Disc brake upgrade

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AndyF said:
Disc O Tech article is the best starting point. You'll need to convert to 5 on 4.5 to get good brakes. I'd say the factory 11.75 rotors with 15 inch wheels is the absolute minimum brake system for a street driven car. DISC-O-TECH: Stop on a dime from Mopar Action and Rick Ehrenberg
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Thanks Andy. Pretty comprehensive article. Lots of good info all in one place. I plan on making the disc brake swap for my 74 Duster an up coming winter project. I really like the authors approach - using existing parts when possible. Even here in the Phoenix, Az area finding 70's and early 80's stuff in the local bone yards is becoming a challenge. Gotta start by doing some measuring on my existing 74 ( originally a /6 car - all drum brake ) Duster. Per all I have read, car should have the larger ball joints and spindle bearings as OEM. Looks like the spindles gotta go anyway. I have been through the entire brake system as it is and with the added weight of a small block motor up front, they aint too good. This car also came with NO sway bars, so I have installed addco bars front and rear. The added bars along with some offset upper control arm bushings ( to get the camber in spec ), the car handles great. Don't want to mess it up by changing the spindle ball joint dimensions. I will probably go with an adjustable proportioning valve, as this car also came with the small 7 1/4" rear axle - which will be another upgrade I will make after the brakes. Thanks again for the article. John
 
BTW, I am running 5 on 4" - 15" wheels now and would like to stay with them if possible. The wheels will handle 11.75" rotors.

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John Cailey said:
Thanks Andy. Pretty comprehensive article. Lots of good info all in one place. I plan on making the disc brake swap for my 74 Duster an up coming winter project. I really like the authors approach - using existing parts when possible. Even here in the Phoenix, Az area finding 70's and early 80's stuff in the local bone yards is becoming a challenge. Gotta start by doing some measuring on my existing 74 ( originally a /6 car - all drum brake ) Duster. Per all I have read, car should have the larger ball joints and spindle bearings as OEM. Looks like the spindles gotta go anyway. I have been through the entire brake system as it is and with the added weight of a small block motor up front, they aint too good. This car also came with NO sway bars, so I have installed addco bars front and rear. The added bars along with some offset upper control arm bushings ( to get the camber in spec ), the car handles great. Don't want to mess it up by changing the spindle ball joint dimensions. I will probably go with an adjustable proportioning valve, as this car also came with the small 7 1/4" rear axle - which will be another upgrade I will make after the brakes. Thanks again for the article. John
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You can ignore everything Ehrenberg said about using the FMJ spindles. Literally everything. Ehrenberg let his imagination run wild and never actually checked the suspension geometry. Needless to say, FMJ spindles work just fine, there’s no “ball joint over angling” and the bump steer change is minimal at best. Depending on your set up, the FMJ spindles may even work better. Which will help your cause in finding a set of spindles, because all the F/M/J/B/R cars are fair game.

If you want to see the suspension geometry numbers, they’re published here

Swapping Disc-Brake Spindles - Mopar Muscle Magazine

Ehrenberg’s article is great for parts identification, but his suspension geometry “analysis” was just made up garbage.
 
John Cailey said:
Maybe look in to some wheel adapters?
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The problem is that wheel adaptors that are worth a crap are at least 20mm thick. Most are actually 1”. Which then makes the backspace an issue, it basically means buying new wheels anyway. Because what you’ve got won’t have enough backspace to handle that kind of adapter.

Assuming you could find a BBP to SBP adaptor.

I actually think your better option would be to convert to the 73+ spindles and 11.75” BBP disks, but have the rotors drilled for the 5x4” pattern. That’s what that MBM or PirateJack kit is doing. They use a 73+ disk conversion but have the rotors drilled for the 5x4” pattern and turn the hub register on the rotor down to fit earlier wheels (some of them anyway). Your aftermarket wheels might not even need the hub register turned down. I mean they do it from rotor blanks so the other pattern isn’t there, but that doesn’t matter. Just press the studs out and have the new pattern drilled.

Sure, every time you replaced the rotors you’d have to do it again. But I don’t think the re-drill would set you back that much. Heck the 13” DoctorDiff cobra style kit I have runs corvette rotors re-drilled for 5x4.5”.
 
I'll have questions on this topic sometime when I raise the funds. I'm leaning toward the ssbc over the others because I would like to retain my original wheels and manual brake MC if possible. I have the old school 14" Indy slot mags, and they are still available in 15" with the 5 on 4 bolt pattern if caliper clearance is an issue, but the center hole won't accommodate the Wilwood set up. My one question for today is....Scarebird. Is that even a viable option? They say that the kit will interfere with the factory sway bar. I called them and asked what aftermarket sway bar they might recommend that would work with their kit. The answer was "I dunno." Not a great selling point there. Being that my wallet is perpetually thin, does anyone have any input on the Scarebird conversion?
 
AndyF said:
Yeah those wheels put you in a tough spot. There really are not any good choices for 5x4 inch brake rotors. I'm not sure what the best path forward is for you.
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As I have already mentioned, SSBC has some nice kits for 5 x 4".
 
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