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As I dive deeper into the specifics of disc brake system design, and what kind of line pressure and clamping force you're looking to build at each caliper for a "performance car" on modern tires, its becoming readily apparent that the 4.54:1 pedal ratio (manual hole) is painfully inadequate for a good manual brake system.
I'd be interested to hear from anyone running manual disc brakes as to what your set up includes as far as master cylinder bore, disc size, and caliper type/piston area. Also what kind of pedal effort/feel you have
I am running the factory non power disc brakes on my 65 coupe. It has a single chamber master cylinder. The pedal pressure is mot excessive. It stops well from any speed. the car does not need power brakes. I also have DOT 5 silicone fluid in the system.
I am running the factory non power disc brakes on my 65 coupe. It has a single chamber master cylinder. The pedal pressure is mot excessive. It stops well from any speed. the car does not need power brakes. I also have DOT 5 silicone fluid in the system.
Same here and I agree with all of it.
However, some have never driven a car without PB and think there is a design flaw in a manual brake system. But there isn't.
I can only comment on the OEM disc brakes. I owned a '65 & '68 equipped with manual brakes that (I felt at the time), required noticeably more force than manual drum brakes. I now drive a '67 with the stock power disc brakes and it is a completely different animal. Much better brake feel - comparable to a "modern car"! If I ever buy another C2 it will definitely be equipped with power brakes.
I had a bud whose not a "car guy" pump the brakes so I could bleed them and he kept telling me the pedal was low. I finally got in and checked it myself, and it was perfect.
Seems he forgot how a manual pedal feels.
Car stops great and no PB needed. Bonus is that the low pedal makes heel-toe downshifting easier.
Last edited by 65tripleblack; 05-24-2017 at 08:44 AM.
I have manual brakes on my 67. I went through every inch of the system when I bought the car (as I do on every vintage car I buy). I've always found the factory disc setup to be one of the most advanced features of a 65-67. For years I also had a C5 and 2 C6's, and even when driving them in the same day I always felt the factory brakes on the 66 and 67's were more than adequate.
I'm sure there are some good aftermarket kits with more modern components, but there is only one disc system that was designed by Chevrolet for a mid year. I trust the men who originally engineered these parts more than any aftermarket supplier. I've been hunting a 63 and I plan to convert my acquisition to factory-type 67 brake system as a first order of business.
What was considered acceptable pedal pressure for brake operation in the 60s was greater than it is now. They will attain 1G stops but you have to tromp down hard on the pedal. I find they work well in conjunction with manual steering and transmission. I look at a drive in my car as being a bit of a lower and upper body work out.
As I dive deeper into the specifics of disc brake system design, and what kind of line pressure and clamping force you're looking to build at each caliper for a "performance car" on modern tires, its becoming readily apparent that the 4.54:1 pedal ratio (manual hole) is painfully inadequate for a good manual brake system.
This doesn't match my experience at all.
My bride's track car runs manual four wheel discs and stops very well without requiring unusual pedal effort. It uses the stock C2 pedal assembly and therefore stock C2 pedal ratio.
Consider the overall leverage ratio which includes not just the pedal arm ratio but also the ratio of wheel cylinder piston area to master cylinder piston area. Too, the radial location of the caliper and the friction coefficient of the pad material affect the pedal effort.
When I was designing the brake system for our track cars, I put together a spreadsheet so I could tweak individual parameters until the numbers made sense. If you aren't using a spreadsheet in the design of your brake system, you should consider doing so. Set your design goals.... maximum pedal effort, overall deceleration at that effort.... then massage the parameters over which you have control until you meet your goals.
R66 has factory manual discs that are fantastic as I feel I have more control over the braking than with power brakes. Pedal pressure is not excessive and the car stops very well. Keep in mind that I am use to older brake systems. I never liked the older power brake systems as they seemed touchy to me even though you can get use to them.
Our 68RS, on the other hand, has manual drum brakes. You have to drive the car with more caution as panic stops can be very exhilarating. With proper maintenance, still stops straight and will lock them up, but with a lot more pedal pressure.
I actually prefer the stock, manual discs, to the factory power system. I've always thought that the pedal "feel" was much better, with the stock manual brakes. Pedal feel for the power system seems numb to me, and lacks feedback.
We're required to use stock D-8 calipers, on the Corvette vintage racers I crew on. We've never used a booster on any of them. We get a better, and more consistent pedal, without power assist. We're always dealing with heat induced fade, and it's easier to deal with and compensate for, without the power assist.
I'd be a little careful about using DOT 5 in rebuilt, sleeved calipers. The following labels are coming on all Lonestar Caliper boxes now. Chemicals in the DOT 5 fluid, are causing premature seal failure. Since Lonestar does calipers for other Corvette brake companies, as well as many of the national parts chains, this may be an issue even if you didn't buy Lonestar branded calipers.
A rather confusing warning, "Using DOT Brake Fluid 'Will Void Warranty.'" Isn't all brake fluid "DOT" rated, whether it is DOT 3, DOT 4, DOT 5 or DOT 5.1? It appears that Lonestar could use another copywriter for their label.
'65 factory non-powered 4 wheel discs. Before getting her on the road (back in '99), all new steel lines and had the original calipers rebuilt with stainless steel sleeves. Added the '67 style dual reservoir, filling the lines with DOT 5 silicone. Haven't touched it since, tripping everywhere. Good, solid pedal pressure, stops straight and I can lock 'em up in a panic stop.
For more than 5 years, I regularly pulled her down from 1/4 mile runs from over 100 mph with no darting, she just slowed her down quickly. 'Suppose since I have no reference to a power assisted set up on these, I am blissful ignorant of an improvement/feel ��
My experience.
05-24-2017, 07:25 AM
Anyone running manual disc brakes?
My '65 has stock manual brakes that work very well. No complaints.
