Frustrated with my brakes

[saltshaker]

I replaced my MC over the winter with a smaller one ..1" vs the older 1 1/8th Corvette MC and changed the pedal ratio from 5.25/1 to 7/1..... I have way to much pedal travel and the car isn't stopping any better...the brakes won't lock up. The car has GM metrics up front and explorer brakes in the rear, any thoughts? I thought about adding a 7" booster,my current MC is for manual brakes and not sure if a booster will work with it.
Jon

[Sminor]

Hey Saltshaker,
I have the same problem. My master cylinder is below the calipers and I have been told that a check valve in the brake line will solve the problem. As I understand it, the master cylinder will not have to push as much brake fluid into the lines to push the brake pads against the rotors. Still waiting to see.
steve

[Seagull81]

If you have a check valve in the line, how does it relieve the fluid back to the master cylinder to release the brakes? What am I missing?

[Rick Parker]

Salty: Contact one of the major brake vendors such as Willwood or Tilton with the diameter of the pistons in the calipers, Rotor diameters, vehicle weight and pedal ratio and they will size the M/C for you. They may even suggest the original M/C with your new pedal ratio. What you have done is ease the effort by reducing the imparted sroke on the M/C but then you also reduced the amount of fluid being moved by reducing the bore diameter. The two combined changes made the pedal much softer but at the sacrifice of less effective brakes.

This will get you going in the right direction: Mark Williams Enterprises - Brake Technical Information
This company is more Drag Race oriented, so keep that in mind, there are others.

[saltshaker]

Thanks, I had spoken with Wilwood and at their suggestion used the current combination. I'm going to bleed the system again this weekend and see if that helps...my concern is that I still can't lock the brakes up!
Jon

[Jerry Clayton]

Being able to lock the brakes up!!!!!!OK, what do you have for tires? How much anti dive is in your front suspension? do you push in the clutch when you brake??What pads are you running front and back?? Do you warm them up before trying max braking?

What does any of those things have to do with locking up the brakes???

[mreid]

Originally Posted by Seagull81

If you have a check valve in the line, how does it relieve the fluid back to the master cylinder to release the brakes? What am I missing?

I consider check valves mandatory if the m/c is not at the highest point of the braking system. They keep most of the fluid in the calipers and cylinders for less pedal travel and much better brakes. They are not true check valves as you are thinking about them. Disk brakes use a 2 lb. and drums a 10 lb. These are the pressures that must be exceeded to allow fluid to return to the m/c, so as I said not a true check valve. Drums require a higher rating as the springs pull the shoes back where disks only have the pressure of the turning rotor.

[Sminor]

Yeah................What HE said!

[convincor]

You call me and waste my time having me figure out what you need to make it work, then turn around and do something else that doesn't work....
and your frustrated...
Good luck.

[convincor]

Originally Posted by Seagull81

If you have a check valve in the line, how does it relieve the fluid back to the master cylinder to release the brakes? What am I missing?

it's not a check valve, it's a residual pressure valve.
And as long as the master is above the calipers you shouldn't need one.
Exception would be drum brakes. The residual pressure is needed to keep the shoe return springs from compressing the wheel cylinders piston back into it's bore.
Wilwood Residual Pressure Valves - SummitRacing.com

[jbcobra67]

I also have a A&C kit. I tried the manual master for the vette, way to big of a bore. I stood on the pedal and barely got it stopped. Switched to the power setup that A&C suggested in the manual and love it. One toe on the pedal will stop my car on a dime at moderate speed. Never tried high speed braking. But I feel it would do fine. I didn't check pedal ratio or any of that, just went with Joe's instructions.

Man I hope convincor is joking.

Joey

[D-CEL]

Saltshaker,

To clarify,By reducing the bore diameter of the M/C you will incease the line pressure at any given pedal pressure, however it will take more pedal stroke to achieve that pressure. This is benificial to a point, as it improves you ability to modulate the brake force, provided you have enough stroke length.

It sounds like you’re on the right track as far as the parts and pedal ratio go.
Do you have braided lines?
Are the F&R pads the same compound?
Bleeding can be a huge pain in the arse.
Did you bench bleed the M/C?
I pressure bleed from the wheels back towards the M/C to get all the major air out. Then finish with a few "pump the pedal" cycles for good measure.
I use a big syringe and clear vinyl tubing, just make sure to watch the fluid level in the reservoir.


Jason

[saltshaker]

Great questions: the front and rear pads are different,the master has now been bench bleed and the brakes seem to be working much better
Jon