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Old 09-30-2019, 12:18 AM   #1
hutchenc
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Default Brake pedal feel/travel with 15/16" MC

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).
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Old 09-30-2019, 01:20 AM   #2
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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.
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Old 09-30-2019, 02:40 AM   #3
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Quote:
Originally Posted by hutchenc View Post
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.
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Old 09-30-2019, 08:50 AM   #4
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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.
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Old 09-30-2019, 03:24 PM   #5
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Quote:
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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.
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Old 09-30-2019, 03:45 PM   #6
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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.
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Old 09-30-2019, 04:13 PM   #7
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We use a plastic hammer to rap the m/c and the wheel cyl/calipers. We sometimes see significant air bubbles being released.
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Old 09-30-2019, 10:07 PM   #8
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Default 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.
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Old 10-02-2019, 09:28 PM   #9
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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.
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Old 10-02-2019, 10:26 PM   #10
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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.

Last edited by Rick_L; 10-03-2019 at 10:43 AM..
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