Dae83048

I on the other hand have been driving my B61 1955 Mack for 20 some years and never touched a valve. I've installed new rear drums (had them custom cast by Dura brake) and gone through all the s cam stuff and pots. I seem to now be having a valve problem. When I apply the foot brake I'm ony getting 60 PSI at the rear pot. I would think it should be more around 100 PSI or full pressure. I would love feedback and the location of good information about these odd Mack air brakes. Thanks David B61

I have a 1955 Mack B61 and as far as I know everything is origional. I rebuilt the brakes a few years ago with new rear drums cast by dura brake. I have the rear brake pots with the big diaphrams and they lock on low air pressure. I don't know what these are called. I don't believe they are spring brakes. Does anybody have a diagram of the system with a discription of how it works. I pulled up to a stop sign the other day fortunatually going very slow pulling my tractor and when I applied the brakes to stop I just kept rolling. I could hear the air and everything seemed ok and I believe they are adjusted ok, I'll check that tomorrow. I put a air pressure guage on the rear brake line and couldn't get more than 60 PSI. I also have a knob on the dash, that turns, that I think adjusts the air to the front brakes. I don't think my front brakes have ever worked. I'm a slow and careful driver. So, if anyone out there can help with information thanks. David B61 oh!, I've had this truck for about 25 years and its been the most reliable vehicle I've ever owned.