. Do you think the line pressure will be back up to way it should be with that MC? I remember you once saying that the larger rotors and such will make pedal effort less, so possibly I could use a bigger bore MC to get less pedal travel? Would there be a noticable difference in using a 1 1/16" bore? I think going to 1 1/8" bore for a manual setup would be too hard. Do you know of any manual MCs with 1 1/16" bores? And I understand that most manual MCs use the long rod so it won't fall out correct?

pdq,
Stay warm!

Bill C.


[This message has been edited by BC (edited 11-27-2001).]

Well, sorry, I screwed up the numbers.
I had assumed your tires you have are 26" and looked them up and they are probably 27" according to a web chart.

I also left some parts of it mis configured with wrong numbers, like the rotor radius, and front end weight.
I had the "wrong" numbers left in from a previous car.

That all moved the brake pedal pressure way up.
I noticed earlier the line pressure was too low in the 700 range. That bugged me and I took another look at it and found the errors. the pedal pressures before were more in line with a stock weight Camaro.

Here are the new calcs and they don't look good for manual brakes on a car that heavy.

Assume 3900 lbs, 55% weight on front wheels, 2145 lbs on front end, 1072 lbs on ONE wheel.

Chevelle brake data, pedal force to lock a front wheel, assumes .9 tire traction coefficient which is a very sticky street tire.
108 lbs - 15/16" ptr - .61
123 lbs - 1" bore -ptr - .53
156 lbs - 1.125"bore ptr- .42
192 lbs - 1.250" bore ptr-.34
ptr is pedal travel to move one side of ONE caliper .010" (pedal travel did not change from before)

Here is the variable and calc chart.
--------BRAKE SYSTEM ANALYSIS---------
VEHICLE: Chevelle manual disc brakes
fpr 123.34669 lb foot pressure on pedal (lb) (100-125 l
6.25 l to 1 brake pedal linkage ratio (to 1)
1 bias percent bias bar setting percent (decimal)
fop 770.9168 lb force on master cyl piston (lb)
1 mdia " master cyl dia
2.9375 cdia " caliper piston dia
a .78539816 master cyl piston area (in sq)
p 981.56176 psi brake line pressure (psi)
1 n qty number of pistons, one side of caliper

ac 6.7771271 " caliper piston area (in sq)
calarea 6.7771271 " caliper total piston area (in sq)
fc 6652.1688 lb clamping force of brake pads (lb)
4.875 r " effective brake rotor radius
.4 c dec lining coefficient (typicaly .30 to .4
t 12971.729 in lb braking torque in inch lbs
13.5 rt " tire rolling radius (inches)
cvol .06777127 caliper vol displaced for .010" moveme
mct .08628906 " master cyl travel " for .010 movement.
ptr .53930664 " pedal travel for .010" pad travel (1 c
f1 960.86883 lb braking force per wheel at tire patch
The assumed tire coefficient of .9 is pretty high for those tires, so the lock point would likely come a bit lower and maybe lower the pedal pressure at lock up 10 or 20 lbs.

I did not allow for forward weight transfer to front wheels as I don't have the wheelbase or center of gravity height. It would add a couple of hundred pounds to the front weight total with half going to each front wheel.

Sorry about the mix up. If some items change a small amount it can change the pedal effort a bunch.

You need a deep hole master cyl for manual brake which is what a Corvette manual MC has.
The 15/16" bore will have a lot of travel unless you use a later aluminum quick take up type. But they have a shallow rear hole and can't be modified.
David

------------------
Check my web page for First Gen Camaro suspension info:
David's Motorsports page (http://ourworld.compuserve.com/homepages/David_Pozzi/)
First Gen Suspension Page (http://ourworld.compuserve.com/homepages/David_Pozzi/first_gen_suspension.htm)
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer



[This message has been edited by davidpozzi (edited 11-27-2001).]

Thanks for the update David, that is quite a difference. I didn't think the first go round sounded right, but you being the brains and all I wasn't going to question it!

Looks like the Corvette MC with 1" bore will be it, I don't think it will be too hard.

Bill C.

I've talked to guys with Camaros that have manual discs, some say it's fine, some say it's way too hard.
With your extra weight and somewhat tall tires, I'd say it's going to be a hard pedal to push.
Be sure to use good high friction "premium" brake pads like Performance friction carbon metallic.
Some of the newer type pads have a higher coefficient of friction which will help.
Brake pads are edge coded typically FF.
The first F rates the friction when pads are cold, the second F rates the hot coefficient.
FF is very common. and designated .35 to .45 friction coefficient.

G is .45 to .55 which would be great.
H is over.55, I doubt you will find pads with this much friction rating.
Don't use pads with an E on them, they are .25 to .35. I doubt you could even find a pad that "hard" anyway.
David

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Check my web page for First Gen Camaro suspension info:
David's Motorsports page (http://ourworld.compuserve.com/homepages/David_Pozzi/)
First Gen Suspension Page (http://ourworld.compuserve.com/homepages/David_Pozzi/first_gen_suspension.htm)
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer

David, thanks for the explanation on pads, that's real handy! I was considering some of the BruteStop pads several people have recommended, but I have a hard time getting info from the parts guys at any local stores. They all just look at you like "Huh?" when you ask about coefficients of friction or ratings or anything. Do you know of any good sources for that kind of info?

Also, have you ever had experience with these guys' products? http://www.carbotecheng.com/prod-ct-compounds.htm

They come highly recommended, but I'm a little afraid to see what the price tag might be! Also, the local Checker Auto here said they could get a ceramic type pad that was even more expensive than the Brutestops, would you recommend the ceramics? I've heard they stop better, handle more heat, and don't wear rotors as fast as semi-metalics, so it seems like they are good all around.

Thanks again,
Bill C.

PS. I ordered the Corvette MC today, so maybe I'll get it on this weekend and let you know how it works.