The reason I am asking cause I just bought my 2nd time around on 14 ply 245/70-19.5 tires on my 20,500/25,500 lb chassis motorhome, the factory had the Goodyear 12 ply but I have upgraded to 14 ply, the thicker the ply the harder the drive but the safety factor goes up, with my trailer/Jeep combo I am 14,300 lbs on the rear axle and with the factory 12 ply I am at max weight or near on tires but with 14 ply I have extra safety for weight and still run 5 psi less.So why does the RV makers or at least in 2008 on mine did they use 12 ply when it was almost at max, was it for a softer ride during test drive for sales or just to save money, when you replace your tires did you up the ply or stay at factory specs.Just some food for thought, I guess the 22.5 folks don't have to worry much about this.:)

On my 2001 Itasca, the placard says to use 245/70 19.5 F (12 ply) tires and 70 psi. How messed up is that? Itasca put G (14 ply) tires on the coach from the factory. They have no explanation as to why. For my weight, I needed approx 85-95 psi in each tire. Best advice is to weigh the coach, know your max rim psi, and air up according to the inflation tables plus 5-10 psi. For a 20,500 chassis, I would think "G" 14 ply tires. Just my opinion, stay away from the G670RV 19.5 tire. I personally don't think it is a good tire.To address your question, I don't know. Cost? ignorance?

Part of my understanding of the ply 12 vs 14 or F vs G rating is the sidewall is stronger and has less flex with higher loads and can handle higher PSI, I could stay with the 12/F ply but with my trailer weight in back the F rated tires will have more flex and run hotter but might run softer, I also hear a lot of blow outs on RV's so I thought the 14/G rated tires would offer a safer ride but a little stiffer at the same PSI.Motorhomes don't do so well in blow outs..

RV tires have a tall sidewall and more plys will stiffen the sidewall and the result is less sway when on the highway with cross winds or passing trucks.

My 31ft Newmar came with G rated Goodyear tires. So that’s what I use and if I ever have to change them, that’s what will go back on. So far no issues with the tires, but like many F53 based motorhomes takes a while and tweaking to get the best ride.

I'm not following why the F rated tire was near it's load max on your motorhome. It has a 3970 pound rating in a dual application, at 95 psi. That's 15880 pounds for your rear axle, still 1500 pounds over your loading and more than 2000 pounds over the axle rating of 13,500 pounds. Sure the G rated tire is rated higher, 17,640 total, but it doesn't seem the F tire was overloaded.Goodyear G670RV inflation tables

12 or 14 ply, What Do You Use On Your Motorhome Tires

14 Replies

timmac
Explorer
Oct 27, 2018
Chum lee wrote:

Actually IMO, the best you could do is NOT run over max gross weight! IMO, most of the tire related crashes are because the vehicle is running with worn out/damaged tires, overspeed, under pressure, and/or over max GCWR, or any combination, not because of the tire sidewall plies. But hey, you're gonna do what you're gonna do!

Chum lee

I am just a tad over max on rear axle and the 6500 lb trailer combo was taking care of by added new frame in back with more strength, air bags and a heavier rated hitch..

Trumpet Player a mechanical engineer here on RV.net certifies my setup.. :B
Trumpet_Player
Explorer
Oct 27, 2018
timmac wrote:
tderonne wrote:
I'm not following why the F rated tire was near it's load max on your motorhome. It has a 3970 pound rating in a dual application, at 95 psi. That's 15880 pounds for your rear axle, still 1500 pounds over your loading and more than 2000 pounds over the axle rating of 13,500 pounds.

Sure the G rated tire is rated higher, 17,640 total, but it doesn't seem the F tire was overloaded.

Goodyear G670RV inflation tables

14 ply/G rated tires have stiffer sidewalls so I will have less flex so the tires should run cooler with heavier loads, I am also over 14,000 lbs on my rear axle when I am towing my trailer, at 90-95 psi I have over 2000 lbs extra safe carrying on the G rated tires and less sidewall flex and that makes me feel a lot safer and to those on the road when I am loaded/towing 26,500 lbs at 65 mph..

To many blowouts from motorhomes already with deaths involved and its not always from under inflated or old tires, sometimes its from running near max weight and hot tires, I am trying to avoid blowouts..

Besides I am running over max so adding some extra safety is at least the best I can do..

"The best I can do?" Really? No, the best thing you could do for the safety of yourself and everyone else on the road is bring your coach into compliance with stated manufacturer weight specifications. Sorry... that is just a simple statement of fact.
Chum_lee
Explorer
Oct 27, 2018
timmac wrote:
Dale.Traveling wrote:
tderonne wrote:
I'm not following why the F rated tire was near it's load max on your motorhome. It has a 3970 pound rating in a dual application, at 95 psi. That's 15880 pounds for your rear axle, still 1500 pounds over your loading and more than 2000 pounds over the axle rating of 13,500 pounds.

Sure the G rated tire is rated higher, 17,640 total, but it doesn't seem the F tire was overloaded.

Goodyear G670RV inflation tables

My thoughts also. The chassis builder installed tires that were well in excess of the axle capacity. Rather than buy a higher load rated tire the OP needs to buy a high load rated coach.

Not so true, the capacity for me and others was near max and with 20,000 lbs or more going down the highway at 65 mph in a big box that does very poorly in a crash only seems logical to up the ply rating to make these motorhomes as safe as possible, do you need me to load videos of motorhome crashes and list the death toll all due to tire blow outs.

Besides I am running over max so adding some extra safety is at least the best I can do.

Actually IMO, the best you could do is NOT run over max gross weight! IMO, most of the tire related crashes are because the vehicle is running with worn out/damaged tires, overspeed, under pressure, and/or over max GCWR, or any combination, not because of the tire sidewall plies. But hey, you're gonna do what you're gonna do!

Chum lee
timmac
Explorer
Oct 26, 2018
Dale.Traveling wrote:
tderonne wrote:
I'm not following why the F rated tire was near it's load max on your motorhome. It has a 3970 pound rating in a dual application, at 95 psi. That's 15880 pounds for your rear axle, still 1500 pounds over your loading and more than 2000 pounds over the axle rating of 13,500 pounds.

Sure the G rated tire is rated higher, 17,640 total, but it doesn't seem the F tire was overloaded.

Goodyear G670RV inflation tables

My thoughts also. The chassis builder installed tires that were well in excess of the axle capacity. Rather than buy a higher load rated tire the OP needs to buy a high load rated coach.

Not so true, the capacity for me and others was near max and with 20,000 lbs or more going down the highway at 65 mph in a big box that does very poorly in a crash only seems logical to up the ply rating to make these motorhomes as safe as possible, do you need me to load videos of motorhome crashes and list the death toll all due to tire blow outs..
Dale_Traveling
Explorer II
Oct 25, 2018
tderonne wrote:
I'm not following why the F rated tire was near it's load max on your motorhome. It has a 3970 pound rating in a dual application, at 95 psi. That's 15880 pounds for your rear axle, still 1500 pounds over your loading and more than 2000 pounds over the axle rating of 13,500 pounds.

Sure the G rated tire is rated higher, 17,640 total, but it doesn't seem the F tire was overloaded.

Goodyear G670RV inflation tables

My thoughts also. The chassis builder installed tires that were well in excess of the axle capacity. Rather than buy a higher load rated tire the OP needs to buy a high load rated coach.
timmac
Explorer
Oct 25, 2018
2oldman wrote:
I don't know why anybody uses "ply" anymore.

Yea it should just be the F, G or H type rating but the tire makers just hang on to that old term.
timmac
Explorer
Oct 25, 2018
tderonne wrote:
I'm not following why the F rated tire was near it's load max on your motorhome. It has a 3970 pound rating in a dual application, at 95 psi. That's 15880 pounds for your rear axle, still 1500 pounds over your loading and more than 2000 pounds over the axle rating of 13,500 pounds.

Sure the G rated tire is rated higher, 17,640 total, but it doesn't seem the F tire was overloaded.

Goodyear G670RV inflation tables

14 ply/G rated tires have stiffer sidewalls so I will have less flex so the tires should run cooler with heavier loads, I am also over 14,000 lbs on my rear axle when I am towing my trailer, at 90-95 psi I have over 2000 lbs extra safe carrying on the G rated tires and less sidewall flex and that makes me feel a lot safer and to those on the road when I am loaded/towing 26,500 lbs at 65 mph..

To many blowouts from motorhomes already with deaths involved and its not always from under inflated or old tires, sometimes its from running near max weight and hot tires, I am trying to avoid blowouts..

Besides I am running over max so adding some extra safety is at least the best I can do..
2oldman
Explorer II
Oct 24, 2018
I don't know why anybody uses "ply" anymore.
theoldwizard1
Explorer II
Oct 24, 2018
Forget ply ratings. The tire wall will tell you the max load. Higher loads mean stiffer side walls and less likelt to sway in the wind.
tderonne
Explorer
Oct 24, 2018
I'm not following why the F rated tire was near it's load max on your motorhome. It has a 3970 pound rating in a dual application, at 95 psi. That's 15880 pounds for your rear axle, still 1500 pounds over your loading and more than 2000 pounds over the axle rating of 13,500 pounds.

Sure the G rated tire is rated higher, 17,640 total, but it doesn't seem the F tire was overloaded.

Goodyear G670RV inflation tables