On Fri, Sep 24, 2010 at 6:30 PM, Randall <tr3driver@ca.rr.com> wrote:
>> Totally unsuitable for something with ABS, where there's a pump that
>> changes fluid pressure to match the wheel's braking ability.
>
> Doesn't seem like a problem to me, since the trailer brakes should already
be
> full on well before any of the tow vehicle wheels starts to slip. B At
worst,
> the controller would need a bit of memory, to keep the trailer brakes on
> during the short interval where the ABS has released the TV brakes.
>
> But at least on my car, the line between the MC and the ABS hydraulic
control
> unit keeps the same pressure; the ABS controller just switches off the
> pressure to the wheel that is slipping. B Since that matches the description
on
> About.com, I'd guess that most of them work the same way. B If there were
> actually a pump changing the pressure into the MC, the pedal would vibrate
a
> LOT harder than it does.
You're right about the pressure between the MC and the ABS control
unit. I hadn't thought about it hard enough. Here's the real
problem:
Find a piece of ice, so you've got zero traction, or very near it.
Slam on your brakes. The pressure between the MC and the ABS control
unit will hit its maximum value. The pressure in the wheel calipers
will be, roughly, zero. What do you want the entirely unmodulated
brakes in the trailer to do? I'd like them to do nothing; you seem to
be arguing for maximum application of non functioning trailer brakes.
Don't suggest pumping the brakes, ABS is far better at it then any
human can be. Yes, ideally the trailer would have ABS, but I don't
know of any small trailers that have them. (It's been required on
semi-truck trailers for 10 years or so.)
>
> http://autorepair.about.com/od/glossary/a/def_ABS.htm
>
> -- Randall
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--
David Scheidt
dmscheidt@gmail.com
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