Got new LT's to Replace P's - Not sure I believe the PSI Advice from the shop

[SteveW2993]

Hi all,

We decided to replace the stock Goodyear Wranglers on our 2018 F-150 with LT tires. Found the ride with the trailer "wiggly/squirmy" with the P tires. They were P275/55R20.

Went to one of our local tire shops. The had a hard time coming up with something for the rim size that was easily available in our area. The eventually recommended the Yokohama Geolandar's in LT275/55R20 120/117S. They are Load Range E, and max out at 80 PSI.

When I asked them what pressures they thought we should run them at based on our use, the answer I got was:

When towing our Passport - 65 PSI
When not - 35 PSI as per door sticker

That doesn't sound right. I thought LT tires had to actually be at a higher pressure than the door sticker for the P tires to have the same load carrying capacity - like in the neighbourhood of 10 PSI more.

Anyone have some experience on this that can maybe provide some advice. If the same load carrying capacity can be met by say using the 10 more PSI example for LT versus P, is there any point pumping them up to 65 PSI when the trailer is on?

Tnx!
-Steve

[slow]

Hi all,

We decided to replace the stock Goodyear Wranglers on our 2018 F-150 with LT tires. Found the ride with the trailer "wiggly/squirmy" with the P tires. They were P275/55R20.

Went to one of our local tire shops. The had a hard time coming up with something for the rim size that was easily available in our area. The eventually recommended the Yokohama Geolandar's in LT275/55R20 120/117S. They are Load Range E, and max out at 80 PSI.

When I asked them what pressures they thought we should run them at based on our use, the answer I got was:

When towing our Passport - 65 PSI
When not - 35 PSI as per door sticker

That doesn't sound right. I thought LT tires had to actually be at a higher pressure than the door sticker for the P tires to have the same load carrying capacity - like in the neighbourhood of 10 PSI more.

Anyone have some experience on this that can maybe provide some advice. If the same load carrying capacity can be met by say using the 10 more PSI example for LT versus P, is there any point pumping them up to 65 PSI when the trailer is on?

Tnx!
-Steve

If you have taken your TV and TV/TT combo across a CAT scale then you have the loads for the TV tires with and without the TT. If not, do so.

Then you can go to the tire manufacturer's website and find the tire load chart to determine the appropriate PSI for your towing and not towing conditions.

IMO: 65 psi on the front TV tires seems high for your setup when towing and will most likely provide a loose steering feel.

[SteveW2993]

Thanks. Yes we’ve had the combination on a CAT scale a couple times, so I have that. I had taken a quick look on the Yokohama website but didn’t come across a chart for LT tires. Found one for their medium truck tires. I’ll look again.

Tnx

[ChuckS]

At your weight 60 psi in those tires is way too much pressure.

For example.. I run 65 front and 80 rear cold psi with a 12 K fifth wheel and diesel. I’d be running those tires at your weight with something more like 40 FRt/ 50 rear which gives you 500 lbs plus headroom.

[SteveW2993]

Found a web site that I think will help me out...

https://tirepressure.com/tire-pressure-charts

[SteveW2993]

At your weight 60 psi in those tires is way too much pressure.

For example.. I run 65 front and 80 rear cold psi with a 12 K fifth wheel and diesel. I’d be running those tires at your weight with something more like 40 FRt/ 50 rear which gives you 500 lbs plus headroom.

Thanks ChuckS. I think I just found at the same time you posted the same table you quoted. Appreciate the insight from your setup. :thumbsup:

And your suggestion pretty much matches up with our scale weights +500.

[ChuckS]

Good deal... you will find your rig will handle much much better at the lower psi setting..front tires will last longer, and most importantly you will have a safer setup due to having more tread surface down on the road at your weight. Safe travels.

[CWtheMan]

Tire industry standards for replacement tires requires, at the very minimum, for the replacement tires to provide a load capacity equal to what the Original Equipment tires provided.

Using the proper inflation charts for each tire size you have provided I have found that your OE tires provided 2184# of load capacity at 35 PSI. That figure includes the mandatory reduction for service on a pick-up truck.

Your replacement tires will provide the necessary load capacity to meet tire industry standards at 48 PSI. I would round it off at 50 PSI which provides 2270# of load capacity per tire.

[SteveW2993]

Tire industry standards for replacement tires requires, at the very minimum, for the replacement tires to provide a load capacity equal to what the Original Equipment tires provided.

Using the proper inflation charts for each tire size you have provided I have found that your OE tires provided 2184# of load capacity at 35 PSI. That figure includes the mandatory reduction for service on a pick-up truck.

Your replacement tires will provide the necessary load capacity to meet tire industry standards at 48 PSI. I would round it off at 50 PSI which provides 2270# of load capacity per tire.
Good to know. Tnx!