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 Post subject: Re: Tundra 7 442
PostPosted: January 12, 2020, 3:39 pm 
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Miatav8,MstrASE,A&P,F wrote:
Had to go back to page 15 to see your setup. There has to be a way for air to get to the top of the reservoirs and I don't see a hole. Oems have vented caps with a rubber seal that deforms to allow the fluid out. Make sure you have a hole in the caps.


Nice catch / Lucky catch. That was way back there in the build, just before we lost the photos. Should not be a problem with the remote reservoirs height.

Looking at the photo, the less-than-full stroke should not be causing any air issues as the air can and will, end up in the reservoirs. I did notice that the connection rubber at the reservoir is too large a size for the tube. Maybe later that was changed?

BTW, did you use compression fittings on all the brake fittings?

I don't see how just raising the M/C and pushrod will help his issue. As a side note, the pushrod will still only move 1/2 inch with less pedal motion. And if the drawing is anything close to the real geometry, pedal pressure during a stop will go up ~2X higher.

I see what I think is Steve's reservoir on eBay. It has the rubber seal, but I see no vent hole in the cap. If it does then drill a couple of very small holes in the caps.

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 Post subject: Re: Tundra 7 442
PostPosted: January 12, 2020, 3:46 pm 
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Tundra 7 wrote:
If I preload the master by 1/2”? Bad idea?


Very bad idea....

NEVER preload the M/C !!!! NEVER.

The M/C piston must retract fully to open the relief port into the reservoir.

The brakes may not fully release, and will not self purge any air bubbles from the M/C.

If the brakes do not release fully they may drag when running and overheat, then when you try to apply the brakes you may have none!

You don't necessarily need to raise the master, but it is best to mount the reservoir above the highest point in the system.
This maintains a slightly positive pressure (gravity) in the system.

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 Post subject: Re: Tundra 7 442
PostPosted: January 12, 2020, 3:50 pm 
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Bent Wrench wrote:
Tundra 7 wrote:
If I preload the master by 1/2”? Bad idea?


Very bad idea....

NEVER preload the M/C !!!! NEVER.

The M/C piston must retract fully to open the relief port into the reservoir.

The brakes may not fully release, and will not self purge any air bubbles from the M/C.

If the brakes do not release fully they may drag when running and overheat, then when you try to apply the brakes you may have none!

You don't necessarily need to raise the master, but it is best to mount the reservoir above the highest point in the system.
This maintains a slightly positive pressure (gravity) in the system.


From his photo on page 15, Steve has what appear to be residual pressure valves on the output of both front and rear M/C's.

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 Post subject: Re: Tundra 7 442
PostPosted: January 12, 2020, 4:10 pm 
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rx7locost wrote:
Miatav8,MstrASE,A&P,F wrote:
Had to go back to page 15 to see your setup. There has to be a way for air to get to the top of the reservoirs and I don't see a hole. Oems have vented caps with a rubber seal that deforms to allow the fluid out. Make sure you have a hole in the caps.



I don't see how just raising the M/C and pushrod will help his issue. As a side note, the pushrod will still only move 1/2 inch with less pedal motion. And if the drawing is anything close to the real geometry, pedal pressure during a stop will go up ~2X higher.


My understanding is that his brakes work and apply, but they are just not very firm and the pedal is going to the floor to provide the limited travel he has. Decreasing the pedal ratio a small amount will make for a firmer pedal and slightly more effort without the pedal bottoming. I don't know how you determined the pedal ratio was halved by moving the pushrod attachment one inch on what appears to be about 6 or 7:1 pedal.

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 Post subject: Re: Tundra 7 442
PostPosted: January 12, 2020, 4:19 pm 
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These are the newer masters. I had a lot of leaking with the orange ones. These are from some hot rod place. All billet aluminum.


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 Post subject: Re: Tundra 7 442
PostPosted: January 12, 2020, 4:27 pm 
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Ok, ok no preload I get it. Never leave a stone unturned.

It is a 6:1 ratio. I measured the travel distance on the rod from set point to fully pushed and it’s only traveling 1/2-3/4” forward. I haven’t messed with this yet. Had to grocery shop. If I cut the mounts and move them forward, lean the pedal to the rear of the car to gain travel that may work.

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 Post subject: Re: Tundra 7 442
PostPosted: January 12, 2020, 4:41 pm 
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You're missing my original point Steve. No matter what you do to the pedal geometry, the pushrod distance will not change. There is nothing wrong with 1/2" pushrod (actually, piston) motion so long as the setup allows for full retraction which means minimal free play in the pushrods when in the relaxed condition. Any issue has to be downstream of the pushrod and pedal. With a 6:1 ratio and 1/2-3/4 pushrod movement, that would be 3" to 4-1/2" pedal movement. That is a LOT of pedal movement before braking occurs. You don't need that much! You do have freeplay in both pushrods at rest, right?

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 Post subject: Re: Tundra 7 442
PostPosted: January 12, 2020, 5:13 pm 
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rx7locost wrote:
You're missing my original point Steve. No matter what you do to the pedal geometry, the pushrod distance will not change. There is nothing wrong with 1/2" pushrod (actually, piston) motion so long as the setup allows for full retraction which means minimal free play in the pushrods when in the relaxed condition. Any issue has to be downstream of the pushrod and pedal. With a 6:1 ratio and 1/2-3/4 pushrod movement, that would be 3" to 4-1/2" pedal movement. That is a LOT of pedal movement before braking occurs. You don't need that much! You do have freeplay in both pushrods at rest, right?

So your point is that the 1/2-3/4” is enough because the fluid is already compressed and can’t anymore so added pressure turns into added force against the already compressed fluid.
I did mock up moving the pedal forward 1.5” laying the pedal back to me and straightening the pedal a little I can get a full 1.5”. I don’t know man it seems like if you have so many inches available you should be using it. Also the full motion at the top of the pedal now is like 3.5 I think I can get 4.5 if I move it. From what your saying it should tighten up in like 2 and be firm? I currently have zero free play. When I push on the pedal I have fluid moving.

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 Post subject: Re: Tundra 7 442
PostPosted: January 12, 2020, 5:18 pm 
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Chuck, I see what you are saying now. If we know he runs out of pedal travel with a 1/2 inch of piston travel, and we know the applied pressure is not sufficient to lock up the wheels, then more pressure can be applied if the pedal allows it. We have not hit peak pressure in full pedal travel. Of course, peak pressure comes at a higher effort by reducing the ratio but there is more clamping pressure to be had.

If he is hitting the pedal stop, then there is more than 1/2 inch of piston travel available to further expand hoses, flex brkts, etc.

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 Post subject: Re: Tundra 7 442
PostPosted: January 12, 2020, 9:04 pm 
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Steve you need free play. Otherwise you may never allow the piston in the M/C to clear the port to the reservoir. Without that port free, you cannot bleed the brakes. Could that be your problem? Completely back off the adjustment in the pushrod assy, then slowly tighten it up until it is no longer free. Then bak it off about 1/2-1 full turn and lock it in place. In the free state, the rod should slightly rattle around between the clevis on the pedal and the hole in the piston.

Steve, FYI. In a properly operating system, the brake process is as follows:

step 1) you start to press on the pedal and take up the slop in the pushrod, Very easy pedal pressure.

step 2) you continue to move the pedal and fluid starts to flow in the lines. Slightly higher pedal pressure as you move the piston and twist the piston seal in the calipers and move the piston ( or stretch the return springs in drum brakes.)

step 3) you continue to move the pedal forward with slightly increasing force/ motion until the pads/ shoes make contact with the rotors/drums.

step 4) At this time, you continue to press on the pedal but the pedal no longer moves. That extra "force" (pressure) is transmitted thru the brake lines but no fluid flows. More pedal pressure = more stopping power. In reality, there is some slight movement as things stress and expand, but that is unintended.

step 5) When you remove your foot from the pedal, the seals on the piston in the calipers pull the piston slightly back into the caliper. this allows the pads to move away from the rotors. ( or the springs on the shoes pull the shoes away from the drum.) this pushes brake fluid back into the M/C and pushes the piston back until they can no longer do so. At this point, a spring inside the M/C will continue to move the piston to the free position. This opens a hole in the M/C that will allow fluid to freely pass from the reservoir to the M/C and back to the reservoir.

Your system is a little more complicated as you are using a dual M/C setup with residual pressure valves. The only thing that will allow the piston on the M/C's fully return is the spring inside the M/C itself. That little spring must not only move the piston back home, but push the pedal back to home too, unless you have a dedicated return spring on the pedal.

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 Post subject: Re: Tundra 7 442
PostPosted: January 12, 2020, 10:56 pm 
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Ok Chuck. I’ll put it back in and adjust the free play. I need tiny vent holes right? The check valves are only 2psi. Being where the masters are I was advised to put them in. So we start again. Thanks buddy for your education again.

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 Post subject: Re: Tundra 7 442
PostPosted: January 13, 2020, 12:12 am 
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Steve, check that the residual pressure valves are installed in the correct orientation. The body should be marked for direction of fluid flow. Normally the arrow points towards the caliper or wheel cylinder. If they're backwards it'll definitely screw things up. Good luck....

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 Post subject: Re: Tundra 7 442
PostPosted: January 13, 2020, 8:00 am 
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BHRmotorsport wrote:
Steve, check that the residual pressure valves are installed in the correct orientation. The body should be marked for direction of fluid flow. Normally the arrow points towards the caliper or wheel cylinder. If they're backwards it'll definitely screw things up. Good luck....

Thanks Bill, they are in right :cry: Hey are you racing at RA this year?

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 Post subject: Re: Tundra 7 442
PostPosted: January 15, 2020, 2:09 pm 
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Tundra 7 wrote:
Hey are you racing at RA this year?


We don't what we're doing yet this year. We really enjoy Road America, The Hawk last summer was amazing, but we're currently talking about going in a different direction this year....maybe the Monterey CA area in August so that we can take in all of the events in Monterey Car Week. I haven't run at Laguna Seca since about 1992 so it's probably time to go back! If we do head to RA I'll let you know.

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 Post subject: Re: Tundra 7 442
PostPosted: January 15, 2020, 2:32 pm 
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BHRmotorsport wrote:
If we do head to RA I'll let you know.
If you decide to head down to RA as in "Road Atlanta" please let me know!
:cheers:
JDK

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