60/40 Rule Rocks

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60/40 Rule Rocks

Postby halfdome, Danny » Wed Sep 13, 2017 9:57 pm

The six teardrops I've made I followed the 60/40 rule where 60% of the frame/chassis is forward of the axle and 40% is behind the axle.
I've made small adjustments over the years to a sweet spot that I'm happy with.
On September 4th we were returning home from Camp Runamuck in Newport WA and we lost pressure in a tire and it literally fell apart with smoke and tire chunks flying everywhere.
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I noticed it was happening immediately, the teardrop didn't sway or anything else, just followed the tow vehicle to the side of the road.
I think the two 12volt deep cell batteries behind the axle may have helped keep the teardrop grounded along with the bikes on the back.
It's was actually 5:45pm but with the thick smoke from the fires it was kinda dark outside.
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The fender got a little dirty but cleaned up easily, nothing else was damaged with the exception of the tire.
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It was so controlled we were amazed since we were traveling on I-90 at the posted speed limit of 70 mph.
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It took AAA 2 hours to get a truck to bring a new HI-RUN (China) tire since I never got around to putting a spare on the teardrop.
Today I bought 2 new Goodyear Endurance St205/75R15 trailer tires (Made In USA) since I noticed the Carlisle tires I had on the TD were also Made In China.
About an hour before our blowout we saw a Casita trailer flipped on it's side and the pick up truck tow vehicle was facing towards the traffic, ouch!!! :frightened:
The 60/40 rule rocks :thumbsup:
:D Danny
Last edited by halfdome, Danny on Fri Sep 15, 2017 4:54 pm, edited 1 time in total.
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Re: 60/40 Rule Rocks

Postby S. Heisley » Thu Sep 14, 2017 7:23 pm

Glad to hear everything had a good ending and you all are safe!
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Re: 60/40 Rule Rocks

Postby woodywrkng » Thu Sep 14, 2017 7:38 pm

How old were the Carlisle tires? My 2 year old "USA Trail" tires made by Carlisle say Made in USA on them. Whew. That's impressive you kept it under control.
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Re: 60/40 Rule Rocks

Postby working on it » Thu Sep 14, 2017 8:39 pm

halfdome, Danny wrote:[color=#4000FF...
It was so controlled we were amazed since we were traveling on I-90 at the posted speed limit of 70 mph.
...
Today I bought 2 new Goodyear Endurance St205/75R15 trailer tires (Made In USA) since I noticed [b][i]the Carlisle tires I had on the TD were also Made In China
....
:D Danny[/color][/i][/b]
woodywrkng wrote:How old were the Carlisle tires? My 2 year old "USA Trail" tires made by Carlisle say Made in USA on them. Whew. That's impressive you kept it under control.
  • Glad you and your trailer are OK. This thread addresses two things that made me choose LT tires over getting "most likely made in China" ST tires for my 2020 lb squareback TTT, recently. My experiences using USA-made ST tires had been uniformly favorable, and with Chinese-made ST tires, mostly unfavorable. Most of my experience had been gained towing a 5-6000 lb tandem axle trailer (with race car aboard), at 70-75 mph on all types of paved roads, mostly. I drive fast, both on the dragstrip and highway, but as I get older I adjust to the traffic flow , which in TEXAS, may be 80 mph.
  • Those speeds are higher than the ST tires are rated for, which is 65 mph. I never knew exactly how fast I would actually drive on trips, so I just ran the maximum cold pressure without adjusting upwards for higher speeds (10 psi more if loads are the same at lower speeds), and if I did adjust to the higher pressure, then it would be too high for all lower speeds. Not a very forgiving regimen, as I see it. I chose LT tires for three main reasons: they're rated at higher speeds carrying comparable loads, I wanted a better tread depth and traction available in LT tires (possibly to use on dirt and loose rock- in wet or dry conditions-, and the fact that all the ST tires I might've bought were made in China (the LT tires I bought were made in an American-run plant in Mexico (as I found out after much research).
  • I must note here, that ST tires, Chinese or not, are probably better on tandem-axle trailers, due to scrubbing when turning, and variable load center most tandems carry. With our small single-axle trailers, we can usually determine the ideal load placement, through trial and error, or by using angib's very useful trailer balance worksheet. And induced tire scrub just doesn't occur on single-axle trailers, which enables me to choose the slightly more flexible sidewalls of LT tires. And the LT tires have a better range of speeds, without having to adjust pressure, than the ST tires (note the thousands of users of LT tires on Expedition Portal, where they are constantly deflating their tires for better off-road traction, and later increasing the tire pressure for street use (though some forget, and the under-inflated tires all survived the higher speeds at too low a pressure). Their experiences on single-axle trailers swayed me into the LT camp Though I may soon have to put new, possible Chinese ST tires on my tandem-axle trailer, due to a much lower price point, and my conviction that the heavier trailer could be hauling heavier loads (requiring stiffer/stiffest sidewalls).
  • The tires I replaced on my single-axle TTT were 12+ year old Carlisle USA Trail ST bias-plies, with several repairs each, and weather-checking apparent on both. I couldn't find identical replacement from Carlisle, guaranteed made in the USA, so I bought LT tires, instead. I still have my old tires, one as a spare, on the trailer, and the other one stored in the darkened garage, to avoid more aging, as a reserve spare. I probably will buy a third LT for a spare, and then the old Carlisles can be re-cycled. Here's an article I found recently, after getting the LT tires, discussing a comparison of the two types on RV trailers and motorhomes: https://rvingwithmarkpolk.com/2012/11/08/trailer-towing-st-tires-vs-lt-tires/
  • 2013 HHRv,"squareback/simple" TTT, semi-offroad? 4x8, 2000+ lbs travel weight
  • featuring: 3500 lb Dexter axle w/brakes & HD leaf spring system > riding on General Grabber 27x8.5-14LT tires, LED lighting inside, A/C & heat, AGM battery 12vdc, 110vac from extended run generator onboard or park power, Coleman dual-fuel stove & Northstar lantern
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Re: 60/40 Rule Rocks

Postby Aguyfromohio » Fri Sep 15, 2017 7:57 am

The 60/40 rule does rock.
It's time to place our axles in our builds, so I used three methods to figure it out.

We designed inside a full 3D solid modeling mechanical CAD system, SolidWorks.
We made a pretty detailed model with many levels of sub assemblies down to individual components like interior wall skins and steel frame members.
SolidWorks will calculate full mass properties like center of gravity, mass, volumes, moments of inertia.... for all the components and every rolled up level of assembly.

First I used the 60/40 rule, and marked it on the floor.

Next I went to the CAD system and entered some of the material properties into some of the components.
Used some shortcuts, made some estimates, and did some spreadsheet calculations.
I marked it on the floor, about an 8 inch range to cover some tolerances.

I'm a mechanical engineer, and my conscience nagged at me to knuckle down and enter density into all those dozens and dozens of component model files.
What a pain, it took hours. Of course I made some typos that generated hilarious results- at one point it told me the trailer weighs twelve thousand pounds. :lol:
Cleaned it up, though I'm still not confident i got all the typos and modeling artifacts out.
I finally got a result and marked it on the floor.

That 60/40 rule falls right into the range of my partial calculations with estimates.
The fully calculated result is a few inches forward, but I think I still have some errors in that elaborate model.

So I did a whole bunch of computer and engineering work to confirm the claim.
We will use the 60/40 location.

The 60/40 rule rocks.

It will be fun to see how the weight on the hitch ball comes out at the end.
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Re: 60/40 Rule Rocks

Postby halfdome, Danny » Fri Sep 15, 2017 4:56 pm

woodywrkng wrote:How old were the Carlisle tires? My 2 year old "USA Trail" tires made by Carlisle say Made in USA on them. Whew. That's impressive you kept it under control.

I put the teardrop on the road June 2015 so they were purchased about 5 months earlier.
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:D Danny
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"Conditions are never just right. People who delay action until all factors are favorable do nothing". William Feather
Don't accept "It's Good Enough" build to the best of your abilities.
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