4 wheel manual disc brakes?

[BRIAN]

Just remember that OEM single piston calipers will need more pressure at the pedal than say wilwood 4 pistons.

There is a great 5 page write up ON HOTRODHEAVEN.COM

Either way just make sure you ge the right sized master it is the key to the whole set up.

[GregWeld]

Several -- in fact -- MANY factors to consider crucial to proper braking - regardless of the power vs manual question. Consider this - how many RACE CARS have power brakes? Almost NONE.

There are several guys on this board that REALLLLLLLLY know about all this stuff... But I'll give you just SOME things to keep in mind. From there - it's up to you to educate yourself on what you need/want.

The key to all of this is to have the proper size of EVERYTHING in the system - because brakes are like the Cam and Head combo - one without the proper other - is a dog...

There's more to it than just the Master cylinder... and the rule of thumb here is the larger the mc bore - the LESS pressure it will make... the smaller the bore - the More pressure they make. A 1 1/8" bore will make about HALF the pressure of a 7/8" bore.

Pedal ratio is critical - 6 to 1 minimum on a MANUAL system. Most P/B systems use 4 to 1. Think about this -- 100 #s of "effort" on a 4 to 1 makes 400 #'s of effort -- vs the 6 to 1 ratio which makes 600 #'s... and DISC BRAKES are all about PRESSURE (there's a volume issue too - but now we're getting technical).

Brake lines - Disc brakes use 3/16" lines -- Drums use 1/4". If you want to make pressure at the master cylinder - and have this pressure all the way to the actual brake - you need the smaller diameter lines... if you go DISC brakes - change the lines if you need to. Why waste all the money and effort on fancy brakes and MC's only to have it not work correctly. Think about headers - fancy cam - fancy heads - poopie little header size is the choke point. (okay - lets not go there with the small pipe torque argument - this is just a basic discussion...LOL)

Brake Bias/Proportioning valve - You want the FRONTS to lock up BEFORE the rears... many factors here - tire size - brake size front vs rear etc... so not every system needs a proportioning valve... if you have huge rear tires and smaller fronts, the tires themselves might set your bias... but - big butt - It's one of those "better to have it, and not need it, than to need it, and not have it" parts. IMHO. The COMBO valves are for factory set up - engineered for a particular tire size and brake size and car weight etc - so an ADJUSTABLE version is what you need. It goes to the REAR brakes - in order to REDUCE the pressure to them - to get the fronts to lock BEFORE the rears. You lock the rears first - you spend a lot of time driving backwards.

Master cylinder BENCH BLEEDING - Skip this part at your own peril. Many "skippers" try to do this after the cylinder is mounted on the car... or don't do it at all. They're dumb and lazy and deserve the hassle they just set themselves up for. There's lots of instructions available for this - but take my word for it - you leave some little itsy bitsy air bubble in the MC - IT WILL reduce the pressure you can make and it WILL poke it's ugly head up just before you hit that tree.

Residual valves - Typically there should be a 10# residual valve (think "check valve") to the rears IF you're running DRUMS (in the rear)... This will "hold" the shoes "at the ready" and not let the wheel cylinder collapse all the way back... Different system -- IF the MC is mounted LOWER than the brake system - you need to run a residual valve to both front and rears. In this case 2# valves for disc system... and the 10# for a drum system - you need these in BOTH lines -- one to the fronts and one to the rear depending on the size examples as given.

Do some research and some reading... don't rely on what your friends "think" you should do... this is too important. The manufacturers have good techs that will help you work towards a solution. Kore3 - Baer - Wilwood - Brembo... all good people that are interested in setting you up with a great braking system.

[Apogee]

Originally Posted by BRIAN

Just remember that OEM single piston calipers will need more pressure at the pedal than say wilwood 4 pistons.

There is a great 5 page write up ON HOTRODHEAVEN.COM

Either way just make sure you ge the right sized master it is the key to the whole set up.

Buyer beware...we've had several customer purchase master cylinders from H-R-H and they have always supplied oversized master cylinders for late-model, C5/C6 big-brake conversions.

You can't say that an OEM single-piston caliper will need more pressure than a 4-piston Wilwood without stating what the piston diameters/areas are for each specific caliper. There are several piston sizes for the OEM cast iron calipers, however they are 2-15/16" diameter for the '69 Camaro application and most other early muscle cars. That piston diameter equates to a 6.77 sq inch piston area and is typically matched with a 1-1/8" bore MC in a boosted application and 1" bore MC in a manual application. Don't assume that all vacuum boosters are equivalent...just because a single 7" diaphragm booster will fit does not mean that it will do the job required.

A C5/C6 2-piston caliper has double the pistons (40.5mm) and not even 2/3 of the overall piston area at 4.00 sq inches. The Wilwood Superlite 6-piston calipers are very similar at 4.04 sq inches. We would run a 15/16" to 1" bore MC in a boosted application and a 7/8" to 15/16" bore MC in a manual application assuming a matched rear disc application. Just for reference, the 4-piston SL calipers range from 2.22 to 5.18 sq inches with all of the various piston sizes and staggers.

Based on the areas stated above, the single piston caliper will need less pressure and more volume than any of the "big-brake" options, and this is true for the majority of the aftermarket big-brake kits on the market today. CPP's kits may be the exception that proves the rule since they use big truck calipers with their kits specifically so that their customers can retain their facotry MC/booster arrangements to save on cost.

"BIG-BRAKES" does not mean big caliper pistons. The rotor is what takes the heat and abuse, so bigger rotors (and pads to a certain extent) are what allow you to brake harder and longer. While smaller caliper pistons reduce the effective brake torque of the system, they give better driver feedback and are more responsive making threshold and trail braking that much easier. Assuming the brakes can achieve lockup with reasonable levels of pedal effort, any brake torque in excess of that is unusable. Once the tires are at their limits, you're done...I don't care how big or small your brakes are.

Tobin
KORE3

[GregWeld]

Good response Tobin -- Thanks for jumping in there and adding your masterful thoughts!

I'm not "technical" enough and didn't want to get into the whole "volume" discussion... figured he'd get that info if he starts researching... I wanted to toss in "food to think about"... and you've done a great job (as usual) in discussing the various systems.

Funny -- Back in high school - everybody wanted to run a 750 Holley on their 283's - cause that's what all the big boys were running.... But when you're in high school you're too lame to really LEARN and RESEARCH what carb you SHOULD have had.... and WE (including myself here) NEVER checked our brakes... it was only a "hurst shifter" and big carb story. NOW, of course, we should be a bit better at these things.... yet the most misunderstood parts of the "hobby" that I encounter almost daily -- BRAKES... and the same guys are making the same mistakes... and there's really quite a bit to learn about this subject. Yet - the "basics" are just that... pretty basic. What I see the most - is the "lipstick on a pig" cover ups... i.e., "My brakes suck" -- so I'll put on a double whammy big doowhop chrome booster... and when that fails... they learn to live with it.

Can't tell you how many "conversions" I've seen where the master cylinder is hooked up backwards... because NOT ALL MC's go front reservoir to front brakes... Or that they're using 1 1/18" MC on all disc system and still have 4:1 pedal ratio... and so on blah blah blah. I do more HOT RODDING than PT shows etc -- and it's really really rampant in the HR scene.... PT folks seem to be a lot more interested in "the facts". Thanks for being here and helping us all!

[Northeast Rod Run]

Originally Posted by GregWeld

Good response Tobin -- Thanks for jumping in there and adding your masterful thoughts!

I'm not "technical" enough and didn't want to get into the whole "volume" discussion... figured he'd get that info if he starts researching... I wanted to toss in "food to think about"... and you've done a great job (as usual) in discussing the various systems.

you've given me plenty more to think about, than I thought I ever would, but that's exactly why I figured I'd ask first. I hate doing something wrong, just because it was "easier" to do it another way, and I was too ignorant to listen to other's advice.

seriously though, I would have never given that much thought into going from stock power disc/drum, to manual disc/disc. I just figured a simple master and adjustable proportioning valve change would do it. all this info overload almost makes me think I want to stay with my current set-up, but I guess I have all winter to research more details before I finally make up my mind

thanks

[GregWeld]

That my friend.... is why we're all here! This is a community... with all the support systems you've ever wanted... and some you probably don't...

Seriously though --- we might have made it info overload for you - but that's why you can just keep posting questions here until you've got it all figured out.

It's all pretty simple really - and like most things - only seems complicated until you "do it" or learn about it...

And by the way -- you don't have to do $12,000 carbon fiber brakes to have "decent" braking - and you don't have to do Wilwood or Baer to be a part of Many of our cars have a real nice set of GM discs up front and they will throw you thru the front window when you hammer 'em...

[GregWeld]

One last thought -- because I just re-read your original post.

Your vacuum is low because of your cam profile... thus you probably have a "hard pedal" and feel like the effort it takes to apply the brakes isn't translating into stopping power?

So -- have you thought about installing a vacuum pump and resevoir... to help with your low vacuum condition? Are you aware of this kind of thing for your brakes? Something simple like this might be all you're looking for - and would make a world of difference.

[Northeast Rod Run]

Originally Posted by GregWeld

One last thought -- because I just re-read your original post.

Your vacuum is low because of your cam profile... thus you probably have a "hard pedal" and feel like the effort it takes to apply the brakes isn't translating into stopping power?

my pedal isn't a "hard pedal". I can't really explain it, but I guess I would say that it has always had a "dead spot" where you can feel the vacuum is missing and you have to wait for it to come back. I did install a canister when I built the car 10 years ago, because I used to have a highrise and dual quads and it really sucked then. the entire brake system was brand new stock. the car still has under 10k since it was built

back when I originally put the car together, there wasn't much aftermarket support, I didn't know anything, and I didn't have much money. now the aftermarket is great, I know enough to get myself in trouble, and I have a little bit of play money, so I think it's time to do some small upgrades, and rims, tires, brakes, and overdrive (I'm currently only getting about 8MPG on the highway) are at the top of the list

[BRIAN]

Kore...I was referring to a GM style single piston vs any say 4 piston,6piston etc type caliper. I may be wording this wrong but what I am getting at is there has to be some pressure required to actuate a single piston cyl before pressure is applied to the rotor? I am not talking cyl sizes. If you were to take two equal sized volume single vs multi piston calipers would there be a difference?

Theory is great but I have swapped wilwood 4 pistons onto a car that had GM singles and there was a difference. Was it piston bore size? Maybe?

Not arguing just looking for good info.

Thanks

[Northeast Rod Run]

thanks for the compliments

I forget what I am pulling for vacuum. I used to have a working gauge on my canister but the car rattled it apart. 17" of vacuum? I don't think I pull 10" (that didn't sound right did it?).

all I can remember, is that after I originally put most of the engine together back when, I was looking to go the fuel injection route but I learned something then. they told me that I would be pulling nowhere enough vacuum to run fuel injection on the car, so that's when I said "screw it" and went with dual quads at the time. if you can't join 'em... beat 'em, or maybe it's supposed to be the other way around...hahahaa

I do get one "ok" hard stop and then probably one "not so good" stop after before I'm empty. I definitely want to go manual for the more constant safety factor, and the coolness of a cleaner looking set-up.