Hot Rods Easy Pedal Effort with Non-Power Brakes?

I'm putting together a 1200-1500 pound track-nosed roadster, and I'd love to use 4-wheel disc brakes--preferably manual, unboosted, to go along with the manual-shift, non-power-steering steering, non-power-windows, no-LED halo lights, and definitely no-engine-cover theme…weight, you know. LEDs are so very heavy.


Years ago, I drove lightweight sports cars with manual front disc brakes, no problem; years before, my knees permitted this. Now, I’d not so sure.

But before I opt for servo-assist, I’d like to explore a dual, i.e., two separate master cylinders braking system as opposed to a tandem, two cylinders in one, master cylinder system.

I read an--advertisement? bench race?—(on eBay, no less) years ago from a fella writing that he “…could make a ’32 roadster using manual dual MCs as easy to brake as power-assisted…”

Is the manual-braking two-MC system easy pedal effort doable?

Or can I accomplish a relatively easy pedal effort with a mainstream non-boosted tandem system?

Eddie

 

I think it depends on the pedal ratio. Something around 5:1 is for power assisted only, 6 or 7:1 works well without booster. If you want it really effortless you could maybe even go to 7,5:1 but you would have a very long pedal travel. If you are limited in pedal travel on your application you can also play with master cyl bore size. Bigger diameter means harder pedal / less travel, smaller bore equals a softer pedal and more travel.

 

On a car that light you could easily run non-power hydraulic drum brakes at all four corners and enjoy good stopping with plenty of "feel" from the peddle. Self energizing drums would make all the better.
-Dave

 

Pedal ratio is only one factor in achieving your goal. There is also the ratio of master cylinder bore to wheel cylinder/caliper diameter. It is not that difficult to achieve. In either case, i.e., pedal ratio or bore sizes, some degree of trade off occurs in pedal travel vs line pressure generated. Even so, it should be well within norms of acceptable pedal travel.

Personally, with a street application, I would utilize a single tandem master for simplicity's (weight ?) sake. The advantage of dual master cylinders is they can be setup to offer easily/quickly adjusted 'bias' as might be desirable in varying race circumstances such as track conditions and/or tire size/tread characteristics.

 

Should be a cinch with such a light car. Others have already pointed out the advantage of leverage in the pedal and a small diameter master cylinder. 2 master cylinders or tandem cylinders are unnecessary and will make it harder to get the result you want.

 

I have a Wilwood dual master set up on my 40 Coupe. I am an old dirt track racer so I was familiar with them and used the firewall mounted, master forward hanging pedal set up. It works great but it actually requires a good bit of pedal effort. I have the 6.25 ratio pedals, they have 7 to 1 ratio also. I have 3/4 masters on both you should be able to tailor the pedal effort with the ratios and bore sizes to an extent but they have several brake clutch pedal set ups with tandem masters available in several different bore sizes.

 

Look at a Corvette Non Power master from 67-76. They are 4 wheel disk and had 4 piston calipers.

 

I run dual MC on an off topic race car that weighs less than 1600 lbs. Racers do use the dual master cylinders to adjust brake bias but once the bias is set up they seldom change it unless they are changing other things that affect braking. More important to racers is safety. If, for example, the MC for the front brakes fails you still have brakes in the back (one MC runs the front brakes and one MC runs the back brakes). You might also consider running drums in the back and disc in the front. As others have said, you can fiddle with the pedal ratio and the MC bore size. You can also fiddle with the wheel cylinder or caliper size as these also have an affect.

 

If you want to get it right the first time, do this...Know your piston size on your calipers and your brake pedal ratio and call wilwood tech. line, they will tell you what size of MC to run and if your brake pedal ratio is right for you
good luck.

 

The pedal motion ratio on early FORD frame mounted pedals just guessing must be 9 or 10" to one. I adapted a duel reservoir master cylinder and GM single piston front calipers onto the 46 pickup in my avatar and it stops excellently with minimal pedal pressure.

 

This is really simple thing to do. I run GM "metric" calipers on the front of my coupester (see avitar photo) and "early" pre-'78 GM calipers on the rear with a generic aftermarket single pedal brake assembly designed for use with the popular "Mustang" style master cylinder. Pete & Jake's offers a 7/8" bore Mustang-style master cylinder with no internal residual pressure valve PN 1118-7/8 that is perfect for this application. I use 2# residual pressure valves in both front and rear lines with an inexpensive Wilwood adjustable proportioning valve in the rear line. Great brakes with very low pedal effort. I have several thousand miles on my car with this setup and it is as close to perfect as it gets.

 

Call master power brakes in North Carolina and talk to them they can help you

 

Gentlemen, thank you all! Pretty much (ahem) put the brakes on doing the two-master-cylinder setup (sorry).

Quoting Fred Kuhn's Brake Handbook (ISBN 0-89586-232-8, 1985), regarding balance bars:
"A balance bar is used to adjust the brake balance for one value of tire grip. It does not (italics mine) compensate for changing road conditions the way a proportioning valve does. For this reason, balance bars usually are not used on road cars."

Along with your comments and guidance (above), my feeling is that I'd probably be as well off with the usual manual tandem M/C matched to the caliper pistons' size with a decent pedal ratio; all carefully matched to each other.
Edward

 

This^^^^

I was a going to say that sizing the masters properly is a big part of the battle and proper peddle ratio. My legs are bad (as in almost ready for braces again) bad and I prefer manual brakes. I take a lot of time and cash outlay making sure that I use the proper master and peddle ratio.

 

How does the balance bar react and push the good side if there is a failure on other side? Is it's pivot limited so as to still permit adequate stroke?

 

Looking at Fred Puhn's (quote source info above) book again, it looks to me (with no experience w/double M/Cs and a balance bar) as though one M/C is circuited to the front brakes, and the other M/C is circuited to the rear brakes; the balance bar itself adjusts r/l providing f/r bias. See how I did that? Yeah, I wear glasses.

Thanks for all your input; I went through all the hydraulic calculations and reread everything written above and...Well, anyway, I gave on the untried, unknown, expensive, complicated, INEXPERIENCED double M/C idea up (sniff)--and decided on power brakes. I just don't think brakes are something I need to be fooling around with. New underfloor power brake setups are basically a commodity anymore, anyway.

STILL--NO freakin' engine cover!

Eddie