QuestionHope your vacation was relaxing. (Then you come back to this!)
Bunch of questions, sorry. But they go together. No hurry.
It's time for tires on my SUV and I will probably be replacing my current set of replacement LTs with more LTs. (The OE tires were P-rated and I appreciate your position on not switching but I still believe I need an LT for my application; long, often rough, remote off-pavement travel a few times a year. I believe I sufficiently understand the pressure issues. In my application, at 35psi for instance, there is a 67% tire load reserve at curb weight which seems to be at least as high as typical OE.) Thanks in no small part to your writings, I'm interested in looking at LT A/Ts with cap plies which, surprisingly, are an option. Some descriptions state nylon cap plies directly, but others say something like "two steel belts reinforced with spirally wound nylon" which I assume means it serves the same purpose as full width cap plies but, perhaps, a little less robustly. Is this close? Does any reference to steel belt reinforcement serve the same circumference stabilizing purpose?
Does the (recent?) inclusion of cap plies in lower speed rated tires throw a bit of a wrench in the consistency of speed ratings? For instance, if a choice came down to a speed rating R with cap plies or speed rating S without, is it possible/likely the R might be the more durable tire?
Unfortunately, choices of load ranges are pretty limited. Many of the tires I'm considering are load E only. My current LT265/70/17 tires are load C and weigh 47lbs (curb weight is 4500lbs). The same tire in load E weighs 54lbs. In surveying various same size A/T LT tires of different brands, I notice a range of tire weights that don't seem to correlate well with nominal load ranges. For instance, one load E tire I'm looking at is 46lbs. Tread volume would not seem to be the primary cause as tread depths, widths, and voids seem to be much too close to account for this. Is it reasonable for me to surmise that tire weight, as opposed to nominal load range (C-E), would have more effect on ride characteristics at usage pressures all can accommodate?
Do differences in load ranges present any problem in comparing speed ratings?
Also, in load/inflation tables, how can high load range tires rate the same as lower load range tires at pressures in common where I'd think tires weighing over 15% more would have to generate/retain more heat? On my own, I might have to infer that heat is mostly about tread.
On the subject of Ps, I'd like to ask one question. (Two A/T tires identical except one LT, one P.) Run slowly at off-road pressure, say, 18psi for long periods, would a P sidewall weaken well before an LT sidewall? (Just flex, no cuts or bruises).
Question recap:
1. Nylon reinforced belts much the same as cap plies?
2. Does any belt reinforcement serve same general purpose?
3. Can existence of cap plies be more important than speed rating?
4. Shop by tire weight instead of load range (usage PSIs<50)?
5. Load range affect speed rating comparison for PSIs in common?
6. Heavier tire should run hotter, yet no adj in load/inflation tables.
7. Underinflated P sidewall last as long as LT? (slow speed flex only)
Thank you very much in advance.
Jeff
AnswerJeff,
-----Hope your vacation was relaxing.------
I was actually taking care of my father who had had open heart surgery. He has recovered nicely. I wasn't sure how much access I was going to be able to get to computer time, so I put myself on vacation so I wouldn't disappoint folks with a lot of unanswered questions.
-----(Then you come back to this!)
Bunch of questions, sorry. But they go together. No hurry.---------
I enjoy answering questions.
-----It's time for tires on my SUV and I will probably be replacing my current set of replacement LTs with more LTs. (The OE tires were P-rated and I appreciate your position on not switching but I still believe I need an LT for my application; long, often rough, remote off-pavement travel a few times a year. I believe I sufficiently understand the pressure issues. In my application, at 35psi for instance, there is a 67% tire load reserve at curb weight which seems to be at least as high as typical OE.) Thanks in no small part to your writings, I'm interested in looking at LT A/Ts with cap plies which, surprisingly, are an option. Some descriptions state nylon cap plies directly, but others say something like "two steel belts reinforced with spirally wound nylon" which I assume means it serves the same purpose as full width cap plies but, perhaps, a little less robustly. Is this close? ---------
Sometimes instead of cap plies, the nylon is only used on the edge edges - and you have portrayed that accurately - cap strips don't work as well as cap plies. BTW, sometimes kevlar is used, but the purpose and the result is the same.
-----Does any reference to steel belt reinforcement serve the same circumference stabilizing purpose?-----
With the exception that cap plies, which you will find listed on the sidewall as part of the materials used, work better than cap strips, which you will not find listed on the sidewall, only in the literature.
----Does the (recent?) inclusion of cap plies in lower speed rated tires throw a bit of a wrench in the consistency of speed ratings?------
Yes
------For instance, if a choice came down to a speed rating R with cap plies or speed rating S without, is it possible/likely the R might be the more durable tire?------
That would be my guess as well.
------Unfortunately, choices of load ranges are pretty limited. Many of the tires I'm considering are load E only. My current LT265/70/17 tires are load C and weigh 47lbs (curb weight is 4500lbs). The same tire in load E weighs 54lbs. In surveying various same size A/T LT tires of different brands, I notice a range of tire weights that don't seem to correlate well with nominal load ranges. For instance, one load E tire I'm looking at is 46lbs. Tread volume would not seem to be the primary cause as tread depths, widths, and voids seem to be much too close to account for this. Is it reasonable for me to surmise that tire weight, as opposed to nominal load range (C-E), would have more effect on ride characteristics at usage pressures all can accommodate?-------
I am always surprised at how little difference in weight ply and belt material differences are between load ranges compared to how much differences otherwise similar tread patterns have. I would not discount tread void in accounting for major weight differences.
1) Given that much of ride quality comes from inflation pressure.
2) Differences between load ranges would be small compared to differences in inflation pressure
3) Much of the weight difference in tires is tread, which will have very little affect on ride.
I tend to think that ride quality is only loosely tied to weight.
-----Do differences in load ranges present any problem in comparing speed ratings?-----
No, you can consider these 2 properties independent of each other.
-------Also, in load/inflation tables, how can high load range tires rate the same as lower load range tires at pressures in common where I'd think tires weighing over 15% more would have to generate/retain more heat? On my own, I might have to infer that heat is mostly about tread.------
The difference in heat generation is more tied to deflection, which is the basis of the load curve. Small differences in construction don't seem to affect heat generation as much as you would think.
----On the subject of pressure, I'd like to ask one question. (Two A/T tires identical except one LT, one P.) Run slowly at off-road pressure, say, 18psi for long periods, would a P sidewall weaken well before an LT sidewall? (Just flex, no cuts or bruises).-----
No, I would expect the LT to weaken first due to cracking of the sidewall - which is where my "No Switch" policy comes from.
Question recap:
1. Nylon reinforced belts much the same as cap plies?----- Sort of
2. Does any belt reinforcement serve same general purpose?------ Yes, but to a lesser degree
3. Can existence of cap plies be more important than speed rating?----- Yes
4. Shop by tire weight instead of load range (usage PSIs<50)?------In this case yes, but for other reasons.
5. Load range affect speed rating comparison for PSIs in common?
6. Heavier tire should run hotter, yet no adj in load/inflation tables.------ Not enough to matter
7. Underinflated P sidewall last as long as LT? (slow speed flex only)---- I think the P would last longer
-------Thank you very much in advance.
Jeff----
You are welcome
Barry
