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Joined: 12 Jul 2007
Posts: 5270
Location: Kunda Park
State:: Queensland
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PostPosted: Fri Jul 13, 2007 2:08 pm    Post subject: DISC BRAKES, TO HAVE OR NOT TO HAVE Reply with quote

Hello again!!
Look, I will update my research on this one at a later date, so others can find it... But there are a few problems we encountered on my last look at the disc brakes.

1) On the issue of wanting disc brakes, good! Good idea that is, but totally impractical and here is why: The proper disc brakes are hydraulic to get enough power to the callipers to squeeze the pads on the disc, called a "rotor". To get that pressure you only have two choices, air over hydraulic to actuate it, or vacuum over hydraulic to get the power to the hydraulic master cylinder. Surge brakes or over-ride, have little adjustment and no breakaway ability, and are illegal over two tonne and don't work well anyway. Air over hydraulic and vacuum over hydraulic, with the adaptation of the tow vehicle, plus tanks on the van for 15 minutes of brake hold in the "break away provision", would cost about $8000 to $10,000 to do properly.. Also the failure of one brake line would bring down the whole system Shocked . If that is not enough, you have to tap into the Vehicle master cylinder, and Toyota said it Voids their Warranty if you do that.

2) So because of the great expense of air over hydraulic or vacuum over hydraulic, they tried to come up with an electric actuator to push on the hydraulic master cylinder.. OK, good in theory. Only one problem, we did not find the operation satisfactory, lacking in adjustment and speed of actuation. One type of new electric hydraulic actuator that we looked at, was a bit weak, so the rotors had to be a soft bronze so the disc pads will grab with less power, and the wear on the corrugation would be way to excessive chattering along. Again, we decided, not practical in the Outback. It is a workable option for boat trailers and surge brakes, but we do not think the soft rotors will last long enough to make it a practical long term system on a caravan. So we abandoned the consideration, in our opinion just not practical. OK?

The 12" Commercial brakes we use are considerably stronger than the 10" 'caravan type'. They are a two piece hub drum, and are larger and wider, and have a larger heat sink value with such a larger mass of steel, so they do not fade as quickly as the 10". Also the corrugation does not chatter them to severe wear like the 10" brakes, and we have had some Customers go over 100,000 kms on the original set. And a failure in one does not affect the others, like in one hydraulic line failing bringing down the whole system. In our opinion, there is no practical alternative to what we are doing.

ALSO: Our 12" brakes are even different than the normal caravan 12" caravan brakes, as our are a two piece hub drum, where the bearing hub will take bigger bearings and the brake drum is pressed on, like on a commercial truck drum, over the hub. Ours is the next grade up from the normal caravan 12" which only take the small bearings and are a one piece drum that does not absorb the heat as well, causing brake fade. Others claim they have 12" brakes as well, but don't use our larger hub-drums and larger bearings...

Kind Regards from the Ranger Smile
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