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Originally Posted by Bill
Hmm, in this case, my skepticism is nearly boundless. If the electric brakes will grab tight enough to lock up the wheel, then hydraulic brakes aren't going to do any better. In practice, both of them should be adjusted to the point where they won't quite lock up in a panic stop - but still, I don't see that hydraulics have any inherent advantage. Of course, a larger tire might possibly enhance deceleration, simply because it puts a larger rubber patch on the road. But for equal tire pressures, even this is pretty iffy (which is why your tire guy suggested the chalk test). But in the end, any claim of deceleration improvement of 4 to 1 is pure bogus hokum unless someone can a) explain how the difference makes it better, and b) provide reasonably scientific measured data. If you actually find some of this, I hope you'll pass it on.
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You ask, I provide.
Here are the results of a fairly scientific study performed for TrailerLife Magazine comparing standard brakes to the Towbrake
Hydropower Disc Brake system. Much of this document was published in the Feb 2005 issue of Trailer Life.
On Page 3 of the document are these numbers for stopping distances
from 60 mph on dry pavement. Tests were done by Towbrake Int'l (the manufacturer and better known as the maker of the VIP Towbrake (aka MountainMaster) device for RV "toads") and George Ripsom for Trailer life:
Truck with OEM trailer brakes: Towbrake: 480 ft; Ripsom (avg): 513 ft; Ripsom (best): 356 ft ("G" force ~.25)
Truck with Disc (controller at just short of lockup): Towbrake: 198 ft; Ripsom: 207 ft. ("G" force ~ .6)
Truck with Disc (controller normal): Towbrake: 310 ft
Note1: IIRC, a typical pickup by itself will have a 60 mph stopping distance of around 160 to 190 feet.
Note 2: These tests were conducted at 25 mph and the results extrapolated for 60 mph tests. Because drum brakes are not as effective at high speed as they are at low speed and because drum brakes overheat/fade much more quickly than disc brakes during a prolonged stop, I strongly suspect the extrapolation actually underestimates the drum brake stopping distance.
Note 3: My memory failed me on the ratio of deceleration between disc and drum...these tests indicate it should be about 2.5 instead of 4. But a factor of 2.5 is still a lot.
My conclusion is that disc brakes (1) will cut anywhere from 50 to 300 feet (probably around 200 ft) from the 60 mph stopping distance and (2) will make the stopping distance with trailer nearly as short as the stopping distance of the truck itself.
I'm personally so impressed with these results (which are the most scientific I've seen) that I'm about 90% sure I will retrofit my trailer with discs before the 2006 towing season. I've already got their documentation (with pricing) and have located a dealer in Wyoming that I can work with for the parts and/or do the install (though it can be a DIY).