Help! Tire Decision: "P" vs LT "C" vs LT "D"

[johncarron]

Ok folks, I need help. I'm about to get a set of Toyo Open Country ATs for my LC (these are great tires, I've got them on my Chevy Blazer). I'm leaning towards the "C" rated LT version, as I do a bit of mild off-road travel from time to time (low range; CDL locked every once in a while) and a lot of winter driving on snow-covered dirt roads in the mtns, but don't want/need the heavier load and pressure ratings of the "D" tire (never tow, though I do load the LC to the hilt at times). My concern with the "D" rating is the required pressure and likely loss of ride quality when on dry pavement (90+% of the time).

Thoughts/Feedback are appreciated.

Oh, and I'm actually leaning towards the OE 265/75 size, not the 285s, as clearance and off-road issues are not as important as being able to get the thing into my garage with a bike rack on top...

thanks.

 

[e9999]

I would go with D. You can always air down a bit if the ride is too harsh on the road, but you'll benefit safetywise when you're heavily loaded. And it's really not that bad in real terms. D may not always be available in smaller sizes, though.

 

[hkeller]

I'm glad this question was asked, as I am on the horns of this same delima. I want the deeper tread of the LT tire (in some insantances the edge of the tread is more agressive as well), but I don't want the harsher ride. The LX rides better than any vehicle I've been in with the stock tires.

Is there such a thing as a 'B' rated LT tire?

Is airing down a 'D' load rated tire, as was previously suggested, always safe?

 

[cary]

I would go with D. You can always air down a bit if the ride is too harsh on the road, but you'll benefit safetywise when you're heavily loaded. And it's really not that bad in real terms. D may not always be available in smaller sizes, though.

That is an old wives tale. A D rated and a C rated tire will have the same load capacity at the same pressure. The difference is that a load rated D tire has a stiffer sidewall that will allow for higher pressures, hence a higher load capacity. C rated tires cap out at 50psi, D 65psi, and E at 85psi.

When going from a P metric tire to an LT you must adjust the inflation pressure. Adding 10psi is a rough adjustment guidline. The LT tire will ride rougher than the p-metric, a reason that most SUV's come with p-metric tires.

If you want more information about this, search my tire inflation threads and the Tire FAQ on the 80 page. I have addressed it with links to relevant articles from Tire Rack and some major tire manufactures.

 

[cary]

I'm glad this question was asked, as I am on the horns of this same delima. I want the deeper tread of the LT tire (in some insantances the edge of the tread is more agressive as well), but I don't want the harsher ride. The LX rides better than any vehicle I've been in with the stock tires.

Is there such a thing as a 'B' rated LT tire?

Is airing down a 'D' load rated tire, as was previously suggested, always safe?

No B rated, and it wouldn't have the load capacity to support the LC. It is not safe to run a D rated tire at lower pressures on the highway, see my above post. For the best ride you will get out of LT tire, use a C rated and add 10psi from stock to adjust for the change from a P metric to LT.

 

[e9999]

That is an old wives tale. A D rated and a C rated tire will have the same load capacity at the same pressure. The difference is that a load rated D tire has a stiffer sidewall that will allow for higher pressures, hence a higher load capacity. C rated tires cap out at 50psi, D 65psi, and E at 85psi.

When going from a P metric tire to an LT you must adjust the inflation pressure. Adding 10psi is a rough adjustment guidline. The LT tire will ride rougher than the p-metric, a reason that most SUV's come with p-metric tires.

If you want more information about this, search my tire inflation threads and the Tire FAQ on the 80 page. I have addressed it with links to relevant articles from Tire Rack and some major tire manufactures.

so what's the old wives tale that I was telling, exactly?

 

[SWUtah]

That is an old wives tale. A D rated and a C rated tire will have the same load capacity at the same pressure. The difference is that a load rated D tire has a stiffer sidewall that will allow for higher pressures, hence a higher load capacity. C rated tires cap out at 50psi, D 65psi, and E at 85psi.

When going from a P metric tire to an LT you must adjust the inflation pressure. Adding 10psi is a rough adjustment guidline. The LT tire will ride rougher than the p-metric, a reason that most SUV's come with p-metric tires.

If you want more information about this, search my tire inflation threads and the Tire FAQ on the 80 page. I have addressed it with links to relevant articles from Tire Rack and some major tire manufactures.

You know I thought I knew a lot of stuff about tires but I did not know this about the LT tires and the 10+ lbs increase pressure to run them safely. I bet there are a lot of people screwing this up and driving unsafe. Thanks for the post.

 

[cary]

so what's the old wives tale that I was telling, exactly?

You cannot use a D range tire and run it at a lower pressure to make up for the ride quality difference. If you are running a 285/75/16 LT tire you need to run about 42 psi to have the proper minimum inflation per Toyota's original load requirements. This is reguardless of if it is a C, D, or E rated tire. You cannot simply choose to run the D rated tire at say, 37psi, it will be underinflated. At the same pressure, a D rated tire will ride rougher than an C tire, because it has a heavier sidewall to deal with the higher pressures it needs to hold to meet its rated load capacity.

 

[e9999]

You cannot use a D range tire and run it at a lower pressure to make up for the ride quality difference. If you are running a 285/75/16 LT tire you need to run about 42 psi to have the proper minimum inflation per Toyota's original load requirements. This is reguardless of if it is a C, D, or E rated tire. You cannot simply choose to run the D rated tire at say, 37psi, it will be underinflated. At the same pressure, a D rated tire will ride rougher than an C tire, because it has a heavier sidewall to deal with the higher pressures it needs to hold to meet its rated load capacity.

I wasn't saying that a D would give as good a ride as a C. I was saying that with a D you have the option of both handling big loads at high pressure and reducing that pressure for softer ride, so more options IMO. Seems to be pretty likely that the ride will be softer at 40 than at 60psi. Whether the tire is "underinflated" at a given pressure would seem to be mostly a matter of how much deformation is acceptable to the user (for wear, safe handling etc). Obviously, our tires can (physically) handle the 6000 lbs at 10 psi too if you want. They are just going to be pretty flat doing that (and unsafe on the freeway).

 

[cary]

I wasn't saying that a D would give as good a ride as a C. I was saying that with a D you have the option of both handling big loads at high pressure and reducing that pressure for softer ride, so more options IMO.

The problem is that you cannot run the D rated tire at lower pressures for a softer ride. The minimum pressure you can run a D rated tire at for road use is the same minimum pressure as you can run a C rated tire. This is because at the same PSI (lets say 40 psi) the D and C will have the same load capacity. If you decide to run the D rated tire at say, 35psi you are then running it underinflated.

A D rated tire does give you more load capacity when inflated past 50psi, but unless you are armored and/or carrying loads in excess of the factory approved weight capacity, there is no need for them.

 

[LXPearl]

My driving is similar to John's and I got the LT with C rating - the Michelin LTX OEM H rated tire was designed for the LX and works great for the type of use described.

 

[SWUtah]

Seems like if you are into off roading and rock crawling then the LT tires would be a good way to go, but if you are mostly on road or some unimproved roads then the best tire would be the "P" rated tires?