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1969 AMX Front Disc Brakes |
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av1956 
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Joined: Jan/03/2013 Location: Smithfield, VA Status: Offline Points: 157 |
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 Topic: 1969 AMX Front Disc BrakesPosted: Apr/21/2021 at 12:51pm |
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Hello,
A quick question ... on my 69 AMX, is it necessary to have a brake booster for front disc brakes? I converted from drum to disc. I read somewhere that the booster is not needed in some cases. Thanks to all. Taco |
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Taco
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AMXFSTBK390
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Joined: Oct/22/2013 Location: SF Bay Area Status: Offline Points: 3489 |
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Posted: Apr/21/2021 at 3:24pm |
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My '57 Chevy 210 wagon was originally 4-wheel drum brakes. The previous owner converted it to non-power front disc brakes with the original drum brakes in the rear. The PO did install a different twin reservoir master cylinder without a brake booster. I like the upgrade a lot.
In your case, the master cylinder may need replacing, too. Also, there is a rear brake proportioning valve that is on all 69 AMX's with disc brakes that may need replacing or removal for the brakes to work properly. When I installed Stainless Steel Brake Corporations rear disc brake conversion kit on my 68 Mustg GT390 FSTBK, the instructions required the in- line residual valve to the rear brakes be removed for the brakes to work properly. The 4-wheel disc brakes worked great. Hopefully someone will chime in who has removed the brake booster on a 69 AMX and explain what needs to be done.
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Heavy 488
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Posted: Apr/21/2021 at 4:11pm |
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Does the pedal have another hole for non power?
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ramblinrev
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Joined: Dec/28/2008 Location: Wisconsin Status: Online Points: 11528 |
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Posted: Apr/21/2021 at 4:19pm |
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You can try with your drum brake master, and see how much pedal effort is required. My guess is that you'll want a booster and the correct master cylinder. To use the drum brake master, you HAVE TO remove the residual check valve in the port (outlet) that goes to the front brakes. Otherwise, the caliper pistons will not be able to retract when you take your foot off the pedal. |
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74 Hornet Hatchback X twins (since 1977)
62 American Convertible (still worth the $50 I spent in 1973!) AMCRC #513, AMO #384 70 AMX 360 4-speed (since 1981) |
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Trader
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Posted: Apr/21/2021 at 5:07pm |
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A 69 AMX is a light car and you don't "need" to have power brakes. Many don't like the lack of pedal "feel" with power brakes.
You do need to size the master cylinder bore size to get optimal braking power and pedal travel. This article will provide some insight on were you need to go if the pedal travel is too short or too long: If ads pop up just go back and forward again and you can read the complete article.
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av1956
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Joined: Jan/03/2013 Location: Smithfield, VA Status: Offline Points: 157 |
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Posted: Apr/21/2021 at 7:35pm |
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Thank you all for your help, I appreciate it. Now time to do some research.
Taco
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Taco
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tomj
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Joined: Jan/27/2010 Location: earth Status: Offline Points: 7539 |
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Posted: Apr/22/2021 at 1:38am |
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I personally hate power brakes. That feather-touch stuff bugs me, as does excess power steering (most american power steering of "our" era). As Trader points out, these are light cars.
I've learned the hard way that proper front end alignment, meaning the stock settings, with correct-offset wheels, not only makes for much easier steering, it is the best setting for handling all othrer things being equal. Increased camber SETTING doesn't improve cornering, especially with cut springs, wrong wheels, etc. (dynamic camber is a different story). Even wide tires aren't bad with manual steering, if the tire patch is close to centered on the virtual kingpin line. Most AMC master cyls have 1" bore. And what ramblinrev says about the check valve. I had good luck with reducing the bore size to fix pedal effort. My roadster has four wheel discs (98 mustang rear) and 1" master and pedal pressure was HEAVY. I dropped t 15/16" and it made a huge difference. DOesn't sound like much, but it's AREA not diameter, and area is radius SQUARED so a small radius (diameter/2) change make a large difference in pressures. Travel is increased proportionately, but you'll be well within the volume. An engineer at C H Topping told me that you can expect one inch of useful pushrod travel without worry. In my setup I was using about .3"! Also this particular master had another compatible with 3/4" but I know now that would be too small. I'm using whatever the part number is for a 1964 Rambler AMerican, turns out to be a common part. The 15/16" master is identical except pushrod depth; I made a second pushrod. The other is in the car tool box, so on the road I could buy the common part and switch back in an emergency. |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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Steve_P
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Posted: Apr/22/2021 at 8:10am |
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I've used up the vacuum and then tried to stop a non-running car with PDB- just rolling down the driveway; it takes an incredible amount of pedal effort. I wouldn't want to drive it that way and try to stop from 60 MPH.
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tomj
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Posted: Apr/22/2021 at 11:04pm |
? But that's not what manual (disc or drum) brakes are like, at all. The non-powered booster is what's absorbing all your effort. Certainly they take more effort than the feather-touch power of the past. But after 10 minutes of driving you'll generally not notice it's different; you adapt pretty quick. |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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sweatlock
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Joined: Apr/28/2014 Location: Largo, FL Status: Offline Points: 3315 |
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Posted: Apr/23/2021 at 7:33pm |
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I had factory manual disc brakes in my ‘77 Pacer X. Worked just fine, was actually one of the better things about the car.
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Steve_P wrote: