Super Singles Rollover Danger?

[cbvet]

Recently got an M813A1 with Michelin 1400X20 Super Singles.
A buddy says he has heard of rollover accidents related to this tire setup.
Anyone familiar with this?
Eric
CBVET

 

[steelsoldiers]

I had the 14R20s on my 923A2 and it never felt unstable in sharp curves at speed.

There are several issues with these big tires though. If one of the front tires blows, the wheel has a good ways to go, about 14", before it hits the pavement. That coupled with a lot of weight on the front end, a panic stop and over-steer could cause a rollover. Another issue is with under-inflation. The 939 series manual recommends 70 PSI for highway speeds. One other issue that your buddy may have heard about was related to the 939 trucks skidding and rolling after a panic stop and over-correction. It was related to air brakes and NDT's. The 14R20 tires actually helped prevent accidents and the ABS MWO almost eliminated the problem.

I don't think you'll have any issues. Just make sure they are in good condition and properly inflated. Check for low tires at every stop.

Enjoy that beast of a truck!!

 

[M543A2]

I do not have one of these trucks. I have heard rumors also about the problem. I can say that I used to take the outer wheels off the rear tandems on my M220 deuce for winter. This helped cut through the snow better. The rims for the dual wheel trucks have a deeper offset than the rims for the single wheel version (M135), so the remaining inner wheels were inset narrower than the ones on the normal single wheel tandem version. The hub offset for the tandems is also different, inset toward the chassis, making for more offset. I thought I might have hurt the stability of the truck, but using it to haul wood out of the woods and fields was no problem. I never got into a situation where I felt there was a danger of roll-over. Now, granted, some careless people can roll over a tank given the right conditions! I would say the truck is OK given one uses good sense in driving it.
Regards Marti

 

[cranetruck]

Locate the center of gravity, should be on the data plate, and make a scale drawing of the truck viewed from front or rear. Draw a line from the CG point to the center of the tire where it touches the ground.
This drawing will show you at what theoretical angle the vehicle will roll over if standing still, at least. Tilt the drawing until the line is vertical and you'll know when.

 

[steelsoldiers]

Or get a forklift and keep raising one side of the truck until it flips

 

[cbvet]

Chris,
Your answer reminds me of the time I bought a Hovercraft. Rated for 600 lbs capacity on water. I asked manufacturer how they came up with that rating.
He said there are engineering books they could use, Coast Guard formulas, & several other methods available.
I asked what formula they used.
He said "We filled it with bricks until it sank"!
Eric
CBVET

 

[cranetruck]

Sorry about being "technical" and I tried to make it simple!!!!

It gets just a little more complicated if you have to recalculate the CG with a load with its own specific CG.
Actually wrote an article on this for MVM a few years ago...

 

[cbvet]

Bjorn,
I understood what you were saying alright, bur Chris' answer WAS funnier.
Eric
CBVET

 

[yorkgulch2]

On an m35 395x20 tires seemed to make it more stable

I tried getting it to roll over but all it will do is fetch and speak!

 

[M813rc]

The main rollover cause appears to be loss of control on wet roads. I have read multiple military accident reports on the 5-ton with the same basic story- wet road, sudden braking, loss of control, slide off road, over she goes. The military has a wet pavement speed restriction of 35mph for 5-tons with the super singles (this from Sarge, who has bucket loads of military driving experience, and a buddy who drove 5-tons in the Marines). This is because they are rather prone to swapping ends on heavy braking when not loaded, encouraged by the lower ground loading of the super singles.
I can attest to this tendancy thanks to some help from a moron in a little car who whipped into my lane, then slammed on the brakes. Trust me, it wasn't fun (neither was extricating the seat cushion from the nether realms). Didn't hit anything though. I learned of the speed restriction AFTER this event! Says Sarge upon hearing my tale of woe- "Oh yeah, by the way....".

Those who have driven civilian pickups know this same end-swap thing is true for them, it's just so much more exciting when your pickup weighs 22000#!

Cheers....R

 

[OPCOM]

I've had people cut me off stupidly like that. I don't feel like it's my duty to risk my own safety or life to accomodate their negligence or stupidity. I'll use the brakes, but swerving is out of the question, as I am top-heavy with 5500 lbs in the bed. I have considered adding an unauthorized second bumper under the current one to help protect the underside of the truck's frontside better and help keep the bulk of the idiot's vehicle out from under the truck.