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Old 04-28-2012, 06:49 PM   #1
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Load range F vs. Load range G

I have been searching threads and cannot find this discussion if it has already been posted, so please forgive me if I tread across a previously discussed tire topic. I am wondering if having a higher load range tire adds any margin of safety. To be specific, I am not speaking about, nor considering exceeding the load limits of the axle or the motorhome, but rather having a tire that is capable of carrying more weight as an added margin of safety. I have seen tire load range charts that seem to indicate that a load range G tire is capable of carrying more load than a load range F tire. I have not found that there is much difference in the cost. Your opinions will be greatly appreciated.

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Old 04-30-2012, 08:38 AM   #2
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If your present tires can carry the maximum axle weight and still have a bit extra margin, then there is no benefit to a higher load range tire. Especially if your normal actual load is well under maximum for the axle. But if the "F" tire is marginal vs the GAWR, then it will be worth the slight extra cost to get a "G".

Another slight benefit may be that the "G" tire can be run at a slightly lower psi fr the same actual load. That can give a bit softer ride.

Addendum: This last sentence is wrong - see follow-up message from Midnightoyl below.
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Old 04-30-2012, 01:35 PM   #3
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Thanks for your response. It is a 1997 Fleetwood Flair with a 10k# axle in the rear and 5300# front. If i am doing this right, that equates to 2500#s per tire rear and 2650 front. Well below the load range max for the F range tire. Or is the math incorrect? I have serious trust issues with tire salesmen as this is certainly NOT my area of expertise.

Again thanks for your help.
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Old 04-30-2012, 03:49 PM   #4
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Quote:
Originally Posted by Gary RVRoamer View Post
If your present tires can carry the maximum axle weight and still have a bit extra margin, then there is no benefit to a higher load range tire. Especially if your normal actual load is well under maximum for the axle. But if the "F" tire is marginal vs the GAWR, then it will be worth the slight extra cost to get a "G".

Another slight benefit may be that the "G" tire can be run at a slightly lower psi fr the same actual load. That can give a bit softer ride.
Actually, no, you can NOt run G rated at a lower PSI...
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Old 04-30-2012, 03:57 PM   #5
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Quote:
Originally Posted by Txcirclem View Post
Thanks for your response. It is a 1997 Fleetwood Flair with a 10k# axle in the rear and 5300# front. If i am doing this right, that equates to 2500#s per tire rear and 2650 front. Well below the load range max for the F range tire. Or is the math incorrect? I have serious trust issues with tire salesmen as this is certainly NOT my area of expertise.

Again thanks for your help.
You are fine.. you will see absolutely no benefit in running a higher rated tire.

The reason the G tires have a higher rating is because they can hold more air pressure. If you are not running wieghts high enough to warrant the higher pressures, then you are just wasting money..

Quote:
The load range or ply rating branded on a tire's sidewall helps identify how much load the tire is designed to carry at its industry specified pressure. Passenger tires feature named load ranges while light truck tires use load ranges that ascend in alphabetical order (letters further along in the alphabet identify stronger tires that can withstand higher inflation pressures and carry heavier loads). Before load ranges were adopted, ply ratings and/or the actual number of carcass plies were used to identify the relative strength with higher numeric ratings or plies identifying tires featuring stronger, heavier duty constructions.
Today's load range/ply ratings do not count the actual number of body ply layers used to make up the tire's internal structure, but indicate an equivalent strength compared to early bias ply tires. Most radial passenger tires have one or two body plies, and light truck tires, even those with heavy-duty ratings (10-, 12- or 14-ply rated), actually have only two or three fabric plies, or one steel body ply.
Tire Tech Information - Load Range/Ply Rating Identification

As an example, notice that the higher load ratings are simply just listing a higher PSI..

http://www.goodyearrvtires.com/pdfs/rv_inflation.pdf
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Old 04-30-2012, 09:23 PM   #6
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Higher load range have more stiffness in the sidewalls so you will see improvement in cornering as the tires will be less prone to washout.

Cheap mod that may have good result but one needs to remember when retiring to not go back and loose the gain
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Old 06-13-2013, 02:50 PM   #7
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I am going to resurect this thread and ask the same question, I read the above and think some is right an some is wrong, namely, the capacity of the F vs G is based upon the amount of air pressure that the tire is capable of holding. In other words, the G tire is rated for higher load based on the maximum pressure it can withstand, both tires at the same PSI are rated to carry the same load.

I am interested in the question of sidewall stiffness and ride comfort. My coach sticker calls for F rated tires, I have G's all around (they have all been replaced by prior owner). I am going to replace steering now and rear next year, based on tire ages on coach, my steering are 5 years old and the rears are only 3 1/2. I have priced Goodyears and there is actually a substantial diff in price for F vs. G. My front axle scale weight is well within the F load range, and I think some of my ride stiffness is result of G tires. Front axle weight with me and wife and full equipment load is 6350, two F's can carry 7940 at 95 psi, or 7030 at 85 which is where I have my G's (same chart).

Based on this I see NO POINT in paying extra for G's for some percieved "safety margin" based on above. If I have the tires properly inflated there is no load capacity difference between them.

I know I have made this confusing but I hope I am getting across the point of my question.
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Old 06-14-2013, 12:12 AM   #8
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As I posted above, I have upsized to a higher load rating to improve the cornering of the vehicle.

It is the cheapest most effective mod that you can do.

If the lower grade has plenty of margin to carry the load then you are correct, no need for the extra investment for added safety margin.

However, the higher rated tires will have a ride that is less prone to washout on cornering and will handle the loading better period.

How does it ride now?

Will the lower rated tire be better?

Who knows as every MH is different and it would be difficult for party X to describe to party Y how some tire may ride unless they had exact same everything except for the tires.
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Old 06-14-2013, 09:01 AM   #9
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On our Winnebago 37g the chassis rating is close to the load range f tires that were original. I bought the new load range h for only $30 total more. Great margin of safety, couldn't tell a difference in ride.
We are lucky to live in a country where we can live and travel safe in an Rv!
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Old 06-14-2013, 09:26 AM   #10
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I looked for the thread I was having a big question about the load ranges and I can't find it.

I went through this last year before I replaced my rear tires with LR-F as Fleetwood called for.

I called Fleetwood and asked them about this issue, because the dealer that sold me the motorhome had installed load range H Gladiator tires on the steering axle, and I wanted to know why they did that. It was all because those tires were cheaper than an RV Load Range F tire.

Fleetwood told me there was no reason to go to a higher load rating tire, the coach is perfectly safe with the LR-F tires. Also, handling, and ride factor in when you are buying RV tires with a higher ply rating. That was per Fleetwood.

Whats funny is I had more luck finding cheaper tires in the load range g and h than the load range F I was looking for at the time.

Anyway, my coach, I replaced the 10 year old Goodyear GV670RV tires with Michelin XRV 245.70.19.5 LR-F tires through the FMCA/Michelin discount program.

In addition, I had Dynabeads installed so they are always in balance.

Couldn't be happier with their performance and ride so far.
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Old 06-14-2013, 12:33 PM   #11
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Exclamation Mea Culpa

I was wrong way back near the beginning of this thread when I said the G-rated tire can run at a "slightly lower pressure" for the same weight and Midniteoyl properly corrected me on that. A different model of tire may need slightly more or less pressure for a given weight, but if it's the same model of tire, the G will use the same pressure as an F for the same weight.
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Old 06-14-2013, 12:49 PM   #12
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I don't think you can automatically assume that a G rated tire will handle better or ride more harshly than an F. It may have stiffer sidewalls as part of increasing the load rating, but there is no real way to know without getting the tire engineer to tell us what, if anything, was done to the tire design increase the rating.

I say "if anything" because it is entirely possible that the two tires are identical in all regards except the rating. This can happen if the manufacture decides it is not economic to design and build two slightly different designs but still wants to have a lower price point for the tire to enhance sales. Stamping an F load range on instead of G is an inexpensive way to justify a different price.

A similar thing occurs when the same tire is made with two different brand names, e.g. a plant producing both Michelin and Goodrich tires (both are Michelin brands). Goodrich generally sells at a lower price point than Michelin, even for the identical tire size and load range tire.

I have no idea if either of these apply to the tires mentioned here, but it is a known technique used in tire production and marketing.
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Old 06-14-2013, 01:18 PM   #13
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Quote:
Originally Posted by Gary RVRoamer View Post
I was wrong way back near the beginning of this thread when I said the G-rated tire can run at a "slightly lower pressure" for the same weight and Midniteoyl properly corrected me on that. A different model of tire may need slightly more or less pressure for a given weight, but if it's the same model of tire, the G will use the same pressure as an F for the same weight.
Your statement was partly right, the partly-right part being that you can run a lower pressure in relation to the tire's maximum pressure rating.

That said, and as a slight hijack to this discussion, I've often wondered about the max pressure/recommended pressure ratings of CAR tires- specifically: I had a '96 Lincoln Mark VIII, which recommends a 30 psi tire pressure. However, that pressure was fine with 32 or 35 max psi tires, but once I put 44 psi max tires on, at 30psi they were half flat. While the car rode like a dream, it handled like I was driving on jello. What I did was take the ratio of a 35 psi max tire (which handled perfectly at 30 psi) to the 30 psi recommended, which is 85.7%, and factored that into the 44 psi tire, which works out to about 38 psi. That's what I ran in those tires, and the car rode nicely and handled perfectly again.

Taking that experience into account, then it would seem prudent that you'd need MORE air in a G rated RV tire for the same weight as an F rated tire. However, the 44 psi car tires had a SOFTER sidewall than the 35 psi tires, which is the opposite -typically- to RV tires--

or is it? Suppose it depends on the who's making the tire... The old Michelins removed from our Allegro have the such flimsy sidewalls I'm surprised they'll hold up a motorhome at all. The Samson's and Sumitomo's that replaced them have MUCH stiffer sidewalls...

No questions, no answers either...
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Old 06-14-2013, 01:24 PM   #14
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The Samson and Sumitomos are truck tires and they do have stronger sidewalls I was told by the tire folks.

Also the RV tires are supposedly softer deliberately for the ride. But who knows, like you said, no questions and no answers.

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