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Mopar Front Disc/Caliper Choices
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Author:  SpaceFrank [ Wed Apr 29, 2015 8:28 am ]
Post subject:  Mopar Front Disc/Caliper Choices
I'm currently using spindles, caliper brackets, calipers, and (11") rotors from an M-body on my road-racing LeMons Dart. The setup works great for this car, at least at our current speed/power levels (which are not spectacular). Car weighs around 3100 lbs. plus driver. Mid-range cam in an otherwise stock motor, Holley 2300 that could probably be tuned better, stock exhaust manifold with a 2.25" pipe and a cherry bomb. We can out-brake much faster cars for 8-hour race sessions, and the pedal never gets soft. Tend to get two races out of a set of front pads (EBC Yellowstuff) and at least twice that from a set of cheap O'Reilly or Rockauto rotors. My ONLY complaint about this setup is that the outer pad on these sliding calipers drags no matter what we try. If it weren't for the increased wear on the outer pad, we'd probably get twice the life out of a set. Might get more speed out of the car without the extra drag, too.

My current plan is to upgrade the brakes after we finally win our class race, which will give us some budget room to make the car faster since we'd be put into the next-faster class. I've already acquired the caliper brackets for larger 11.75" rotors. It's my understanding that my existing calipers will bolt right onto the larger bracket and work just fine with the larger rotors, but I want to see first if there's a better caliper option available. My searches of this forum lead me to believe that the pin-type calipers are not a good choice. Is there a better sliding-type caliper than the one I'm currently using? Even with brand-new calipers and grease on the channels, we still get brake drag. This might go without saying, but phenolic pistons are a no-go.
Author:  SlantSixDan [ Wed Apr 29, 2015 9:43 am ]
Post subject:  Re: Mopar Front Disc/Caliper Choices
Quote:
This might go without saying, but phenolic pistons are a no-go.
How come?
Author:  Dart270 [ Wed Apr 29, 2015 12:21 pm ]
Post subject: 
I always thought pin type calipers were better, but I have never really used stock calipers.

If you want something better for the track and more flexible, and you have a bit more cash, then get 11.75" rotors and 4-piston Wilwood dynalite or dynapro calipers on AREngineering adapter brackets. These will bury the stock Mopar calipers performance-wise and you will have better pad wear and bigger compound selection. Brake expenses are not limited, and it sounds like you are spending a lot on pads and rotors, so you may as well go big or go home... I have a set of these that have been working on my 64 Dart (1999 install), and now are on the 68 Dart. Never rebuilt the calipers and have 60+k road miles plus tons of track miles on them.

Lou
Author:  SpaceFrank [ Wed Apr 29, 2015 9:25 pm ]
Post subject: 
Lou- I don't have much data on it, but the comments I read when I searched this forum said the pin-type calipers flex more when the brakes are applied. The sliding calipers work fine for us; I just wish we could find a way to avoid the outer pad dragging. I saw you mention the Wilwood setup in an old thread, but I didn't see anything on their website. I guess I'll have to call them. How much do pads for those Wilwoods run? The "semi-race" pads we use are about $100 a set.



Dan- Phenolic resin is a better thermal insulator than steel, so phenolic pistons allow less heat to be transferred into the brake fluid. My understanding is that the intent is to keep your brake fluid from overheating and boiling under short-term hard use. Unfortunately, this also means your calipers and pads retain more heat than they would with steel pistons. Phenolic doesn't really melt from what I understand, but it does start to decompose at a relatively low temperature compared to steel. According to the reports I've heard from LeMons racers, the phenolic pistons can get so hot that they either get soft and fail outright, or they just keep so much heat in the pads that the backing plates turn into play-doh. One guy with a relatively large and well-cooled brake setup said they typically last him fine for one race, but the pistons get hard and crumbly and need to be replaced as a wear item.

Anyway, we run a good high-temp fluid (Motul 600), and we've never experienced brake fade in this car running steel-piston calipers, so fluid temp doesn't appear to be an issue for us. All we do is bleed the front corners at a minimum before every race to make sure the fluid isn't burnt. We've run the same calipers without a rebuild for the car's entire racing career at this point. In short, while I'm sure they'd be fine for most street applications, it seems that they don't hold up under continuous, heavy race usage.
Author:  Reed [ Wed Apr 29, 2015 11:24 pm ]
Post subject: 
For what it is worth, both my 89 Ford E-150 van and my sister's 03 Buick Rendezvous were originally built with front disc calipers that used phenolic pistons. The pistons gradually degraded until they started cracking. Eventually the cracking became so bad that the pistons flexed in the bore, got jammed, and seized with the braked locked on. I replaced them all with steel piston calipers. Granted, the van had about 170,000 miles on it when the pistons went and the Buick had about 130,000 miles.
Author:  Dart270 [ Thu Apr 30, 2015 5:58 am ]
Post subject: 
I am not sure who is selling the caliper adapters, but AREngineering.com makes them. Andy may sell them on that site. If Andy or others don't have them listed, call/email him and he can make you a set.

Calipers are Wilwood, universal for 1" rotors. Pads are $40-100/set depending on compounds. I have never put on a set that cost more than $60.

Lou
Author:  Joshie225 [ Thu Apr 30, 2015 8:03 am ]
Post subject: 
I used stock sliding calipers on my '66 Dart road racer and the pads wore evenly. I ran Raybestos Super Stop pads as they were far and away the best I found so of course they have been discontinued. I have a new set left, but no car which they will fit.

Are the caliper stands nice and smooth where the caliper rests? If there are any grooves or irregularities where the pads or calipers bear on the mount they can hang up.
Author:  SpaceFrank [ Thu Apr 30, 2015 12:48 pm ]
Post subject: 
The sliding surfaces on the caliper bracket/hanger/stand (I assume these are all referring to the same thing) are not perfectly smooth. They came off a junkyard car and were a little rusty. I hit them with some rough-grit sandpaper and applied a little high-temp grease whose name I forget. I guess that's not good enough.

The caliper brackets I have for 11.75" rotors were powder coated when I got them. I'll have to check and see if they're in better shape.
Author:  SlantSixDan [ Thu Apr 30, 2015 1:50 pm ]
Post subject: 
Interesting info on the phenolic pistons—thanks!
Author:  Sam Powell [ Sun May 03, 2015 3:59 am ]
Post subject: 
Quote:
The sliding surfaces on the caliper bracket/hanger/stand (I assume these are all referring to the same thing) are not perfectly smooth. They came off a junkyard car and were a little rusty. I hit them with some rough-grit sandpaper and applied a little high-temp grease whose name I forget. I guess that's not good enough.

The caliper brackets I have for 11.75" rotors were powder coated when I got them. I'll have to check and see if they're in better shape.
I think there is your problem. I have been told you can weld in those low spots and then grind it smooth so you have a fresh, smooth surface. I know what you are talking about. I had sliding caliper 73 Dart disks and calipers/adapters on this car at first, and I could hear it rubbing. They also clunked when I stepped on the pedal as the play was taken out fore and aft. I replaced that set up with a pin type I got off a later model B body, and that problem went away. However, I would be hesitant to race with the pin type. My intuition tells me that the rubber bushings around the pins are going to fail with that heat. They are not too glamorous, but the old Mopar sliders seem pretty durable and sturdy until those slider surfaces get worn. If you upgrade to the bigger disks, won't you have a different adapter? What condition are those adapters in?

Sam
Author:  SpaceFrank [ Wed Jun 10, 2015 7:10 am ]
Post subject: 
I may be upgrading from 11" to 11.75" rotors soon. Just to make sure, are the front wheel bearings the same between these two disc sizes? I'd imagine they are, since it's the same spindle.
Author:  Dart270 [ Wed Jun 10, 2015 8:39 am ]
Post subject: 
IIRC, they are, and I believe the same for 10" drums too.

You might look to verify on rockauto for bearing part numbers for 78 Chrysler Cordoba (11.75" rotors) and 1974 Dart (11" or really 10.87" rotors).

Lou
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