You can use the tires to correct the speedo.....

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I guess you have to be in the right place at the right time.

How long ago did you buy a $50 disc brake parts car? Scrap car bodies are $180/ton right now. Even a gutted A-body is worth over $130 in scrap.

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Joshua

I might be about 30 years out of date on this but, got to wonder about manual disc brakes. Mind you the only car I've ever driven with manual discs was a 69 Barracuda with a factory big block. No room for the power booster, so manual discs. The brake pedal effort on this car was off the charts. The car did stop, but would have been unpleasant on a regular basis.

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66 Valiant, 225.
84 Van, 225.
71 Maxi-Van, 318
60 Valiant wagon, 225
87 Maxi-Van, 318 4spd

Well, if you want to make the trip to my place April 26th there is going to be a little get together and you can drive my '67 Valiant with manual late model A body disc brakes. The pedal is firm, but it's better than most 9" drum cars.

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Joshua

Has anyone (everyone?) seen the Jeep Grand Cherokee rear disc brakes on an 8 1/4 rear end? Apparently it's real and it works. Might have to do this for my 8 1/4. I actually might try this on my Dakota first and if I'm happy with that then the Valiant. Then I'd have a bunch of drums to give away.

Since the BBP 7 1/4 has the same bolt pattern for the backing plates and axle to housing flange dimensions that this would probably work for the 7 1/4.

http://www.dippy.org/forum/index.php?act=ST&f=2&t=1935&

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Joshua

I don't know, my wife has a Grand Cherokee... I wonder if I'll be divorced or shot, if I do a midnight rear disc brake swap.....

-D.Idiot


"Hmmmm....I got a spare F/M/J body 8.25 in the shed I wonder if that might have the proper offest to fit nicely under and A-body..."

5 1/2 years ago. I had to pull it from a field.

Rear disc brakes are not required but they are nice to have. I'd suggest going up to the bigger 11.75 rotors up front and driving the car for a while to see what you think.

I have a couple of customers who road race their A body cars with 13 inch rotors up front and 10 inch drums in the rear. These are cars that get up over 100 mph on the front straight at Portland International and then pull down for the S curve.

But I understand the desire to do the change to rear discs while you have it all apart. Be careful when selecting the rear calipers though. Biggest problem I see with these Frankenstein swaps is that people do not get the proper bias between the front and rear piston sizes. You can't just mix and match parts without paying attention to the bias or else the car won't stop very well.

Thanks for that tip about the rear calipers - I had forgotten about that.
At this point, it looks like I'm most likely going to be keeping the 7 1/4 2.94 I've got in the car for a bit longer, as it looks like I might have a pretty decent highway commute til I get out of grad school (I'm transferring next winter to start upper division undergrad work.. ) and those gears, as I've learned, are pretty nice highway gears.

So at this point, I'm revising a little. Unless there are disc spindles out there that might work with that rear end (anybody have any ideas?) it looks like I may just swap out to the 10" drums if I can rather than the 9" I have right now - I just really feel uncomfortable with the idea of having 9" brakes (not) adequately stopping on the highway in the event of an emergency. Either way I'll still do the front disc conversion.

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<i>D'Artagnan</i>
<img src="http://img.photobucket.com/albums/v432/stephaniexchaos/dart/th_IMG_0326_zpsumhhfxi0.jpg">

If I was cash limited (I recall those days) I'd just do the 11.75 swap up front and call it good. Make sure the rear drums are working properly and you should be fine, even with 9 inch drums. The fronts do 75% of the work. FMJ knuckles aren't too hard to find in the wrecking yards, Cordoba rotors are cheap at NAPA and so are the FMJ rear hung calipers. Hardest thing to find is the tall caliper adapters for the 11.75 rotors. I used to have a big box of them but I've given them all away over the years.

Biggest hassle is you'll want to carry two spare tires for the different bolt patterns but those cars have big trunks.

I agree that properly adjusted, and up-to-snuff front disk, rear drum set-up stops you as well as disks. However, the front to rear bias of a mixed set up changes with changes of traction (rain). The lock up point on drums requires less line pressure in the dry than in the wet. This means that in the rain, a front disk rear drum set up is more likely to lock up the fronts first if you have them set up well for the dry.

Also, drums are more prone to the kind of malfunction that can make one wheel lock up and throw you into a spin. I went to rear disks when the car went into a spin one night in panic stop to avoid a deer. The right rear drum locked up, and the rear spun left.

Sam

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I agree with Sam. If any kind of adverse weather is anticipated the 4 wheel disc is better. After years of Volvo driving its hard to go back to crude drum setups.

I agree its important to balance front/rear bias. I was well pleased when my disc/disc setup needed no prop valve with a stock A body Master cylinder. (75 Dart disc brake)

My " science" for my car was to use similar sized vehicles for both ends of the braking system. The fronts are from a 3500lb late A and the rears from a 3700lb Explorer. By using the metering system off the late A I was able to achieve balanced braking without adding extra metering(adjustable prop valve).

With similar sized tires and weight to my wifes Eagle Talon TSI AWD I am able to stop the Valaint as quickly from 80mph .....on wet pavement.....

Frankly I would add rear discs long before going to Viper calipers and 10" rear drums ....Overkill on one end and Neanderthal on the other.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

I would agree, unless you did the 11.75"/Viper setup. Don't think you gain any braking force from the Viper calipers without the bigger rotors, per what I saw in Ehrenberg's article. I'm sure repeatability is up, and maybe feel, but the front doesn't have any more brake than before so drums in the rear aren't really that out of place.

At the same time, Tim Werner seems to do just fine with the 13"/Viper setup on the front and 10" drums on the back. He doesn't seem to be missing anything (out runs the Vipers and Vettes on the road courses), but I wonder if he wouldn't see a difference with disks on the back.

Either way, it's going to be disks for me.

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

Yep, Tim's car hangs with some pretty fast hardware at the track and he is running the 13 inch Vipers up front and 10x2 drums in the rear.

Tim is planning to change over to rear disc brakes this year but last time I talked to him he was in the "feature creep" mode. He was thinking about going with a B body rearend in order to get rid of the wheel spacers. If I remember correctly his rear disc kit uses Mustang calipers and Toyota rotors. It is a rear disc kit that I sold him but it has been sitting in his garage so long that I've forgotten what it looks like!

I was going to put rear discs on my car but I got into the feature creep so I just bagged it and left the 11 inch drums on there. It works great with the big 13 inch rotors up front. The drums are easy to adjust and the e brake works nice. They are heavy as heck so I'd like to switch to disc. I cacluated that I'd save about 20 lbs per side if I went with a lightweight rear disc.