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-   -   Low Brake Pedal (http://www.hotrodders.com/forum/low-brake-pedal-29299.html)

Bill Ford 12-03-2003 09:28 AM

Low Brake Pedal
 
Building a '33 Ford street rod - have Chevy metric calipers on front and Cadillac E-brake calipers on rear. Using a manual Corvette disc/disc MC. Unable to get a high pedal, currently have hard and relatively good brakes with about 3 1/2 - 4" stroke. But that puts the pedal uncomfortably close to the floor (about 2" from floor). Pedal ratio is about 6:1.

Does anyone have knowledge or experience using a "quick take up" (step bore) MC such as from a manual '88 Chevy S-10? From what I read this MC provides an inital slug of fluid at low pressure from a 1 1/8" piston to "take up the slack" and then the 24mm (15/16") pistons take over to provide the braking presssure.

What do you think? Any other ideas?

astroracer 12-03-2003 09:41 AM

Porportioning Valves?

Bill Ford 12-07-2003 11:41 AM

Yes, I have an adjustable proportioning valve in the rear lines but it is currently wide open. I'm not concerned at this point with rear brake lock-up. I just am trying to solve the low pedal problem.

astroracer 12-07-2003 05:50 PM

Residual valves?

S10Fan 12-07-2003 07:15 PM

I have a 1987 S-10 with the same brake setup as yours. The S-10 MC wouldn’t work for me. I’m currently working with a MC from a 94 Blazer (1 1/8 bore). My pedal came up some but not enough. The truck stops really well but I can’t handle the low pedal. So far I’ve used 2 quarts of Dot 3 bleeding the brakes with no difference. I plan to bypass the prop valve next weekend and see what happens. The Blazer MC is a reman, I guess it could be a bad one. The Pontiac Fiero crowd uses the Blazer MC works really well for those cars (4 wheel disk).

jimmyd 12-07-2003 07:45 PM

There is a rod that is between the booster and the master cylinder, if all else is okay with your system. Stops everytime, no leakage, etc, try adjusting this rod. Make it longer, a little at a time, too much and she will lock up on you going down the road , as it gets hotter, the fluild expands, applying the brakes.

You can actually hear this rod hitting the mc if it is real quite. There should be a fraction of an inch clearence. I'd say an eigth of an inch or less clearance.

Try that.

Jimmy in nc

Bill Ford 12-08-2003 12:45 PM

Thanks for the replies everybody.

Astroracer: I have 2 lb residual valves fore and aft of the MC.

Jimmyd: I am using a 1" Corvette manual MC with less than 1/8" clearance on push rod.

S10Fan: could you expand on the problems you had with the '88 S-10 MC? Does the 1 1/8" Blazer MC require a lot of foot pressure?

My thought was to go smaller in MC primary/secondary bore to put out more line pressure with same foot pressure.

I'm beginning to wonder if I have the "reduced drag" style calipers on the front. Does anyone know how to tell without taking the caliper apart?

S10Fan 12-09-2003 04:35 AM

The stock S-10 MC was very spongy and went pretty much to the floor. The Blazer MC “feels” a lot better but I still have a low pedal problem. I emailed the MC rebuilder prior to buying the Blazer unit any they agreed the Blazer unit would be a better choice due to it having a larger bore size. On the other hand, several guys on a S-10 forum (95 and up S-10’s) have converted using late model Camaro/Firbird rear disk with no problems using the stock MC. The problem with mine may very well be something other than the MC, I just haven’t found it yet.

BTW, if any of you guys are rotor experts, I need a little help.

I’m using 77 Caddy brackets and calipers for my setup. The 80 Eldo brackets, calipers and rotors wouldn’t line up the rotor properly. The Eldo rotors fit the 77 Caddy stuff perfect except for the rotor diameter. The 77 was 11 inches, the Eldo is 10.5 inches. I’d really like to find a rotor that matches the Eldo 10.5 exactly but with an 11-inch diameter. I emailed Bendix and they refused to help (too many lawyers). I’ve been through the rotors at my local Advance to a point where they lock the door when I pull up! LOL!!

Frisco 12-09-2003 04:38 AM

Go to http://www.hotrodheaven.com/tech/bra...kes1_index.htm
for some very good info concerning brakes. :thumbup:

There are nine pages.

Bill Ford 12-09-2003 02:19 PM

Am I being overly concerned about my pedal travel? What is normal pedal travel for 4 wheel disc brakes with a 1" manual MC?
Anyone with the same or similar setup?

S10Fan 12-31-2003 08:13 PM

Update……….

My parts guy exchanged my MC with another one and the pedal travel improved significantly. I still need to bleed the brakes one more time which should improve pedal travel a little more.

tm454 01-01-2004 03:40 PM

I am using the 67 Corvette master cylinder disc/disc on my 53 chevy and have a lot of pedal travel too then very good brakes. I was hoping to hear the 2lb residual valve would solve my problem. You decided to use the manual brakes too. I didn't want to mess with the power setup, now I'm wondering if I was wrong to go manual??


Tazz


Rat Rods Rule!

Bill Ford 01-03-2004 09:43 AM

Tazz, thanks for your input. Your experience makes me feel better about my setup. I was concerned that I had something set up incorrectly. Apparently you (we) are going to have a good bit of pedal travel with a 1" MC. I guess I could try a 1 1/8" MC which I understand will reduce pedal travel but will require more foot pressure to achieve the same clamping pressure.

I took my car out yesterday (I live on a rural dead-end road) and worked the brakes pretty hard. It seems to stop satisfactorily but I was unable to lock up either end from any speed. A booster may be the way to go :confused:

Good luck with your project.

P. S. All the residual valves do is keep fluid from draining back into the MC where the MC is at or below the calipers.


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