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Old 07-24-2018, 10:45 AM   #1
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Trailer Brake Stopping Power as Percentage of Weight

Regardless of what they start out as, most towing threads end up turning into one of two things; A Propride vs. Everything Else "discussion", or truck vs. car "discussion". In the truck vs. car discussions braking performance is routinely brought up as an advantage of one over the other. Truck enthusiasts argue trucks are heavier, have larger brakes and more stopping power, while the car crowd cites more stability and better handling under braking.

All these discussion got me wondering, what percentage of an AS trailer's weight are the trailers brakes capable of stopping when you need to stop as fast as you can?

Of course there are loads of variables including, the specific model trailer, what brakes, are the brakes adjusted correctly, what payload, how fast can the TV brake, etc. So, the question and answers are of course going to be somewhat vague.

So is the OEM braking system in an AS designed to provide 100% of it's own braking power, or does is depend on the TV for a percentage of it? If so, what percentage do you think it is? If you have customized your brakes to disc, what percentage do you think you get?

Wild ass guesses are perfectly welcome.
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Old 07-24-2018, 11:02 AM   #2
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Since the Airstream brakes are quite capable of locking up all the wheels, I suspect that the OEM brakes are quite powerful enough to stop the AS all by itself. I was quite capable of smoking all 8 of the tires on my rig (four on the AS, 4 on the TV) in panic stops in downtown Phoenix when needed. (Have I mentioned how much I despise the rush hour traffic in Phoenix lately?)

One of the weird side effects of Hensley-designed hitches (Hensley Manufacturing or ProPride versions) is the "Hensley Bump".

This occurs when the trailer brakes do not come on hard enough or fast enough, and although it does not result in sway, results in a bump sensation when braking hard.

The cure is to increase the brake gain setting, and in the case of my Tekonsa P3 controller, increase the initial braking force curve to be more aggressive than the normal default setting. The upshot is, IMHO, what you are doing is making sure the brakes on the Airstream are set to provide most, if not ALL the braking needed for the weight of the AS.

I find that getting the brake controller set just right to avoid the 'Hensley bump' effect seems to set me up so the trailer does all of it's own braking effort. I do have to fiddle with brake gain number each time I head out, because the trailer loading varies quite a lot each trip. The initial force adjustment seems to stay the same (P1 or P2 IIRC) (Ditto having to tune WD jack height (overall WD tension) slightly on each trip as well, for the same reason.)
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Old 07-24-2018, 11:28 AM   #3
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Tandem axle trailers will stop without requiring the TV to supply any of the braking force. Be sure and have the electronic bake control set up properly and the trailer tires not over inflated (follow the load table for the correct PSI). Single axle trailers do not stop as well as they only have two brakes.
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Old 07-24-2018, 11:51 AM   #4
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Locking the brakes .... smoking the tires is not the best braking performance as it means traction was lost and the tire is skidding. So, as with all things RV - it depends. There is sufficient brake power to stop the tires from rotating. Is there enough control to stop the coach in a short distance as one would want in an emergency?

That requires a properly set brake controller. A properly set controller takes some testing. The brakes also require periodic adjustment for best performance. Self adjusters need backing and pull through sites don't provide much of that.

Slowmover suggests the Tuson anti-lock brake upgrade. It or something similar should be part of a high performance towing package. Upgrading the trailer brakes to match up with the TV brake performance sounds quite logical. Some day, an integrated TV/Coach brake and stability control system will be the goto solution.

https://tusonrvbrakes.com/products/abs

There is also an issue with the available friction from the tire contact patch. You might expand the discussion on tires to that issue. The Michelin 15" is a 235 and the Goodyear is a 225. Would that make a difference? Would the tread material make a difference? Would the wet pavement performance be something to consider? What is more important - fuel economy, tire life, load capacity, sway resistance, or braking performance?

So, no anti-lock = the trailer brakes are not good enough to match the stopping performance of many tow vehicles. However, improvement on several levels is viable. As a start, test and tune. You can also slow down and maintain more following distance when towing. It is towing and it's different. Pat
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Old 07-24-2018, 01:25 PM   #5
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As I've mentioned in another thread, technology does not cure 'stupid'. Fancy hitches, upgraded tires, trailer disc brake systems, active trailer anti-skid systems, and the like should be thought of as safety and handling enhancements, not an invitation to drive as fast as possible...

Many accidents, including ones leading to destructive trailer roll-overs initiated by uncontrolled sway incidents, can be attributed to "speed too great for conditions".

There is no real need to tow any trailer at speeds above the posted truck, trailer, and towing speed limit. In California, its set at 55 MPH. I've lost count of the number of rigs going by me at way over that limit, and I usually am glad to see them go past me safely--so I don't get caught up in the aftermath.

Yeah, its good to have your setup such that the tires, hitch, brakes, and tow vehicle can support moving out at greater speeds--Texas is one example of a place that does not place reduced speed limits on towed vehicles, IIRC. But why push it?

Being ABLE to tow at 65+ miles per hour does not mean you NEED to tow at those speeds. Slow down, relax, and enjoy the scenery at a much slower pace. Doing that improves your chances of surviving the experience without breaking equipment, causing injuries, or losing lives.
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Old 07-25-2018, 09:27 AM   #6
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Quote:
Originally Posted by rmkrum View Post

Yeah, its good to have your setup such that the tires, hitch, brakes, and tow vehicle can support moving out at greater speeds--Texas is one example of a place that does not place reduced speed limits on towed vehicles, IIRC. But why push it?

Being ABLE to tow at 65+ miles per hour does not mean you NEED to tow at those speeds. Slow down, relax, and enjoy the scenery at a much slower pace. Doing that improves your chances of surviving the experience without breaking equipment, causing injuries, or losing lives.
Well said. A word to the wise should be sufficient . . .
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Old 07-25-2018, 12:38 PM   #7
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If you have a Tuson Direclink brake controller, properly adjusted, you will not experience the Hensley/ProPride bump when stopping. That is one reason Airstream sells and installs them at the Factory Service Center. That is the smoothess controller I have ever used, bar none. The reason it is so effective is that it uses the OB-II socket for TV bracking signal input thus eliminating any delay in the TT braking system, even with electric/hydraulic disc brakes.
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Old 07-25-2018, 12:50 PM   #8
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The standard brakes on modern Airstreams are drums, so the brake system's ability to stop the trailer depends on how much you've been using the brakes over the past few minutes. Over-used, drum brakes WILL get to the point at which they can no longer dump enough heat to the atmosphere to be effective, but when they're cool they work quite well. As a test I've stopped my rig from 20ish MPH using only the trailer brakes, and as long as I wasn't being hamfisted with the controller and locking up the trailer wheels the braking force is significant. Less braking than the full system, of course, since the 5000-lb truck was also relying on the trailer's brakes.
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Old 07-25-2018, 01:34 PM   #9
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A Dissenting Opinion, sort of.....

As with most such questions, the true answer is "it depends...." My 9100# Classic 30 had the same 4 - 12"x2" drum brakes as my 6300# Safari 25. Clearly the 25 was over-braked, or the 30 was under-braked, or both.

While you do not want to lock up your trailer brakes in a panic stop (that is why all newer motor vehicles have anti-lock brakes) you do want to have enough braking power to be just below that limit. My Classic did not. The Classic brakes were properly adjusted and the linings were not excessively worn nor was there any evidence of grease, glazing, or burning.

Referring to ADVENTURE.AS' signature "One test is worth a thousand 'expert' opinions" I did a test. The bottom line is I doubled the braking power of my Classic 30 by converting it to disc brakes. Before the conversion, I got the distinct feeling that the trailer was pushing the truck. After the conversion, while I do experience the "Hensley Bump" in a panic stop, after less than a second the disc brakes spool up and the trailer pulls back into its normal towing position. This tells me that the trailer is not only doing its fair share of the braking, but helping (if just a little) to stop the truck.

For the results of my test of trailer brake stopping power, refer to the first post in the thread:

http://www.airforums.com/forums/f439...ss-177345.html


Your mileage may vary....a lighter trailer may do just fine with the OEM brakes, but even if initially adequate, they will fade and they do not like getting wet. Discs do not have those problems, at least not to anywhere near the degree that drums do.



Al
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Old 07-25-2018, 03:33 PM   #10
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Hi

I've never found the braking on the trailer to be inadequate. Maybe I just don't drive fast enough

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Old 07-25-2018, 05:01 PM   #11
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I'm with RM on this. Every time I tow the brakes get tested/tuned and the brake controller adjusted. Simply knowing the rig will stop in a predictable manner is a good thing.
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Old 07-25-2018, 05:10 PM   #12
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My absolute favorite thing is departing a campground on a dirt or gravel road.

There I can get the rig up to 25-30 MPH, and push the manual brake control to full on. At which the AS tires should lock and slide.

The cloud of dust from all four wheels lets me know I'm about right on the adjustments...and my brakes are responding.

Then, when I get to the paved road, I can refine the setting a bit. It also lets me get up to towing speed and see how the rig is handling. Porpoising on the front end means tighten WD a bit. Eventually I'll be able to hit a switch to do that with the power WD jacks I'm rigging.

As Wally Byam once said, "Make no changes, only improvements.." I guess it's up to me, then.
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Old 07-25-2018, 05:40 PM   #13
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I feel that my truck and trailer stop better together than the truck does by itself. The trailer brakes are excellent.

I may also have done a big smokey burnout while towing my racecar trailer by pulling the lever on the trailer brakes and laying on the throttle.
Don’t try that.
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Old 07-26-2018, 06:51 AM   #14
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The brakes on the Classic have always worked very well, especially after the TruControl, adjust it once for load and let it do it's job.
No brake bump. (if strut bars adjusted properly).

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