Re: M101 trailer weight capacity

From: MV (MV@dc9.tzo.com)
Date: Fri Mar 17 2006 - 06:54:07 PST


Yes, bias ply tires heat up a lot more than radials. Heat kills tires -
if they get hot enough the cords separate and a blowout occurs. Radials
run much cooler.

I have to admit that I'm not that familiar with the specifics on the
M101 trailer, and the government tends to greatly underrate the MVs.

You need to look at your trailer from a "weakest link" perspective. If
the tires are rated at 6600 lbs in total and the everything else can
handle that but the wheels are only good for 5000 lbs total - then you
are stuck with weak wheels and a reasonable rating of 5000 lbs.

Also, you need to think about axle rating. Most 3" diameter axles -
tube axles (which I think the M101 has) - are good for at least 5000
lbs. Some 3" diameter tube axles with .25" wall are used in on the road
application at up to 7000 lbs.

Make sure your bearings are well greased. At every stop while traveling
with a load I do a walk around and touch each hub and tire. You can
usually spot failing bearings that way before something catastrophic
occurs and tell if you are pushing your tires too hard. In 20 miles not
much should be heating up at all. If something is getting hot in 20
miles - you may have a problem. But keep in mind that hubs can also get
hot from hot brake drums on long downhill descents.

Regarding springs - most trailer springs are at full load when they are
deflected or pushed up 1 inch when loaded statically and you are not
moving. I know that doesn't seem like a lot but you need to remember
that they deflect a lot more than that due to shock loads like bumps and
potholes.

So you can check for spring overload rather easily - measure the axle to
frame dimension when unloaded (only the trailer itself is resting on the
springs), and then load up the trailer. If the new dimension is has
decreased by more than 1 inch, then you are definitely overloading the
springs. (Remember that the empty trailer was already deflecting the
springs somewhat before you put the load on it.)

Another thing to consider is the trailer frame. The M101's tongue
doesn't look all that heavy. Keep a look out for cracks - they would
most likely appear near where the tongue comes out from under the
trailer body.

You need to keep about 15% of the trailer weight on the hitch. Some
people try to run 10% or less, but that is asking for trouble especially
  with a tall trailer that can rock backwards and unload the tongue
under some circumstances. That means that if you have a 5000 lbs
trailer you should have about 750 lbs on the tongue. Seems like a lot,
and it is, but loosing control of your truck and trailer due to a
whipping trailer makes for a very bad day if you make it. This is why
gooseneck and fifth wheel trailers are so popular.

I was involved in a wreck with a large travel trailer and a car that had
insufficient tongue weight on the Pennsylvania tollway - we did a 360 on
the tollway before the car stopped nose first into a bridge abutment.
No one was seriously injured. Car and trailer were totaled. I was
quite young at the time, but you only live through that mistake once and
then you will make sure it never re-occurs!

Dave

Darrell Ramsell wrote:
> Thank you Dave for this info. This is a character of the bias tire that
> I was not aware of.
>
> I actually have a set of radials but I've kept the bias tires because I
> have run-flats for them but not the radial. The cargo I carry is very
> heavy and expensive. The last thing I want to see is the trailer
> flipping from a blow out and spewing my merchandise all over the road.
> I figured that should a tire go the run-flats will prevent this.
>
> I have another question for you. What is the proper way to calculate
> the weight load on the tires? From your reply is sounds like I might
> not be doing right. It is my understanding that you add the max weight
> of the tires and make sure the load doesn't exceed the combined tire
> rating. So if each wheel has a max rating of 3,300lb that 6,300lb minus
> the load of 4,500lb (3,000 load + 1,500 trailer). That leaves an excess
> of 2,100 lb. I thought this was more than sufficient safety cushion.
> If this is not right please let me know. (I'm sure many of you trucker's
> can help me with this one.)
>
> I also want to mentioned that before I started doing this. I asked
> several people who owns an M-101 trailer as well as people on this list
> was and what was the risk of exceeding the weight rating? Most told me
> that with military trailers, their weight rating is for off road but for
> HWY use you can essentially double that.
>
> I also replaced the shocks with a new heavy duty type and replaced the
> leaf springs with one that has an extra leaf. I don't know if this
> increases it's load capacity (Does it?) but I didn't do it for this
> reason. I did it as an added safety measure. I also replaced the U
> bolts with new ones too. I also know the axle rating is involved in this
> equation too but I don't know enough about the M-101 axle's capability.
>
> I've been towing a load, with my HMMWV, of approximately 3,000lb once a
> month for over a year now. The distance I drive is 20 mile and almost
> all of it on the HWY. I always try not to exceed 50 mph when I'm
> driving with this load. I inspect the trailer after every haul and have
> not noticed any damage. The only thing I have notice is that the inner
> side walls of the tire occasionally rub against the trailer (this most
> likely occurs when I hit a pot hole or a large bump) but it has been
> light and there has been no noticeable loss of rubber on the tire.
> Anyway, the main reason I'm mentioning this is to simply share my
> experience.
>
> If anyone has anything useful to add, I'd like to hear it.
>
> Thanks
>
> Darrell
>
>
>
> ----- Original Message ----- From: "MV" <MV@dc9.tzo.com>
> To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
> Sent: Wednesday, March 15, 2006 10:28 AM
> Subject: Re: [MV] M101 spacers
>
>
>> While that trailer might be able to handle 3000 lbs on it (but just
>> barely?) those tires would have about 2000 lbs on each one at that
>> point and while that is not a lot, bias belt tires really don't handle
>> running at the limit on load and while driving at high speeds.
>> Radials do much better and can be pushed a lot harder than bias belt
>> tires without failing.
>>
>> Life is short and can be shorten even further by using lousy tires.
>>
>> Dave
>>
>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>.
>>
>> djslager@mail.icongrp.com wrote:
>>
>>> Well I have seen alot of miss use of equipment all so, the trailer is
>>> not
>>> rated for that, why not put 6 ton in it and kill it faster........ My 2
>>> cents.......... Just dont kill someone else..........Doug Slager
>>> ----- Original Message ----- From: <M35A2USA@aol.com>
>>> To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
>>> Sent: Wednesday, March 15, 2006 5:49 AM
>>> Subject: Re: [MV] M101 spacers
>>>
>>>
>>>
>>>> I had a friend who was towing a M101 trailer with over 3K lbs in it
>>>> and
>>>
>>>
>>> both
>>>
>>>> bias 900s blew at the same time on the interstate... interesting
>>>> ride RAM
>>>>
>>>>
>>>> ===Mil-Veh is a member-supported mailing list===
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>>>
>>>
>>>
>>>
>>> ===Mil-Veh is a member-supported mailing list===
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>>>
>>
>> ===Mil-Veh is a member-supported mailing list===
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>>
>
>
> ===Mil-Veh is a member-supported mailing list===
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> To reach a human, contact <ackyle@gmail.com>
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>



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