Comparing brake temps
 

Noticed surge brakes seem weaker than normal this year. Pulled off the wheels and calipers/pads look new. Brake fluid found full. Took apart the sliding portion of the Myco hitch to see if anything looked bad. Nothing bent, rusted or broken found but did discover 2 snubbers in there that I didn't know about. I assume they are there to dampen the shock when extending/retracting the sliding mechanism. Not sure if they need to be changed or not during drum/disc brake conv. If their length was wrong for the master cyl type, seems like they could prevent full actuation of brakes??

I swapped from factory drum (1989 vintage) to Kodiac Disc W/SS rotors 4 or 5 years ago and they seemed OK but never really had to push them. New/matching disc-rotor type master cyl was also installed with the discs. Brakes are only installed on front axle (tandem).

Today, I took it down a nearby secluded road for some brake testing. Brought a thermal camera with me to compare brake temps.

Made 7 or 8 consecutive "max braking" stops from 35-40 MPH and took temp readings.
Truck (2500HD) brake rotors were 260-265 degs F on all 4 corners.
Trailer brake rotors were 160 degs on both sides.
Truck and trailer brakes both started out "cold".

The 100 deg difference seems to confirm the trailer brakes aren't doing their share.
Anyone else tried this before and/or know about the snubbers??

If the trailer was empty during this testing I'd not expect the brakes to get as hot as the truck brakes. If loaded then I agree, you have either too little actuator travel (your snubber theory may be worth looking at some more) or a hydraulic problem, improper bleeding, etc.

Boat was on the trailer for the brake testing.
When I had the sliding mechanism apart, I looked at the breakaway brake lever mechanics and discovered it directly engages the master cyl, so the sliding part is removed from the equation. I removed the 2 pieces that would hold the lever up if actuated so I was feeling only the resistance of the hydraulics. It felt very firm so doubt there's much if any air in the system.

In regards to the snubber theory, maybe I can do some testing with the snubbers removed?? After doing some reading last night, found that removing the snubbers may cause violent oscillation or chatter of the brakes. I'll give Myco a call tomorrow and see what they have to say.

Only other theory I have is the brake pads may be contaminated, but since both sides were within 1 deg of each other, it seems unlikely.

I'm not sure you can compare rotor temperature between tow vehicle and trailer. It might not be an apples to apples comparison.

I agree it may not yield valid results. I know some members are pretty diligent in regards to checking stuff like this. Was hoping someone had tried this before.

One thing for sure, I'm not comfortable with how long it takes to stop. I know EOH is the way to go but the boat isn't getting used much (been out once this season for a maint run) and may not around a lot longer so hate to dump a bunch of money into it now.

I would put brakes on the other axle. Some states require brakes on both axles.

I had kodiac ss disc on my dual axle trailer with surge brakes and never had any issues. EOH is better in sure but I never had a need for it. Trailer was around 6500lbs loaded towing with a Tahoe.

The truck has to out-brake the trailer. That's what enables the surge brakes to work. You have probably 2-3X the pad size on the truck brake calipers than compared to the trailer. That additional friction alone will account for the difference in temps.

I agree the truck has to out-brake the trailer for the surge brakes to work but it seems like if everything was working correctly, the trailer master cyl would continue to compress and applying more and more press to the trailer brakes and should lock-up the trailer brakes at some point or at least get them really hot.

Also, since the boat/trailer weighs more than the truck and the trailer only has 2 smaller discs compared to the truck having 4 larger discs, it seems like the trailer brakes should be absorbing more energy and get hotter than the truck brakes.

In regards to the pad surface being larger on the truck causing more friction, you would have to assume the brake line press was the same. I'm thinking the trailer brake line press would be significantly higher since there's thousands of pounds pressing on the trailer master cyl during a panic stop.

Since disc brakes are not self-energizing like most drum brakes, you need more press to achieve the same amount of braking force. To get more brake line press, the master cyl piston would need to be smaller. A smaller dia master cyl piston would need more travel to provide the same amount of fluid displacement. If the travel was restricted, master cyl may not achieve sufficient press. Man, lots of variables involved with this. It's giving me a headache!

They're both decelerating at the same rate. So IMO for the trailer to progressively increase pressure the truck would have to slow at a faster rate.
How will it do that as they are connected?
Only within the travel of the brake coupler.

That's the whole nature of them, tow vehicle slows, trailer doesn't want to, it surges forward, applies the trailer brakes, it slows, which reduces the pressure applied to the trailer master cylinder, which in turn reduces the trailer braking.
So it's proportional to the rate the truck is slowing.
Anytime the trailer tries to out brake the tow vehicle (slow at a faster rate) it reduces the braking as the coupler then gets pulled out of actuation.

IMO you'll never get the trailer brakes to out brake the tow vehicle in a surge brake setup.
Think of this.
If the surge trailer brakes locked up and no tow vehicle brakes are even applied what happens? The trailer decelerates at a faster rate than the tow vehicle, inertia of the tow vehicle pulls the coupler out and no brakes are applied.


"Seems weaker" is so subjective especially if you had no baseline data from when you installed them.
I.e., brake line pressure, rotor temp, stopping distance.

If everything checks out and they've been installed 5 ish years.
I'd stop thinking about it and go boating.

.

In certain circumstances the surge brakes can out-brake the tow vehicle but just for a split second, then they release, trailer surges fwd and the cycle repeats causing a violent shudder. That's what the snubbers are designed to prevent.

Maybe think of it this way:
If braking system is working perfectly, the trailer should brake almost as well as the tow vehicle. The difference being what activates the brakes.
Since the tow vehicle has 4 large brakes and the trailer only has 2 smaller brakes (and the boat/trailer weighs a little more that the truck), the 2 trailer brakes would be forced to absorb more energy than any 2 of the 4 brakes on the truck and thus be hotter.

I realize my impressions are subjective however it's that 31 years of pulling boats and the seat-of-the -pants feel that tells me something isn't right. The truck is being pushed significantly more than it should.

For the last few years the trip to the ramp required very little braking along the way so the brakes never got a serious test. (when pulling the boat, I drive like a grandpa on qualudes)
Last winter they installed a traffic light at the bottom of a large hill that's also going around a curve. I've only been thru it once with the boat and it was green. It got me thinking what if it was red. I'm pretty sure I wouldn't have been able to stop in time with my current arraignment even approaching at 10 MPH below the speed limit. That's what got me testing my max braking capability. In other words, the brakes may have been like this the whole time.

If you can't stop your trailer at 10mph, it shouldn't be on the road.

That I agree with, but only a split second as you said.

Did you say trailer is a 1989?
Maybe it needs a master cylinder.

Master cyl was replaced during the disc brake conversion with a disc type master cyl abt 5 years ago.

Trailer stops from 10 MPH. It was running 10 MPH below the 55 MPH speed limit going down a steep hill and around a corner where I was concerned abt it not stopping in time.

I found a thread on this site where a member was having the violent brake shudder issue. He had a buddy drive the tow vehicle while he rode in a different vehicle next to the trailer and saw the front axle tires lock and release rapidly causing the tires to repeatedly hop abt an inch off the ground then it occurred. When the snubbers were examined, they had little to no resistance. Snubbers were replaced and issue went away.

I sent an email to Myco support. Awaiting a reply..

IF… boat and trailer 5-6k and brakes only on one axle, after several panic stops on test drive I would expect temp to be over 160. If your sure there is no air, is base brake system good? Pads wearing even? Slides free? Pistons move freely? Calipers on correctly?(bleeder at top)
I don’t know, but do stainless rotors require a specific type pad?

I believe boat is 6800 lbs dry + alum Myco trailer, soo,,, ~9000 lbs as it sits??
Master cyl feels firm when actuated via the breakaway lever w/cheater pipe..
Brake rotors/pads look new. Sliders are sliding. Pistons not sticking and bleeder is up.
Purchased the drum/disc conversion new as a kit so pads should be the right ones. Don't think SS rotors need special pads, but never had to replace them.

Got to thinking abt the reverse solenoid and wondering if it may have something to do with what I'm seeing. I know what it does, but not sure exactly how it works. Need to dig into that next.

I know for a fact that I wasn't able to back it into the shop (slightly uphill) w/o the trailer wiring plugged into the truck in prev years, so guess I could try that "test".

It energizes and stops flow from master cylinder from the reverse light circuit so that you can back up. A line lock in essence.
If it is energized all the time, then yeah you'll have issues

I’m surprised a set up that heavy doesn’t have brakes on both axles and equally surprised the brakes aren’t getting hot.
Interesting thought on reverse solenoid though. Maybe leaking by solenoid or wiring issue on trailer getting feed back to it?

Just convert to electric over hydraulic and be happy with it. Surge brakes aren't worth the trouble anymore.

Think I found the issue.
I was using the breakaway lever to bleed the brakes just to be sure. Placed a section of square tubing over the breakaway lever for leverage. When acuuating the lever, it felt firm. However when I applied a bit more force, the lever moved considerably. Then noticed when I put the extra press on the lever, the master cyl moved aft a half inch or more.. Pulled the master cyl out and found its mounted to a spring loaded mechanism. After a certain amount of press is applied. The master cyl moves limiting the amount of brake press that can be obtained.

Now need to figure out what to do abt it. Wondering if the mechanism is sprung for drum brakes (that need less press than disc) to prevent wheel lockup??

Considering welding it together but still awaiting reply from Myco.
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May have to. Dont really want spend the coin since it's not getting used much. Also want to see what can be done with what I have now.

After more thought, welding the mechanism would likely prevent the breakaway lever from reaching the locked position, so that's out.
Found parts breakdown on Myco site that shows the master cyl spring mechanism. I see different options for the master cyl between drum and disc but only appears to be one spring mechanism available. Thinking i need more spring tension..Maybe the springs lost tension over time?? They are a bit rusty..

Stopped by the local trailer dealer yesterday and they had the spring mechanisms for the master cyl. Sales guy said he never sold a set in the 3 years he's been there. The dusty price tag said $23/ea but he had to raise it a little since it was an old price. They are $40/ea now.

Got the left and right sides for ~$60. Tried to come up with a way to measure the spring tension on the bench but wasn't successful. These things are STIFF. The new ones look almost identical but did notice the springs are compressed slightly more (~1/4 in) on the new ones.

Installed them last night and noticed the breakaway lever is noticeably stiffer. Went for a test drive today. Did the same routine along the same path as prev. Ambient temp also the same.
All the truck brake rotors again at 250-260 degs F. Trailer brakes now 220 degs on both sides. Not as hot as I hoped for but a definite improvement.
Braking feels much better. I can feel the rear of my truck squat a little now during heavy braking (which it didn't before) and truck isn't being pushed nearly as much.

Before the test drive I placed a short piece of vac hose over one of the protruding rods the master cyl slides on to indicate if the spring assy were actually being compressed during heavy braking. They are..

Not EOH, but I still consider this repair well worth the investment. BTW, my coupler/actuator is a Titan 10.

FWIW, Myco recommends replacing them every 10 years. They also sale new master cyls with the spring mechanisms already installed (they refer to them simply as "brackets")..

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Good info. Never would have guessed.

Me either. It may just be a Myco thing.

Surge brake systems are awesome for a u haul trailer. With the development of modern EOH systems why even consider a 50 year old system that will forever plagued with the same issues? Time after time the same stuff? Switch over to EOH and your life will be lots better.......Easy backing up, Braking while backing down a ramp (not sliding), no sticking, no surge slam ect ect....Just sayin

I have none of those issues with my surge brakes, then again I have much more diving experience than most.