Wheel Wells and Tire Failure

perhaps overkill but the amount of money invested in my tm and for the safety of my family, i replace both tires on the anniversary date of my purchase. cost for new(2) good year marathon 287.00

[Denny_A]

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Maybe the exercise I went thru is much ado about nothing - if the axle's max is a few hundred lbs more.


Denny_A

OK, here's the scoop.

My math on the tire loading was correct. With equalizer installed and trailer loaded to max, they use 600 lbs as the tongue weight (or 14.7% of max gross, whereas I used 480 lbs). Therefore, 400 lbs (2/3) is transferred to the tow vehicle. So the force on the tires will be 4070 lbs (2720 model) - 400 lbs = 3670 lbs. The two tires are rated at  3740 lbs total. The 2720 has the greatest MGVW, therefore other models, 2619 and 3023 are less affected.

According to Mike Hulsey, the axle is rated for 3500 lbs. Howsomever - the wheel weight and axle weight are not counted in the total. Standard practise? Sprung vs. unsprung weight, and Mfr has already accounted for it's own axle. Axle plus wheels is more than 150 lbs. I will assume 170 lbs, for a reason which will be obvious.

This means that the 3500 lb limit should be figured this way:

    GVWR - WDH to tow vehicle - axle/wheel combo.

    (4070 - 400 -170) lbs = 3500 lbs

Mike also mentioned they asume that when the WDH is connected the front of the tow vehicle is not lower (relatively) than the rear of the car. As in NOT transferring excess download to the trailer.

Mike Hulsey told me that an organization which weighs and tests travel trailers has reported to them that TrailManor's units have tested as advertised, whereas many, many TT's were designed employing real fuzzy math in determining GVWR.

I hope I didn't cause any problems with my ramblings. If anything, I feel MORE confident that TM has applied sound enginering principles in designing and building their unique trailer. So, for me at least, this has been a useful, enlightening exercise!


Denny_A    :P

Great Information!

Thanks for making all the phonecalls and calculations.  Sorry I missed the math error earlier (I should have said +/- 100lb as CYA).

I guess I'll still weigh my trailer some time soon.  When I do, I'll post the results.  Perhaps we can start another thread for owners to post their various findings???

[Bill]

Excellent idea - I would like to see some results.

BTW, where would one get a TM weighed? If you pull into a truck stop with a scale, that scale probably has a max capacity of 100,000 pounds, and an accuracy of (maybe!) +/- 2 % of full scale, which is 2000 pounds. This is plenty accurate for your average 18-wheel over-the-road truck, but it seems silly to pull in with my TM, ask for the weight, and expect it to be accurate within 50 or 100 pounds.

Bill

[Denny_A]

Excellent idea - I would like to see some results.

BTW, where would one get a TM weighed? If you pull into a truck stop with a scale, that scale probably has a max capacity of 100,000 pounds, and an accuracy of (maybe!) +/- 2 % of full scale, which is 2000 pounds. This is plenty accurate for your average 18-wheel over-the-road truck, but it seems silly to pull in with my TM, ask for the weight, and expect it to be accurate within 50 or 100 pounds.

Bill

Truck scales are generally segmented; anywhere from 2 to 4 separate segments. Three is what I've seen.

They actually are very accurate. I usually park my van on one segment and the trailer on another. If weighed that way, the print out will show both weights; that is 1) tow vehicle weight + WDH down force, and 2) actual force on the trailer wheels.  My local truck stop charges $7 a pop. For another $7, I disconnect the trailer, so that the tow vehicle and the trailer actual wts are recorded. The tow vehicle wt decrease and the trailer wt increase should be identical, since total weight must remain constant. It is also a good cross-check on scale accuracy!

If you stay in/with the tow vehicle on one weighing be sure to do the same during the next weighing. If a trucker pulls up to the scales just as you're starting this process, and he's in a hurry, he'll just squash you.    So check with the folks inside first so they know if you're going to be reweighing. They get confused if you don't. Ask me how I know. On 2nd thought, don't!


Denny_A

Suggestions for finding scales.  1- look under Public Scales in your yellow pages.  2- Look for businesses that sell firewood  (sometimes rather than measure it by the cord, they weigh it.) 3- Businesses that buy scrap metal and aluminum cans.  4- If you live in the country, look for feed and grain businesses. 5- Some of the larger truck stops have scales as you suggest.  If they are off by 2% the total amount would be less than a huge trucks weight.

Hal

ps.  I just looked in our city phone book.  I found five or six under Scales Public rather than Public Scales.  Any type business in which people bring a product or buy a product that needs to be weighed may have a scale.  For example, we have a scrap paper buyer. Possibly an ice company or coal.

Hal

  I was told by the folks who run the A'weigh We Go motor home & trailer weighing clinic that if you take your rig to a scale regulated by the ICC, (a highway trucker scale), and if the official notices that your rig is overloaded they can make you park it right there.
  Our 3124 weighed in at 4800 lbs, just 200 lbs under the limit, when we had it checked by A'weigh We Go at the TM national rally in Rapid City, SD.
  We were told at the clinic that the Gross Combination Weight Rating (GCWR) limit of the tow vehicle is very important. This is the weight of the vehicle & trailer, both loaded and "ready to go". Your GCWR limit might be in your vehicle's owner's manual or you can get it from the manufacturer.
 In my case I changed out the rear axle ratio on my tow vehicle to come into compliance.

Bruce

There was an article last year in a magazine for boat trailer manufacturers and an a bi-monthly camping magazine.  Three manufacturers responded, Goodyear, Carlisle and ?.  I may be able to find the article if anyone is interested. I downloaded it and saved it somewhere.  That was where the 65mph-speed rating came from.  I also found out something interesting while reading tire data sheets Friday.  If you put a passenger tire on a light truck, the load rating drops 10%.  According to the shop owner, this is because more stress is placed on the sidewall due to the height of a truck or van vs a car.  Michelin once   :'( offered a Load Range "D" truck tire, LT215/75R15.  For a 14" LRD, someone makes one that was for the Toyota RV's.  I could see the need for a stiff sidewall on a 5th wheel or full height trailer, but I have known people who pull boat trailers on speed rated car tires and have done so for many years and at high speeds and they would never go back to a "trailer" tire.  One interesting note from the Michelin web site was that a 2 pound increase in air pressure appears to change a 100 mph rated tire to a 112 mph rating.???    http://tires.michelin-us.com/assets/pdfs/doc_ltxms.pdf
I guess this means, really watch the tire pressure.

[Bill]

If anyone makes a 14" Load Range D trailer tire, I sure would like to know about it.

Bill