The Disk Brake Diary.....Thread covering Disk swap on a '63

[edpol]

"Bottom of the barrel" in this case, are drum brakes up front. Properly set up and adjusted, even the smaller mid-size disc system is way more than marginally better than the old front drum system.
I wouldn't even have considered using the mid size brakes, until I experienced the difference myself. I was taken completely by surprise.
For many of us, these are beautiful, smooth riding, comfortable cars, with some shortcomings, i.e., a four wheel drum brake system. All we want is to increase the stopping power while driving within 5-10 mph of speed limits, without changing the look of the car, and for under $1000. These mid size brake kits offer those alternatives.

[edpol]

FWIW, GM Metric calipers are OEM for mid '80's Cadillac Seville's, including those with diesel engines. Gas engine Seville's weighed over 3700 lbs. Diesel models weighed slightly over 4200 lbs. They use 10 1/2" rotors.

[edpol]

Before making a 140mph blast, I'd make damn sure the brakes, clutch tranny, gears, and scattershield were top notch.
In my younger days, when I was into HP cars, I spared no expense on getting the best of the best. The goal was always to be the fastest on the block, whether starting or stopping.
The goal now, in addition to other changes, is to improve the stopping power as much as possible, as inexpensively as possible, without changing the outward appearance of the car. Therefore, larger brakes are not an option.
If I wanted to go for bigger wheels, then I'd go with bigger brakes. It would actually be easier to fit 13.5" discs with Wilwood 6 piston calipers on these spindles. The extra 1 1/8" allows a longer caliper, with wider mounting. Not that I'd go that route for the kind of driving I do, But I'd definitely go with Crown Vic calipers and 12" rotors. That seems to be a fairly easy mod for under $400. The only drawback for some of us, is that caliper brackets would have to be fabricated.
I looked into 4 piston Wilwoods, and there are some that are reasonably priced that will fit. But the brake pad area is woefully small. I'm trying to get my hands on a KH caliper. 14" wheels may fit when using smaller rotors, but I won't know for sure until I can find one cheap just for fitting purposes. If I do, and it works, then it's just a matter of finding them with stainless steel pistons.

[novanutcase]

I hear ya BD! I used to own an '03 'Stang that I built to run around the open course and Autocross. Maximum Motorsports Max Grip Box race suspension and lightened the hell out of it for quicker runs. When it came to brakes I went with a set of Wilwood SL6's in front and DL4's in back. WOW! What a set of brakes! Thank god I had my harness on or they would have put me through the windshield. Now THOSE are some brakes!!

When it comes to safety equipment I usually go overkill just to err on the side of safety. On my Nova build I bought a fire suppression system from Safecraft. I'll probably never use it but if I ever have to I'll thank god that I did!

John

[edpol]

the day I cant build for speed or HP is the day I drive a Kia!!!

I used to say a Corolla. When the day came, I ended up with a Saturn. Too small, too hard to get in and out, so now I have a Windstar.

Hopefully Treozen, you'll get things sorted out soon, so we know how easy or difficult it is to fine tune the conversion.

[novanutcase]

I hear ya BD! I used to own an '03 'Stang that I built to run around the open course and Autocross. Maximum Motorsports Max Grip Box race suspension and lightened the hell out of it for quicker runs. When it came to brakes I went with a set of Wilwood SL6's in front and DL4's in back. WOW! What a set of brakes! Thank god I had my harness on or they would have put me through the windshield. Now THOSE are some brakes!!

When it comes to safety equipment I usually go overkill just to err on the side of safety. On my Nova build I bought a fire suppression system from Safecraft. I'll probably never use it but if I ever have to I'll thank god that I did!

John

You are right they are incredible, Always cracks me up to see a car with high HP and crappy brakes. The Nova build is quite the machine and you are taking the Safety to a whole new level with that build good work!

I hear ya! I can't tell you how many drag cars I've seen with huge motors and crap brakes! I guess they like hitting the wall at the end of the run! There was an absolutely awesome Chevelle at Irwindale running a blown Dart 540ci with......DRUM BRAKES!!! WTF???

John

[Treozen]

Hopefully Treozen, you'll get things sorted out soon, so we know how easy or difficult it is to fine tune the conversion.

Well, we're a bit closer....

The new calipers went on easily and I was able to use the spacers I received with the kit. I also discovered that one of my new front rubber hoses had failed - weeping fluid where the rubber hose connects to the metal fitting.

The brakes work better - but still not right. The pedal is firmer, but seems like it still takes too much effort to brake (though the amount of foot pressure needed seems to vary) and the pedal is still a bit softer than ideal. The car does stop better however and I believe I have the fronts locking with effort, where they wouldn't lock at all before. based on what I've done and how the brakes are working now, here are the options to get them right:

1) Proportioning Valve. It is possible my Prop valve isn?t doing its job. I find this doubtful though because the prop valve I?m using is a very common design used on GM cars of similar weight and brake design for literally years. I?ve used one myself on my 57 Chevy. Its possible an adjustable prop valve would be better, but I doubt its causing the issues as described.

2) Bleeding ? This one is almost certainly at least partly to blame. I performed a fairly ?Neanderthal? bleed job and so if I get a handy helper next time, I might get more air out. I could also try my pressure bleeder again, but I?m not convinced it?s doing its job properly.

3) Vacuum Booster. A 7? booster is really too small for a 4000 Lb car. According ?Street Rodder Magazine? and a few other resources I looked at, a 7? booster has a boost rating of 38, whereas a 9? booster (I believe the stock booster is 9?) has a rating of 95 (single diaphragm in both cases). I?ve no idea what the ?ratings? mean in context, but relative to each other, it?s a significant difference. In another example, assuming all other specs are constant (foot pressure, M/C bore, Pedal Ratio) a 9? booster provides double the pressure-boost of a 7?. I don?t have room for a dual-diaphragm design (too long) but I might get a 9? booster in provided I can swap out (or make) the connection to the bracket and pedal linkage.

If I had to, I could live with the brakes as-is, but they are not all that confidence-inspiring ? my 57 Chevy ? while a very different car ? has a very similar brake system, and it stops very nicely. Key difference?....manual brakes. Pedal ratio will be better and M/C bore smaller. So I?m leaning towards the booster for the T-Bird.

[edpol]

Is the master cylinder in the kit a step bore? (AKA quick take up) According to what's on the Net, this type of MC is required with low drag calipers. Without it, MP brakes says you'll never get a hard pedal, others say the lack of a step bore MC causes excessive travel. If it is indeed a step bore, maybe you need to tweak the push rod length.
Also, it's possible that newer after-market metric calipers have been redesigned, and some are not low drag. It's suggested you ask the mfgr. if they are. Which new ones did you get?
I'm beginning to see why GM liked low drag calipers so much. Backing off the rotor by as much as 1/8", they were able to make some very heavy vehicles with small 10 1/2" rotors. With 15" vented wheels, there was less need for 12" rotors to help dissipate heat. These include 3800 lb. Seville's and Riviera's. Seville's with diesel engines also used these calipers and rotors, and weighed as much as our cars.
So now I'm looking for MC's designed for low drag brakes, but can't find any info pertaining to push rod length. All I keep coming up with is the push rod type. "Dimple".
The guy whose car I drove said he used a residual pressure valve for the front brakes to get the pedal hard. I didn't push him for more info, but I'm finding this is not a long term solution. Sooner or later, without the right MC, he will have problems with the low drag calipers. I'm pretty sure he said he used a '72 or '73 F100 MC.
Seems like the makers of the kits aren't aware of this problem, or are just withholding info so as not to discourage potential customers.

[edpol]

Just found out some more info. Low drag wasn't introduced until 1982. All the metrics made from '78-'81 were NOT low drag. These are the calipers best used for these conversions, if you want to keep it as simple as possible.
The problem is, the early and later models weren't separated by many of the rebuilders, so it's hit or miss getting the caliper you want, if the people who sell the kits just provide rebuilt calipers.
Most of the aftermarket calipers are new, not rebuilt, so I guess it's just a matter of calling to confirm whether they're low drag or not.
AFCO specifies their metric calipers for '78-'81. I'll call Jegs tomorrow to get more info.
I guess I jumped the gun about GM's joy about the low drag calipers. They were used for '79-'81 Seville's, Riviera's and Toronado's, still with 10.5" rotors.

[Treozen]

Just found out some more info. Low drag wasn't introduced until 1982. All the metrics made from '78-'81 were NOT low drag. These are the calipers best used for these conversions, if you want to keep it as simple as possible.
The problem is, the early and later models weren't separated by many of the rebuilders, so it's hit or miss getting the caliper you want, if the people who sell the kits just provide rebuilt calipers.
Most of the aftermarket calipers are new, not rebuilt, so I guess it's just a matter of calling to confirm whether they're low drag or not.
AFCO specifies their metric calipers for '78-'81. I'll call Jegs tomorrow to get more info.
I guess I jumped the gun about GM's joy about the low drag calipers. They were used for '79-'81 Seville's, Riviera's and Toronado's, still with 10.5" rotors.

Yep ? your data is much the same as I discovered. I purposefully ordered a set of US Brakes calipers to get away from the low-drag versions. US brake uses original castings but the caliper is not low drag (so I?m told) and performance thus far would seem to agree.

Some thoughts on your quest to find a step-bore Master - There are few things to consider when looking at a step-bore (quick take-up) Master cylinder ? for one, they are reportedly harder to bleed properly and generally more expensive than the straight bore versions. Their failure rate seems to be higher as well ? but the biggest issue will be the vacuum booster ? Most QTC master cylinders have a large bore at the back, bigger than will fit into a standard vacuum booster designed for a regular M/C. I did find a few that might fit, but they also had a pretty small piston bore ? say 7/8ths which compared to the 1 &1/8 bore on the M/C more commonly used, is quite a difference. As I understand it, you?d get higher pressure but at the cost of pedal travel. Now last I read, I thought you were going with the larger Chevelle caliper? You wouldn?t need a step-bore for those, even the rebuilt ones.

As for the residual pressure valve ? I?ve read about people using those to counter low-drag calipers, some say it works, others report near-disasters. I?ve also read that some have used a 2lb with success while others had to go with a 10lb. I have a 10lb to the rear ? as appropriate for this design, but under normal circumstances, you only need residual valves to the font if your M/C is under the floor, and thus lower than the caliper ? and even then its only a 2lb valve.

I have a 9? booster on its way ? not sure if it will fit up to the brake pushrod, but I?ll find a way.

[edpol]

If those are the calipers specified for '78-'81, they're the same calipers I was looking at.
After looking at the process of switching to a step bore system, I'm going to use the original 9 1/4" booster, and just change the master to a dual.
Centric 130.65012 for '72 F250 has the same depth as the '63 Tbird. They have 9/16" ports, but it's easy enough to step down when hooking up to the prop valve. I'd rather do that than mess with push rod lengths.
I'll deal with the strut when the time comes.

[Treozen]

I'm going to use the original 9 1/4" booster, and just change the master to a dual. Centric 130.65012 for '72 F250 has the same depth as the '63 Tbird.

I'd watch the height on that sucker - Its hard to tell from just the picture, but it looks quite a bit taller than the C3 vette version I used and I'm going to have to run a pretty big spacer as it is to get my cross brace back on - either that or I think you can convert to a later T-Bird shock tower brace. Looks like the Reman version is $15 at Autozone - might be worth picking up to test with - My stock booster worked fine - I'd need to replumb the brake lines to the prop valve but thats no biggie. Better if the 9" booster I ordered fits, but this might be a decent back-up plan

Also - Looks to me that the version with 9/16 fittings in both ports and 1" bore is for front drum, manual brake application - I can't be sure but you probablly need to get one designed for front disks and power brakes.

[edpol]

Oops. Wrong number. 130.65013 is for discs. 9/16" front, 1/2" rear. Someone mentioned using this MC, but I can't remember who or where.
The big GM calipers MIGHT work, but it was too close to the spindle flange to take a chance. After looking from all angles, (a mirror is now my favorite invention) it looked like at least 1/8" would have to be ground off the top left of the flange in order to keep using 14" wheels.
I spoke to a GM mechanic about the metric calipers. ( For once, I was glad there was a long line at Wendy's) He said you need to use the older style with a straight bore MC. He also said to be careful about the prop valve. They look the same, but are specific in design for each application. There were different rear brakes within the same model as well, which would affect the proportioning ratio. Factors like the size of the rear brakes, wheel cylinder bore, width of the shoes, etc. all change the math. He said with the big rear brakes on our cars, you want less pressure to the rear wheels, otherwise they will lock up too soon. An adjustable prop valve is a good tool to determine the amount of proportioning, but they have to be replaced. They are not DOT approved.
He also said to check the master. The biggest difference between disc/drum and drum/drum MC's, is that the former have residual pressure valves built into the rear circuit. Adding 10# more may be your problem. Generally, conversions include an RP valve, because it's assumed the vehicle owner isn't changing the MC.
Naturally, I asked about using metric calipers for our cars, since the '85 Seville diesel is so close in weight, but the larger '85 Caddies used the larger brakes. He said the wheelbase and track widths are longer and wider on the bigger cars, therefore need bigger brakes. He said to do a comparison, if the numbers are close, metrics should be OK for our cars.
Results: Seville WB is 1" longer, front track is 1.7" narrower, rear track is .6" wider. That's pretty damn close.

[Treozen]

He also said to check the master. The biggest difference between disc/drum and drum/drum MC's, is that the former have residual pressure valves built into the rear circuit. Adding 10# more may be your problem. Generally, conversions include an RP valve, because it's assumed the vehicle owner isn't changing the MC.

It?s something to watch for, but not the issue for me. In my case I?m using a C3 corvette master, which is actually Disk/Disk - the only difference is that there's no built in residual valve and you have a larger rear reservoir, but that just means you?re carrying a bit more fluid, no downside to a larger reservoir (that I?m aware of) and the C3 corvette master is a common application for disk conversion while retaining rear drums ? it?s the exact set-up I have on my 57 Chevy except the brakes are manual. Not that you?d want to, but you can also easily remove the built-in residual valves without otherwise damaging the M/C ? or so I?m told.

If the 9" booster and a better bleed doesn?t fix it, I?ll be going to an adjustable prop valve next.

[edpol]

That was a good choice, using a disc/disc MC. It leaves you with a few options, like converting the rears at a later time without having to change the master.