Trailer Brake Adjustment?

Offgrid, with all due respect you lost me. Way to complicated. The BLUF is the front brakes are designed differently than rears. They are larger and have better ventilation. If you look at your brakes the surface area should be obvious. I have worked on brakes for a long time, never got into the depth you are currently talking about. Sincerely hope you come to an understanding of your issues. I'd suggest a brake designer who can speak at your level. It's not scientific but known anomaly that rear brakes can overheat before fronts in a downhill descent. Also a known is there is a difference in the proportional braking of a hydraulic system vice an electric proportional braking system. Good luck.

Sure lostagain, but my issue is that I don’t seem to be getting any significant brake action from the trailer brakes. BTW, I’ve never been over Ebbets but have been over Taioga several times. I would put up a couple of the WV EW 2 lane highways in competition. The Sierra has one big 6000 ft or so climb followed by a big descent. The Appalachians have 8 or more 2000 ft climbs and descents. So maybe 2-3 x as much elevation change. 3 hours into the mountains and you’re still going at it.

Mcarter, sorry for the physics. Maybe the metric units are also putting you off. I just think in metric after 40 years, it’s so much easier. If only we quit handcuffing our young engineers and scientists with out medieval system of measures...

Anyhow, the point of the heating calcs is that I would expect 100-ish degree f temp rises on all 3 axles on these descents and I’m not getting that on the trailer brakes.

I did try running down a 2000 ft descent with just the TV but I don’t think the results are very useful. If I went down with the same speeds and gearing as I did with the trailer I wouldn’t have needed any braking at all so I just drove as I normally would when not towing. Brake temps were about the same on the rears as with the trailer but the fronts came up quite a lot so they were only about 10 deg F lower. If you get why that would happen let me know.

Sure the front brakes are much more massive than the rears. Thats because in a hard (about 1G) stop the 50/50 weight distribution changes to maybe 75/25, so you can apply about 3x the braking force on the fronts before the contact patch begins to skid. None of that applies to mostly engine braking while towing on a downhill grade of course.

Anyhow I’m pretty sure in my particular case that I need to increase my trailer brake action, somewhere in between stopping the rig on flat ground and incipient skidding at 20mph . I think I’ll try adjusting the controller gain so that the trailer brakes stop the rig on a 10% incline when fully engaged manually. That should increase the braking effort without getting to the point of skidding.

Offgrid,

No alibi to me is necessary, I understand you are a physics guy. That's fine. My concern is I have never seen anybody adjust a brake by temp, especially in an abnormal test like downhill with an engine brake, and the knowledge that that environment increases rear brake temps. Personally I would never adjust my trailer to equal my TV, not only does it have smaller, different brakes, it has a different braking system than the TV. I don't want my trailer to stop the TV, I want it to "load" the TV and assist stopping. I think your TV is doing the majority of braking which is OK and it is exhibiting normal issues with rear brakes heating. So you lost me with a plan to make TT brakes work more, run hotter and somehow cool rear TV brakes.

Glueguy, Discs on all 4 corners on Highlanders. Of course rears are much smaller capacity brakes.

Mcarter, I’m not looking for the trailer brakes to run hot, just to show some heating to confirm that they are actually doing something under real world conditions. For me running up and down through the Appalachians is probably my worst case braking scenario.

So to report, at an 8 setting the trailer brakes hold the rig on about a 10% grade, but won’t stop it if it’s moving. For comparison 3 holds it at idle on the flat and 4 stops it. I also could never get to lockup on the flat either.

At 8 I still get no heating on the trailer brakes on grades. At 10 I got a little, about 90-100 deg driving agressively enough to be at about 200-240 on the TV rears and 180–190 or so on the fronts.

Interestingly I got this heating on the drivers side brake, the the passenger side was basically still nearly ambient temp.
The drivers side also showed more wear when I replaced the old brakes last week. Out of the (very wet from Michael) mountains now so when I get home I’m going to ring out my wiring. I tested the magnets so I know I’m gettjng current to the pass side brake but maybe not as much as the drivers. I suspect that might be causing part of my problem.