Poll: Classic 30 - Can you lock your brakes?

[Al and Missy]

If you have a Classic 30 (or any other 2-axle trailer in the 9000# range) and have standard electric brakes, can you turn your brake controller up high enough to lock the brakes on a hard surface at about 20 mph?

[ghaynes755]

Al I asked that question last year during factory service. The answer was no. If you want lockup upgrade to hydraulic brakes. Installed something like $400 or so per wheel as I remember.

[Al and Missy]

Thanks Gary,

I don't want to lock them up but I do want the braking power that setting the controller just to, but not at, the locking point will give. I'm not there. My truck, towing the 25 set just before lockup, would stop about as good as the truck alone. The trailer brakes alone would stop the combination reasonably well. I am far from that point with the Classic 30 S/O at 9100#. While the trailer weight has increased about 45% the weight of the combination has only gone up 18%. I think 18% increase in stopping distance is a reasonable expectation under the circumstances. I think I am getting a substantially bigger change in my stopping distance.

Al

[Al and Missy]

I did a pseudo-test of stopping distance today. I timed a stop from 30 mph with the trailer brakes alone and with the truck (disc and exhaust brakes) and trailer brakes, although at that speed I don't think the exhaust brake is doing much.

Trailer brakes only - 15 seconds
All brakes - 5 seconds
This tells me that the trailer brakes are providing approximately 1/2 as much stopping power as the truck brakes. I don't know for sure whether this is good or bad, but I don't think it is good.


What I deduce from this (by serious approximation) is:
30 mph = 44 feet per second.
For the all brakes:Average speed during the stop - 22 fps
Stopping distance from 30 mph = 22 fps * 5 seconds = 110 feet.

The force required to stop the truck from 60 mph is 4 times the force required at 30, so the stopping distance is multiplied by 4, i.e. 440 feet, but may be less due to the increased effort that would probably be applied by the exhaust brake.

I also compared the engine rpm to break the trailer brakes loose when the brake controller was set to 100% and again when the breakaway switch was activated. There was a slight improvement in brake performance in the breakaway switch case. I observed some corrosion on the umbilical connector so I'm going to try to clean it up and re-test.

I previously measured the brake line current with the breakaway switch activated and it was correct, so the brake controller is putting out pretty close to the proper current.

So my conclusion is that either there is something wrong with my brakes, or they just aren't capable of exerting enough braking power to lock the brakes at 20 mph. I adjusted the brakes so I know that is not it. The only things I haven't checked are drum wear and glazing of the shoes, either of which could lead to reduced performance.

I'm leaning toward fitting disc brakes. I'd really like to get something on the order of equal braking power from the trailer as compared to the truck since the weight of the two are very close. Otherwise the trailer will be pushing the truck in a panic stop.



Al

[xrvr]

The greatest braking force is just before lockup. So you may not want your brakes to be locked and skidding.

[Al and Missy]

Originally Posted by avionstream

The greatest braking force is just before lockup. So you may not want your brakes to be locked and skidding.

Thanks, but the way to adjust the controller is to run it up until the brakes lock at 20 mph and then back it off until they don't. I can't get close to locking the brakes at 20 mph.

Al

[xrvr]

Gotcha, okay.