Disc brake conversion, is a booster required? (1 Viewer)

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cjgoode

cjgoode

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Been looking at all the disc brake posts and stuff, I know I would need a disc brake master cylinder, proportion valve etc, but is a booster required. I rarely see it mentioned in the conversion threads. I like the drum brakes, but if a 76 + disc axle comes my way want to know what my options are.

Does anyone have 76+ disc axles without a booster, if so how welll does it work? My preference would be no booster if it still works good.

Do those who did discs with a booster on a pre 1972 body and a stock f engine have pictures, did it interfere with the carb?
 
I think degnol is using a 60's corvette mc w/o a booster w/ his DB setup.
 
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I haven't done it on a 40 yet but I've ran unassisted discs before and plan to with my crawler with triple master cylinders for brake and clutch. What you need to do to make a system that feels good but still stops is take into account the pedal leverage and master cylinder bore size to caliper bore size ratio. By changing these around you can find a combination that provides adequate line pressure without requiring legs of steel, just know that you will need to push the pedal further depending on if you change around the pedal lever lengths.
 
easy enough to get a booster and not worry about it isnt it?

seems more complicated,

unless you like pushing hard on the brakes,

granted if you go through bsilvas process it should be hard to push them but alot more complicate if oyu ask me
 
Not sure if this helps but I just finished converting to 60 disk brakes on my 72 only to find out that my booster was bad. Had to stand on the brake to get it to stop. Just had booster rebuilt by booster Dewey and am looking to get it back in this weekend.
 
camcruiser13 said:
easy enough to get a booster and not worry about it isnt it?

seems more complicated,
Click to expand...

Couple quick calculations really, figure out the total mechanical advantage of the current brake system using the brake pedal lever length and ratio between the surface areas of the master cylinder piston and the pistons of one side of the calipers. Then multiply that by a coefficient for the power assist. The formulas can easily be found online for the leverage and hydraulic mechanical advantages.

Now mess with the brake pedal length and master cylinder piston surface area to gain that mechanical advantage back. Like I said, the total travel also changes but it's by no means a dangerous system. Roadracers and roundy round circle track guys run without power assist using the same principle I'm using. :meh:
 
I have discs front and rear with the stock (i think?) master cylinder with the residual valve removed. Stops ok. I have no doubt that it would stop better with a booster.
 
I'd like to go disc at all 4 corners with no booster just because if/when I'm in a steep hill climb situation and stall out I don't have to rely on vacuum to get me stopped. I'm not totally sure if I'm thinking correctly, but I know that on my boosted vehicles it takes a lot of pressure to stop them when the engine is off. I hope that if I'm wrong I will be corrected (Pretty sure I will be, That's the beauty of this site).
 
fjjonnie said:
I'd like to go disc at all 4 corners with no booster just because if/when I'm in a steep hill climb situation and stall out I don't have to rely on vacuum to get me stopped. I'm not totally sure if I'm thinking correctly, but I know that on my boosted vehicles it takes a lot of pressure to stop them when the engine is off. I hope that if I'm wrong I will be corrected (Pretty sure I will be, That's the beauty of this site).
Click to expand...

If the booster is working properly, you should be good for at least 1-2 brake applications without the engine running. After that, you'll have to stand on the brakes.
 
mrjay2u said:
I am using the corvette M/C, prop valve and 2# resid valves on my 4 wheel disc brakes. Stops straight and quickly.
Click to expand...

bsilva132 said:
I think degnol is using a 60's corvette mc w/o a booster w/ his DB setup.
Click to expand...

I had a '69 Corvette with a 427, about 500hp and no booster, all OEM. The brakes rocked. I wouldn't hesitate to do it in a 40. There is a 1-ton truck application as well, so I have heard.
 
Anyone have any experience with 7" dual-diaphragm brake boosters?
 
no booster brakes

I've been thinking about this for awhile. On my 1970 fj40, I'm getting around to a mini truck ps and disk brake conversion. I think I'm pretty good on the ps conversion, I have to just hook every thing up when I get the tub back on. On the disk brakes, I got the bigger 92' 4runner calipers for the front and plan to keep the old 9mm drum rears for now. I'm in the process of fabbing up new lines to the back, all 10mm except for the 9mm nuts to the drum wheel cylinders. I plan to try a booster/mc combo from a 90's geo metro. It's Aisin, and I can run it with the rib adapter-- I won't have to cut the firewall rib. Someone in the 45 section did it on a 60's fj45 with drums and it worked well. If it doesn't do the job, I might try the corvette mc. Here's a link to a site that has some good info.

Brake Upgrade

Good luck! ty
:beer:
 
I have a 1966 GMC 3/4 ton 4x4 running 35's with front disc/ rear drum and it has no brake booster. It is a much heavier vehicle and it stops on a dime without much pressure at all, actually with about the same as my disc brake 40 with a booster, so I think it is totally doable. I don't know much about all the piston size ratio stuff but I know that gmc is fine without the booster.
 
texcwa said:
...Just had booster rebuilt by booster Dewey and am looking to get it back in this weekend.
Click to expand...

"booster Dewey" Do you have contact infornmation?

Thanks,
Chris
 
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