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Old 07-22-2018, 03:02 PM   #1
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Problems of a dolly with surge brakes on steep downgrades

I am trying to decide what dolly to buy. I prefer surge brakes however I've read in numerous places that they are not ideal in mountainous locations as they have a tendency to overheat on long and/or steep downgrades. Apparently this can happen even without the towing vehicle's brakes being applied. A manufacturer who sells both types also informed me that "all surge brakes will do this". I live in WA so whether I travel East or South, I will encounter long 5% or 6% grades.
On the other hand, I understand electric brake dollies need the addition of a brake controller. I haven't found if one can simply tie into the brake lights of the towing vehicle to activate the dolly's brakes.
So, I'm a dilemma as to which way to go. I must use a dolly as my 2015 Ford Escape cannot be towed 4 wheels down. Any suggestions would be greatly appreciated.

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Old 07-22-2018, 03:59 PM   #2
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As usual it depends.... With surge brakes the application of the brakes is set by the weight of the dolly and vehicle pushing on the coach. How fast you are going, the weight of the vehicle, the amount and length of the grade are all entering arguments to how much you heat up the brakes. On the Colorado back roads, I usually come down the mountain in second gear at 20 to 30 mph. When I was new at this mountain RV driving, I would stop after about 5-6 miles and check the trailer brakes with my infrared temp thermometer. The temps were in the 300 to 500 degree range which I consider normal. Coming out of the Eisenhower tunnel heading East to Denver, I did stop once to check the brakes. They were 700 degrees so we just stayed at the pull-out for 15 minuter so let them cool. I was coming down the Interstate at 55 mph. I tow a 2800 lb pickup on a 450 lb dolly. On my Master Tow you can change the braking level but the factory setting is good for me.
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Old 07-22-2018, 04:55 PM   #3
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The Master Tow dolly looks like it uses drum brakes (see here: https://www.mastertow.com/towdollies ).

The Acme EZE-Tow dolly uses vented disc brakes: https://cartowdolly.com/tow-dolly-features/ I wonder if they can handle the heat a little better.

Sure I'm a little biased: We haven't had any issues with our EZE-Tow but then we also mostly tow in MI, OH, etc. (e.g. "flat" states). A few weeks ago we did return from a trip to DC and back which included driving through hilly PA without any dolly issues (yeah I know: The east coast's hills are nothing compared to the west coast's mountains).
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Old 07-22-2018, 05:47 PM   #4
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Yep, 10x2.25" self-adjusting drum brakes with a 1" master cylinder. You are correct bigger disk would be better but for my application the drums work well on most occasions. After all, my Rampside has 12x2 drum brakes and stops well.
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Old 07-22-2018, 06:20 PM   #5
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We haven't had any issues with our MasterTow dolly and the factory setting for surge brakes either.
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Old 07-23-2018, 02:37 AM   #6
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I have an EZE-tow and live in the mountains, and haven't had any problems so far. Jst have to be careful and not get going too fast going downhill.
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Old 07-23-2018, 02:49 AM   #7
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Originally Posted by dpbain1 View Post
On the other hand, I understand electric brake dollies need the addition of a brake controller. I haven't found if one can simply tie into the brake lights of the towing vehicle to activate the dolly's brakes.
So, I'm a dilemma as to which way to go. I must use a dolly as my 2015 Ford Escape cannot be towed 4 wheels down. Any suggestions would be greatly appreciated.
Tow dollies with surge brakes have been around a long time and are very reliable, I’ve had two different ones over the years and never had any problems, even in the mountains.

Electric brakes require a dedicated brake controller which can be adjusted for sensitivity and amount of braking. Brake lights would be either on or off and wouldn’t be able to modulate the amount of braking, also the lights wouldn’t be able to handle the load.

My vote would be for surge brakes and the simplicity that goes with them.
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Old 07-23-2018, 03:30 AM   #8
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And therein lies the problem. People say they're Ok if you just take it slow. And how do you take it slow on a long, steep grade? Either you brake, or downshift, or do both, all of which will cause the surge brakes to engage. Kind of a Catch 22 it seems to me.
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Old 07-23-2018, 10:59 AM   #9
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I've had 17 boats with trailers in my life...only one had surge brakes...and for that reason. Any type of steep incline will cause that effect. But, it sounds as if it's not that big of an issue from those that have used a tow dolly. If you try to back up an incline it can lock them up as well, but who backs up with a tow dolly? You also get that "clunking" back and forth every time you stop and start. personally, I prefer electric. All new pickups, including my 550 chassis, come standard with factory installed brake controllers. With electric brakes you can manually apply them slightly and separately from your truck/coach brakes if you're in a situation that calls for it.
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Old 07-23-2018, 11:07 AM   #10
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Originally Posted by dpbain1 View Post
And therein lies the problem. People say they're Ok if you just take it slow. And how do you take it slow on a long, steep grade? Either you brake, or downshift, or do both, all of which will cause the surge brakes to engage. Kind of a Catch 22 it seems to me.
So you're going downhill. You want to go slower. You either downshift or hit the coaches brakes. This causes the towed surge brakes to engage proportional to the inertial force of the towed vehicle's "push" against the coach. When the towed vehicle's brakes engage it slows down and there is no longer an inertial push against the coach. No inertial push against the coach equals no surge braking action.

If adjusted properly how do the towed vehicles brakes overheat unless the coaches brakes also overheat? You have to be constantly decelerating for the surge brakes to be constantly applied.

What am I missing?
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Old 07-23-2018, 11:13 AM   #11
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If you’re running a steady speed downhill the brakes won’t engage, only when braking or downshifting which is what you want them to do. If your trailer brakes don’t engage then your RV will be doing the braking for both vehicles which will be an extra load that will cause overheating of the RV brakes. Just because you’re going downhill doesn’t mean the dolly brakes will automatically engage, they need a stopping force on the RV. No offense please, but you’re over thinking this. The surge brakes are meant to slow the tow dolly and take the load off the RV brakes.

If you have electric brakes they will engage on a downhill when you apply the RV brakes and stay engaged until you take your foot off the brake. If you only downshift an electric brake dolly will now start to “push” the RV because they have no signal to activate them, again, more load on the RV.

Surge brakes mimic the actions of the RV, you brake, they brake to keep the braking loads more equal. Perhaps a trip to a “good” dealer would be helpful, they could point out the differences and assist you with your decision. Just make sure whoever you talk to has actual experience with both types of dollies.
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Old 07-23-2018, 11:14 AM   #12
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Once it pushes forward and applies the brakes it stays forward with brakes applied until you can "pull away" from it as in starting off from a full stop or starting up a hill. There is no spring loaded force that pushes it back while going downhill. As you stated...this force is probably reduced a little once the force is equalized, but they do stay applied until the actuator is extended.
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Old 07-23-2018, 11:18 AM   #13
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So you're going downhill. You want to go slower. You either downshift or hit the coaches brakes. This causes the towed surge brakes to engage proportional to the inertial force of the towed vehicle's "push" against the coach. When the towed vehicle's brakes engage it slows down and there is no longer an inertial push against the coach. No inertial push against the coach equals no surge braking action.

If adjusted properly how do the towed vehicles brakes overheat unless the coaches brakes also overheat? You have to be constantly decelerating for the surge brakes to be constantly applied.

What am I missing?
Going downhill the toad is getting a constant deceleration that is a fraction of gravity and thus the surge brakes are partially engaged.

As you mention, however, there is a feedback mechanism of sorts: The fractional g will cause the brakes to engage pulling the car back disengaging the surge brakes. At some point the system will find a steady state of partial brake application.

Gritz: We get no clunking at all with the surge brakes on our EZE Tow. It is a hydraulic proportional system and not an on/off thing. Thus there is very little movement in the tongue when the brakes engage or disengage (even slightly). I probably get more clunking/slack in the play of the receiver in the hitch than with the surge brakes.
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Old 07-23-2018, 12:18 PM   #14
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I've always preferred electric brakes (and a controller); because you can always feed in some braking, if things start dancing around in the lane behind you...
But I've never towed anything much over 2 tons anyway...
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Old 07-23-2018, 12:21 PM   #15
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Once it pushes forward and applies the brakes it stays forward with brakes applied until you can "pull away" from it as in starting off from a full stop or starting up a hill. There is no spring loaded force that pushes it back while going downhill. As you stated...this force is probably reduced a little once the force is equalized, but they do stay applied until the actuator is extended.
The "pull away" force is applied once you stop braking due to the toad brakes still being applied until they cause the toad to "pull away". No hill or full stop is required.
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Old 07-23-2018, 12:35 PM   #16
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It's all about "downhill inertia" generated solely by the runaway affect of the tow dolly against the braking force of the towing vehicle.


inertia. [(i-nur-shuh)] In physics, the tendency for objects at rest to remain at rest, and for objects in uniform motion to continue in motion in a straight line, unless acted on by an outside force. (See Newton's laws of motion.)

Once the brakes are applied on the dolly, they will not back off unless the force between them is reversed...there is no spring in the actuator. I agree that the pressure will be relieved a good bit once you let off the MH brakes, but not totally until the pulling force by the MH is stronger than the drag affect of the dolly.
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Old 07-23-2018, 12:37 PM   #17
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And YES, Bob...I did stay at a Holiday Inn Express last night!!
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Old 07-23-2018, 12:40 PM   #18
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And YES, Bob...I did stay at a Holiday Inn Express last night!!
Why are you staying at Holiday Inn when you have a MH?
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Old 07-23-2018, 12:41 PM   #19
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it's all about "downhill inertia" generated solely by the runaway affect of the tow dolly against the braking force of the towing vehicle.


inertia. [(i-nur-shuh)] in physics, the tendency for objects at rest to remain at rest, and for objects in uniform motion to continue in motion in a straight line, unless acted on by an outside force. (see newton's laws of motion.)

once the brakes are applied on the dolly, they will not back off unless the force between them is reversed...there is no spring in the actuator. I agree that the pressure will be relieved a good bit once you let off the mh brakes, but not totally until the pulling force by the mh is stronger than the drag affect of the dolly's brakes.
ftfy
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Old 07-23-2018, 01:01 PM   #20
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Here is a pretty cool, short, video/animation showing surge brake operation:
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