Class 1 Pro-Am Brake bleeding questions

OffRoadGeorge

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I have the Pro-Am slotted rotors, new pads and calipers with a turning brake. We are having a terrible time to get the brakes bled properly, soft peddle and will not skid to a stop.

We have bled the brakes probably 50 times, tried myself, then took it to the shop that built the car, he bled them for 2 hours no improvement. Tried a different shop they replaced both CNC master cylinders and they tried a bleeding machine as well as by hand, still soft and will not skid. Now at the 3rd shop an old timer said lift up the rear end to help the air out and bleed, he even bled the turn brake, still barely stops.

I request advice the 3 shops are all reputable and gave it their best but the brakes are still not working good.

What should I do to bleed these brakes properly?

Do these brakes just suck?
 

Bajades

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I have the Pro-Am slotted rotors, new pads and calipers with a turning brake. We are having a terrible time to get the brakes bled properly, soft peddle and will not skid to a stop.

We have bled the brakes probably 50 times, tried myself, then took it to the shop that built the car, he bled them for 2 hours no improvement. Tried a different shop they replaced both CNC master cylinders and they tried a bleeding machine as well as by hand, still soft and will not skid. Now at the 3rd shop an old timer said lift up the rear end to help the air out and bleed, he even bled the turn brake, still barely stops.

I request advice the 3 shops are all reputable and gave it their best but the brakes are still not working good.

What should I do to bleed these brakes properly?

Do these brakes just suck?
My guess is that you are not developing enough hydraulic line pressure because your master cylinder is too big, or your pedal leverage ratio is not high enough. You need to develop at least 850 to 1000 psi of line pressure to get decent stopping power (Kartek sells a gauge to measure line pressure at the caliper). Also, you want to use the Wilwood gold backing plate pads and not the black ones they typically come with. To get my 6-piston Pro-Am brakes to work adequately, I had to reduce my master cylinder size front and rear, go to the gold pads and install residual valves. Still takes quite a bit of pedal force to lock them up on pavement, but in the dirt they work fine. I use a simple pressure bleeder and it bleeds them just fine (Google "Motive pressure bleeder").

http://www.nxtbook.com/nxtbooks/advanstar/dirtsports_200808/index.php?startpage=48
 

Giant Geoff

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If the calipers only have 1 bleed screw, make sure it’s on the top because air rises and gets trapped in high spots.
One trick I do is drill out the filler cap on the CNC res. and put in a tire valve stem to pressurize it, Just make sure you run down the 4 flat head screws on the top or the pressure will blow the seal out the sides so put less then 10 psi. each time you bleed.
 

OffRoadGeorge

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Bajades, My car has CNC 3/4 masters front and rear. Is this size too large?

Also I am not familair with residual valve, what is this?
And your car is awsome!

Giant Jeff, The Pro-Am calipers have top and bottom bleeders. So I bleed the botom then the top valve?
 
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Fourstroker

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If the calipers only have 1 bleed screw, make sure it’s on the top because air rises and gets trapped in high spots.
One trick I do is drill out the filler cap on the CNC res. and put in a tire valve stem to pressurize it, Just make sure you run down the 4 flat head screws on the top or the pressure will blow the seal out the sides so put less then 10 psi. each time you bleed.
Learned that trick from your good buddy Tom Reynolds. I would never install another set of pedals without that setup. Best part is you only need one cap done that way.

Bajades, My car has CNC 3/4 masters front and rear. Is this size too large?

Also I am not familair with residual valve, what is this?
And your car is awsome!

Giant Jeff, The Pro-Am calipers have top and bottom bleeders. So I bleed the botom then the top valve?
The residual pressure valve is basically a check valve. It holds a minimum 2psi of pressure on the caliper. Makes it so you don't have to pump the pedal to stiffen your pedal up. I would not even bother bleeding the bottoms. Everything will come out the top.

My guess would be that you have air in your turning brakes. If your turning brakes are floppy or will not stiffen up then that is your problem. Pretty easy to do but you will have to manually pump the brakes to do it. If thats the case post up and I can explain how to do it.
 

OffRoadGeorge

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Yes please I would apreciate the guidance on bleeding the turn brake. Right now the turn brake is soft when you pull it back.


I found out I do have the 2 psi residual valve and also the longest peddle ratio.


Thank you thank you for the adivse so far!
 

Fourstroker

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Yes please I would apreciate the guidance on bleeding the turn brake. Right now the turn brake is soft when you pull it back.


I found out I do have the 2 psi residual valve and also the longest peddle ratio.


Thank you thank you for the adivse so far!
OK here's the quick and dirty.

Set up your bleed man at the left rear tire. Yes this is a 2 man job the first time.

1. Pull up the left handle as far as it will go. If its a single handle puch it as far that direction as you can

2. Pump the brake pedal 3 or 4 times then hold while still holding upward( or sideward) pressure on the handle.

3. Hold both the pedal and the handle and have your bleed man turn the bleed valve open. Push the brake pedal to the floor.

4. Bleed man shut the valve. Repeat until the left handle is still like the brake.

5. Switch the bleedman to the other side, grab the other handle and repeat.

This will ensure that your brakes are bled properly but not that you have fixed all of your braking problems. Good luck!
 

Bajades

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Bajades, My car has CNC 3/4 masters front and rear. Is this size too large?

Also I am not familair with residual valve, what is this?
And your car is awsome!

Giant Jeff, The Pro-Am calipers have top and bottom bleeders. So I bleed the botom then the top valve?
The 3/4 master cylinders should be fine with 4 piston calipers.

You only need to bleed from the top bleeder (air will rise to the top of the caliper on each side).

Fourstroker's bleed procedure is perfect for manual bleeding, but I still struggled to get all the air out while bleeding manually. The Motive bleeder made it quick and easy to purge all the air from the system. The trick is to buy an extra master cylinder cap and bladder. Tap the spare cap and thread in a barbed fitting for the pressure line from the bleeder and cut a hole in your spare bladder (allows fluid to flow from the bleeder to the cylinder, but keeps the cylinder sealed). Pressurize the system to 25 psi and purge the air at the bleed nipples. Make sure to keep adequate fluid in the pressure bleeder reservoir.
 

OffRoadGeorge

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Bajades,

The fronts are 4 piston and the rears are 6 piston. For the 6 piston rears is the 3/4 ok?

Thank you and I'm ordering the bleeding system today.
 

Bajades

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Bajades,

The fronts are 4 piston and the rears are 6 piston. For the 6 piston rears is the 3/4 ok?

Thank you and I'm ordering the bleeding system today.
The 3/4" master will supply more pressure (ie braking force) but require more stroke from the master cylinder. I was told by Roy at ProAm that the 3/4" may not have enough volume for the 6 piston slave, but I can't vouch for that from actual testing. I'm running 7/8" masters front and rear with 6 piston calipers all the way around. My brakes work well, but I would prefer them not to require as high pedal effort as they currently have. I did not want to add more stroke to the brake pedal so I have accepted the compromise. You may also have an issue with brake bias with different calipers front and rear and the same size masters. This may be a non-issue, however, as you may be able to dial in the proper balance with the brake bias adjuster.

I would get the brakes bled properly and try them with your current setup. If the stroke is too long but the braking force is good you can always easily change one or both the masters to 7/8".
 

OffRoadGeorge

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Bajades,

Chris at Kartek recomended 1 inch for the rears today. Did you have to go down from 1 inch to 7/8?

Also could the pistons in the calipers leak air in? There is no sign of brake fluid leaking.
Thanks
 

Bajades

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Bajades,

Chris at Kartek recomended 1 inch for the rears today. Did you have to go down from 1 inch to 7/8?

Also could the pistons in the calipers leak air in? There is no sign of brake fluid leaking.
Thanks
I started with one inch masters front and rear but I could not generate enough pressure to lock up the brakes on pavement. I dropped down to 7/8" masters and switched to the gold Wilwood pads to improve the braking. Remember, brake pressure varies with the square of the diameter of the master cylinder, so a small change makes a significant difference. For example, the same pedal force that would make 1000 psi with a 7/8" master would only make 765 psi with a 1" master.
 

FullsizeFun

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#1 Issue = Turning Brakes
#2 Issue = CNC Master
#3 Issue = Master Cyl Bore Dia
#4 Issue = Improper Bleeding

The issue could be a combination of these things.

First if your turning brake is mushy that tells me they need to be bled. This will cause your rear brakes to be mushy because the pressure from the master has to pass through the turning brakes before it gets to the calipers.

CNC masters need to be slightly modified to work properly. The cap and the diaphram need to be vented to the outside to prevent creating a vacuum in the reservior. (usually only an issue that worsens as the pads wear). I believe Pro-am recommends Tilton Master cyl.

Also believe a 7/8 master is what is recommended for the Pro-am 6 piston calipers.

The Calipers have 4 bleeders on them, this means 2 are always pointing up. make sure you are bleeding from both sides of the caliper not just one side.

Call Pro-am and talk to Roy if the issue is not resloved. (even though there is a 99.9% chance it is not the calipers, he will still help you out)
 

Giant Geoff

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I just leaned a new trick, and here is the problem I found.

You have 1 pedal pushing on 2 cylinders, 1 cylinder gets hard and one can not because the equalizing rod can’t push on the unbleed side and just swivels. Here is how I bleed the second side. On the bleed side pull the rod off the heim, cut 2 pieces of 7/8x.188 boss and slide them in between both hiems to stop the movement and you will now be able to pump the last cylinder to get presser. This will prevent the equalizing rod from see-sawing witch reduce your throw, you now have the cylinder isolated to make rod plunge that helps bleed the final cylinder.
 

D-rek

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I have the same setup and I and have 1" and 7/8" master cylinder and my car stops awesome. I had small 3/4" master cylinders and the pedal would bottom out before the brakes would lock up.
 

OffRoadGeorge

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Thank you guys for all of the tips we are going to try bleeding again and replacing the masters. The tips provided will help!

Thanks!
 

FullsizeFun

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Also, what pads are you running? What color is the steel backing of the pads, black or gold?
 

mebuildit

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I have some Pro Am's on my buggy and they have the gold pads. What is the difference between the two? Why are the Gold better?
 
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