Brake test

Paul I have hydroboost so pressure is no problem, but for manual brakes you need all the line pressure you can get. I don't feel that balance bars and MC sizes will fully compensate for mis-sized calipers. To prove the point the guys that spend big $$$$ on wilwood setups use 4 piston calipers with about 3 times the surface area of the Cobra rear caliper. All the mustang brakes were designed to be run with a booster. If you want good manual brakes you need to spend 3k on the wilwood setup.

I learned the hard way that proportioning valves can fail. Had that valve been reducing the rear to keep them from locking bad things could have happened when it failed. I know that reducing the front is different, but it is far safer than trusting a PV to reduce the rear. At this point I would like to dial it in to be balanced without any external aids.
 
PaulProe said:
The Thunderbird SuperCoupe and the Lincoln Mark VIII use the same rear brake system. Both use the same rotor and caliper. The caliper is 1.78 bore.

There is some mis-conception/wrong info floating around the internet about the calipers being different. NOT SO. The mistake is attributable to the Dorman parts catalog that shows the rear bore diameter as 54mm which it is not. That is the dimension for the front.

My 2c

Paul
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Paul, not sure if your referring to my post about differences in piston size or something else? I was comparing a stock Mustang cobra caliper to a Lincoln caliper, not Lincoln to T-bird.
There is a difference between the later Lincoln and T-bird in they use different thickness pads. The T-bird had a thick rotor, and the newer Lincoln's have a thinner rotor. Using a T-bird caliper with the thinner rotor runs the risk the piston could push out if the pads wear too thin.
 
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Fat finger post - corrected
 
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Mike & Rich

Mike, you're right - you need to size piston calipers and master cylinders to get in the ballpark and then fine tune with the balance bar. No way you're going to make up a 4:1 differential.

Rich,
The early SuperCoupes (87-92) used the thick rotor. They changed to thin vented rotors in 93 thru 97 which carried into 98 for the Lincoln. You're right about the mis-match of thin rotor with thick rotor calipers. Can be catastrophic failure.

My concern was that Mike went off on a wild goose chase looking for the mystical large piston Lincoln caliper, only to find out it doesn't exist (please don't ask me how I know about this search :( )

Paul
 
New Brakes!!!!!

Monday T-bird caliper:
I started investigating better brakes monday by buying a T-bird caliper and bracket. After a few hours looking at it on the car I realized the bracket would be difficult to make and would take alot of trial and error welding and cutting. As I thought about how little of a difference the clamping force would be I decided to investigate a more drastic change.

Tuesday Drastic Measures:
Tuesday morning I returned the T-bird caliper and went searching for rotors to work with my 2 piston PBR's. I knew I would need a thick rotor so I only looked at front rotors. I found that to get a large enough area in the hat for the axle flange to fit you need a fairly large rotor. The 13" cobra rotors fit fine but I wanted something smaller for the rear. All the 10-11.5" rotors were too small in the hat area. I went to the local Oreiley auto parts and hooked up with a fellow gearhead. We started pulling rotors off the shelf and could not find something that would work. I was about to give up for the day when he happened to try a 2009 Mustang Bullett....perfect fit! It is a 12" front rotor and the hat area fits perfect. I brough it home and started measuring. I figured out a way to make the mounting bracket with no offsets which simplifies the process.

Out comes the grinder and drill. I used about 8 cutting discs and a hole saw to make the final product. Here comes the 2 piston rears!

Start with a 6" x 7" x 1/4" plate steel:
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Cut a hole where you need it:
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Cut the bottom so it goes on without axle removal:
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Drill the necessary holes in just the right spots:
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Mount it up:
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Grind the tangs off the PBR bracket for spacing:
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Bolt the bracket on:
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Now make a mirror image of the prototype and shape it into a "P". Left "P" bracket is the prototype and right one is the production piece.
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After a little massaging bolt it all together:
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All the pics here:
Rear PBR brake project pictures by mmarshall01 - Photobucket

Now to test for brake bias!
 
Wow, very nicely done. Shows what you can do with enough patience, a little spare time, the right tools and mad skills. Making the bracket without having to create an offset that matches consistently had to be a real relief. Good job!
 
Purple Venom said:
looks great mike. You want the tester again?
Click to expand...

Thanks for the compliments!

Yes I would like to test it again but probably not this week. I need to catch up around the house before I head off to work again.

Keith I did not make any spares, but I did make this:
Just print it off and get to work. I have the hole saw if anyone wants to try one.

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I did the 1st road test today and so far no big issues on the rear brake setup. I half expected the rears to lock early, but was proven wrong. I found a large secluded parking lot and simulated some autocross turns under heavy braking. During a 1G turn I increased brakes slowly until the front locked. The rears never locked and I could not get the rear to step out no matter what I tried. I suspect I still may have some air in the lines/caliper, so another bleed is called for. Another good test will be the pressure gages to see what the actual clamping force is.

On a side note on the way home I ran it pretty deep into a wide sweeper and tried to tighten it up and induce a slide like normal. The car just stuck due to some really grippy asphalt which really suprised me. When I looked up to see what it pulled on the G meter this is what I saw:

Wow 1.47G's on street tires!
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I have done a second bleed on the brakes and they are better. After some more testing I am finding they are almost perfectly balanced. During straight ahead braking the rears will lock very slightly before the fronts but the car skids straight ahead. If I try to turn or try to induce a spin by snapping the steering the fronts lock 1st and the car plows straight ahead. It appears that any additional side loading during turns on the front tires takes away traction and causes them to lock earlier. Nothing ugly so far!

So far I have only tested up 50 mph and will wait for my next race to really push it hard. Then the hard part will be testing in the 100 mph range. That will have to wait for a road course.

The brakes are easy to modulate and it takes considerable effort to get either end to lock. I am only locking them up because I am trying to. I am pretty happy with everything and look forward to building confidence in the new system on the racetrack.

If anyone has a nightmare senario that may cause the back to come around I would love to hear it. The only thing I can think of I have yet to try is braking during an austrailian flick (aka rally turn). If there is anyway that I can find to induce a spin then I will tone the rears down slightly.
 
To bring this back a little bit - Mike, have you had a chance to do any further testing on your setup? With my current need to replace some parts on my braking system, thought it might be a good time to upgrade. My thought with my CURRENT setup is to use a Hawk Blue 9210 or other full race pad to increase the pad's abilities, knowing the limitations of course of my system, and go with a blue 9210 up front or HP Plus. I think the reason I toasted my pads at Hallet was due to the extreme temps, not only from using the breaks but the air temps as well. Even though we did a full cool down lap, when I brought the car in and parked it for 30 minutes or more, the pads cooked themselves. I don't know, it's all science that I don't understand. I'm a bolt it up and go person, not so much a research and trial and error person.

Looking at Kerry's 2007 post about Lincoln Mark VIII rear calipers, maybe I should go that route with my 11.65" rear rotors?
 
Tim my rear brakes are great. They are so good I am going to try returning to a CNC MC setup instead of the hydroboost. If it works I will then be able to adjust the bias properly. This will help when I finally put some wider tires in the back as that will require more rear bias than I have now.

Check out this porterfield fact sheet. I like them mostly because they share some actual CF data. I have also heard good things about their pads.

http://porterfield-brakes.com/images/portrace2008_11_06_02_43_53.pdf

If your going to stay with your smallish calipers, then the R4-1 might be the way to go. I would be happy to help cut some brackets if you want to try some monster brakes on the back. We could probably do a couple of brackets in just a couple of hours. Here is the template to refresh your memory.

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