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Old 07-30-2013, 04:53 PM #31
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Quote:
Originally Posted by JB. View Post
That could be a problem because it, too, requires reading.

But this thread isn't really about any "solution" to LT tire pressure because there is no single answer. However, for set and forget simplicity, it's hard to go wrong with simply matching factory load reserve.

This thread was simply intended to make known a non-intuitive fact about the load carrying differences between P and LT tires. Since it's a non-intuitive fact that has been shown over time to not stick easily, I attempted to make it easier by making it visual.

What people do with the information is a separate subject, but it's information worth knowing.
I for one appreciate your thread on LT tires. I have learned quite a bit from your link to the tire engineer and your posts and as I am getting old it's tough to teach me new things lol. Thanks!
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Old 07-30-2013, 04:56 PM #32
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Quote:
Originally Posted by JB. View Post
That could be a problem because it, too, requires reading.

But this thread isn't really about any "solution" to LT tire pressure because there is no single answer. However, for set and forget simplicity, it's hard to go wrong with simply matching factory load reserve.

This thread was simply intended to make known a non-intuitive fact about the load carrying differences between P and LT tires. Since it's a non-intuitive fact that has been shown over time to not stick easily, I attempted to make it easier by making it visual.

What people do with the information is a separate subject, but it's information worth knowing.
Excellent information presented. Glad you posted the graphs so the data is preserved if the links eventually go dead.

Thanks,

David
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Old 07-30-2013, 07:02 PM #33
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Quote:
Originally Posted by JB. View Post
That could be a problem because it, too, requires reading.

But this thread isn't really about any "solution" to LT tire pressure because there is no single answer. However, for set and forget simplicity, it's hard to go wrong with simply matching factory load reserve.

This thread was simply intended to make known a non-intuitive fact about the load carrying differences between P and LT tires. Since it's a non-intuitive fact that has been shown over time to not stick easily, I attempted to make it easier by making it visual.

What people do with the information is a separate subject, but it's information worth knowing.
That's what I completely agree with.
Good info and it's up to people what to do with it : )
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Old 12-09-2014, 04:54 PM #34
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Crossposting for visibility from my other thread. 265/70/17 C load.

I'm not understanding this footprint for LT load range tire here. I know to get the same load rating as stock I need to be at 44psi, but this doesn't look right to me. Shouldn't I have even wear all the way across to the end of the lugs?

The first pic is my chalk test at 40psi.

The second is my tire footprint on a dirty paved road at 44 psi. You can see an inch or so on each side that has no contact.

Now, I think I get a fairy flat footprint at 38 psi (no pic), but I feel like that's a little low + it ends up driving a little wiggly and loose.
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LT tires need more air pressure.-photo-dec-08-5-11-07-pm-jpg  LT tires need more air pressure.-photo-dec-09-1-26-30-pm-jpg 
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Old 12-09-2014, 05:28 PM #35
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On mine LT C load I keep around 36psi for the past 3 years (80,000km /50,000 miles) with no issues. No trying get stock load rating though, simply using Gross Axle Weight Ratings as per manual.
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Old 12-09-2014, 05:42 PM #36
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Thanks, I was driving at 35 psi for awhile which prompted me to make a thread on why my 4R was so touchy on the highway. I found that pressure to affect my ride negatively on the highway. Bumping the pressure up really helped stability. My main concern now is traction and safety through the winter.
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Old 12-09-2014, 08:18 PM #37
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Quote:
Originally Posted by dirtysparks View Post
I'm not understanding this footprint for LT load range tire here. I know to get the same load rating as stock I need to be at 44psi, but this doesn't look right to me. Shouldn't I have even wear all the way across to the end of the lugs?
For your sanity, forget the chalk test.

Just monitor wear, it works much better. It's a direct indicator that utilizes time and takes driving habits into account. Any possible sub-optimum wear will happen so slowly that you'll have plenty of time to make any psi adjustments if you rotate normally, but adjustments probably won't be necessary.
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Old 12-10-2014, 11:10 AM #38
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Thanks for the reply.

So is it possible that driving at 35 psi for the first 5K miles has worn the outer edges to the point that at proper psi would leave the edges of the treadblocks with minimal contact? It doesn't seem like it would wear that fast - i'll have to get out the tread depth guage and check. I'm having a hard time looking at the dirt pattern on the tire and thinking I'm getting the best traction/footprint possible.

At 44 psi, it rides great, handles fine and has good road manners. BUT now that winter is here, I don't want to be rolling down the snow and ice on a doughnut shape that doesn't utlize all the tread. I'm sure after driving enough the center will wear and the outer edges will start to make contact.

I'm also not quite sure how to monitor for sub optimum wear.
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Old 12-10-2014, 06:03 PM #39
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Quote:
Originally Posted by dirtysparks View Post
Thanks for the reply.

So is it possible that driving at 35 psi for the first 5K miles has worn the outer edges to the point that at proper psi would leave the edges of the treadblocks with minimal contact? It doesn't seem like it would wear that fast - i'll have to get out the tread depth guage and check. I'm having a hard time looking at the dirt pattern on the tire and thinking I'm getting the best traction/footprint possible.

At 44 psi, it rides great, handles fine and has good road manners. BUT now that winter is here, I don't want to be rolling down the snow and ice on a doughnut shape that doesn't utlize all the tread. I'm sure after driving enough the center will wear and the outer edges will start to make contact.

I'm also not quite sure how to monitor for sub optimum wear.
If you want to play around with all this, that's fine.

If you'd like to be done with it, just pick the psi that gives you the handling you want (since you're in a reasonable psi range) and then pay attention to the wear at whatever interval makes you comfortable (not going longer than rotation schedule). To track the wear over time, pick two or three spots on the tire and take a few guage measurements to establish a consistent reading and note the readings and measurement location. Pictures make it easy to keep track.

Within a reasonable psi range, the tread wear effect due solely to pressure is very subtle and the evenness of the wear over time will be dominated by driving conditions, so trying to take care of it up front with a chalk test is not very useful.

As for the winter footprint, the difference in footprint coverage between 38 and 44 psi would be very small, and the slightly more concentrated ground pressure at 44psi might well give you better winter road performance.
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Old 03-12-2015, 01:44 PM #40
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So, what pressure should I be running LT265/70R17 BFG TA KO2 on stock 2015 SR5P here in San Diego?

35?

44?
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Old 03-12-2015, 11:01 PM #41
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Quote:
Originally Posted by jicko View Post
So, what pressure should I be running LT265/70R17 BFG TA KO2 on stock 2015 SR5P here in San Diego?

35?

44?
What did the shop set them at?

Since that tire comes in both C and E Ranges with different load indexes, then somewhere between 34.8 and 52.2
***bad math with no idea what I'm doing below***
Using the Toyota axle weight / 2 method:
C Range (Load Index 112) = 34.8
E Range (Load Index 116) = 43.1

Using the Toyota stock P load scaling method:
C range = 42.2
E Range = 52.2

Let us know what you find works best for you.


FYI: I'm getting LT265/70R17 C Range Load Index 112 Duratracs installed and plan on running 42 psi to start. I might drop them down and then crank them back up depending upon how they break-in.
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Old 08-14-2015, 08:01 AM #42
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thanks for the info
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Old 09-12-2015, 04:16 AM #43
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Nice work, tagged
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Old 09-12-2015, 04:30 PM #44
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Quote:
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So, what pressure should I be running LT265/70R17 BFG TA KO2 on stock 2015 SR5P here in San Diego?

35?

44?
Discount tires set them at 40psi.

I am currently running 45psi, after starting at 44 (prorated from the pressure of P tires), and going +/-1, +/-2 etc.. testing.... and finding that 45psi runs the best for me.
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Old 09-13-2015, 03:13 AM #45
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Maybe I missed it while skimming this thread, but I didn't see any mention of the fact that a P-metric rated tire's load carrying capacity, is derated by a factor of 1.10 (approx. 9%) when used in a Van, Pick up, or SUV application. As required by Federal Motor Vehicle Safety Standards.

So when looking at a load inflation table for a P-metric tire, reduce the load carrying capacity of the tire by a factor of 1.10, to arrive at the true load carrying capacity in a Van, Pick up, or SUV application, for a given inflation PSI.
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