Tell me about your offroading with P-rated tires.

[rook]

This is one of a few examples: http://www.toyota-4runner.org/showthread.php?t=53612&page=3

Scroll down to see the Nitto TG flat.

My opinion is that the Nitto TG is not really a hardcore off-road tire like the BFG AT KO or even the Goodyear SilentArmor. If you read Nitto's website, then you will see that more than half of its advertisement is about its ON-ROAD mannerism. No 3-ply sidewall. Its sidewall is no stronger than your average highway-bias SUV tire (REVOs, Michelin, etc.). Airing down exposes a lot of the sidewall. Therefore, your sidewall is very vulnerable to rocks. If your sidewall is not strong, then you're asking for trouble. I hope that you got LT Nittos, and not P-rated Nittos. When i had Nittos a few years ago, i had the chance to feel the thickness of the sidewall (prior to tire dealer putting them on my truck). The sidewall is NOT thick at all!

Other reasons, see my discussion with Josh: http://www.toyota-4runner.org/showthread.php?t=47021&page=3&highlight=nitto+airing

Scroll down to read my posts (if you really want more explanation).

Now, just to prove my point even further, Nittos has come out with a true off-road tire: http://nittotire.com/#index.tire.trailgrappler This tire is worth it IMHO. And you can clearly see that Nitto advertises this tire as an off-road proven tire...while the TG is more of a highway tire with aggressive thread.

I wonder if this FJ owner was concerned about his Nittos?

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[Thai]

I wonder if this FJ owner was concerned about his Nittos?

http://lh5.google.com/picklesandjames/RzEZqLhr3NI/AAAAAAAAHOc/0sZGXjIZ_4A/s800/view_10.jpg

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Did he have Nittos? What kind were they? Did he air down? Was there even any sharp rocks or anything close to that??

 

[BlairB]

Did he have Nittos? What kind were they? Did he air down? Was there even any sharp rocks or anything close to that??

Yes he does, they are 325/65/18 Terra Grapplers. That truck has seen basically every type of terrain so it is safe to assume it has seen sharp rocks and such.

Here is his build thread

http://www.fjcruiserforums.com/forums/member-build-ups/39482-air2air-s-buildup-summary.html

 

[Thai]

I remember him...didn't he have a cracked fender or something and thus had to rebuild his whole FJ!! Did he tell you how many Nittos he has blown?

 

[Thai]

The other question i have is...does air2air have sponsorship deal with Nittos? He created a beast out of a FJ...that can't be cheap...i did not read his whole tread. Isn't his FJ on sale at one point? I thought that it was up for sale pretty soon after he completed the mods? Or am i remembering the wrong person?


Back on topic, is 325-Nitto P-rated? Probably not. Thus, it is still NOT a good idea to get P-rated tire for off-roading.

 

[Will_4R]

Is the only advantage to using LT-rated tires offroad their durability? Is their only disadvantage onroad noise, ride stiffness and maybe fuel economy (no safety issue)? I can understand why manfufactures tell you not to replace LT-rated tires with P-rated tires, but why do they also tell you not to replace P-rated tires with LT?

It seems a lot of popular A/T tires have more selection in P-rated models than LT. I thought the main point of LT tires was a higher load rating (resulting in stronger sidewall for offroading). But, looking at the specs for the Firestone Destination AT in a 256-70 R17, the P-rated version has a slightly higher load capactiy:

2470 lbs @ 50 psi (max) for load range C LT and
2535 lbs @ 44 psi (max) for P-rated.

Now I am confused.

 

[JB.]

Now I am confused.

Don't blame ya. I've seen reference to emails from tire companies and even received one myself with inaccurate info about this subject. Tire charts and recommendations suffer from over-simplification in the first place. Throw in two different tire types with different design standards and intended usages from companies dealing with liability and regulatory issues plus the fact that tire design is as much art as science, and you get some inconsistencies.

Is the only advantage to using LT-rated tires offroad their durability? Is their only disadvantage onroad noise, ride stiffness and maybe fuel economy (no safety issue)? I can understand why manfufactures tell you not to replace LT-rated tires with P-rated tires, but why do they also tell you not to replace P-rated tires with LT?
It seems a lot of popular A/T tires have more selection in P-rated models than LT. I thought the main point of LT tires was a higher load rating (resulting in stronger sidewall for offroading). But, looking at the specs for the Firestone Destination AT in a 256-70 R17, the P-rated version has a slightly higher load capactiy:

There is a statistical safety issue. Whether it's enough for any particular person to worry about is another question, but it's there.

Tire air volume supports load. That can be increased by more air in a bigger space or by more air in the same space, i.e., pressure. LTs support more load because they can handle more pressure. It's not a straight tradeoff, though. By being thicker and stronger to handle more pressure they start at a load disadvantage compared to Ps because the thicker tread and carcass not only results in slightly less air chamber volume but, more importantly, it also generates and retains more heat which is the biggest enemy of a tire. So size for size and psi for psi, LTs start out playing catch up with Ps in load capacity until, at a certain point approximately 8-15psi higher (depending on size), they catch Ps in load capacity and then surpass them as pressure increases up to designed maximum. As to the reason it's not advised to switch from P to LT. Under-inflation and neglect is considered a widespread problem with tires especially in hot states. Presumably, the thinking is that the problem can only be worse with switched out LTs.

2470 lbs @ 50 psi (max) for load range C LT and
2535 lbs @ 44 psi (max) for P-rated.

When doing the calculations for load capacity between P and LT, the capacity for Ps is reduced 10% when used on an SUV or Light Truck due to the possibility of over-loading and rougher treatment. The capacities for standard P-rated tires are based on 35psi and no additional load carrying capacity is officially assigned when using more pressure as in the 44psi above. So the numbers above could look as below for comparison purposes:

2470 lbs @ 50 psi (max) for load range C LT
2305 lbs @ 35 psi (or 44 or even 51) for standard P-rated. (10% de-rated)
For reference the LT would be 1980 lbs @35psi.

More discussion in the link below. A load/inflation table is linked in the first post. Down the page a little ways I made a chart that may give you a little perspective on making sense of this issue.

http://www.toyota-4runner.org/showthread.php?threadid=40803

 

[rook]

I thought the main point of LT tires was a higher load rating (resulting in stronger sidewall for offroading). But, looking at the specs for the Firestone Destination AT in a 256-70 R17, the P-rated version has a slightly higher load capactiy:

2470 lbs @ 50 psi (max) for load range C LT and
2535 lbs @ 44 psi (max) for P-rated.

Now I am confused.

Remember that load capacity is for highway use. When off roading, we air our tires down, the extra sidewall plies help keep the tire on the rim and reinforce the sidewall. If considering offroad AT's look for a tire that has been designed to be aired down.

GY Wrangler Silent Armor has durawall (sp)
BFG has tri-gard
Cooper uses Armor-Tek
Pro Comp has tri-ply

Each tire has built in strength to the carcass to maintain durability when on the trails.

 

[Will_4R]

Thanks for the detailed reply JB.

It is hard to tell what really makes a p-rated AT tire anymore offroad worthy than other all round p-rated tires. My Michelin Cross Terrains have proven to be pretty good, but other "road" tires I have used on other vehicles didn't take long to get chewed up on gravel roads.

 

[JB.]

It is hard to tell what really makes a p-rated AT tire anymore offroad worthy than other all round p-rated tires...

As far as I know, it's just the more aggressive tread.

If there's anything different with the carcass I'm unaware of it. It would seem logical to me to make them Extra Load tires (stronger P-rated tires) but the XL designation is seldom used. I suppose it's possible companies use an XL carcass but don't label it as such since the tire is expected to possibly see some rougher treatment. Since that would be extra expense, it seems more likely that they're just what they appear to be -- standard (SL) P-rated tires with all-terrain tread.

 

[G.I.G.]

I have P-rated Revo's and they have preformed well for me. I would say I am a "moderate" wheeler, doing about 6-10 trail runs per year. It is probably safe to say P-rated Revo's fall on the road friendly side of the A/T tire spectrum, where as a BFG A/T KO is more of a true off-roading A/T. I have not had any problems with my Revo's off-road and I air down regularly. I also live and wheel in CO where you come across a lot of sharp rocks. So far, they only thing that has held me up has been a lack of a lift, not my P-rated A/T tires.

I think what I am getting at is that you need to look at your overall driving habits, both on and off road, and figure out what tire is best for you. If you are looking for an A/T tire for your daily driver so you can do the occasional easy or moderate off-road trail, a P-rated A/T tire is probably more than sufficient. If you are looking to go wheel'n more often and pushing the limits of your 4R a little more, an LT-rated A/T tire or even a M/T might be a better fit for you. I've gone wheel'n with guys (including ric and A10MileHusker) that were running the stock Dunflops and they did much better than I was expecting. However, they were playing with fire and ultimately ran into problems on the trail with their H/T tires (ric's video in this thread is a perfect example).

With all of that said, I will probably go with a LT-rated A/T for my next tire.

 

[Will_4R]

I read up on the Goodyear Silent Armour that Rook made reference to. It is advertised as having a reinforced sidewall and rim protector and is suppose to me more resistant to chipping and cutting, but is still P-rated. At least based on the way these AT tires are marketed, it sounds more offroad worthy than the Revos, Destinations or other P-rated ATs. Although maybe not as tough at BFGs or other LT tires, maybe it is a better comprimise between on and offroad. One thing I notice about most AT tires regardless of P or LT rating is that there is more shoulder tread. I have not looked at hte other ATs Rook mentions, but it seems some designed to me more durable even if P-rated.

 

[rook]

I read up on the Goodyear Silent Armour that Rook made reference to. It is advertised as having a reinforced sidewall and rim protector and is suppose to me more resistant to chipping and cutting, but is still P-rated. At least based on the way these AT tires are marketed, it sounds more offroad worthy than the Revos, Destinations or other P-rated ATs. Although maybe not as tough at BFGs or other LT tires, maybe it is a better comprimise between on and offroad. One thing I notice about most AT tires regardless of P or LT rating is that there is more shoulder tread. I have not looked at hte other ATs Rook mentions, but it seems some designed to me more durable even if P-rated.

GYSA's are available in both P and LT rated. I believe they refer to the LT's as "pro grade"

 

[JB.]

...P-rated Revo's have preformed well for me...6-10 trail runs per year...no problems with my Revo's off-road and I air down regularly. I also live and wheel in CO where you come across a lot of sharp rocks...

Thanks. Exactly the kind of feedback I was looking for.

I don't live in Colorado but I've done quite a bit of wheeling there and know well those sharp rocks.