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Groover's avatar
Groover
Explorer II
Apr 27, 2016

Electric brake effectiveness

I recently purchased a new bumper pull trailer with two 7K axles under it and load it to about 12,000lbs. I am pulling it with an equally new Ford truck with max trailer tow and brake controller. While the brakes on the trailer definitely do something it does not seem like nearly enough. To test the effectiveness of the brakes I made sure that the break-away battery was fully charged, pull the pin and then pulled the trailer with my 5,600lb truck on gravel. I then put the pin back in and repeated the experiment with the brake controller maxed out. I got about the same results both times: the truck struggled but did pull the trailer and the trailer brakes did not lock up. This tells me that the braking effort of the two 7K axles combined was less than 5,000lbs. That would explain why it takes a long time to stop. Since the brakes were made by Dexter I called them and they told me that it was normal for new trailer brakes to have as little as 25% effectiveness and that as many as 30 hard stops and an adjustment were needed to wear them in before they work at full potential. Has anyone else ever heard of a similar situation?

For some background info: I am getting 11.3V in the braking circuit at the trailer tongue which drops to 10.3V at the rear axle. Each axle draws 6amps. Dexter recommends 10.5V at the rear axle so I am not far off the mark. I am planning to improve the wiring by pulling a second wire to reduce voltage drop but that is not really the question I have. I am wondering about having to do an extensive break-in and brake adjustment before they work properly. The trailer company seems to be way out of their element on this sublject.

25 Replies

  • Retired_JSO's avatar
    Retired_JSO
    Explorer
    May 10, 2016
    The effort adjustment set with the dash info display on new ford trucks allow 3 adjustments. Low, Medium and High controls how aggressive the voltage to the trailer is. It should not be confused with the Gain adjustment.
  • Lynnmor's avatar
    Lynnmor
    Explorer
    May 10, 2016
    Groover wrote:
    If heat or wear become an issue I will upgrade the rear to 3 1/2" brakes.

    I am really amazed at the difference burnishing the brakes made and feel that not being informed of that when purchasing a new trailer put my life and a lot of others at risk.


    Before adding your "resistor" I would have pulled the drums to see what is in there.

    What do you mean about 3 1/2" brakes?

    Just think, a previous poster said "Bedding won't really do much for performance overall."
  • Groover's avatar
    Groover
    Explorer II
    May 10, 2016
    I got to try the brakes on dry asphalt and could lock up the front axle with the brake controller on 7.5 or 8 and they still seem to be getting better. Even with the front axle locking I still did feel like I was getting as much braking as I wanted and the only solution was to increase the braking effort of the rear axle. The only way to do that was to turn up the brake controller. Not wanting to lock up the front axle too much at the higher gain I went in search of a resistor to bring the front back down to where it was at the lower brake controller setting. At my local building supply store I found a 65' spool of 20 gauge 2 conductor wire for a doorbell at a very reasonable price. I tied the two conductors together at one end so that I effectively have a 130' of single strand then put this in series with the front brakes, using wire ties to tie the entire spool to the axle. It will still lock the front tires but only after getting a lot more effort from the rears. I am quite pleased with the stopping effort now and feel much safer. My infrared thermometer indicates that the rear axle is now doing about 2/3 of the braking. If heat or wear become an issue I will upgrade the rear to 3 1/2" brakes.

    I am really amazed at the difference burnishing the brakes made and feel that not being informed of that when purchasing a new trailer put my life and a lot of others at risk. This needs to be better communicated.
  • BenK's avatar
    BenK
    Explorer
    May 02, 2016
    Here is a good site if anyone wishes to learn a bit more about friction materials
    for vehicles.

    It is geared for the mud hen (OEM or stock) level. Higher end stuff will have
    better performance to out right scary for street. Found some really, really cool
    stuff when designing windgenerator disc brakes...they were so good, it would
    stop the hub so fast the blades would break off...so my aerodynamists calculated


    Properties of Friction Lining and Pad Materials (Automobile)
    autobrake autobrakefriction frictionmaterial


    At/above that temp, the friction material will outgas much, much more
    and 'float' the friction material off the cast iron surface (fad). The
    stuff I use is off this chart to give perspective on what 'performance'
    level vs OEM is. The 'good material' is what I consider HD stuff you
    can buy at local auto supply stores

    Notice that their performance drops off at around 300C...about 572F
    for the 'good material' and about 200C..about 392F for their OEM stuff

    coefficentoffriction
  • Groover's avatar
    Groover
    Explorer II
    May 02, 2016
    I did the burnishing procedure and the brakes are working much better. I can now lock up the front axle in gravel even after reducing the gain to 7.5 from 10. I did check the drum temperature after doing the burnishing procedure and it read about 310F so they still got fairly warm even with only moderate braking and allowing two or three miles of slow driving between between applications. I did try to keep the gain down to 4.0 during the burnishing. This temperature is right on what the Dexter guy told me so it seems to work. The brakes had to cool down for the improvement to be really noticeable. Unfortunately, by the time they were cool it had started raining so I don't have dry pavement results yet but hope to get that tomorrow.

    My only concerns now are the nature of linked axles to skid the front axle and the possibility of fading if 300F causes fade. I least I got to a point where I feel that I can drive reasonably safely under normal conditions. If I ever get $600 to blow I may try to upgrade the rear axle from 12" X 2" brakes to 12 1/4" X 3 3/8". Thay might solve both of my remaining concerns.

    Thanks for the good info.
  • mkirsch's avatar
    mkirsch
    Nomad II
    Apr 28, 2016
    450F is on the ragged edge IMHO.

    I've never had any of my trailers' brakes so hot I could smell them. The brakes on my enclosed trailer will jerk your head forward if set to aggressively. My big flatbed's brakes leave a little to be desired, but they are effective.
  • Golfcart's avatar
    Golfcart
    Explorer
    Apr 28, 2016
    I know in the real world you cant just "take it easy" as there might be an emergency where you have to jack your brakes.. but still try to drive very conservatively until you get some good adjustments and break in time on your controller/brakes

    I really think your best solution is to.. take it easy lol.. for a couple hundred miles pulling. If they dont work themselves in good form, start tearing them apart and find the fault. overheating your brakes will end up causing more harm than good.
  • Turtle_n_Peeps's avatar
    Turtle_n_Peeps
    Explorer
    Apr 28, 2016
    Lynnmor wrote:
    Turtle n Peeps wrote:
    Please don't listen to the guy at Dexter, he's an idiot.

    The proper way to bed in brakes.


    That link is for disk brakes.

    The part about a film is correct. The newer drum type trailer brakes use an adhesion technology that is different than the old asbestos friction materials. Till the brake shoes wear to conform to the drum diameter, and lay down a film, full braking power will not be realized. The problem with hard braking with new electric brakes is that the magnets will be over worked and will gall the armature surfaces because they have yet to be seated.



    LOL, they haven't used asbestos in brakes since I had to adjust carburetors or change points. :B
    Disk or drum it doesn't really matter. The point is, you don't want to glaze the pads or shoes. You want to build up the film gradually and not smoke you hell out of the friction material.

    The part about the armature is very true and that's why my advice is the same to the OP, don't listen to the Dexter guy, he's an idiot. :)

    PS. My experience with trailer brakes is this. Bedding won't really do much for performance overall. It's very negligible at best. I've seen a lot of junk trailer brakes out there from the factory. It seems like the newer they are the more they are likely to be junk. I have a set of 50's axels on my car trailer and it will smoke all 4 tires at 70 miles/hour at full load if I want.
  • Lynnmor's avatar
    Lynnmor
    Explorer
    Apr 28, 2016
    Turtle n Peeps wrote:
    Please don't listen to the guy at Dexter, he's an idiot.

    The proper way to bed in brakes.


    That link is for disk brakes.

    The part about a film is correct. The newer drum type trailer brakes use an adhesion technology that is different than the old asbestos friction materials. Till the brake shoes wear to conform to the drum diameter, and lay down a film, full braking power will not be realized. The problem with hard braking with new electric brakes is that the magnets will be over worked and will gall the armature surfaces because they have yet to be seated.

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