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Old 06-16-2010, 04:17 PM   #1
brulaz
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Default Tacoma+Elkmont weights

Not sure where to put all this. The admin may want to move it.

Anyway, here is some weight info, calculations and speculation about our Tacoma + Elkmont combo.

We found a CAT scale on our current trip that measures 3 axles simultaneously. I ran across it three times for only $15; well worth it. Each time I tried to line up the truck at the same position, but the operator didn't think that was really necessary.

The first time was truck+trailer with WDH 800# spring bars cinched up to the max:
Steer Axle: 2760#
Drive Axle: 2940#
Trailer Axle: 3240#
Total: 8940#

Then I removed the WDH spring bars and got this:
Steer Axle: 2400#
Drive Axle: 3500#
Trailer Axle: 3040#
Total: 8940#

Finally we dropped the trailer:
Steer Axle: 2700#
Drive Axle: 2580#
Trailer Axle: 0#
Total: 5280#

So the loaded trailer weight is only 3660# (8940-5280), well below it's rated GVWR of 4230# and below the Tacoma's trailer hauling capacity of 6500#. The trailer was reasonably well loaded for these measurements: maybe 12gal freshwater, 40# propane, packed frig, all our other food, clothes, cookware, bicycle. I've also replaced the original battery with two golf cart types and add a 2gal water pressure tank. The trailer's dry weight with all the factory options, and before my mods, is declared to be 2980#, so we added about 680#.

At the WDH's max setting, an additional 200# (3240-3040) is put on the trailer axle. But that 3240# is still below the trailer's GAWR of 3619#, with 379# available.

The trailer's tongue weight, without the WDH spring bars, is 620# (3660-3040). That's 17% of the trailer's weight, pretty high. With the WDH, the tongue weight is reduced 200# to 11.5% of the trailer weight.

At the truck, the WDH removes 560# from the drive axle and adds 360# to the steer axle (the other 200# going to the trailer axle). The drive axle weight with WDH (2940#) is below its GAWR of 3110#, but the steer axle is 5# over its GAWR of 2755#. Without the WDH, the drive axle would be over-loaded by 390#.

The measured combined weight of 8940# is well below the Tacoma's GCWR of 11100#. But the Tacoma's GVWR of 5450# is exceeded by 250# (5700 = 2760+2940).

The truck was loaded with a cap, two kayaks, two people, 5gal water, bicycle, computer gear, outdoor rug&chairs, misc. boards and tools. Since taking these weights, we've moved the water, computers and some tools back to the trailer as it has more available capacity. This should put our steer axle weight under its GAWR.

My interpretation of all these #'s and ratings is that the Tacoma's axles, suspension, engine, transmission and drive train are capable of handling our Elkmont+load. And even though we are not close to exceeding the Tacoma's GCWR and trailer hauling capacity, we are close on the GAWRs, so we have to be careful.

But by exceeding the GVWR, I suspect that we are exceeding the truck's braking capacity (the GCWR assumes your trailer has brakes and can stop itself). I'm not sure whether this rating has more to do with long, down-hill braking or emergency braking. I can (and do) use the transmission to brake on long hills as the rear brakes are the old-fashioned drum type, not disk, and probably prone to over-heating.

As for emergency braking, I'm not sure what to do. By setting the Prodigy brake controller higher (7), I can use the trailer brakes to help stop the truck, but they get very hot and grabby in stop/go city traffic, so I've dialed them lower (5). But maybe dialing them back up would provide shorter stopping distances? Even when dialed high, I've never had the trailer brakes lock up, so maybe I'm being too cautious.

Two more things:
There is link posted on this board somewhere that explains how to calculate the weight your WDH will shift to the trailer axle. Because I've got my 800# spring bars cinched up to their max with only 5 links between the spring bar to frame hook, I made the calculation assuming each bar levered 800#. The result was a 210# weight shift, pretty darn close to that 200# measured. You can also calculate the weight taken off the drive axle and put on the steer axle and these calculations were reasonable too, though not quite as close to the measured.

I've gone to the full cinched up position on this 800# WDH because all lesser tensions allow the front end to rise slightly, and in this position the truck+trailer has the most solid, "planted" feel. Also, sway becomes negligible, and sway bars unnecessary.
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Old 06-16-2010, 05:19 PM   #2
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Wow, that is some of the best weight info we've seen! I'm particularly impressed at how well it demonstrates the effect of a WDH. Some members have been skeptical ... but I think that is over now.

Thanks for posting it. I think we will refer to it often.

Bill
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Old 06-16-2010, 07:52 PM   #3
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Quote:
Originally Posted by brulaz View Post
Even when dialed high, I've never had the trailer brakes lock up, so maybe I'm being too cautious.
You really never want the trailer brakes to lock up. Your TV has much better quality anti-lock brakes than the trailer. In a panic stop with locked trailer brakes, the trailer will have less friction than the TV, and it will tend to make choices completely on it's own about whether to try to pass you on the left or on the right. And, if you set the controller so that the trailer just almost-but-won't-quite lock up on dry pavement, you still have to think about how this will work someday on wet pavement. I'm a fan of practicing these things in a big parking lot by yourself somewhere until you have some idea about how your rig will behave.

Because of uncertainties like these, I would never tow a heavy trailer in snow except in some dire circumstance.
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Old 06-17-2010, 05:16 AM   #4
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Bill, somehow I knew you would like it.

Quote:
Originally Posted by Mr. Adventure View Post
And, if you set the controller so that the trailer just almost-but-won't-quite lock up on dry pavement, you still have to think about how this will work someday on wet pavement.
Yes, this is how the trailer brakes should be set up according to the Prodigy manual (which was what I was referring to). But, it doesn't seem right, and I've set them a lot lower.

I like the parking lot suggestion and hope to give that a try, after tying things down in the trailer.
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Old 06-17-2010, 09:39 AM   #5
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Great job of getting that rig weighed and analyzing the results. I'm sure that you feel much better, more confident and knowledgeable about your rig.

I find it interesting that the only people that seem to have their rigs weighed are the ones that don't have issues with being too heavy. It seems like it should be the other way around. It appears that some feel that the problem doesn't exist if they don't know about it.

Anyway, glad that you had the rig weighed. I'm impressed that it is as light as it is. I look forward to pulling it someday.
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Old 06-30-2010, 05:29 PM   #6
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Never got to a parking lot to test the brakes on this Tacoma+Elkmont combo as we had to cut our trip short for family reasons. But there were several very steep, curvy grades on the Cabot Trail in Cape Breton, Nova Scotia, and we did have to make an emergency stop along the way.

The emergency stop caused the truck tires to squeal but not the trailer, as the brake controller was at a fairly low setting of 5. And there was a slight jack-knifing as the trailer pushed the truck forward a little. Luckily there was no damage, but I reset the Prodigy brake controller to 7 and plan to leave it there from now on.

The 7 setting came from those long down-hill grades in Cape Breton, most of the time in third gear, often in second and once even in first gear. Despite the low gearing, braking was always necessary. There were frequent scenic pull-outs available, and I used those to test the trailer and truck drum brake temperatures with the spit test (put a little spit on it and time how long it takes to evaporate). After trying different brake controller settings, it seemed that 7 gave about the same temperature on both sets of drums. At 9, the trailer brakes got hotter than the truck brakes and vica-versa at 5.

The thing I don't like about the 7 setting is that the brakes seem grabby during urban stop-and-go, and the trailer braking can be felt before the truck's. But this can be lived with.
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Old 06-30-2010, 06:36 PM   #7
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Grabby during stop and go? Yup, I've experienced the same thing, with both my Jordan Ultima and my Prodigy. Never figured out what to do about it, but since low-speed grabbiness is a small price to pay for good high-speed braking, I'm with you, and I live with it. Annoyed beats dead any day.

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Old 06-30-2010, 08:37 PM   #8
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Bill & Bruce,

I found this writeup on grabby brakes: Better Braking Report by HENSLEY MFG. INC.
http://www.brake-controller.com/news...ng_report.html

Quote:
On most brake controllers, the driver adjusts this initial power output with the GAIN control. That way, the power can be reduced in city driving to keep the trailer from “grabbing” the brakes, resulting in the “bobble head” effect on the tow-vehicle occupants. The safety issue here is that the driver can fail to turn the gain back up for high-speed driving, which can result in an accident in a panic stop situation.
Mike
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Old 07-01-2010, 07:19 AM   #9
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Interesting article. As an electrical engineer, I take exception to some of the things they said. But there is no doubt that Hensley builds decent stuff.

They did point out that disc brakes are better at high speeds, and drum brakes are better at low speeds, which is something I hadn't really considered. I haven't found a reliable source for this conclusion, either, but it does seem to match the observed low-speed grabbiness. Dexter Axle (maker of the TM axle assemblies) does make disc brakes for trailers. I wonder if they behave differently?

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Old 07-01-2010, 09:54 AM   #10
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I've used 4 different brake controllers on my TM:

1. A cheap time-based controller.
2. Hensley's controller
3. Chevy's integrated brake controller
4. Ford's integrated brake controller

The only one I wouldn't use again is the time-based controller. IMHO you are taking your life into your hands with a time-based controller. It's not worth it, and I think these unsafe devices should be banned from sale.

I noticed a bit of difference between Hensley's controller and the Ford/Chevy integrated controller - but very little, and certainly not enough to be unsafe. Based on the small difference in ride quality between the 3 decent controllers I've used, I have a hard time seeing how the Hensley controller could possibly be either safer or significantly better for the ride than the Prodigy - just based on how the devices all work. I really don't think Hensley has justifications for the extra cost compared to the Prodigy - but I haven't towed with the Prodigy, so I could be full of it. But if I had it to do over again, I would have tried the Prodigy first.

(for reference, having towed with Hensley, Chevy, and Ford, I'd pick the Chevy controller first, the Ford one second, and the Hensley one third - but all worked well)
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