Tire Rating Questions

[THoltz]

I have Michelin LT 235 85R 16 which are load range E tires. The sidewall rating says for rating for single rear wheel tire is 3300 lbs and for dual is 2700.



My questions are:



Why is the rating per tire less for a dual application than a single?



For a dually, is the total load rating for rear tires 4 X 2700 lbs?

 

[georgej]

The lower rating when duelled is because of lack of airflow between the tires. I believe the rear capacity is the axle rating not the tires. .

 

[Bob Cochran]

I alsl believe it you load the duals to 3300LBS the side walls will expand enough that they can rub when tire flexes. This rubbing is not a good thing either.

Yes the tire load rating is 4 x 2700 lbs but not necessarily the axle rating. That you can get off the axle rating shown I believe in the glove box.

 

[GAmes]

I alsl believe it you load the duals to 3300LBS the side walls will expand enough that they can rub when tire flexes. This rubbing is not a good thing either.



Yes the tire load rating is 4 x 2700 lbs but not necessarily the axle rating. That you can get off the axle rating shown I believe in the glove box.

I don't know why the tires are rated for less weight when used as a duel but that is a plausable reason. However the axle rating (which is on the tag on the door post BTW) is not necessarily the real weight rating of the axle. Mine reads GAWR REAR 3402 KG (7500 LB) WITH TIRES LT215/85R16D RIMS AT 16X6. 0 COLD 413 KPA (60 PSI)



So if I upgrade to LT235s load range E, what is the axle rating? If I deflate the tires to 50 PSI what is the rating? If I inflate them to 80 PSI, what is the rating? See where I'm going with this? I have a Dana 80 and I know good and well the manufacturers rating is more than 7500 pounds.



Tires have different load capabilities according to how much air pressure is in them, and to get the maximum tire life they should be inflated according to how much weight they are carrying. I have found 55 in the rear and 65 in the front, even though they are capable of holding 80 gives me 100k miles or more of service AND a fairly decent ride.

 

[Bob Cochran]

It does not matter what your tire rating is the axle rating does not change. So having said that if you put a high enough load rated tire that is above the axle rating it does not raise the axle rating. Lowering the tire pressure rating does not lower the axle rating either but does lower the tire load rating as does increasing the tire pressure to max sidewall pressure raises tire loading to the weight rating on side wall.

You can either use a chart provided by Dodge or work up a ratio to determine the required best tire pressure for a given weight. Lets see if I can remember my old math!!!!

Weigh the truck axle at a scale. Take that axle weight and divide by 2 or if you can get individual wheel weight(that's best). Then take the max tire pressure on side wall, side wall weight rating at that tire pressure make this into an equation(OR RATIO) to X over your actual weight on that tire. When you solve for X you have your tire pressure for that weight. Now depending on tire rubber compounds, tread type, ride, manufacturer, personnel preference, etc. some have found slightly higher or lower tire pressure results in some improvement in those areas by experimentation.

Hope that helps some and I made some little bit of sense.

 

[THoltz]

Good tip Bob!



I come thru your way a few times a year on my way to White Mtns to go fishing. I enjoy Big Lake, Reservation Lake, Luna Lake, West & East forks of Black River.

 

[Bob Cochran]

Good tip Bob!



I come thru your way a few times a year on my way to White Mtns to go fishing. I enjoy Big Lake, Reservation Lake, Luna Lake, West & East forks of Black River.

I have been fishing Big Lake since 1970 and the others as well. Unfortunately the last couple of years have not done so. Things just seem to happen keeping me from going!!!

 

[DennyDay]

Keep in mind, regardless of the specification weight capacity of your truck, if you are stopped and weighed, the only weight the DOT is going to look at is the tag weight and the tire capacity, go over either of these and you have a ticket. If you have had a serious accident that may have been caused by over loading, investigators will weigh your truck and load and compare that to the tire capacity and plate capicity of the truck

 

[CUMMINZ]

Consider the photos below. My 06 dually while on a set of portable scales and one wheel off the side of the road will show you how easy it is to overload one dually tire. Remember your wheels are rated 2600 pounds. You can put 3500 pounds on a wheel very easy. The reason for tire manufacturers to reduce dual tires loading.



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[GAmes]

If you have had a serious accident that may have been caused by over loading, investigators will weigh your truck and load and compare that to the tire capacity and plate capicity of the truck

I am so tired of reading this internet "fact".

How about posting a link to where that has actually happened. Here's a start, the Ford 250 that crossed the median and killed two people in the SeaTac area a couple years ago.

 

[RVTRKN]

I have personely have never seen anybody being weighed with an RV (non commercial) or with an overloaded non commercial vehicle, but it doesn't mean it doesn't happen. Don't go over the advertised axle weight rating, and the tire rating better have at least the same rating or more than the axle rating.



DOT will ticket you and it won't be cheap, as well as holding your vehicle until the weight is adjusted to under the axle ratings, and that alone could cost you more than the ticket. An accident investigation is less likely but it also can happen, just pay attention to your ratings and you will have no worry.

 

[GAmes]

Even commercially the only time the weigh station has paid any attention to the weight is Arizona because they base their permit on wt/miles. They have never compared that weight to my tire ratings though. If DOT cared a whit about overloaded RV pullers (as in 36 to 40 footers hooked to 2500s) they would have more infractions with them than with 18 wheelers. I agree that if you aren't plated for the weight you are hauling getting a ticket in you home state will happen, but as we all know most states will allow you to register for any weight you want. There is no accurate way to determine axle ratings so that isn't a potential ticket. DOT regs regarding axle weights are purely based on road damage and I seriously doubt any of us will exceed 20,000 pounds on either front or rear axle or be pulling a trailer that exceeds tandem weight limits.