Home Made Park Brake

[joes mack]

i know that the early 70s trucks had a set of park brake chambers mounted on the frame rails in front of the rear axles i was wondering what type of set up this is i have a cut off from a 72 dm 600 that was the same specs as my 69 and i was wondering what kind of linkage it has. im thinking of puting it on my truck if it dont require too much fab work for the linkage. i have the mounts and the z bars that go through the frame. i guess thats what they are called. the chambers are froze up but 24/24 chambers are the same size. any info on this setup would a great help.. joe

[joes mack]

do any of you have any exp with this setup (good,bad) i have been thinking about it and it seems to me that when the truck would go through a dip that when the rear axles rotate on the trunion that it would aply the brakes. this setup would have to have a cable from the z bar to the slack adjuster for the service brakes to work properly wouldint it. im really hoping that this would be a fairly simple and cheap fix for a park brake being that the parts to convert it over to a maxi brake setup arent cheap. and with the current brake setup that i have doesnt have enough clearence for the 24/24 chambers muchless the more desired 30/30 ones .... joe

[CML Service]

do any of you have any exp with this setup (good,bad) i have been thinking about it and it seems to me that when the truck would go through a dip that when the rear axles rotate on the trunion that it would aply the brakes. this setup would have to have a cable from the z bar to the slack adjuster for the service brakes to work properly wouldint it. im really hoping that this would be a fairly simple and cheap fix for a park brake being that the parts to convert it over to a maxi brake setup arent cheap. and with the current brake setup that i have doesnt have enough clearence for the 24/24 chambers muchless the more desired 30/30 ones .... joe

Hi Joe, Not sure your plans for the truck. But in my opinion brakes are something that should never be compromised or re-engineered unless you have an excellent working knowledge of them. I have a 1967 DM with 50K axles and bought the Maxi chambers for it. This axle setup mounts the cans horizontally above the axle. The Mack part number for the Maxi's is 5369*MA15772*. Current price is around $350 ea. Consider that the roto-chambers that are on there are likely old and fatigued. They are not cheap either. Also consider that these parts are not going to get cheaper or easier to get in the future. So like we have heard so many time "do it right the first time". A $1500 upgrade on your brake system could be much cheaper than the damage that could be done when your truck rolls away while loading it.

While on the subject of safety and reliability and not to single anyone out. I've been disturbed by the number of trucks I see at the shows with obvious mechanical and safety defects (poor condition split rims, no parking system). We all need to step up to the plate and do our own policeing of our hobby. If at some point there is an accident or fatality due to these defects at a show the insurance companys will make this hobby unaffordable. Personally I demand my trucks be safe and capable of doing the work they were designed to do. It's not uncommon for me to roll off the scale grossing 80,000 with my B model. My truck might have worn paint and rough sheet metal but the chassis is 100%.

Chuck