re PMetric on light trucks ... deleted, plenty of good answers
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LT vs P-metric
- Thread starter Oldswagon
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Originally Posted By: MNgopher
Links:
Rubber Manufacturers Association
Click on the pdf file, a couple pages in it goes into the derating.
Lots of other links out there as well.
Interesting, thank you!
Links:
Rubber Manufacturers Association
Click on the pdf file, a couple pages in it goes into the derating.
Lots of other links out there as well.
Interesting, thank you!
My van takes this exact size of tire. Its placard says P235/75R15XL. I bought some Cooper Discoverer ATR LT-metric tires for something like $470. They have been really nice, but one of them did take a pretty big weight (some people around here get riled up about that).
The P235/75R15XL tire has a 990 kg load rating, which means it has a 900 kg rating for light trucks. An LT235/75R15 LRC tire has a "direct" load rating of 900 kg.
Here's a question for the real tire gurus here. Why does an XL tire with load index 108 have a 990 kg rating, while an SL tire with load index 108 has a 1000 kg rating? I think it's really goofy that the same load index means two different ratings depending on the tire size.
Also, +1 on the look of OWL tires. The previous owner put OWL tires on the van, and I thought it looked silly. You can mount them blackwall-out, which is what I did for the ATRs.
The P235/75R15XL tire has a 990 kg load rating, which means it has a 900 kg rating for light trucks. An LT235/75R15 LRC tire has a "direct" load rating of 900 kg.
Here's a question for the real tire gurus here. Why does an XL tire with load index 108 have a 990 kg rating, while an SL tire with load index 108 has a 1000 kg rating? I think it's really goofy that the same load index means two different ratings depending on the tire size.
Also, +1 on the look of OWL tires. The previous owner put OWL tires on the van, and I thought it looked silly. You can mount them blackwall-out, which is what I did for the ATRs.
Originally Posted By: Stu_Rock
.....
Here's a question for the real tire gurus here. Why does an XL tire with load index 108 have a 990 kg rating, while an SL tire with load index 108 has a 1000 kg rating? .....
Sorry, it doesn't. A Standard Load (SL) P235/75R15 has a 105 Load Index and an Extra Load (XL) P235/75R15 has a Load Index of 108.
By contrast an LT235/75R15 Load Range C has a Load Index of 104 / 101 (Single / Dual)
.....
Here's a question for the real tire gurus here. Why does an XL tire with load index 108 have a 990 kg rating, while an SL tire with load index 108 has a 1000 kg rating? .....
Sorry, it doesn't. A Standard Load (SL) P235/75R15 has a 105 Load Index and an Extra Load (XL) P235/75R15 has a Load Index of 108.
By contrast an LT235/75R15 Load Range C has a Load Index of 104 / 101 (Single / Dual)
Thanks for the response--you're one of the "gurus" I had in mind. But your answer does not address the question that I asked. I asked about different sizes.
If you go look at, say a P245/70R17 SL tire, it has a load index of 108 and a load rating of 1000 kg. But a P235/75R15 XL tire has a load index of 108, and a load rating of 990 kg. What's up with that?
If you go look at, say a P245/70R17 SL tire, it has a load index of 108 and a load rating of 1000 kg. But a P235/75R15 XL tire has a load index of 108, and a load rating of 990 kg. What's up with that?
Originally Posted By: Stu_Rock
If you go look at, say a P245/70R17 SL tire, it has a load index of 108 and a load rating of 1000 kg. But a P235/75R15 XL tire has a load index of 108, and a load rating of 990 kg. What's up with that?
I believe it's mostly the contained volume of air. More contained air generally means a higher load rating. I'm sure there are a million variables that affect that, but that's how it generally works I think.
If you go look at, say a P245/70R17 SL tire, it has a load index of 108 and a load rating of 1000 kg. But a P235/75R15 XL tire has a load index of 108, and a load rating of 990 kg. What's up with that?
I believe it's mostly the contained volume of air. More contained air generally means a higher load rating. I'm sure there are a million variables that affect that, but that's how it generally works I think.
Originally Posted By: Stu_Rock
Thanks for the response--you're one of the "gurus" I had in mind. But your answer does not address the question that I asked. I asked about different sizes.
If you go look at, say a P245/70R17 SL tire, it has a load index of 108 and a load rating of 1000 kg. But a P235/75R15 XL tire has a load index of 108, and a load rating of 990 kg. What's up with that?
Sorry I misinterpreted your question, but from the way it was worded, it wasn't clear what you were describing. I think I now understand what you're asking.
European based tires use the Load Index as the primary method of communicating the load carrying capacity of tires - and the numbers will always be exact. For everyone else, the load carrying capacity is calculated first, then the Load Index number is assigned. That means that for many tires the Load Index is subject to "rounding down".
If you look closely at a given tire size (try several because this doesn't always work), you will find that even though the tire size is the same, there will be different load carring capacities (and sometimes different Load Indices). That's beacuse there is a historical difference between the ways the load was calculated. It doesn't mean the tires behave differently relative to load vs pressure, it's just that the method used to describe that relationship is based on different theoretical studies and they came up with slightly different answers.
Thanks for the response--you're one of the "gurus" I had in mind. But your answer does not address the question that I asked. I asked about different sizes.
If you go look at, say a P245/70R17 SL tire, it has a load index of 108 and a load rating of 1000 kg. But a P235/75R15 XL tire has a load index of 108, and a load rating of 990 kg. What's up with that?
Sorry I misinterpreted your question, but from the way it was worded, it wasn't clear what you were describing. I think I now understand what you're asking.
European based tires use the Load Index as the primary method of communicating the load carrying capacity of tires - and the numbers will always be exact. For everyone else, the load carrying capacity is calculated first, then the Load Index number is assigned. That means that for many tires the Load Index is subject to "rounding down".
If you look closely at a given tire size (try several because this doesn't always work), you will find that even though the tire size is the same, there will be different load carring capacities (and sometimes different Load Indices). That's beacuse there is a historical difference between the ways the load was calculated. It doesn't mean the tires behave differently relative to load vs pressure, it's just that the method used to describe that relationship is based on different theoretical studies and they came up with slightly different answers.
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Oldswagon - Yes...the Bridgestone Revo's DO come in an LT load rating, however not in that size. If you were willing to move up to a 31x10.50 R15, which is a slight tad wider/taller and would fit your Suburban perfectly, you could get the LT version.
You could mount that size on your current rim too and not have any issues.
I run the Revo's on 2 trucks, both in the LT265/75 R16; one truck is running 10-ply load range E, other truck is running 6-ply.
The truck running 6-ply's is much lighter then your suburban, but I would not dream of ever putting P-rated or XL tires on it again; I've found the LT's to be much more stable, sure footed and last longer.
FWIW....Revo's are pricey, but I love them, they are fantastic.
You could mount that size on your current rim too and not have any issues.
I run the Revo's on 2 trucks, both in the LT265/75 R16; one truck is running 10-ply load range E, other truck is running 6-ply.
The truck running 6-ply's is much lighter then your suburban, but I would not dream of ever putting P-rated or XL tires on it again; I've found the LT's to be much more stable, sure footed and last longer.
FWIW....Revo's are pricey, but I love them, they are fantastic.
Oldswagon
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I just ordered the LT235/75-15 Kumho's today. I looked at the BFG A/T's, the Revo's, and the Michlen LTX's, and all were great, but I just can't afford the extra dough for the other tires right now. The Kumho's were a fair bit cheaper.
Hopefully these tires will be good. I will probably take the winter tires off sometime in March. Hopefully they are decent, I am sure they will be better than my BFG Long Trails. The Kumho's on our Honda have been awesome so far.
Oh, and I did consider the 31 x 10.5 tires, but again, the price just contiunes to climb. I am sure they wouldn't help my fuel economy either. I actually wouldn't mind a little large tire on the 'burb, since the stock ones are a little on the small side.
Hopefully these tires will be good. I will probably take the winter tires off sometime in March. Hopefully they are decent, I am sure they will be better than my BFG Long Trails. The Kumho's on our Honda have been awesome so far.
Oh, and I did consider the 31 x 10.5 tires, but again, the price just contiunes to climb. I am sure they wouldn't help my fuel economy either. I actually wouldn't mind a little large tire on the 'burb, since the stock ones are a little on the small side.
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I'm running tires 2 sizes bigger then what my Rodeo came with, have owned the truck for 13yrs, don't notice any mileage difference regarding fuel consumption.
However, it's not as long or as heavy as a burb either.
However, it's not as long or as heavy as a burb either.
Can't go wrong with your choice Oldswagon, who knows, you may just find a mpg increase with a stiffer casing having a more efficient roll under all that weight as long as the tread isn't drastically more agressive...... Ramblin that is just odd, what is your transmission, a 3 sp auto maybe, the only time I've seen or heard of same or better mpg with a bigger tire is from reduced rpm's, it usually results in less mpg. My '08 srt8 improved with bigger tires, a hair over 1mpg better from the reduced cruising rpm's.
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