Recommended PSI

[Thylacine76]

Upgraded my tires to BFG ALL-Terrains (245/60-R18). What is the recommended PSI for this size? Should they be the same as the 225/60-R18's that I replaced?

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[Arcee]

Best to just start with what was recommended for the OEM tires. For example, if the original tires were to be at 33psi just start there. Then adjust as you see fit.

 

[jkeaton]

Door sticker. But, be prepared for arguments.....just like asking what's the best oil to use.

 

[Tigger]

If ever in doubt, go with the 33 on the door. Then, depending on your wants (smoother ride, better gas mileage, etc) you can adjust. Or, you can go with the rule of 80% of max stated on the tire, which many suggest, but that will most likely be well above the 33.

And for what it’s worth, I inflated the tires you are describing to 37 on my OBX as that best suited my tastes.

 

[Thylacine76]

I've got them currently at 35 psi. Will see how it is.

 

[Mark S.]

You can use this tool over at www.tiresize.com to get a good approximation.

https://tiresize.com/pressure-calculator/

 

[Tucats]

Speaking of tire pressure, is anyone having a problem with their TPMS? (Tire Pressure Monitoring System) After changing over to my snow tires this year my TPMS lite comes on after driving about 20 kms. I took my BS into ANDY'S tire in Kingston NS and they couldn't fix (reset) them. They suggested that I take it to a FORD dealership. Everything worked fine last year.

 

[Discount Tire]

Speaking of tire pressure, is anyone having a problem with their TPMS? (Tire Pressure Monitoring System) After changing over to my snow tires this year my TPMS lite comes on after driving about 20 kms. I took my BS into ANDY'S tire in Kingston NS and they couldn't fix (reset) them. They suggested that I take it to a FORD dealership. Everything worked fine last year.

Does the TPMS light flash at start up and then go solid, or does it stay solid?

 

[sajohnson]

You can use this tool over at www.tiresize.com to get a good approximation.

https://tiresize.com/pressure-calculator/

Survey sez:

OEM Size (225/60R18 SL) Load Capacity: 1636 lbs. @ 33 psi.

New Size (245/60R18 SL) Load Capacity: 1658 lbs. @ 28 psi.

(I wasn't sure about the load rating so I selected "SL" for both)

That is a very cool calculator -- thanks for sharing!

I am surprised that going from 225>245 dropped the recommended pressure so much (5 psi).

Another way to confirm the proper pressure is to refer to the tire mfr's "load & inflation tables". Basically do the same thing manually.

 

[Tucats]

Discount Tire - Starts out flashing then soon goes solid.

 

[Mark S.]

Survey sez:

OEM Size (225/60R18 SL) Load Capacity: 1636 lbs. @ 33 psi.

New Size (245/60R18 SL) Load Capacity: 1658 lbs. @ 28 psi.

(I wasn't sure about the load rating so I selected "SL" for both)

That is a very cool calculator -- thanks for sharing!

I am surprised that going from 225>245 dropped the recommended pressure so much (5 psi).

Another way to confirm the proper pressure is to refer to the tire mfr's "load & inflation tables". Basically do the same thing manually.

I don't think the change in tire pressure recommended by the calculator has to do with tire width, I think it's due to the increase in load index. The OE tire's load index is 100, vs the BFG's load index of 105. I believe the load capacity displayed by the calculator is what the tire can carry at that tire pressure, not the tire's maximum load capacity. In other words, the BFG tire's load capacity is 1658 at 28 PSI, but if you inflate it to 33 PSI the load capacity would be higher.

You can read more about load index at this link.

 

[sajohnson]

I don't think the change in tire pressure recommended by the calculator has to do with tire width, I think it's due to the increase in load index. The OE tire's load index is 100, vs the BFG's load index of 105. I believe the load capacity displayed by the calculator is what the tire can carry at that tire pressure, not the tire's maximum load capacity. In other words, the BFG tire's load capacity is 1658 at 28 PSI, but if you inflate it to 33 PSI the load capacity would be higher.

You can read more about load index at this link.

Good info at the link. The Tire Rack is generally reliable.

I've mentioned in previous posts that my wife and I own an RV on a Sprinter 3500 cab-chassis (dual rear tires) -- that's why I mentioned the tire mfr's "load & inflation tables".

Yes, the calculator uses the pressure input by the user -- 33 psi in this example (not max pressure) -- and higher pressure in any tire = higher load capacity..

I mentioned 225 vs 245 as a way to differentiate between the two otherwise identical tire sizes. I could have said OE vs BFG.

The increased load rating of the 245 is due to its greater volume, which, in this case is due to the increased width (all else is equal). Needless to say, width alone is not an indicator of load rating. Interior volume and "ply rating"/construction are the 2 main factors. From MT:

"The average motorist might think that his tires' rubber and steel belts support the vehicles' weight, but air pressure actually carries the load. The greater the tire's internal air volume, the more weight it can theoretically support.":
https://www.motortrend.com/how-to/1407-understanding-tire-load-ratings/

 

[Discount Tire]

Discount Tire - Starts out flashing then soon goes solid.

Typically speaking...When the light flashes and then goes solid, there is an issue with the sensors themselves. The common issues could be as simple as the sensor batteries are starting to, or have failed. Another common issue is improper installation. (Broken during install). You can go to your local tire retailer and have the sensors scanned to determine the root cause.

 

[Tucats]

Thanks for your reply. I will do that.

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