twinboys = FAIL

 

DO what i do Run 3/4 ton front rims (utra goliath 3/4 ton fronts) and ultra goliath dually rear

rims ...

 

Really? After all the facts that I have presented?

What do you call someone who cannot disprove facts and instead chooses to IGNORÆ#% them?

I challenge you to pinpoint any small error I have made (fact or logic) that debunks my conclusion.

 

You're full of crap algebra and all, seen it with my own 2 eyes so you can talk all your formulas and crap untill you run them you're full of it. Draw a line on both tires directly at the bottom pointing to the ground. Now have someone move the truck ahead till the outside tire has made one revolution and line is back pointing straight at the ground. Now look at where the line is on the inside tire and try and tell me you're not scrubbing it along the ground.

 

I don't undersand your experiment. I'm pretty sure the line on the inside tire will also be pointing down?
I am intrigued. Please explain.

Are these different size tires? same size tires? tell me what happens.

 

Not hardly dont you understand circumference ? They are different size tires, do you even know what this thread is about

 

Ok so, I chalk the side wall of the two mismatched dual tires vertically in the 6 O'clock position. my partner pulled the truck ahead until the outside chalk mark is once again in the 6 O'clock position. When I look at the chalk mark on the inside dual, it too is again in the 6 O'clock position. Did I do this right? I'm not sure what result you are expecting.

"I am not scrubbing it along the ground." (I assume you mean one of the tires)
Am I supposed to see some indication that one of the tires did scrub?

When you do this is the chalk mark on the inside dual somewhere besides the 6 O'clock position?

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Here is the "thought experiment" that disproves my theory:

According to my logic, the distance an axle travels per revolution is equal to the calculated circumference of the tire. Calculated from the radius measured to the ground. this measurement changes according to amount of air in tire and the amount of load to squat the tire.

Since a speedometer measures rotation per unit time, and not the actual distance per unit time, the speedometer's accuracy must me dependant on how much the tire is squatted. But, a speedometer is independent of the load and/or tire pressure.

 

Dude were talking about having two DIFFERENT SIZE tires just because you have a truck with mismatched tires are they different sizes ? Anyways I'm done arguing with you obviously your book smarts are way ahead of me, you're just lacking in hands on sense.

 

I know this is an old thread but I couldn't help being interested.


I found this an interesting theory and saw it posted on another forum as well...smaller inside rear tires acting as a load bearing set only under high load, but not creating any friction (or wear on the inside tire) for lightly loaded conditions.


I also followed along as people with real life experience say they saw the smaller tire "scrubbed" and worn fast in real life experience with tractor trailers having tires with dissimilar wear next to each other......the smaller diameter tire gets destroyed fast they say.


Twinboys here tried to use diameter/radius to explain how they would not scrub, saying the larger tire has the same effective radius as the smaller tire because it is being compressed under load more, and he is somewhat correct about that.


Drawing a line on either tire and watching them rotate wont help. As Twinboys pointed out, both lines on both tires will travel the 360 degrees of a circle together...every single time the wheel turns.


But the factor nobody considered is surface area of the tread of the larger tire compared to surface area of the tread of the smaller tire. The smaller tire will travel a given number of inches in one complete revolution. This is the circumference. Lets call that circumference "X inches" of travel.


But the larger tire will have a little more rubber to go around a single time. If you measure its circumference it is bigger...likely by several inches...than the smaller tire. Lets call it's circumference the sum of what the smaller circumference is (X inches) plus some amount since it is bigger the difference between the smaller circumference tire and larger in inches is Y.


So...
Small tire on inside = X inches of travel in one revolution (circumference)
Larger tire on outside = X inches + Y inches


Lets take two examples:
285/75/16 has a circumference of 103.1 inches
285/80/16 has a circumference of 106.6 inches


Lets say the first of those two was the inside tire, and the second is the outside tire. SURE, under heavy load the taller outside tire's sidewall will flex and the tire will squat more than the inside tire.


BUT no matter how much the tire sidewall squats, the outside tire still has 106.6 inches worth of rubber to travel in one revolution. It WILL travel that far because it is the heavier loaded tire.


But the inside tire is loaded less, and will only travel 103.1 inches on its own tread...and since it is loaded lighter it will literally drag another 3.5 inches EVERY single time it goes around if it is touching the ground...it has no choice but to cover 106.6" too.


This is why guys with experience in the field see the shorter, more worn of two side by side tractor trailer tires literally eaten away FAST.