smorse54 Posted October 29, 2011 Share Posted October 29, 2011 Hi guys, I'm putting together an 84 Superliner with AL40 suspension. This has 16.5 by 7" Q plus shoes, I'm planning on putting one R-12 service brake valve for each drive axle. My concern is what crack pressure to use, 3,4,or 5.5 lbs. Don't know what would have been factory, and this suspension was from a '99 CH so it had ABS. This will be a working tractor pulling a pnuematic tank at 80,000 gross. These tanks are very light and tend to lock up when braking empty, so I thought of going with a 3 lb. crack pressure on tractor to compensate. Any input appreciated, Steve Quote Link to comment https://www.bigmacktrucks.com/topic/21332-r-12-valves/ Share on other sites More sharing options...
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