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

wildtoad
Explorer II
Oct 24, 2018
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.
rgatijnet1
Explorer III
Oct 24, 2018
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.
timmac
Explorer
Oct 24, 2018
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..
kmb1966
Explorer
Oct 24, 2018
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?

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

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