Tire Load Indexes vs. Max Axle Weight

[Japple55]

Hello all,
I hope you can help clear up my understanding of tire load indexes.

I'm looking to replace all 6 tires on my Itasca Sunstar 30T (31' gasser). Front and rear GAWRs are 7,000 and 12,000, respectively. Manufacturer recommends (per the Winny cockpit tag) tires sized 245/70 R19.5 LR-G 133/132L.

Only one tire dealer near me with facilities to install tires on a Class A, and he is pushing 16 ply Hankooks with a load rating H.

Using the front axle as an example: if the GAWR is only 7,000, doesn't that mean the front tires (theoretically) need to have only a 3,500 max load index (assuming weight is evenly distributed)? If I exceed 3500 on both, I've exceeded the GAWR.

And if the above is true, isn't a tire with a load rating of H just an unnecessary additional expense for this coach?

I'm currently looking at the Sumitomo ST719s LR-G, which have a load index of 133/131N instead of the recommended 133/132L. Given the GAWR above, isn't the slight drop in dual load index of the Sumi irrelevant at those levels? Or am I just way off base, here.

TIA,
Jim

[reeman]

Originally Posted by Japple55

Hello all,
I hope you can help clear up my understanding of tire load indexes.

I'm looking to replace all 6 tires on my Itasca Sunstar 30T (31' gasser). Front and rear GAWRs are 7,000 and 12,000, respectively. Manufacturer recommends (per the Winny cockpit tag) tires sized 245/70 R19.5 LR-G 133/132L.

Only one tire dealer near me with facilities to install tires on a Class A, and he is pushing 16 ply Hankooks with a load rating H.

Using the front axle as an example: if the GAWR is only 7,000, doesn't that mean the front tires (theoretically) need to have only a 3,500 max load index (assuming weight is evenly distributed)? If I exceed 3500 on both, I've exceeded the GAWR.

And if the above is true, isn't a tire with a load rating of H just an unnecessary additional expense for this coach?

I'm currently looking at the Sumitomo ST719s LR-G, which have a load index of 133/131N instead of the recommended 133/132L. Given the GAWR above, isn't the slight drop in dual load index of the Sumi irrelevant at those levels? Or am I just way off base, here.

TIA,
Jim

Take into consideration the conditions under which you drive. If it is a large amount of 70 mph plus freeway then do not skimp on tire quality unless you intend to change tires more frequently.
A good exercise is to ride in a vehicle behind the coach watching carefully for tire performance as someone else drives it down the road. I have seen far too many RVs of all types with very poor tire stability at high speeds coaches as well as trailers.

If tires feel right and track well then they are the right product ones that are cheap low spec inevitably cause tracking problems even when fully inflated. The cheap tire kings that came with our trailer were not great and always felt like they could break loose and cause sway. Any tire that flexes side to side too much can feel better going over bumps but the compromise is not worth the risks with heavy vehicles like motor homes and travel trailers.

[SgtB]

Originally Posted by Japple55

Hello all,
I hope you can help clear up my understanding of tire load indexes.

I'm looking to replace all 6 tires on my Itasca Sunstar 30T (31' gasser). Front and rear GAWRs are 7,000 and 12,000, respectively. Manufacturer recommends (per the Winny cockpit tag) tires sized 245/70 R19.5 LR-G 133/132L.

Only one tire dealer near me with facilities to install tires on a Class A, and he is pushing 16 ply Hankooks with a load rating H.

Using the front axle as an example: if the GAWR is only 7,000, doesn't that mean the front tires (theoretically) need to have only a 3,500 max load index (assuming weight is evenly distributed)? If I exceed 3500 on both, I've exceeded the GAWR.

And if the above is true, isn't a tire with a load rating of H just an unnecessary additional expense for this coach?

I'm currently looking at the Sumitomo ST719s LR-G, which have a load index of 133/131N instead of the recommended 133/132L. Given the GAWR above, isn't the slight drop in dual load index of the Sumi irrelevant at those levels? Or am I just way off base, here.

TIA,
Jim

Hi Jim, this is Jim here as well. Friend you are going to get a ton of answers and some will be presented in a manner that you would think are fact, and they usually aren't. They are all opinions, even those coming from manufacturers are sometimes opinions based on nothing. I have been an RV-er since 1967, am 82 years old and have owned every type except a class B and the new Super C. So, let me give you my "opinion". I like Michelins, yes I know they are somewhat pricey, but if you are an FMCA member, which you should be, again my opinion, they offer a deal on them . You pay for them, they are sent to a mech of your choice and you pay him to balance and mount. Price is reasonable. You do not need anything above a G rating. The gentleman before me first talked about driving 70MPH. You should not be driving at that speed in the first place. What I like about Michelin is they make RV tires, they publish a tire guide that tells you exactly how to weigh your rig and use their chart to carry the proper amount of tire pressure in each tire. I know of no other tire manufacturer who go to that extent for RV-ers. I'd venture to say that many RVs on the road are carrying the incorrect amount of tire pressure; they need to read Michelin's RV tire booklet. So, have I answered your question? Probably not, I merely gave you my opinion based of many years of RVing and have never had a tire issue on the road. Why, because mine and my DW's lives are riding on them so I take care of them. Hope I have been a tad helpful. Semper Fi, Jim

[reeman]

Originally Posted by SgtB

Hi Jim, this is Jim here as well. Friend you are going to get a ton of answers and some will be presented in a manner that you would think are fact, and they usually aren't. They are all opinions, even those coming from manufacturers are sometimes opinions based on nothing. I have been an RV-er since 1967, am 82 years old and have owned every type except a class B and the new Super C. So, let me give you my "opinion". I like Michelins, yes I know they are somewhat pricey, but if you are an FMCA member, which you should be, again my opinion, they offer a deal on them . You pay for them, they are sent to a mech of your choice and you pay him to balance and mount. Price is reasonable. You do not need anything above a G rating. The gentleman before me first talked about driving 70MPH. You should not be driving at that speed in the first place. What I like about Michelin is they make RV tires, they publish a tire guide that tells you exactly how to weigh your rig and use their chart to carry the proper amount of tire pressure in each tire. I know of no other tire manufacturer who go to that extent for RV-ers. I'd venture to say that many RVs on the road are carrying the incorrect amount of tire pressure; they need to read Michelin's RV tire booklet. So, have I answered your question? Probably not, I merely gave you my opinion based of many years of RVing and have never had a tire issue on the road. Why, because mine and my DW's lives are riding on them so I take care of them. Hope I have been a tad helpful. Semper Fi, Jim

Absolutely true with a travel trailer or RV that one should ignore fast moving freeway transport trucks, greyhound buses and just let them roar down the pavement along with the passenger cars at and over the speed limit.

Here in BC Canada the Coquilhalla HWY has long sections of 120 kph/ 75 mph speed limit stretches some of which are notorious for flipping transport vans and especially RVs and travel trailers.

RVs driven at today's freeway speeds are much more dangerous than most people think because they do not plant heavy loads on the tires and by and large have less braking and stopping power than commercial equipment. Most cannot even be used with tire chains and sway in high cross winds like driving an unloaded van box trailer or bob tailing to a haul without adequate weight on the drive axles.

Ignore speed limits and drive the conditions with constraints relative to the nature of the vehicle. Choose the best tires that you can afford and never ignore running gear or skimp on the quality of any parts you choose to repair or replace. Is the best advice I can give.
It is important to remember that the more surface area of rubber contacting the road the heavier the load needs to be to avoid skid from light contact or worse hydroplaning in the rain. Choose RV tires that give you the best grip profile for your weight per surface area of rubber contact.

[SgtB]

Originally Posted by reeman

Absolutely true with a travel trailer or RV that one should ignore fast moving freeway transport trucks, greyhound buses and just let them roar down the pavement along with the passenger cars at and over the speed limit.

Here in BC Canada the Coquilhalla HWY has long sections of 120 kph/ 75 mph speed limit stretches some of which are notorious for flipping transport vans and especially RVs and travel trailers.

RVs driven at today's freeway speeds are much more dangerous than most people think because they do not plant heavy loads on the tires and by and large have less braking and stopping power than commercial equipment. Most cannot even be used with tire chains and sway in high cross winds like driving an unloaded van box trailer or bob tailing to a haul without adequate weight on the drive axles.

Ignore speed limits and drive the conditions with constraints relative to the nature of the vehicle. Choose the best tires that you can afford and never ignore running gear or skimp on the quality of any parts you choose to repair or replace. Is the best advice I can give.
It is important to remember that the more surface area of rubber contacting the road the heavier the load needs to be to avoid skid from light contact or worse hydroplaning in the rain. Choose RV tires that give you the best grip profile for your weight per surface area of rubber contact.

Amen to everything stated!

[Ray,IN]

The only downside to installing a higher load range is, the sidewalls are somewhat stiffer, which might negatively affect ride.
My MH requires LR G tires too, but I installed LR H. They were the same price as LR G Sailun truck tires.
FWIW, in 2017 I bought 6 new Sailun S637 LR H truck tires, the final bill was $1,380. Today Sailun tires are much more well-known and the pandemic-induced inflation has doubled the price.
When you read the specs for both Sailun truck tires and Michelin RV tires, they are the same construction. Both are USDOT approved.