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Old 05-10-2019, 09:14 AM   #15
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Quote:
Originally Posted by CapriRacer View Post
I am not a fan of replacing P type tires with LT type tires.

Having said that, I think in your case, the real benefit is with the increased inflation pressure
Thanks again CapriRacer. As long as I didn't really screw up buying these tires I'm good and can always switch back in a couple years.

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Originally Posted by WhereStream View Post
Would you mind explaining the chalk test? That's something new to me.

Thanks.

First thing is if CapriRacer is still watching this thread to get his take on the chalk test for setting pressure. Is it a valid way to dial in psi?

Chalk test is pretty simple, just draw a chalk line across the tread of your tire, then with whatever load you plan on carrying, drive 100 ft. or so and check the line to see if it is wearing off evenly across the tread or unevenly, more in the center, more on the edges. Adjust your psi up or down until you get it wearing evenly. If you start with high psi you can take your rig somewhere like a parking lot and slowly let air out until you get even wear.
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Old 05-10-2019, 09:39 AM   #16
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Quote:
Originally Posted by smithcreek View Post
Chalk test is pretty simple, just draw a chalk line across the tread of your tire, then with whatever load you plan on carrying, drive 100 ft. or so and check the line to see if it is wearing off evenly across the tread or unevenly, more in the center, more on the edges. Adjust your psi up or down until you get it wearing evenly..
Good to know. Thanks.
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Old 05-10-2019, 09:40 AM   #17
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Originally Posted by smithcreek View Post
. First thing is if CapriRacer is still watching this thread to get his take on the chalk test for setting pressure. Is it a valid way to dial in psi? ...
I am not a fan of the chalk test.

If steer tires tend to wear in the shoulders and drive tires tend to wear in the center, how can you use wear to decide if the pressure is correct.

And my experience says that this wheel position effect is stronger than the affect inflation pressure has. Plus there are other things that also have a stronger affect.

When I was a tire designer, I could alter the footprint pressure distribution which has an affect on how even the wear is. I noted that some of my competitor's tires didn't have very good footprints. so their wear patterns (and therefore the chalk test) would lead one to a wrong conclusion.
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Old 05-10-2019, 11:48 AM   #18
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I believe tire wear on the outside of a rear drive tire is definitely under inflation. Turning wheels may be subject to scrub butI don't think rear wheels are, except in very specific circumstances that are not the normal use and wear & tear.
I run full inflation on my P type rear truck tires just to be ready for trailering. They definitely run harsh at full pressure but I don't want to be resetting pressure every time I pick up the trailer.
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Old 05-15-2019, 10:06 AM   #19
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As the other actual tire engineer on this thread Capri and I almost always agree.
Some additional comments.


1. It is the inflation that carries the load, not the tire sidewall construction. You will only get the load capacity of LR-E as marked on the tire sidewall if you inflate to LR-E inflation as marked on the tire sidewall (80 psi in this case)


2. Anyone that changes from OE tires to something else MUST become smarter than the person inflating the tires, and must specify to that person the inflation you want.


3. Chalk test is sometimes OK but the best way to learn the MINIMUM inflation for your tires is with actual scale weights when truck & trailer are fully loaded and then use Load Inflation tables (available on my blog and on tire company web sites) to learn the MINIMUM inflation to run.


4. Capri and I both recommend you should have a minimum of 15% more load capacity than needed on trailer application tires.


5. I suggest you add 10% to the inflation number found on the Load tables for motor vehicle application.


6 On Towables with tandem axles, I strongly suggest that people run the tire sidewall pressure as their minimum. The only exception would be if you have increased the LR of your trailer tires more than one level. (LR-C > LR-E could use 65 as their cold) This is because of the Interply Shear that can result in belt separation and tire failure.
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Old 05-15-2019, 10:52 AM   #20
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Excellent information, thanks Roger. I'm good for now, just driving the truck around by itself. We have a trip planned for Memorial Day weekend and first stop is going to be the local CAT scales to do any final changes to the hitch and tire pressures. Our FC20 is a single axle, I'm hoping to get individual weights for each tire this time around. From the layout of the FC20 I've wondered if it was heavy on the passenger side, so it interesting to see.

I printed a Load/Inflation chart to bring along. Knowing your recommendations for increasing load capacity is very helpful.
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Old 05-15-2019, 11:47 AM   #21
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Overkill

Why would you want to put an E load range tire on a Toyota Tacoma? Tires are way overrated load carry for a smaller truck
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Old 05-15-2019, 02:30 PM   #22
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^Sometimes tire selection is not just about on-road load capacity, but also off-road qualities including tread pattern, durability, etc. Some sizes just don't come in P-metric types tires.

I have also gone to a Load Range E LT type tire for the added performance and durability off-road. Like the OP, I have had to increase tire pressures (32 to 36PSI) per the load rating tables. Under tow, I use 44 PSI not so much for more load support, but the added stability it affords.
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Old 05-16-2019, 06:04 AM   #23
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Quote:
Originally Posted by upszeke View Post
Why would you want to put an E load range tire on a Toyota Tacoma? Tires are way overrated load carry for a smaller truck
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... not so much for more load support, but the added stability it affords.
I said earlier that the E-rated tires were overkill as far as weight capacity goes, so that's not what I was looking for. Since we bought our AS at the start of last year I'm always trying to improve how well my rig tows as a whole. It has towed well from the start, but along the way I've made small but meaningful improvements. Things like drilling a new hole to shorten the hitch shank, changing the height and angle of ball mount, dialing in the weight distribution using 1/2" bolts in the weight distribution chains, etc.

When it came time for new tires I figured it was worth trying an E rated tire to see if it added any extra stability, like pteck said. Originally I though it was the heavier sidewall itself that provides the benefit, but the tire experts pointed out it's actually the fact that you can, and need to, run them with higher psi.
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