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Shamrock_HeavyHaul

How Hard Is It To Replace The Maxi Brake Chambers To A Modern Brake Chamber?

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I want to replace the maxi brake chambers on my B73 with a more modern brake chamber like trucks use today, how hard is that and what parts are required, i would like to see pictures of a set up. I am thinking spring and that means time to restart the resto!!!!!!!

Thomas :mack1:

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Hi Shamrock, I'm not sure if this is any help to you or not but here's my experience. My '61 B61 was a tractor that I turned into a single axle dump. All it had was a drum parking brake on the drive shaft and single acting air chambers on the rear brakes. One day while loading it on a hill, off it went without me behind the wheel. I picked up a pair of spring set air release chambers which fit without any modification. Then I put a parking brake valve in the dash and ran the plumbing to the chambers to release the springs and a supply line to the valve. The service line remained unchanged. This truck has lever type actuating cams and not the wedge style. If this is any help to you let me know, I've got a digital camera and can go into more detail. Bob Martyn

I want to replace the maxi brake chambers on my B73 with a more modern brake chamber like trucks use today, how hard is that and what parts are required, i would like to see pictures of a set up. I am thinking spring and that means time to restart the resto!!!!!!!

Thomas :mack1:

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Hi Shamrock, I'm not sure if this is any help to you or not but here's my experience. My '61 B61 was a tractor that I turned into a single axle dump. All it had was a drum parking brake on the drive shaft and single acting air chambers on the rear brakes. One day while loading it on a hill, off it went without me behind the wheel. I picked up a pair of spring set air release chambers which fit without any modification. Then I put a parking brake valve in the dash and ran the plumbing to the chambers to release the springs and a supply line to the valve. The service line remained unchanged. This truck has lever type actuating cams and not the wedge style. If this is any help to you let me know, I've got a digital camera and can go into more detail. Bob Martyn

I know about spring brakes but how do they differ from maxi brakes? How does the maxi brake lock the tires? Oh and how does the wedge type brakes work versus the s cam style, anyone have a diagram of this?

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My goodness Thad, that's a lot of info in such a short email!!! LOL

"S" cams roll and are operated, by air, at 0 degrees to the brake linning.

Wedge brakes are 90 degrees to the linning, and "Wedge" the brake shoes out.

Saw an old Mack with what may have been an up-grade kit for Maxi/Spring brakes (they're the same thing). Had the spring cans bolted to the frame between cab and drive axle. There was a cable comming out of the can and running down and back to the slack adjusters. When the switch was operated, the spring would pull the cable which pulled the slack adjuster, which pulled the brakes on!!

Packer

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My goodness Thad, that's a lot of info in such a short email!!! LOL

"S" cams roll and are operated, by air, at 0 degrees to the brake linning.

Wedge brakes are 90 degrees to the linning, and "Wedge" the brake shoes out.

Saw an old Mack with what may have been an up-grade kit for Maxi/Spring brakes (they're the same thing). Had the spring cans bolted to the frame between cab and drive axle. There was a cable comming out of the can and running down and back to the slack adjusters. When the switch was operated, the spring would pull the cable which pulled the slack adjuster, which pulled the brakes on!!

Packer

Thanks for the info Packer!

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I know about spring brakes but how do they differ from maxi brakes? How does the maxi brake lock the tires? Oh and how does the wedge type brakes work versus the s cam style, anyone have a diagram of this?

Here is a diagram of wedge brakes. I always change them over to cam brakes the first time they give me any trouble. As far as putting maxis on a cam brake truck goes the only time they don't bolt right up is on some of the older 29.000 and 55.000 rears where the maxi is larger in diameter than the old rotochamber and it hits the back side of the wheel.

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I know about spring brakes but how do they differ from maxi brakes? How does the maxi brake lock the tires? Oh and how does the wedge type brakes work versus the s cam style, anyone have a diagram of this?

Wedge :(

Cam :D

I tried to put this in as a picture. It is a wedge diagram. It came out as an attachment

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They make 2 differnt size chambers 24 and 30, the 24 is smaller than the 30, as for wedge brakes i would stay away those or switch over to S cam, wedge brakes are junk, when they are working they are all right but the S cam is alot better.

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My B had roto chambers on it. They were mounted inboard enough that I put #30's on it and had no modifications to do. It was a simple install....cheap too!

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I know about spring brakes but how do they differ from maxi brakes? How does the maxi brake lock the tires? Oh and how does the wedge type brakes work versus the s cam style, anyone have a diagram of this?

Maxi brake diagram. I'm going to try to make this a picture. Oh yeah something I should mention. If you have never taken a maxi apart don't. That rear chamber has a spring in it that is exerting about 1800 pounds of force. IT CAN KILL YOU.

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My B had roto chambers on it. They were mounted inboard enough that I put #30's on it and had no modifications to do. It was a simple install....cheap too!

that was the problem with my first B model.. the mounting tabs were very close to the tire/ rim.. only roto chambers or small (not suitable)spring brake brake cans could be used. Luckly the rears on the 2nd B model I have the tabs farther from the tires and can accept spring brakes.

Trent

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Well thomas do you have Maxi spring brake chambers on the truck now with 2 air line to each? If you have the Mack piston type service chambers [one line] and those are NOT Roto chambers but a piston type. To use spring brakes [ regular 2 diaphram stype] where there was just the piston type service can you will have to weld/fabercate some offset mounting brackets and get some offset slack adjusters. A picture of what you have now would be a big help.

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I'll get a picture today, i want to put the spring brake chamber on instead of the big old iron maxi? that i have on the truck

Thomas

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"MAXI" BRAKE WAS A BRAND NAME OF ONE OF THE FIRST SPRING BRAKE UNITS. IN THE EARLY 60'S, THEY WERE ALL "RETRO-FIT" MAXI IS NOW OWNED BY MIDLAND, WHICH IS OWNED BY HALDEX. MAXI'S WERE A PISTON STYLE SPRING BRAKE WITH A DIAPHRAGM SERVICE CHAMBER.. MOST SPRING BRAKE WENT TO DOUBLE DIA CHAMBERS FOR EASE OF REBUILDING. NOW, MOST OF THOSE ARE SEALED UNITS, BECAUSE OF THE DANGER OF THOSE NOT KNOWING HOW OR IF TO CAGE THE SPRING. TO RETRO FIT TO AN OLDER TRUCK, WE HAVE ALL THE VALVES AND UNITS TO DO IT.

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They make 2 differnt size chambers 24 and 30, the 24 is smaller than the 30, as for wedge brakes i would stay away those or switch over to S cam, wedge brakes are junk, when they are working they are all right but the S cam is alot better.
yeah,I had to replace A brake chamber not long ago,and had to order the 24/24 chamber because the 30/30 chamber would rub the inside of the tire.

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About how much would it cost to convert from the older brake systems to a maxi barke

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One thing you should do if it's not already there is fit relay valves to the spring brake circuit. This allows faster actuating and release of the spring side of the chambers. When I restored my White 4000, I even put QR valves in the lines to ensure they actuated quickly. Nothing worse than thinking your park brake is on only to realise your still rolling a little. I have done a quick schematic of how you should plumb it all up if that's any help. I can't say what prices are like over in the US, but here in Australia 30/30 brake chambers are around $65 new each, relay valves about $120 and quick release valves about $25.

post-2107-1208567930_thumb.gif

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