Chevy Tri Five Forum banner

1 - 20 of 36 Posts

·
Registered
Joined
·
2,635 Posts
Discussion Starter #1
I have bled my brakes twice now (once the old fashioned way and again with a power bleeder).

I have a decent pedal, but I'm not sure if it's right. I have to push it pretty far to engage it and if I pump it, I get a better pedal. There are no leaks.

This is a 15/16" bore Wilwood tandem MC. I did bench bleed the MC, but I'm wondering if I should do it again?

Oh...I have the brake pedal clevis in the stock location. This is a manual application btw.

Thoughts?

I haven't driven it on the road yet...just on my long dirt driveway. It stops OK, but I've not really tested it.

Also, brakes are C5 Corvette with 13" rotors up front and stock disc brakes from an 8.8 Exploder out back (11.25" rotors).
 

·
Premium Member
Joined
·
13,132 Posts
I have the willwood 15/16 master on my car and it is firm with about 1.5" pedal movement for full brake lock. it did take some serious bleeding to get it there.
 

·
Registered
Joined
·
42 Posts
I have bled my brakes twice now (once the old fashioned way and again with a power bleeder).

I have a decent pedal, but I'm not sure if it's right. I have to push it pretty far to engage it and if I pump it, I get a better pedal. There are no leaks.

This is a 15/16" bore Wilwood tandem MC. I did bench bleed the MC, but I'm wondering if I should do it again?

Oh...I have the brake pedal clevis in the stock location. This is a manual application btw.

Thoughts?

I haven't driven it on the road yet...just on my long dirt driveway. It stops OK, but I've not really tested it.

Also, brakes are C5 Corvette with 13" rotors up front and stock disc brakes from an 8.8 Exploder out back (11.25" rotors).
As you know from my other thread, I don't have your set up, but I have had a 1" for a long while on a couple of cars and there is some travel... maybe 1" for notable engagement and maybe 2" for hard braking near lock up and 3" to lock up. But I have GM single pistons on smaller rotors so it's not the most high tech. However, what I can say is that on any of my systems I've ever had, the biggest thing if I can double pump and get way better is there has been some type of adjustment issues at the pads. For instance, if you have a mechanical parking brake, some of those rear brake calipers need to be adjusted. if there is just one pad rattling around very loose, it'll effect your pedal more than you might imagine. good luck.
 

·
Registered
Joined
·
5,712 Posts
A 2psi residual, in the rear line, mounted as close to the m/c, may help w/ the travel.
We use 2psi on disc/disc, and 10psi on the disc/drum.
 

·
Registered
Joined
·
2,635 Posts
Discussion Starter #5
I have the willwood 15/15 master on my car and it is firm with about 1.5" pedal movement for full brake lock. it did take some serious bleeding to get it there.
How many times did you have to bleed it? Method?

I'm getting a lot more travel than that...I must have air somewhere in there.
 

·
Premium Member
Joined
·
13,132 Posts
I just use the good ole pedal pump method with my wife on the pedal and me at the bleeder screws. I make 2 trips around the car and all is good.
 

·
Registered
Joined
·
5,712 Posts
We use a plastic hammer to rap the m/c and the wheel cyl/calipers. We sometimes see significant air bubbles being released.
 

·
Registered
Joined
·
1,736 Posts
Brake Pedal feel/travel with 15/16 MC

Do you know what the piston area is on the calipers? I bet your pedal ratio is 5.75 to 1. Just went through this and ended up putting a Aerospace Components MC(chrysler) 1 1/8 MC. The Wilwood is valved 2:1 the AC is 60/40. AC wants a 7:1 pedal ratio. So to achieve that I purchased Lokar replacement pedal. It has a brake pedal ratio of 6:1. I drilled another hole to raise it further. AC is making a brake kit for my application that will fit the Heidts spindles. Waiting on my kit to come back but its supposed to stop on a dime and give me change back.
 

·
Registered
Joined
·
2,635 Posts
Discussion Starter #9
Do you know what the piston area is on the calipers? I bet your pedal ratio is 5.75 to 1. Just went through this and ended up putting a Aerospace Components MC(chrysler) 1 1/8 MC. The Wilwood is valved 2:1 the AC is 60/40. AC wants a 7:1 pedal ratio. So to achieve that I purchased Lokar replacement pedal. It has a brake pedal ratio of 6:1. I drilled another hole to raise it further. AC is making a brake kit for my application that will fit the Heidts spindles. Waiting on my kit to come back but its supposed to stop on a dime and give me change back.
The front calipers are C6 Corvette calipers with dual 40.5mm pistons. They're floating calipers. Haven't done the math yet, but that's about 1.6" in diameter per piston. They're obviously much smaller than a typical single piston caliper from the 70's.
 

·
Registered
Joined
·
35,321 Posts
A couple of comments.

The pedal travel and feel is going to be a function of both the master cylinder and calipers.

For example, if you used a 15/16" master cylinder and Chevelle single piston iron calipers, you'd have a lot of travel. But with your C6 calipers, not nearly as much.

Same with how the brakes feel. 15/16" m/c will have more clamping force with the Chevelle calipers than with the C6 calipers.

There may be no one here that has that combination, but it shouldn't be too far from some Wilwood calipers which have similar piston area and are used with the 15/16" master cylinder.

If your brake pedal comes up or feels firmer after a 2nd pump, first thought is you still have air in the system.
 

·
Registered
Joined
·
2,635 Posts
Discussion Starter #11
A couple of comments.

The pedal travel and feel is going to be a function of both the master cylinder and calipers.

For example, if you used a 15/16" master cylinder and Chevelle single piston iron calipers, you'd have a lot of travel. But with your C6 calipers, not nearly as much.

Same with how the brakes feel. 15/16" m/c will have more clamping force with the Chevelle calipers than with the C6 calipers.

There may be no one here that has that combination (unless JT is going to), but it shouldn't be too far from some Wilwood calipers which have similar piston area and are used with the 15/16" master cylinder.

If your brake pedal comes up or feels firmer after a 2nd pump, first thought is you still have air in the system.
Rick...I think you're right. I'm 99% sure I have air somewhere in the system because I definitely get a better pedal if I pump it a few times after the initial application.

I'm gonna bench bleed the master again, then bang on it with a mallet, and then bleed the whole system twice again and bang on every one of the calipers. I didn't hit them with a rubber mallet the last two times so I'm wondering if there's air trapped in some small pockets.

I'll worry about the MC if I keep getting the same result from bleeding. I've read in many other places that this master works well in manual brake applications with smaller caliper pistons.

Worse comes to worst...I have a Hydratech hydroboost unit sitting a shelf ;)

One question...will it be more effective to have a buddy work the brake pedal for me while I crack the bleeders (old fashioned method) vs. using a power bleeder at 15 PSI? I have a Motive Power Bleeder btw...it works nicely, but I can't get it to work at much over 15 PSI before it starts spewing brake fluid out from the master. I feel like the line pressure from someone pushing on the brake pedal will generate more line pressure (and maybe push out some trapped bubbles more easily)?
 

·
Registered
Joined
·
5,712 Posts
"I have a Motive Power Bleeder btw...it works nicely, but I can't get it to work at much over 15 PSI before it starts spewing brake fluid out from the master."

We tried one of those systems, and got the same issue....A mess. Returned for a refund, and went back to the pump/bleed method.
 

·
Registered
Joined
·
35,321 Posts
Consider this. If 15 psi won't move fluid through an open bleeder, there's a blockage somewhere.

First thing to do if you can't get fluid out of a bleeder is to pull it out and see if the bleed holes are blocked by crud. Better yet, do it before you fill the system with fluid, or simply install new bleeder screws.

Another thing to do if your pressure bleeder won't hold 15 psi at the m/c is to put a ball valve on the air supply and don't turn the air on until you've opened your clean bleeder valve.
 

·
Registered
Joined
·
1,736 Posts
Brake Pedal feel/travel with 15/16 MC

Not discounting air in the system, but it could very well be your not pushing enough fluid with the caliper pistons you have. Not sure what you have. That is what I experience with mine. I needed more volume along with leverage to get the pressure needed to adequately stop my car. I have four piston calipers on all four corners Front is 1.750 piston and Rear uses 1.625 & 1.750. As you can see I have to move a lot of fluid. Once back on the road I can let you know what I experience.
 

·
Premium Member
Joined
·
1,768 Posts
"I have a Motive Power Bleeder btw...it works nicely, but I can't get it to work at much over 15 PSI before it starts spewing brake fluid out from the master."

We tried one of those systems, and got the same issue....A mess. Returned for a refund, and went back to the pump/bleed method.
I've had pretty good luck with my Motive bleeder if I use 2 C-Clamps to secure the lid to MC....(as opposed to that goofy chain they supply)
 

·
Registered
Joined
·
35,321 Posts
it could very well be your not pushing enough fluid with the caliper pistons you have.
Doubtful that's a problem, as even 7/8" bore master cylinders can be used with the Corvette calipers.
 

·
Administrator
Joined
·
48,461 Posts

·
Registered
Joined
·
2,635 Posts
Discussion Starter #20
Consider this. If 15 psi won't move fluid through an open bleeder, there's a blockage somewhere.

First thing to do if you can't get fluid out of a bleeder is to pull it out and see if the bleed holes are blocked by crud. Better yet, do it before you fill the system with fluid, or simply install new bleeder screws.

Another thing to do if your pressure bleeder won't hold 15 psi at the m/c is to put a ball valve on the air supply and don't turn the air on until you've opened your clean bleeder valve.
Fluid flows freely from all bleed screws...I'm just wondering if the old fashioned method will be more effective.

I was out of town all weekend so I'll give it another shot this week as soon as I can find a helper.
 
1 - 20 of 36 Posts
Top