2015 Stock tires OK for towing?
10-11-2015, 03:46 PM
#11
Grumpy Old Man
Ignore all the amateurs on the internet and go by what the pros say. The pros are the engineers at the Tire and Rim Assn (TRA). The TRA load/inflation table is the "bible" to answer your question.
Membership in the TRA is expensive, so it's difficult to find a copy of the annual TRA report that includes the load/inflation tables for your tires. Because of fear of lawsuits, most tire manufacturers now simply tell you to follow the vehicle manufacturer's requirements for tire PSI. So if you want to sue somebody, you can sue Ford or GM but not Goodyear or Michelin.
But some tire manufacturers still produce the load/inflation tables for the size tires they sell. Toyo is one such manufacturer. The load/inflation tables apply to all brands of tires, so a table put out by Toyo is good for any other brand of tire.
https://toyotires2-1524598101.netdna...0623_Final.pdf
TRA load/inflation table for P275/55R20 111 SL
PSI :.. 26 ....... 29...... 32 .... 35--44*
Max
Load . 2094 . 2216 . 2315 . 2403
* PSI between 35 and 44 dos not increase load capacity, but does increase speed capacity.
So weigh the truck, and divide the axle weights by two to get the weight on each tire. Then apply the above table. If the load on the front axle is less than 4,188, then you don't need more than 26 PSI in the front tires.
I'm usually loaded right up against the GVWR of my F-150 when towing, if not overloaded by 100 pounds or so. So I always pump up my P-series rear tires to 44 PSI, and have never had any tire problems on my tow vehicle.
With P-series tires, there is such a small spread between under-inflated and over-inflated that it's not big deal to me. But on my F-250 with LT tires there's a big difference between the load capacity at 45 PSI vs. 80 PSI, so I rely on the load inflation table for those tires.
Last edited by smokeywren; 10-11-2015 at 03:57 PM.
The following 2 users liked this post by smokeywren:
Ricktwuhk (10-11-2015),
Velosprout (10-19-2015)
10-13-2015, 09:28 PM
#12
Ignore all the amateurs on the internet and go by what the pros say. The pros are the engineers at the Tire and Rim Assn (TRA). The TRA load/inflation table is the "bible" to answer your question. Membership in the TRA is expensive, so it's difficult to find a copy of the annual TRA report that includes the load/inflation tables for your tires. Because of fear of lawsuits, most tire manufacturers now simply tell you to follow the vehicle manufacturer's requirements for tire PSI. So if you want to sue somebody, you can sue Ford or GM but not Goodyear or Michelin. But some tire manufacturers still produce the load/inflation tables for the size tires they sell. Toyo is one such manufacturer. The load/inflation tables apply to all brands of tires, so a table put out by Toyo is good for any other brand of tire. https://toyotires2-1524598101.netdna...0623_Final.pdf TRA load/inflation table for P275/55R20 111 SL PSI :.. 26 ....... 29...... 32 .... 35--44* Max Load . 2094 . 2216 . 2315 . 2403 * PSI between 35 and 44 dos not increase load capacity, but does increase speed capacity. So weigh the truck, and divide the axle weights by two to get the weight on each tire. Then apply the above table. If the load on the front axle is less than 4,188, then you don't need more than 26 PSI in the front tires. I'm usually loaded right up against the GVWR of my F-150 when towing, if not overloaded by 100 pounds or so. So I always pump up my P-series rear tires to 44 PSI, and have never had any tire problems on my tow vehicle. With P-series tires, there is such a small spread between under-inflated and over-inflated that it's not big deal to me. But on my F-250 with LT tires there's a big difference between the load capacity at 45 PSI vs. 80 PSI, so I rely on the load inflation table for those tires.
10-13-2015, 09:52 PM
#13
Grumpy Old Man
Always check tire PSI, or add air to your tires, when the tires are cold - after several hours sitting in the shade and not rolling. Best is first thing in the morning before you crank the engine. Best is to have an air compressor at home so you don't have to drive somewhere before you can add PSI.
But if you can't do that, then a temporary fix is to check the PSI when the tires are cold, and write down the cold PSI for each tire. When you finally get to a source for air, then check the PSI again. Subtract the cold PSI from the hot PSI and note the difference for each tire. Then subtract the cold PSI from 44 and note the difference for each tire. Add those two differences together to see how much PSI to add to each tire.
Example: Cold PSI = 33. Hot PSI after driving to the air source = 40. Goal is 44 PSI cold. So add 11 PSI plus 7 PSI for a total of 18 PSI to the 33 PSI you began with. 33 + 18 = 51 PSI temporary inflation pressure until you can do it right later. That technique won't be perfect, but I'll bet you'll have very close to 44 cold PSI the next morning before you crank the engine.
Last edited by smokeywren; 10-13-2015 at 10:13 PM.