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#1 DH1 ONLINE  

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Posted April 26, 2010 - 07:07 PM

I drive a 1997 Western Star Triaxle boom truck For a living, it's a company truck we supply and delivery landscapers material, concrete products and natural stone, all heavy stuff. My trucks GVWR is 86,000 lbs. Just got 6 new drive tires (rear) for it today, tires that are suppose to be on it are 16pl., which is what they took off, new tires are 14pl. and only hold 105psi. of air, 16pl. holds 120psi of air. Tire size the same.
The problem is first load they put on my truck the new tires budge out more than the ones they took off and I'm not maxed out.
Tire shop says the new tires are fine for my truck.
Door sticker on my truck says "tire size, 16pl, at 120psi, for so much weight (load).
Question: Am I worried about nothing or is there something wrong here?
Would like to here your opinions on this.

:anyone:

#2 hydriv OFFLINE  

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Posted April 26, 2010 - 09:08 PM

First off, I find it pretty unusual to not put a full line of new rubber on an axle unless the "old pair" were at least 80 percent. Anything less than 80% tread depth is just asking for quicker wear on the two new tires that were placed next to the old ones. If they were less than 80%, then we would have opted for 8 new tires and just held the old pair for use on the drop axle down the road.

Sorry but I digress. Back to your question.

The 16 ply rating tires have a load rating of H whereas the 14 ply rating tires are a G rating. The correct max inflation for a G rating tire is 105 compared to the 120 PSI needed to max out the H load rated tire.

If you had 8 new H rated tires on the rear instead of 8 new G rated tires, the TOTAL load carrying capacity would be increased by only 2.2 tons. Not much, in the overall scheme of things. We ran tri-axle Fords dump trucks that could carry a 22 metric tonne payload legally on Ontario roads and we did this on G rated rubber inflated to 105 psi. You truck can't carry that much payload because your truck is already burdened with the weight of the crane but of course, that isn't the issue because the real issue is the gross vehicle weight of the truck as allowed by MTO rules.

Your max payload is governed by the axle spread of your bogies, in part. No one would spec a truck like yours with a 54" spread but they might have used a 60" spread instead of the 72" spread that is the legal max allowed to try to obtain the max load carrying capacity. Also at issue is the placement of the drop axle on the truck because all of this has to do with preventing damage to the road surfaces. In other words, the max load you can legally carry on your truck isn't governed by the ply rating of the rubber as much as you might think it is. Overall length of the truck along with axle spacing plays a much greater part than tire ply rating.

Just be thankful that Ontario isn't like some of the USA jurisdictions or you'd be running two self-steering drop axles with 11:00 x 22 singles on them. Michigan is one of the worst states for this. I've seen Michigan trailers with seven axles on them and they don't carry any more payload than what we carry here in Ontario.

So if you are still confused... let me put it this way. Nothing is wrong here and you have nothing to worry about.

#3 DH1 ONLINE  

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Posted April 26, 2010 - 09:49 PM

Hi sounds like you know what your talking about.
They put 6 drive tires on now, last fall I got 2 16pl load H ones put one.
This truck has 72" rear axle spread, front and drop axles are super singles 445s.
We sell by the pound not kg that's why I talk in pounds, our scale is set in pounds.
My truck can carry 48,000 pounds with 300-400 to spare, and be just under 86,000lbs.
The truck has a Stealmaster crane on it mounted at the back, 22ft deck. Same as most brick company's.

Everyday I have at least 1 load where I maxed out, just don't want to get stuck at a MTO station being overweight because somebody didn't want to spend the money for the proper tire on the truck.

Edited by DH1, April 27, 2010 - 06:10 PM.


#4 chopperfreak2k1 OFFLINE  

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Posted April 27, 2010 - 06:57 PM

i'm no genius, but i would want the 16 ply tires for sure!

#5 hydriv OFFLINE  

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Posted April 27, 2010 - 09:22 PM

i'm no genius, but i would want the 16 ply tires for sure!


Then I suggest that you call up Doug's boss and explain to him why Doug needs 16 ply rubber on his truck.

#6 DH1 ONLINE  

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Posted April 27, 2010 - 10:18 PM

Then I suggest that you call up Doug's boss and explain to him why Doug needs 16 ply rubber on his truck.


Small world. Where you from?

Edited by DH1, July 12, 2010 - 08:40 PM.





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