Technical Changing pedal ratio vs. adding power brakes? 61 Vette

Hi, my wife has a bad right knee due to an old injury, and it's hard for her to apply a lot of pressure on the brake pedal. The 61 Corvette is mostly stock with manual 4 wheel drums. Her left foot is busy with the clutch, and she doesn't want a slippy, sloppy, stinky fluid coupling.
I could install a power brake booster, but that has its drawbacks.

What about altering the pedal ratio? Could that make enough difference? Has anybody tried it?

Thanks, Joel

 

Have you considered upgrading to disk bakes on the front ?
I need a lot less pedal pressure to stop on my 57 after going to a basic GM caliper and disk set up that was pretty cheap . Then you get much much better more predictable braking and modern bearings VS the old roller( edit ball) bearings .
Only down side was I gained a 1/2 of track width on each side but here are kits that do not do that now .

 

No, this car is an all original survivor. So no major mods like disc brakes are on the agenda.

 

No help here, but I'll be interested in any replies...

It's doable, but the cost is increased pedal travel. Will you have enough?

 

Didn’t Jim @squirrel do only a Wilwood disc swap yet still retained the stock master and brake lines?

 

You mean old BALL bearings , right

 

yeah, I put wilwoods all around my 62, but kept the stock MC (removed the RPV from it).

I doubt that it has less pedal effort now, though.

Smaller bore MC or larger bore WCs would do it. Drilling a new hole further up for the pushrod might or might not work, since the pushrod would be at an angle?

No easy answer to getting old and having health issues, unfortunately.

 

Shoe compound makes a difference regarding pedal effort , glazed brake drums do as well .

 

That’s exactly what I hoped the answer would lead to.

 

Correct

 

I also kept the stock master cylinder and all the original steel lines . I kept all the original parts in a tote marked Corvette shit in case when I'm dead and gone the new owner decides he doesn't want to stop as well again .
I just did the GM rotors with a bearing adapter and single piston GM rotor all off the shelf stuff . I figured if ti stops a 70's Camero OK its a huge up grade over the gen 1 / 49 chevy stuff . I understand the OPs reasoning for not wanting to change it . That siad my car is 100% reversable and honestly id have not allowed my wife to have driven it the way the brakes were . .Cold they were unpredictable thee first time applied and more than once it almost caused me to crash . I tried different shoes and drums and it was better but never great . If he is OK with a non stock brake booster I'm sure it will work as there are kits to do it .

I have Wilwoods on my Model A Pu and there really nice more brake than the tires can handle and over kill unless I was road racing a 1928 PU LOL . The weight reduction is a good thing

 

As mentioned, softer brake block might be an answer....or just a bunch of new/like brake components on the existing set up.
I was surprised how much better (with less brake pedal pressure) my drum/drum Roadster stopped after I did a break refresh on it.
There were two pistons, one each on two different wheel positions, that were gummed up with whatever that combination of aluminum against iron is, with a little bit of brake fluid added in. I am always amazed how I can be faked out by thinking past the basics first....

 

Thanks for all the reply's. When I drive the car, I have no issue with the adequacy of the manual drum brakes. It's a light car, we live in the plains, not the mountains, and she is not an aggressive driver. So there is really no motivation to dump the drums. The only issue is the pedal effort for her. I actually bought a Masterpower brake booster that comes with it's own dual master cylinder that I expect would solve the pedal effort problem, but upon looking at the installation instructions, I don't really want to install it if there is an alternative. Separating the front and rear brake lines will be more complex and require more alteration than I anticipated, and there is no vacuum port in the intake manifold, and no room for a spacer under the carb. So I'd have to drill and tap the manifold. Do I dare do that on the engine, or pull the intake? It's doable, but I'm not looking to get into a major project if I don't have to. Too many irons in the fire right now.
I don't think she would mind longer pedal travel if the pedal effort lightened up. I wonder if there is an off the shelf 3 bolt single master cylinder with a smaller bore that I could try?

 

Like some have said, I think I'll start with sanding/deglazing the drums and new shoes. Maybe that will be enough.

 

If this car still has the original single circuit. simply add a remote PBR VH44 brake booster.
These go inline [and can be mounted anywhere you are prepared to plumb to]

The VH44 is designed for 4 wheel drum vehicles.



You could also [if you don't want add a booster] put a smaller diameter tandem M/C
This has the same effect as altering the pedal ratio, and result in more pedal travel.
But if you do this, look for a small diameter quick uptake [aka stepped bore] M/C

I did this with my Lotus Cortina , I used a 3/4" M/C to increase clamping pressure but the initial pedal travel was unnerving .
Then I found an early Mercedes Benz M/C that was 19mm [3/4"] AND stepped bore. This gave me high pedal and good clamping pressures

 

The stock 1938 Chevy pedal ratio in my car was more suited for power brakes, oddly enough. It would stop but needed considerable pedal effort. We often joked that’s why the steering wheel had a dish in it, from all the leverage needed to stop.

I had enough with all that so I fixed the pedal ratio to be suited for manual brakes, then called Wilwood and got a recommendation for a MC bore size… wow, the brakes are amazing now. Less leg effort, more pedal swing. Wish I would have fixed that years ago.

 

A friend had a 37 Buick street rod with 4 wheel drum brakes. It never stopped great, so he put on a disc brake kit on the front. Now it would barely stop at all. No one could figure out why. I finally crawled under the dash and measured the pedal ratio. It was 3 to one. Drilled a new hole 1" above the old hole in the pedal arm. The rod from the pedal had a .5 offset built in to it. I just flipped it over so it lined up with the new hole. Now the pedal ratio is 5 to one. The brakes will now put you through the windshield if you slam them on. So if you can get an offset push rod from the pedal to the master cylinder and move the pivot point to change the pedal ratio, it can make a world of difference.

 

Chevy changed the brakes in 1951, from Huck, to Bendix type. The "modern" brakes are pretty good.

Did you know that when Chevy started putting disc brakes on all Camaros in 1970, they also made the power booster be standard equipment? Because it takes more pedal effort to stop with discs.

 

I can say with all certainty that it stops better and easier now with a stock master cylinder and the dish brakes i have than it ever did before with multiple sets of shoes and drums I tried. Pedal travel is about the same with How I have it now .

Pretty sure manual disk brakes were standard on the gen 2 Camero until 76 and the pedal ratios were different as well . Pedal ratio is 5.36:1 (manual) and 3.52:1 (power)

 

The brakes are a Bendix system so to upsize the wheel cylinder diameter "should" be relatively easy. Bendix wheel cylinders are usually available in a wide variety of diameters but also check their fitment dimensions variations etc.
ROCKAUTO is showing 1" as the standard front and rear diameter and 1-1/8" as the heavy duty front version ..... going to the 1-1/8" cylinder is a +26.5% surface area (and force) increase ..... I've seen Ford use >1-3/8" cylinders.
Suggest that you take the original front cylinder to your parts supplier and do some comparison measuring ..... mounting detail + C/L offset + hose thread size + diameters + LH & RH versions ...... also check the Ford variants.
https://www.rockauto.com/en/catalog...1325449,brake+&+wheel+hub,wheel+cylinder,1952
https://www.rockauto.com/en/catalog...1492350,brake+&+wheel+hub,wheel+cylinder,1952
Good luck ..... please keep us updated.

 

I have a GM single master cylinder with three bolt mounting flange that I would donate to this project, if you want to find someone to reduce the bore from 1 inch tp 7/8 inch.

 

That inch and 1/8 wheel cylinder swap sounds like a cheap and easy fix that might work pretty good. Thank you

 

I appreciate the offer on the master cylinder donation! I could do the bore reduction on the master cylinder, but I'm unsure how difficult it would be to find a 7/8 piston that was compatible in all of the other ways. I did look bit online and didn't see a 3-bolt 7/8 master cylinder.

 

Wheel cylinder swap from 1" to 1 1/8" sounds easy and inexpensive. It's definitely worth a try.

 

Please take note that the Corvette 1" cylinders have 3/8" hose connection and the 1-1/8" Corvette ones have a 7/16" thread diameter.
The 1-1/8" Ford F250 ones have the 3/8" hose thread but you'd need to check their fitment dimensions compared to your Corvette ones.

 

I would change the master cylinder first before doing wheel cylinders. A good 3/4 or 7/8" bore master can make a huge difference in how the brakes feel.

 

The brake pedal assemble on the 62 vette is very much like the tri 5 Chevys. Some of the tri 5 brake kits had us drill a new hole in the brake pedal arm.

 

How much trouble would it be to make a 3 to 2 bolt adapter; and a longer pushrod. kinda like ones that bolt up to early Ford pedal assy's.

Might make finding a master cylinder easier.