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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Re: 60/40 Rule Rocks

Postby elcam84 » Tue Sep 26, 2017 10:13 am

Yeah best to stay with the us made tires. And don't forget to have them balanced using a lug centric adapter.

As for the 60/40 rule it is typically misunderstood and misused. The rule is 60% of the loaded trailer weight in front of the axle centerline. It is not length of trailer is is weight.

Teardrops will end up with the axle further rearward than say a utility trailer which will have it further forward. Teardrops have much of their weight at the very rear where as other trailers have their loads typically at the front of the trailer. Hence it is determined on weight placement not trailer length. The starting point for typical trailers is for every foot in box length you place the axle 1" to the rear of box centerline. Then you adjust that depending on how the trailer will be loaded.

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Re: 60/40 Rule Rocks

Postby dancam » Tue Sep 26, 2017 1:02 pm

With the 60/40 are you calculating just the box or deck area of the trailer or the tongue too?

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Re: 60/40 Rule Rocks

Postby Aguyfromohio » Tue Sep 26, 2017 3:54 pm

elcam84 wrote:... As for the 60/40 rule it is typically misunderstood and misused. The rule is 60% of the loaded trailer weight in front of the axle centerline. It is not length of trailer is is weight...


You might want to rethink that.
My understanding is different.
Last edited by Aguyfromohio on Tue Sep 26, 2017 4:12 pm, edited 2 times in total.
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Re: 60/40 Rule Rocks

Postby Aguyfromohio » Tue Sep 26, 2017 4:10 pm

dancam wrote:With the 60/40 are you calculating just the box or deck area of the trailer or the tongue too?

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Snooping around the threads I found I should use the length of the deck (box) only ignoring the hitch length forward of the deck.
That's what I used and it agreed very well with my more elaborate calculations.

It would be nice if one of the experienced masters around here can confirm that.
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Re: 60/40 Rule Rocks

Postby elcam84 » Mon Oct 02, 2017 11:55 am

Aguyfromohio wrote:
elcam84 wrote:... As for the 60/40 rule it is typically misunderstood and misused. The rule is 60% of the loaded trailer weight in front of the axle centerline. It is not length of trailer is is weight...


You might want to rethink that.
My understanding is different.
Do a quick Google search on trailer axle placement and even the first result shows the proper starting position.

60/40 is for weight distribution but not to exceed tongue weight rating of the hitch.

Axle placement is 1" rearward of box centerline of every foot of box length. Tongue is not measured. But this is the starting point.

A teardrop will need the axle further rearward due to being heavily weighted to the rear. A trailer for a glider will have the axle roughly at the middle. But final placement is based on weight not length of trailer.

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Re: 60/40 Rule Rocks

Postby Camp4Life » Mon Oct 02, 2017 12:25 pm

This 60/40 rules is far too ballpark IMO. The proper way is to have 10-15% of the trailer's weight on the tongue. Anything else is guestimating. :thinking:

I know some TD's are ultralight, but you have to take your tow rating into consideration. A 1000 lbs trailer being pulled by a half-ton pickup truck won't be phased by slight differences, but when you're using a smaller car/suv, you might be playing close to your vehicle's hitch rating, payload, and GAWR/GVWR, in which this case, the 10-15% rules is very important.

Just my 2 cents.
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Re: 60/40 Rule Rocks

Postby Aguyfromohio » Mon Oct 02, 2017 1:18 pm

Thanks elcam84 and Camp4Life.
I asked for comment from the masters around here and you folks chimed in as requested, much appreciated.

I guess I was just lucky that 60/40 by length-excluding-hitch came out so close to the results of the more detailed calculations.
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Re: 60/40 Rule Rocks

Postby Camp4Life » Mon Oct 02, 2017 2:00 pm

Aguyfromohio wrote:Thanks elcam84 and Camp4Life.
I asked for comment from the masters around here and you folks chimed in as requested, much appreciated.

I guess I was just lucky that 60/40 by length-excluding-hitch came out so close to the results of the more detailed calculations.


That would be lucky, yes :thumbsup:

If you truly want to get into the nitty gritty of if you're towing safely, the first two are easy.

1) Tow under your limit for your car and its hitch rating
2) Ensure weight is not being taken off of your front wheels (VERY DANGEROUS!)

#2 is especially important for steering, and because front brakes do the majority of braking. This is easy to test. Measure the height of your fender from the ground with no trailer. Attach the trailer and measure again. If the front raises up more than 1/4 inch, you have too much weight being taken off of your front wheels. This again is ballpark, hit the scales to know for sure!

Speaking of scales, you can find these (IE CAT Scales) at truckstops and garages. Usually under 10 bucks to use and free to re-weigh once. They measure the weight of each axle one at a time.

Your vehicle will have Front GAWR (Gross Axle Weight Rating) and Rear GAWR, sometimes found in your door jamb, or in your owner's manual. When you weight your axles, your rear cannot be overloaded, and your front should weigh more with the trailer than without.

If your front axle weighs LESS with the trailer attached, you need to move some weight to the back of the trailer, or use a weight distributing hitch.

Remember that your maximum tow rating of your vehicle and your max hitch weight are 2 different things. Just because your hitch can handle X lbs, doesn't mean the vehicle can. Hitch rating is what the hitch can structurally handle by itself. For example, my hitch on my F-150 is rated for 11,000 lbs, but my truck can only tow 8,300 lbs. The latter is derived from the configuration (Super Crew cab), engine and drivetrain.

I'll leave it at that for now. There's much more to consider, like GCWR, GVWR, but you only get into those with much larger trailers.

:beer:
Last edited by Camp4Life on Mon Oct 02, 2017 2:01 pm, edited 1 time in total.
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Re: 60/40 Rule Rocks

Postby elcam84 » Mon Oct 02, 2017 2:01 pm

Aguyfromohio wrote:Thanks elcam84 and Camp4Life.
I asked for comment from the masters around here and you folks chimed in as requested, much appreciated.

I guess I was just lucky that 60/40 by length-excluding-hitch came out so close to the results of the more detailed calculations.
Thing is every trailer will be different because they are all loaded different.

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